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rocksdb/db/db_impl.cc
Haobo Xu 1afdf28701 [RocksDB] Compaction Filter Cleanup 
Summary: This hopefully gives the right semantics to compaction filter. Will write a small wiki to explain the ideas.

Test Plan: make check; db_stress

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11121
2013-06-14 14:23:08 -07:00

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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "db/db_impl.h"
#include <algorithm>
#include <climits>
#include <cstdio>
#include <set>
#include <string>
#include <stdint.h>
#include <vector>
#include <unordered_set>
#include "db/builder.h"
#include "db/db_iter.h"
#include "db/dbformat.h"
#include "db/filename.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/memtablelist.h"
#include "db/merge_helper.h"
#include "db/table_cache.h"
#include "db/version_set.h"
#include "db/write_batch_internal.h"
#include "db/transaction_log_iterator_impl.h"
#include "leveldb/compaction_filter.h"
#include "leveldb/db.h"
#include "leveldb/env.h"
#include "leveldb/merge_operator.h"
#include "leveldb/statistics.h"
#include "leveldb/status.h"
#include "leveldb/table_builder.h"
#include "port/port.h"
#include "table/block.h"
#include "table/merger.h"
#include "table/table.h"
#include "table/two_level_iterator.h"
#include "util/auto_roll_logger.h"
#include "util/build_version.h"
#include "util/coding.h"
#include "util/logging.h"
#include "util/mutexlock.h"
#include "util/stop_watch.h"
namespace leveldb {
void dumpLeveldbBuildVersion(Logger * log);
// Information kept for every waiting writer
struct DBImpl::Writer {
Status status;
WriteBatch* batch;
bool sync;
bool disableWAL;
bool done;
port::CondVar cv;
explicit Writer(port::Mutex* mu) : cv(mu) { }
};
struct DBImpl::CompactionState {
Compaction* const compaction;
// If there were two snapshots with seq numbers s1 and
// s2 and s1 < s2, and if we find two instances of a key k1 then lies
// entirely within s1 and s2, then the earlier version of k1 can be safely
// deleted because that version is not visible in any snapshot.
std::vector<SequenceNumber> existing_snapshots;
// Files produced by compaction
struct Output {
uint64_t number;
uint64_t file_size;
InternalKey smallest, largest;
};
std::vector<Output> outputs;
std::list<uint64_t> allocated_file_numbers;
// State kept for output being generated
unique_ptr<WritableFile> outfile;
unique_ptr<TableBuilder> builder;
uint64_t total_bytes;
Output* current_output() { return &outputs[outputs.size()-1]; }
explicit CompactionState(Compaction* c)
: compaction(c),
total_bytes(0) {
}
};
struct DBImpl::DeletionState {
// the list of all live files that cannot be deleted
std::vector<uint64_t> live;
// a list of all siles that exists in the db directory
std::vector<std::string> allfiles;
// the current filenumber, lognumber and prevlognumber
// that corresponds to the set of files in 'live'.
uint64_t filenumber, lognumber, prevlognumber;
// the list of all files to be evicted from the table cache
std::vector<uint64_t> files_to_evict;
};
// Fix user-supplied options to be reasonable
template <class T, class V>
static void ClipToRange(T* ptr, V minvalue, V maxvalue) {
if (static_cast<V>(*ptr) > maxvalue) *ptr = maxvalue;
if (static_cast<V>(*ptr) < minvalue) *ptr = minvalue;
}
Options SanitizeOptions(const std::string& dbname,
const InternalKeyComparator* icmp,
const InternalFilterPolicy* ipolicy,
const Options& src) {
Options result = src;
result.comparator = icmp;
result.filter_policy = (src.filter_policy != nullptr) ? ipolicy : nullptr;
ClipToRange(&result.max_open_files, 20, 1000000);
ClipToRange(&result.write_buffer_size, ((size_t)64)<<10,
((size_t)64)<<30);
ClipToRange(&result.block_size, 1<<10, 4<<20);
if (result.info_log == nullptr) {
Status s = CreateLoggerFromOptions(dbname, result.db_log_dir, src.env,
result, &result.info_log);
if (!s.ok()) {
// No place suitable for logging
result.info_log = nullptr;
}
}
if (result.block_cache == nullptr && !result.no_block_cache) {
result.block_cache = NewLRUCache(8 << 20);
}
result.compression_per_level = src.compression_per_level;
if (result.block_size_deviation < 0 || result.block_size_deviation > 100) {
result.block_size_deviation = 0;
}
if (result.max_mem_compaction_level >= result.num_levels) {
result.max_mem_compaction_level = result.num_levels - 1;
}
return result;
}
DBImpl::DBImpl(const Options& options, const std::string& dbname)
: env_(options.env),
dbname_(dbname),
internal_comparator_(options.comparator),
options_(SanitizeOptions(
dbname, &internal_comparator_, &internal_filter_policy_, options)),
internal_filter_policy_(options.filter_policy),
owns_info_log_(options_.info_log != options.info_log),
db_lock_(nullptr),
mutex_(options.use_adaptive_mutex),
shutting_down_(nullptr),
bg_cv_(&mutex_),
mem_(new MemTable(internal_comparator_, NumberLevels())),
logfile_number_(0),
tmp_batch_(),
bg_compaction_scheduled_(0),
bg_logstats_scheduled_(false),
manual_compaction_(nullptr),
logger_(nullptr),
disable_delete_obsolete_files_(false),
delete_obsolete_files_last_run_(0),
purge_wal_files_last_run_(0),
last_stats_dump_time_microsec_(0),
stall_level0_slowdown_(0),
stall_memtable_compaction_(0),
stall_level0_num_files_(0),
started_at_(options.env->NowMicros()),
flush_on_destroy_(false),
stats_(options.num_levels),
delayed_writes_(0),
last_flushed_sequence_(0),
storage_options_(options) {
mem_->Ref();
env_->GetAbsolutePath(dbname, &db_absolute_path_);
stall_leveln_slowdown_.resize(options.num_levels);
for (int i = 0; i < options.num_levels; ++i)
stall_leveln_slowdown_[i] = 0;
// Reserve ten files or so for other uses and give the rest to TableCache.
const int table_cache_size = options_.max_open_files - 10;
table_cache_.reset(new TableCache(dbname_, &options_,
storage_options_, table_cache_size));
versions_.reset(new VersionSet(dbname_, &options_, storage_options_,
table_cache_.get(), &internal_comparator_));
dumpLeveldbBuildVersion(options_.info_log.get());
options_.Dump(options_.info_log.get());
#ifdef USE_SCRIBE
logger_.reset(new ScribeLogger("localhost", 1456));
#endif
char name[100];
Status st = env_->GetHostName(name, 100L);
if(st.ok()) {
host_name_ = name;
} else {
Log(options_.info_log, "Can't get hostname, use localhost as host name.");
host_name_ = "localhost";
}
last_log_ts = 0;
}
DBImpl::~DBImpl() {
// Wait for background work to finish
if (flush_on_destroy_) {
FlushMemTable(FlushOptions());
}
mutex_.Lock();
shutting_down_.Release_Store(this); // Any non-nullptr value is ok
while (bg_compaction_scheduled_ || bg_logstats_scheduled_) {
bg_cv_.Wait();
}
mutex_.Unlock();
if (db_lock_ != nullptr) {
env_->UnlockFile(db_lock_);
}
if (mem_ != nullptr) mem_->Unref();
imm_.UnrefAll();
}
// Do not flush and close database elegantly. Simulate a crash.
void DBImpl::TEST_Destroy_DBImpl() {
// ensure that no new memtable flushes can occur
flush_on_destroy_ = false;
// wait till all background compactions are done.
mutex_.Lock();
while (bg_compaction_scheduled_ || bg_logstats_scheduled_) {
bg_cv_.Wait();
}
// Prevent new compactions from occuring.
const int LargeNumber = 10000000;
bg_compaction_scheduled_ += LargeNumber;
mutex_.Unlock();
// force release the lock file.
if (db_lock_ != nullptr) {
env_->UnlockFile(db_lock_);
}
log_.reset();
versions_.reset();
table_cache_.reset();
}
uint64_t DBImpl::TEST_Current_Manifest_FileNo() {
return versions_->ManifestFileNumber();
}
Status DBImpl::NewDB() {
VersionEdit new_db(NumberLevels());
new_db.SetComparatorName(user_comparator()->Name());
new_db.SetLogNumber(0);
new_db.SetNextFile(2);
new_db.SetLastSequence(0);
const std::string manifest = DescriptorFileName(dbname_, 1);
unique_ptr<WritableFile> file;
Status s = env_->NewWritableFile(manifest, &file, storage_options_);
if (!s.ok()) {
return s;
}
file->SetPreallocationBlockSize(options_.manifest_preallocation_size);
{
log::Writer log(std::move(file));
std::string record;
new_db.EncodeTo(&record);
s = log.AddRecord(record);
}
if (s.ok()) {
// Make "CURRENT" file that points to the new manifest file.
s = SetCurrentFile(env_, dbname_, 1);
} else {
env_->DeleteFile(manifest);
}
return s;
}
void DBImpl::MaybeIgnoreError(Status* s) const {
if (s->ok() || options_.paranoid_checks) {
// No change needed
} else {
Log(options_.info_log, "Ignoring error %s", s->ToString().c_str());
*s = Status::OK();
}
}
const Status DBImpl::CreateArchivalDirectory() {
if (options_.WAL_ttl_seconds > 0) {
std::string archivalPath = ArchivalDirectory(dbname_);
return env_->CreateDirIfMissing(archivalPath);
}
return Status::OK();
}
void DBImpl::PrintHistogram(Histograms histogram_type, std::string name) {
assert(options_.statistics);
HistogramData histogramData;
options_.statistics->histogramData(histogram_type, &histogramData);
Log(options_.info_log, "%s statistics Percentiles :", name.c_str());
Log(options_.info_log, "50 : %f ",histogramData.median);
Log(options_.info_log, "95 : %f ", histogramData.percentile95);
Log(options_.info_log, "99 : %f\n", histogramData.percentile99);
}
void DBImpl::PrintStatistics() {
auto dbstats = options_.statistics;
if (dbstats) {
Log(options_.info_log,
"Statistics counters:\n"
"File opened:%ld closed:%ld errors:%ld\n"
"Block Cache Hit Count:%ld Block Cache Miss Count:%ld\n"
"Bloom Filter Useful: %ld \n"
"Compaction key_drop_newer_entry: %ld key_drop_obsolete: %ld "
"Compaction key_drop_user: %ld\n",
dbstats->getTickerCount(NO_FILE_OPENS),
dbstats->getTickerCount(NO_FILE_CLOSES),
dbstats->getTickerCount(NO_FILE_ERRORS),
dbstats->getTickerCount(BLOCK_CACHE_HIT),
dbstats->getTickerCount(BLOCK_CACHE_MISS),
dbstats->getTickerCount(BLOOM_FILTER_USEFUL),
dbstats->getTickerCount(COMPACTION_KEY_DROP_NEWER_ENTRY),
dbstats->getTickerCount(COMPACTION_KEY_DROP_OBSOLETE),
dbstats->getTickerCount(COMPACTION_KEY_DROP_USER));
PrintHistogram(DB_GET, "DB_GET");
PrintHistogram(DB_WRITE, "DB_WRITE");
PrintHistogram(COMPACTION_TIME, "COMPACTION_TIME");
}
}
void DBImpl::MaybeDumpStats() {
if (options_.stats_dump_period_sec == 0) return;
const uint64_t now_micros = env_->NowMicros();
if (last_stats_dump_time_microsec_ +
options_.stats_dump_period_sec * 1000000
<= now_micros) {
// Multiple threads could race in here simultaneously.
// However, the last one will update last_stats_dump_time_microsec_
// atomically. We could see more than one dump during one dump
// period in rare cases.
last_stats_dump_time_microsec_ = now_micros;
std::string stats;
GetProperty("leveldb.stats", &stats);
Log(options_.info_log, "%s", stats.c_str());
PrintStatistics();
}
}
// Returns the list of live files in 'live' and the list
// of all files in the filesystem in 'allfiles'.
void DBImpl::FindObsoleteFiles(DeletionState& deletion_state) {
mutex_.AssertHeld();
// if deletion is disabled, do nothing
if (disable_delete_obsolete_files_) {
return;
}
// This method is costly when the number of files is large.
// Do not allow it to trigger more often than once in
// delete_obsolete_files_period_micros.
if (options_.delete_obsolete_files_period_micros != 0) {
const uint64_t now_micros = env_->NowMicros();
if (delete_obsolete_files_last_run_ +
options_.delete_obsolete_files_period_micros > now_micros) {
return;
}
delete_obsolete_files_last_run_ = now_micros;
}
// Make a list of all of the live files; set is slow, should not
// be used.
deletion_state.live.assign(pending_outputs_.begin(),
pending_outputs_.end());
versions_->AddLiveFiles(&deletion_state.live);
// set of all files in the directory
env_->GetChildren(dbname_, &deletion_state.allfiles); // Ignore errors
// store the current filenum, lognum, etc
deletion_state.filenumber = versions_->ManifestFileNumber();
deletion_state.lognumber = versions_->LogNumber();
deletion_state.prevlognumber = versions_->PrevLogNumber();
}
// Diffs the files listed in filenames and those that do not
// belong to live files are posibly removed. If the removed file
// is a sst file, then it returns the file number in files_to_evict.
// It is not necesary to hold the mutex when invoking this method.
void DBImpl::PurgeObsoleteFiles(DeletionState& state) {
uint64_t number;
FileType type;
std::vector<std::string> old_log_files;
// Now, convert live list to an unordered set, WITHOUT mutex held;
// set is slow.
std::unordered_set<uint64_t> live_set(state.live.begin(),
state.live.end());
for (size_t i = 0; i < state.allfiles.size(); i++) {
if (ParseFileName(state.allfiles[i], &number, &type)) {
bool keep = true;
switch (type) {
case kLogFile:
keep = ((number >= state.lognumber) ||
(number == state.prevlognumber));
break;
case kDescriptorFile:
// Keep my manifest file, and any newer incarnations'
// (in case there is a race that allows other incarnations)
keep = (number >= state.filenumber);
break;
case kTableFile:
keep = (live_set.find(number) != live_set.end());
break;
case kTempFile:
// Any temp files that are currently being written to must
// be recorded in pending_outputs_, which is inserted into "live"
keep = (live_set.find(number) != live_set.end());
break;
case kInfoLogFile:
keep = true;
if (number != 0) {
old_log_files.push_back(state.allfiles[i]);
}
break;
case kCurrentFile:
case kDBLockFile:
case kMetaDatabase:
keep = true;
break;
}
if (!keep) {
if (type == kTableFile) {
// record the files to be evicted from the cache
state.files_to_evict.push_back(number);
}
Log(options_.info_log, "Delete type=%d #%lu", int(type), number);
if (type == kLogFile && options_.WAL_ttl_seconds > 0) {
Status st = env_->RenameFile(
LogFileName(dbname_, number),
ArchivedLogFileName(dbname_, number)
);
if (!st.ok()) {
Log(
options_.info_log, "RenameFile type=%d #%lu FAILED",
int(type),
number
);
}
} else {
Status st = env_->DeleteFile(dbname_ + "/" + state.allfiles[i]);
if(!st.ok()) {
Log(options_.info_log, "Delete type=%d #%lld FAILED\n",
int(type),
static_cast<unsigned long long>(number));
}
}
}
}
}
// Delete old log files.
size_t old_log_file_count = old_log_files.size();
// NOTE: Currently we only support log purge when options_.db_log_dir is
// located in `dbname` directory.
if (old_log_file_count >= options_.keep_log_file_num &&
options_.db_log_dir.empty()) {
std::sort(old_log_files.begin(), old_log_files.end());
size_t end = old_log_file_count - options_.keep_log_file_num;
for (unsigned int i = 0; i <= end; i++) {
std::string& to_delete = old_log_files.at(i);
// Log(options_.info_log, "Delete type=%d %s\n",
// int(kInfoLogFile), to_delete.c_str());
env_->DeleteFile(dbname_ + "/" + to_delete);
}
}
PurgeObsoleteWALFiles();
}
void DBImpl::EvictObsoleteFiles(DeletionState& state) {
for (unsigned int i = 0; i < state.files_to_evict.size(); i++) {
table_cache_->Evict(state.files_to_evict[i]);
}
}
void DBImpl::DeleteObsoleteFiles() {
mutex_.AssertHeld();
DeletionState deletion_state;
FindObsoleteFiles(deletion_state);
PurgeObsoleteFiles(deletion_state);
EvictObsoleteFiles(deletion_state);
}
void DBImpl::PurgeObsoleteWALFiles() {
int64_t current_time;
Status s = env_->GetCurrentTime(&current_time);
uint64_t now_micros = static_cast<uint64_t>(current_time);
assert(s.ok());
if (options_.WAL_ttl_seconds != ULONG_MAX && options_.WAL_ttl_seconds > 0) {
if (purge_wal_files_last_run_ + options_.WAL_ttl_seconds > now_micros) {
return;
}
std::vector<std::string> wal_files;
std::string archival_dir = ArchivalDirectory(dbname_);
env_->GetChildren(archival_dir, &wal_files);
for (const auto& f : wal_files) {
uint64_t file_m_time;
const std::string file_path = archival_dir + "/" + f;
const Status s = env_->GetFileModificationTime(file_path, &file_m_time);
if (s.ok() && (now_micros - file_m_time > options_.WAL_ttl_seconds)) {
Status status = env_->DeleteFile(file_path);
if (!status.ok()) {
Log(options_.info_log,
"Failed Deleting a WAL file Error : i%s",
status.ToString().c_str());
}
} // Ignore errors.
}
}
purge_wal_files_last_run_ = now_micros;
}
// If externalTable is set, then apply recovered transactions
// to that table. This is used for readonly mode.
Status DBImpl::Recover(VersionEdit* edit, MemTable* external_table,
bool error_if_log_file_exist) {
mutex_.AssertHeld();
assert(db_lock_ == nullptr);
if (!external_table) {
// We call CreateDirIfMissing() as the directory may already exist (if we
// are reopening a DB), when this happens we don't want creating the
// directory to cause an error. However, we need to check if creating the
// directory fails or else we may get an obscure message about the lock
// file not existing. One real-world example of this occurring is if
// env->CreateDirIfMissing() doesn't create intermediate directories, e.g.
// when dbname_ is "dir/db" but when "dir" doesn't exist.
Status s = env_->CreateDirIfMissing(dbname_);
if (!s.ok()) {
return s;
}
s = env_->LockFile(LockFileName(dbname_), &db_lock_);
if (!s.ok()) {
return s;
}
if (!env_->FileExists(CurrentFileName(dbname_))) {
if (options_.create_if_missing) {
// TODO: add merge_operator name check
s = NewDB();
if (!s.ok()) {
return s;
}
} else {
return Status::InvalidArgument(
dbname_, "does not exist (create_if_missing is false)");
}
} else {
if (options_.error_if_exists) {
return Status::InvalidArgument(
dbname_, "exists (error_if_exists is true)");
}
}
}
Status s = versions_->Recover();
if (s.ok()) {
SequenceNumber max_sequence(0);
// Recover from all newer log files than the ones named in the
// descriptor (new log files may have been added by the previous
// incarnation without registering them in the descriptor).
//
// Note that PrevLogNumber() is no longer used, but we pay
// attention to it in case we are recovering a database
// produced by an older version of leveldb.
const uint64_t min_log = versions_->LogNumber();
const uint64_t prev_log = versions_->PrevLogNumber();
std::vector<std::string> filenames;
s = env_->GetChildren(dbname_, &filenames);
if (!s.ok()) {
return s;
}
uint64_t number;
FileType type;
std::vector<uint64_t> logs;
for (size_t i = 0; i < filenames.size(); i++) {
if (ParseFileName(filenames[i], &number, &type)
&& type == kLogFile
&& ((number >= min_log) || (number == prev_log))) {
logs.push_back(number);
}
}
if (logs.size() > 0 && error_if_log_file_exist) {
return Status::Corruption(""
"The db was opened in readonly mode with error_if_log_file_exist"
"flag but a log file already exists");
}
// Recover in the order in which the logs were generated
std::sort(logs.begin(), logs.end());
for (size_t i = 0; i < logs.size(); i++) {
s = RecoverLogFile(logs[i], edit, &max_sequence, external_table);
// The previous incarnation may not have written any MANIFEST
// records after allocating this log number. So we manually
// update the file number allocation counter in VersionSet.
versions_->MarkFileNumberUsed(logs[i]);
}
if (s.ok()) {
if (versions_->LastSequence() < max_sequence) {
versions_->SetLastSequence(max_sequence);
last_flushed_sequence_ = max_sequence;
} else {
last_flushed_sequence_ = versions_->LastSequence();
}
}
}
return s;
}
Status DBImpl::RecoverLogFile(uint64_t log_number,
VersionEdit* edit,
SequenceNumber* max_sequence,
MemTable* external_table) {
struct LogReporter : public log::Reader::Reporter {
Env* env;
Logger* info_log;
const char* fname;
Status* status; // nullptr if options_.paranoid_checks==false or
// options_.skip_log_error_on_recovery==true
virtual void Corruption(size_t bytes, const Status& s) {
Log(info_log, "%s%s: dropping %d bytes; %s",
(this->status == nullptr ? "(ignoring error) " : ""),
fname, static_cast<int>(bytes), s.ToString().c_str());
if (this->status != nullptr && this->status->ok()) *this->status = s;
}
};
mutex_.AssertHeld();
// Open the log file
std::string fname = LogFileName(dbname_, log_number);
unique_ptr<SequentialFile> file;
Status status = env_->NewSequentialFile(fname, &file, storage_options_);
if (!status.ok()) {
MaybeIgnoreError(&status);
return status;
}
// Create the log reader.
LogReporter reporter;
reporter.env = env_;
reporter.info_log = options_.info_log.get();
reporter.fname = fname.c_str();
reporter.status = (options_.paranoid_checks &&
!options_.skip_log_error_on_recovery ? &status : nullptr);
// We intentially make log::Reader do checksumming even if
// paranoid_checks==false so that corruptions cause entire commits
// to be skipped instead of propagating bad information (like overly
// large sequence numbers).
log::Reader reader(std::move(file), &reporter, true/*checksum*/,
0/*initial_offset*/);
Log(options_.info_log, "Recovering log #%llu",
(unsigned long long) log_number);
// Read all the records and add to a memtable
std::string scratch;
Slice record;
WriteBatch batch;
MemTable* mem = nullptr;
if (external_table) {
mem = external_table;
}
while (reader.ReadRecord(&record, &scratch) && status.ok()) {
if (record.size() < 12) {
reporter.Corruption(
record.size(), Status::Corruption("log record too small"));
continue;
}
WriteBatchInternal::SetContents(&batch, record);
if (mem == nullptr) {
mem = new MemTable(internal_comparator_, NumberLevels());
mem->Ref();
}
status = WriteBatchInternal::InsertInto(&batch, mem);
MaybeIgnoreError(&status);
if (!status.ok()) {
break;
}
const SequenceNumber last_seq =
WriteBatchInternal::Sequence(&batch) +
WriteBatchInternal::Count(&batch) - 1;
if (last_seq > *max_sequence) {
*max_sequence = last_seq;
}
if (!external_table &&
mem->ApproximateMemoryUsage() > options_.write_buffer_size) {
status = WriteLevel0TableForRecovery(mem, edit);
if (!status.ok()) {
// Reflect errors immediately so that conditions like full
// file-systems cause the DB::Open() to fail.
break;
}
mem->Unref();
mem = nullptr;
}
}
if (status.ok() && mem != nullptr && !external_table) {
status = WriteLevel0TableForRecovery(mem, edit);
// Reflect errors immediately so that conditions like full
// file-systems cause the DB::Open() to fail.
}
if (mem != nullptr && !external_table) mem->Unref();
return status;
}
Status DBImpl::WriteLevel0TableForRecovery(MemTable* mem, VersionEdit* edit) {
mutex_.AssertHeld();
const uint64_t start_micros = env_->NowMicros();
FileMetaData meta;
meta.number = versions_->NewFileNumber();
pending_outputs_.insert(meta.number);
Iterator* iter = mem->NewIterator();
const SequenceNumber newest_snapshot = snapshots_.GetNewest();
const SequenceNumber earliest_seqno_in_memtable =
mem->GetFirstSequenceNumber();
Log(options_.info_log, "Level-0 table #%llu: started",
(unsigned long long) meta.number);
Status s;
{
mutex_.Unlock();
s = BuildTable(dbname_, env_, options_, storage_options_,
table_cache_.get(), iter, &meta,
user_comparator(), newest_snapshot,
earliest_seqno_in_memtable);
mutex_.Lock();
}
Log(options_.info_log, "Level-0 table #%llu: %lld bytes %s",
(unsigned long long) meta.number,
(unsigned long long) meta.file_size,
s.ToString().c_str());
delete iter;
pending_outputs_.erase(meta.number);
// Note that if file_size is zero, the file has been deleted and
// should not be added to the manifest.
int level = 0;
if (s.ok() && meta.file_size > 0) {
edit->AddFile(level, meta.number, meta.file_size,
meta.smallest, meta.largest);
}
CompactionStats stats;
stats.micros = env_->NowMicros() - start_micros;
stats.bytes_written = meta.file_size;
stats.files_out_levelnp1 = 1;
stats_[level].Add(stats);
return s;
}
Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit,
uint64_t* filenumber) {
mutex_.AssertHeld();
const uint64_t start_micros = env_->NowMicros();
FileMetaData meta;
meta.number = versions_->NewFileNumber();
*filenumber = meta.number;
pending_outputs_.insert(meta.number);
Iterator* iter = mem->NewIterator();
const SequenceNumber newest_snapshot = snapshots_.GetNewest();
const SequenceNumber earliest_seqno_in_memtable =
mem->GetFirstSequenceNumber();
Log(options_.info_log, "Level-0 flush table #%llu: started",
(unsigned long long) meta.number);
Version* base = versions_->current();
base->Ref();
Status s;
{
mutex_.Unlock();
s = BuildTable(dbname_, env_, options_, storage_options_,
table_cache_.get(), iter, &meta,
user_comparator(), newest_snapshot,
earliest_seqno_in_memtable);
mutex_.Lock();
}
base->Unref();
Log(options_.info_log, "Level-0 flush table #%llu: %lld bytes %s",
(unsigned long long) meta.number,
(unsigned long long) meta.file_size,
s.ToString().c_str());
delete iter;
// re-acquire the most current version
base = versions_->current();
// There could be multiple threads writing to its own level-0 file.
// The pending_outputs cannot be cleared here, otherwise this newly
// created file might not be considered as a live-file by another
// compaction thread that is concurrently deleting obselete files.
// The pending_outputs can be cleared only after the new version is
// committed so that other threads can recognize this file as a
// valid one.
// pending_outputs_.erase(meta.number);
// Note that if file_size is zero, the file has been deleted and
// should not be added to the manifest.
int level = 0;
if (s.ok() && meta.file_size > 0) {
const Slice min_user_key = meta.smallest.user_key();
const Slice max_user_key = meta.largest.user_key();
// if we have more than 1 background thread, then we cannot
// insert files directly into higher levels because some other
// threads could be concurrently producing compacted files for
// that key range.
if (base != nullptr && options_.max_background_compactions <= 1) {
level = base->PickLevelForMemTableOutput(min_user_key, max_user_key);
}
edit->AddFile(level, meta.number, meta.file_size,
meta.smallest, meta.largest);
}
CompactionStats stats;
stats.micros = env_->NowMicros() - start_micros;
stats.bytes_written = meta.file_size;
stats_[level].Add(stats);
return s;
}
Status DBImpl::CompactMemTable(bool* madeProgress) {
mutex_.AssertHeld();
assert(imm_.size() != 0);
if (!imm_.IsFlushPending()) {
Log(options_.info_log, "Memcompaction already in progress");
Status s = Status::IOError("Memcompaction already in progress");
return s;
}
// Save the contents of the earliest memtable as a new Table
// This will release and re-acquire the mutex.
uint64_t file_number;
MemTable* m = imm_.PickMemtableToFlush();
if (m == nullptr) {
Log(options_.info_log, "Nothing in memstore to flush");
Status s = Status::IOError("Nothing in memstore to flush");
return s;
}
// record the logfile_number_ before we release the mutex
VersionEdit* edit = m->GetEdits();
edit->SetPrevLogNumber(0);
edit->SetLogNumber(logfile_number_); // Earlier logs no longer needed
Status s = WriteLevel0Table(m, edit, &file_number);
if (s.ok() && shutting_down_.Acquire_Load()) {
s = Status::IOError(
"Database shutdown started during memtable compaction"
);
}
// Replace immutable memtable with the generated Table
s = imm_.InstallMemtableFlushResults(
m, versions_.get(), s, &mutex_, options_.info_log.get(),
file_number, pending_outputs_);
if (s.ok()) {
if (madeProgress) {
*madeProgress = 1;
}
MaybeScheduleLogDBDeployStats();
// we could have deleted obsolete files here, but it is not
// absolutely necessary because it could be also done as part
// of other background compaction
}
return s;
}
void DBImpl::CompactRange(const Slice* begin, const Slice* end) {
int max_level_with_files = 1;
{
MutexLock l(&mutex_);
Version* base = versions_->current();
for (int level = 1; level < NumberLevels(); level++) {
if (base->OverlapInLevel(level, begin, end)) {
max_level_with_files = level;
}
}
}
TEST_CompactMemTable(); // TODO(sanjay): Skip if memtable does not overlap
for (int level = 0; level < max_level_with_files; level++) {
TEST_CompactRange(level, begin, end);
}
}
int DBImpl::NumberLevels() {
return options_.num_levels;
}
int DBImpl::MaxMemCompactionLevel() {
return options_.max_mem_compaction_level;
}
int DBImpl::Level0StopWriteTrigger() {
return options_.level0_stop_writes_trigger;
}
Status DBImpl::Flush(const FlushOptions& options) {
Status status = FlushMemTable(options);
return status;
}
SequenceNumber DBImpl::GetLatestSequenceNumber() {
return versions_->LastSequence();
}
Status DBImpl::GetUpdatesSince(SequenceNumber seq,
unique_ptr<TransactionLogIterator>* iter) {
// Get All Log Files.
// Sort Files
// Get the first entry from each file.
// Do binary search and open files and find the seq number.
std::vector<LogFile> walFiles;
// list wal files in main db dir.
Status s = ListAllWALFiles(dbname_, &walFiles, kAliveLogFile);
if (!s.ok()) {
return s;
}
// list wal files in archive dir.
std::string archivedir = ArchivalDirectory(dbname_);
if (env_->FileExists(archivedir)) {
s = ListAllWALFiles(archivedir, &walFiles, kArchivedLogFile);
if (!s.ok()) {
return s;
}
}
if (walFiles.empty()) {
return Status::IOError(" NO WAL Files present in the db");
}
// std::shared_ptr would have been useful here.
std::unique_ptr<std::vector<LogFile>> probableWALFiles(
new std::vector<LogFile>());
s = FindProbableWALFiles(&walFiles, probableWALFiles.get(), seq);
if (!s.ok()) {
return s;
}
iter->reset(
new TransactionLogIteratorImpl(dbname_,
&options_,
storage_options_,
seq,
std::move(probableWALFiles),
&last_flushed_sequence_));
iter->get()->Next();
return iter->get()->status();
}
Status DBImpl::FindProbableWALFiles(std::vector<LogFile>* const allLogs,
std::vector<LogFile>* const result,
const SequenceNumber target) {
assert(allLogs != nullptr);
assert(result != nullptr);
std::sort(allLogs->begin(), allLogs->end());
long start = 0; // signed to avoid overflow when target is < first file.
long end = static_cast<long>(allLogs->size()) - 1;
// Binary Search. avoid opening all files.
while (end >= start) {
long mid = start + (end - start) / 2; // Avoid overflow.
WriteBatch batch;
Status s = ReadFirstRecord(allLogs->at(mid), &batch);
if (!s.ok()) {
if (CheckFileExistsAndEmpty(allLogs->at(mid))) {
allLogs->erase(allLogs->begin() + mid);
--end;
continue;
}
return s;
}
SequenceNumber currentSeqNum = WriteBatchInternal::Sequence(&batch);
if (currentSeqNum == target) {
start = mid;
end = mid;
break;
} else if (currentSeqNum < target) {
start = mid + 1;
} else {
end = mid - 1;
}
}
size_t startIndex = std::max(0l, end); // end could be -ve.
for( size_t i = startIndex; i < allLogs->size(); ++i) {
result->push_back(allLogs->at(i));
}
if (result->empty()) {
return Status::IOError(
"No probable files. Check if the db contains log files");
}
return Status::OK();
}
bool DBImpl::CheckFileExistsAndEmpty(const LogFile& file) {
if (file.type == kAliveLogFile) {
const std::string fname = LogFileName(dbname_, file.logNumber);
uint64_t file_size;
Status s = env_->GetFileSize(fname, &file_size);
if (s.ok() && file_size == 0) {
return true;
}
}
const std::string fname = ArchivedLogFileName(dbname_, file.logNumber);
uint64_t file_size;
Status s = env_->GetFileSize(fname, &file_size);
if (s.ok() && file_size == 0) {
return true;
}
return false;
}
Status DBImpl::ReadFirstRecord(const LogFile& file, WriteBatch* const result) {
if (file.type == kAliveLogFile) {
std::string fname = LogFileName(dbname_, file.logNumber);
Status status = ReadFirstLine(fname, result);
if (!status.ok()) {
// check if the file got moved to archive.
std::string archivedFile = ArchivedLogFileName(dbname_, file.logNumber);
Status s = ReadFirstLine(archivedFile, result);
if (!s.ok()) {
return Status::IOError("Log File Has been deleted");
}
}
return Status::OK();
} else if (file.type == kArchivedLogFile) {
std::string fname = ArchivedLogFileName(dbname_, file.logNumber);
Status status = ReadFirstLine(fname, result);
return status;
}
return Status::NotSupported("File Type Not Known");
}
Status DBImpl::ReadFirstLine(const std::string& fname,
WriteBatch* const batch) {
struct LogReporter : public log::Reader::Reporter {
Env* env;
Logger* info_log;
const char* fname;
Status* status; // nullptr if options_.paranoid_checks==false
virtual void Corruption(size_t bytes, const Status& s) {
Log(info_log, "%s%s: dropping %d bytes; %s",
(this->status == nullptr ? "(ignoring error) " : ""),
fname, static_cast<int>(bytes), s.ToString().c_str());
if (this->status != nullptr && this->status->ok()) *this->status = s;
}
};
unique_ptr<SequentialFile> file;
Status status = env_->NewSequentialFile(fname, &file, storage_options_);
if (!status.ok()) {
return status;
}
LogReporter reporter;
reporter.env = env_;
reporter.info_log = options_.info_log.get();
reporter.fname = fname.c_str();
reporter.status = (options_.paranoid_checks ? &status : nullptr);
log::Reader reader(std::move(file), &reporter, true/*checksum*/,
0/*initial_offset*/);
std::string scratch;
Slice record;
if (reader.ReadRecord(&record, &scratch) && status.ok()) {
if (record.size() < 12) {
reporter.Corruption(
record.size(), Status::Corruption("log record too small"));
return Status::IOError("Corruption noted");
// TODO read record's till the first no corrupt entry?
}
WriteBatchInternal::SetContents(batch, record);
return Status::OK();
}
return Status::IOError("Error reading from file " + fname);
}
Status DBImpl::ListAllWALFiles(const std::string& path,
std::vector<LogFile>* const logFiles,
WalFileType logType) {
assert(logFiles != nullptr);
std::vector<std::string> allFiles;
const Status status = env_->GetChildren(path, &allFiles);
if (!status.ok()) {
return status;
}
for (const auto& f : allFiles) {
uint64_t number;
FileType type;
if (ParseFileName(f, &number, &type) && type == kLogFile){
logFiles->push_back(LogFile(number, logType));
}
}
return status;
}
void DBImpl::TEST_CompactRange(int level, const Slice* begin,const Slice* end) {
assert(level >= 0);
InternalKey begin_storage, end_storage;
ManualCompaction manual;
manual.level = level;
manual.done = false;
manual.in_progress = false;
if (begin == nullptr) {
manual.begin = nullptr;
} else {
begin_storage = InternalKey(*begin, kMaxSequenceNumber, kValueTypeForSeek);
manual.begin = &begin_storage;
}
if (end == nullptr) {
manual.end = nullptr;
} else {
end_storage = InternalKey(*end, 0, static_cast<ValueType>(0));
manual.end = &end_storage;
}
MutexLock l(&mutex_);
// When a manual compaction arrives, temporarily throttle down
// the number of background compaction threads to 1. This is
// needed to ensure that this manual compaction can compact
// any range of keys/files. We artificialy increase
// bg_compaction_scheduled_ by a large number, this causes
// the system to have a single background thread. Now,
// this manual compaction can progress without stomping
// on any other concurrent compactions.
const int LargeNumber = 10000000;
const int newvalue = options_.max_background_compactions-1;
bg_compaction_scheduled_ += LargeNumber;
while (bg_compaction_scheduled_ > LargeNumber) {
Log(options_.info_log, "Manual compaction request waiting for background threads to fall below 1");
bg_cv_.Wait();
}
Log(options_.info_log, "Manual compaction starting");
while (!manual.done) {
while (manual_compaction_ != nullptr) {
bg_cv_.Wait();
}
manual_compaction_ = &manual;
if (bg_compaction_scheduled_ == LargeNumber) {
bg_compaction_scheduled_ = newvalue;
}
MaybeScheduleCompaction();
while (manual_compaction_ == &manual) {
bg_cv_.Wait();
}
}
assert(!manual.in_progress);
// wait till there are no background threads scheduled
bg_compaction_scheduled_ += LargeNumber;
while (bg_compaction_scheduled_ > LargeNumber + newvalue) {
Log(options_.info_log, "Manual compaction resetting background threads");
bg_cv_.Wait();
}
bg_compaction_scheduled_ = 0;
}
Status DBImpl::FlushMemTable(const FlushOptions& options) {
// nullptr batch means just wait for earlier writes to be done
Status s = Write(WriteOptions(), nullptr);
if (s.ok() && options.wait) {
// Wait until the compaction completes
s = WaitForCompactMemTable();
}
return s;
}
Status DBImpl::WaitForCompactMemTable() {
Status s;
// Wait until the compaction completes
MutexLock l(&mutex_);
while (imm_.size() > 0 && bg_error_.ok()) {
bg_cv_.Wait();
}
if (imm_.size() != 0) {
s = bg_error_;
}
return s;
}
Status DBImpl::TEST_CompactMemTable() {
return FlushMemTable(FlushOptions());
}
Status DBImpl::TEST_WaitForCompactMemTable() {
return WaitForCompactMemTable();
}
Status DBImpl::TEST_WaitForCompact() {
// Wait until the compaction completes
MutexLock l(&mutex_);
while (bg_compaction_scheduled_ && bg_error_.ok()) {
bg_cv_.Wait();
}
return bg_error_;
}
void DBImpl::MaybeScheduleCompaction() {
mutex_.AssertHeld();
if (bg_compaction_scheduled_ >= options_.max_background_compactions) {
// Already scheduled
} else if (shutting_down_.Acquire_Load()) {
// DB is being deleted; no more background compactions
} else if (!imm_.IsFlushPending() &&
manual_compaction_ == nullptr &&
!versions_->NeedsCompaction()) {
// No work to be done
} else {
bg_compaction_scheduled_++;
env_->Schedule(&DBImpl::BGWork, this);
}
}
void DBImpl::BGWork(void* db) {
reinterpret_cast<DBImpl*>(db)->BackgroundCall();
}
void DBImpl::TEST_PurgeObsoleteteWAL() {
PurgeObsoleteWALFiles();
}
void DBImpl::BackgroundCall() {
bool madeProgress = false;
DeletionState deletion_state;
MaybeDumpStats();
MutexLock l(&mutex_);
// Log(options_.info_log, "XXX BG Thread %llx process new work item", pthread_self());
assert(bg_compaction_scheduled_);
if (!shutting_down_.Acquire_Load()) {
Status s = BackgroundCompaction(&madeProgress, deletion_state);
if (!s.ok()) {
// Wait a little bit before retrying background compaction in
// case this is an environmental problem and we do not want to
// chew up resources for failed compactions for the duration of
// the problem.
bg_cv_.SignalAll(); // In case a waiter can proceed despite the error
Log(options_.info_log, "Waiting after background compaction error: %s",
s.ToString().c_str());
mutex_.Unlock();
env_->SleepForMicroseconds(1000000);
mutex_.Lock();
}
}
// delete unnecessary files if any, this is done outside the mutex
if (!deletion_state.live.empty()) {
mutex_.Unlock();
PurgeObsoleteFiles(deletion_state);
EvictObsoleteFiles(deletion_state);
mutex_.Lock();
}
bg_compaction_scheduled_--;
MaybeScheduleLogDBDeployStats();
// Previous compaction may have produced too many files in a level,
// So reschedule another compaction if we made progress in the
// last compaction.
if (madeProgress) {
MaybeScheduleCompaction();
}
bg_cv_.SignalAll();
}
Status DBImpl::BackgroundCompaction(bool* madeProgress,
DeletionState& deletion_state) {
*madeProgress = false;
mutex_.AssertHeld();
while (imm_.IsFlushPending()) {
Log(options_.info_log,
"BackgroundCompaction doing CompactMemTable, compaction slots available %d",
options_.max_background_compactions - bg_compaction_scheduled_);
Status stat = CompactMemTable(madeProgress);
if (!stat.ok()) {
return stat;
}
}
unique_ptr<Compaction> c;
bool is_manual = (manual_compaction_ != nullptr) &&
(manual_compaction_->in_progress == false);
InternalKey manual_end;
if (is_manual) {
ManualCompaction* m = manual_compaction_;
assert(!m->in_progress);
m->in_progress = true; // another thread cannot pick up the same work
c.reset(versions_->CompactRange(m->level, m->begin, m->end));
if (c) {
manual_end = c->input(0, c->num_input_files(0) - 1)->largest;
} else {
m->done = true;
}
Log(options_.info_log,
"Manual compaction at level-%d from %s .. %s; will stop at %s\n",
m->level,
(m->begin ? m->begin->DebugString().c_str() : "(begin)"),
(m->end ? m->end->DebugString().c_str() : "(end)"),
(m->done ? "(end)" : manual_end.DebugString().c_str()));
} else if (!options_.disable_auto_compactions) {
c.reset(versions_->PickCompaction());
}
Status status;
if (!c) {
// Nothing to do
Log(options_.info_log, "Compaction nothing to do");
} else if (!is_manual && c->IsTrivialMove()) {
// Move file to next level
assert(c->num_input_files(0) == 1);
FileMetaData* f = c->input(0, 0);
c->edit()->DeleteFile(c->level(), f->number);
c->edit()->AddFile(c->level() + 1, f->number, f->file_size,
f->smallest, f->largest);
status = versions_->LogAndApply(c->edit(), &mutex_);
VersionSet::LevelSummaryStorage tmp;
Log(options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
static_cast<unsigned long long>(f->number),
c->level() + 1,
static_cast<unsigned long long>(f->file_size),
status.ToString().c_str(),
versions_->LevelSummary(&tmp));
versions_->ReleaseCompactionFiles(c.get(), status);
*madeProgress = true;
} else {
MaybeScheduleCompaction(); // do more compaction work in parallel.
CompactionState* compact = new CompactionState(c.get());
status = DoCompactionWork(compact);
CleanupCompaction(compact);
versions_->ReleaseCompactionFiles(c.get(), status);
c->ReleaseInputs();
FindObsoleteFiles(deletion_state);
*madeProgress = true;
}
c.reset();
if (status.ok()) {
// Done
} else if (shutting_down_.Acquire_Load()) {
// Ignore compaction errors found during shutting down
} else {
Log(options_.info_log,
"Compaction error: %s", status.ToString().c_str());
if (options_.paranoid_checks && bg_error_.ok()) {
bg_error_ = status;
}
}
if (is_manual) {
ManualCompaction* m = manual_compaction_;
if (!status.ok()) {
m->done = true;
}
if (!m->done) {
// We only compacted part of the requested range. Update *m
// to the range that is left to be compacted.
m->tmp_storage = manual_end;
m->begin = &m->tmp_storage;
}
m->in_progress = false; // not being processed anymore
manual_compaction_ = nullptr;
}
return status;
}
void DBImpl::CleanupCompaction(CompactionState* compact) {
mutex_.AssertHeld();
if (compact->builder != nullptr) {
// May happen if we get a shutdown call in the middle of compaction
compact->builder->Abandon();
compact->builder.reset();
} else {
assert(compact->outfile == nullptr);
}
for (size_t i = 0; i < compact->outputs.size(); i++) {
const CompactionState::Output& out = compact->outputs[i];
pending_outputs_.erase(out.number);
}
delete compact;
}
// Allocate the file numbers for the output file. We allocate as
// many output file numbers as there are files in level+1.
// Insert them into pending_outputs so that they do not get deleted.
void DBImpl::AllocateCompactionOutputFileNumbers(CompactionState* compact) {
mutex_.AssertHeld();
assert(compact != nullptr);
assert(compact->builder == nullptr);
int filesNeeded = compact->compaction->num_input_files(1);
for (int i = 0; i < filesNeeded; i++) {
uint64_t file_number = versions_->NewFileNumber();
pending_outputs_.insert(file_number);
compact->allocated_file_numbers.push_back(file_number);
}
}
// Frees up unused file number.
void DBImpl::ReleaseCompactionUnusedFileNumbers(CompactionState* compact) {
mutex_.AssertHeld();
for (const auto file_number : compact->allocated_file_numbers) {
pending_outputs_.erase(file_number);
// Log(options_.info_log, "XXX releasing unused file num %d", file_number);
}
}
Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
assert(compact != nullptr);
assert(compact->builder == nullptr);
uint64_t file_number;
// If we have not yet exhausted the pre-allocated file numbers,
// then use the one from the front. Otherwise, we have to acquire
// the heavyweight lock and allocate a new file number.
if (!compact->allocated_file_numbers.empty()) {
file_number = compact->allocated_file_numbers.front();
compact->allocated_file_numbers.pop_front();
} else {
mutex_.Lock();
file_number = versions_->NewFileNumber();
pending_outputs_.insert(file_number);
mutex_.Unlock();
}
CompactionState::Output out;
out.number = file_number;
out.smallest.Clear();
out.largest.Clear();
compact->outputs.push_back(out);
// Make the output file
std::string fname = TableFileName(dbname_, file_number);
Status s = env_->NewWritableFile(fname, &compact->outfile, storage_options_);
if (s.ok()) {
// Over-estimate slightly so we don't end up just barely crossing
// the threshold.
compact->outfile->SetPreallocationBlockSize(
1.1 * versions_->MaxFileSizeForLevel(compact->compaction->level() + 1));
compact->builder.reset(new TableBuilder(options_, compact->outfile.get(),
compact->compaction->level() + 1));
}
return s;
}
Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
Iterator* input) {
assert(compact != nullptr);
assert(compact->outfile);
assert(compact->builder != nullptr);
const uint64_t output_number = compact->current_output()->number;
assert(output_number != 0);
// Check for iterator errors
Status s = input->status();
const uint64_t current_entries = compact->builder->NumEntries();
if (s.ok()) {
s = compact->builder->Finish();
} else {
compact->builder->Abandon();
}
const uint64_t current_bytes = compact->builder->FileSize();
compact->current_output()->file_size = current_bytes;
compact->total_bytes += current_bytes;
compact->builder.reset();
// Finish and check for file errors
if (s.ok() && !options_.disableDataSync) {
if (options_.use_fsync) {
StopWatch sw(env_, options_.statistics, COMPACTION_OUTFILE_SYNC_MICROS);
s = compact->outfile->Fsync();
} else {
StopWatch sw(env_, options_.statistics, COMPACTION_OUTFILE_SYNC_MICROS);
s = compact->outfile->Sync();
}
}
if (s.ok()) {
s = compact->outfile->Close();
}
compact->outfile.reset();
if (s.ok() && current_entries > 0) {
// Verify that the table is usable
Iterator* iter = table_cache_->NewIterator(ReadOptions(),
storage_options_,
output_number,
current_bytes);
s = iter->status();
delete iter;
if (s.ok()) {
Log(options_.info_log,
"Generated table #%llu: %lld keys, %lld bytes",
(unsigned long long) output_number,
(unsigned long long) current_entries,
(unsigned long long) current_bytes);
}
}
return s;
}
Status DBImpl::InstallCompactionResults(CompactionState* compact) {
mutex_.AssertHeld();
// paranoia: verify that the files that we started with
// still exist in the current version and in the same original level.
// This ensures that a concurrent compaction did not erroneously
// pick the same files to compact.
if (!versions_->VerifyCompactionFileConsistency(compact->compaction)) {
Log(options_.info_log, "Compaction %d@%d + %d@%d files aborted",
compact->compaction->num_input_files(0),
compact->compaction->level(),
compact->compaction->num_input_files(1),
compact->compaction->level() + 1);
return Status::IOError("Compaction input files inconsistent");
}
Log(options_.info_log, "Compacted %d@%d + %d@%d files => %lld bytes",
compact->compaction->num_input_files(0),
compact->compaction->level(),
compact->compaction->num_input_files(1),
compact->compaction->level() + 1,
static_cast<long long>(compact->total_bytes));
// Add compaction outputs
compact->compaction->AddInputDeletions(compact->compaction->edit());
const int level = compact->compaction->level();
for (size_t i = 0; i < compact->outputs.size(); i++) {
const CompactionState::Output& out = compact->outputs[i];
compact->compaction->edit()->AddFile(
level + 1,
out.number, out.file_size, out.smallest, out.largest);
}
return versions_->LogAndApply(compact->compaction->edit(), &mutex_);
}
//
// Given a sequence number, return the sequence number of the
// earliest snapshot that this sequence number is visible in.
// The snapshots themselves are arranged in ascending order of
// sequence numbers.
// Employ a sequential search because the total number of
// snapshots are typically small.
inline SequenceNumber DBImpl::findEarliestVisibleSnapshot(
SequenceNumber in, std::vector<SequenceNumber>& snapshots,
SequenceNumber* prev_snapshot) {
SequenceNumber prev __attribute__((unused)) = 0;
for (const auto cur : snapshots) {
assert(prev <= cur);
if (cur >= in) {
*prev_snapshot = prev;
return cur;
}
prev = cur; // assignment
assert(prev);
}
Log(options_.info_log,
"Looking for seqid %ld but maxseqid is %ld", in,
snapshots[snapshots.size()-1]);
assert(0);
return 0;
}
Status DBImpl::DoCompactionWork(CompactionState* compact) {
int64_t imm_micros = 0; // Micros spent doing imm_ compactions
Log(options_.info_log,
"Compacting %d@%d + %d@%d files, score %.2f slots available %d",
compact->compaction->num_input_files(0),
compact->compaction->level(),
compact->compaction->num_input_files(1),
compact->compaction->level() + 1,
compact->compaction->score(),
options_.max_background_compactions - bg_compaction_scheduled_);
char scratch[256];
compact->compaction->Summary(scratch, sizeof(scratch));
Log(options_.info_log, "Compaction start summary: %s\n", scratch);
assert(versions_->NumLevelFiles(compact->compaction->level()) > 0);
assert(compact->builder == nullptr);
assert(!compact->outfile);
SequenceNumber visible_at_tip = 0;
SequenceNumber earliest_snapshot;
SequenceNumber latest_snapshot = 0;
snapshots_.getAll(compact->existing_snapshots);
if (compact->existing_snapshots.size() == 0) {
// optimize for fast path if there are no snapshots
visible_at_tip = versions_->LastSequence();
earliest_snapshot = visible_at_tip;
} else {
latest_snapshot = compact->existing_snapshots.back();
// Add the current seqno as the 'latest' virtual
// snapshot to the end of this list.
compact->existing_snapshots.push_back(versions_->LastSequence());
earliest_snapshot = compact->existing_snapshots[0];
}
// Is this compaction producing files at the bottommost level?
bool bottommost_level = true;
for (int i = compact->compaction->level() + 2;
i < versions_->NumberLevels(); i++) {
if (versions_->NumLevelFiles(i) > 0) {
bottommost_level = false;
break;
}
}
// Allocate the output file numbers before we release the lock
AllocateCompactionOutputFileNumbers(compact);
// Release mutex while we're actually doing the compaction work
mutex_.Unlock();
const uint64_t start_micros = env_->NowMicros();
unique_ptr<Iterator> input(versions_->MakeInputIterator(compact->compaction));
input->SeekToFirst();
Status status;
ParsedInternalKey ikey;
std::string current_user_key;
bool has_current_user_key = false;
SequenceNumber last_sequence_for_key __attribute__((unused)) =
kMaxSequenceNumber;
SequenceNumber visible_in_snapshot = kMaxSequenceNumber;
std::string compaction_filter_value;
std::vector<char> delete_key; // for compaction filter
MergeHelper merge(user_comparator(), options_.merge_operator,
options_.info_log.get(),
false /* internal key corruption is expected */);
for (; input->Valid() && !shutting_down_.Acquire_Load(); ) {
// Prioritize immutable compaction work
if (imm_.imm_flush_needed.NoBarrier_Load() != nullptr) {
const uint64_t imm_start = env_->NowMicros();
mutex_.Lock();
if (imm_.IsFlushPending()) {
CompactMemTable();
bg_cv_.SignalAll(); // Wakeup MakeRoomForWrite() if necessary
}
mutex_.Unlock();
imm_micros += (env_->NowMicros() - imm_start);
}
Slice key = input->key();
Slice value = input->value();
if (compact->compaction->ShouldStopBefore(key) &&
compact->builder != nullptr) {
status = FinishCompactionOutputFile(compact, input.get());
if (!status.ok()) {
break;
}
}
// Handle key/value, add to state, etc.
bool drop = false;
bool current_entry_is_merged = false;
if (!ParseInternalKey(key, &ikey)) {
// Do not hide error keys
// TODO: error key stays in db forever? Figure out the intention/rationale
// v10 error v8 : we cannot hide v8 even though it's pretty obvious.
current_user_key.clear();
has_current_user_key = false;
last_sequence_for_key = kMaxSequenceNumber;
visible_in_snapshot = kMaxSequenceNumber;
} else {
if (!has_current_user_key ||
user_comparator()->Compare(ikey.user_key,
Slice(current_user_key)) != 0) {
// First occurrence of this user key
current_user_key.assign(ikey.user_key.data(), ikey.user_key.size());
has_current_user_key = true;
last_sequence_for_key = kMaxSequenceNumber;
visible_in_snapshot = kMaxSequenceNumber;
// apply the compaction filter to the first occurrence of the user key
if (options_.compaction_filter &&
ikey.type == kTypeValue &&
(visible_at_tip || ikey.sequence > latest_snapshot)) {
// If the user has specified a compaction filter and the sequence
// number is greater than any external snapshot, then invoke the
// filter.
// If the return value of the compaction filter is true, replace
// the entry with a delete marker.
bool value_changed = false;
compaction_filter_value.clear();
bool to_delete =
options_.compaction_filter->Filter(compact->compaction->level(),
ikey.user_key, value,
&compaction_filter_value,
&value_changed);
if (to_delete) {
// make a copy of the original key
delete_key.assign(key.data(), key.data() + key.size());
// convert it to a delete
UpdateInternalKey(&delete_key[0], delete_key.size(),
ikey.sequence, kTypeDeletion);
// anchor the key again
key = Slice(&delete_key[0], delete_key.size());
// needed because ikey is backed by key
ParseInternalKey(key, &ikey);
// no value associated with delete
value.clear();
RecordTick(options_.statistics, COMPACTION_KEY_DROP_USER);
} else if (value_changed) {
value = compaction_filter_value;
}
}
}
// If there are no snapshots, then this kv affect visibility at tip.
// Otherwise, search though all existing snapshots to find
// the earlist snapshot that is affected by this kv.
SequenceNumber prev_snapshot = 0; // 0 means no previous snapshot
SequenceNumber visible = visible_at_tip ?
visible_at_tip :
findEarliestVisibleSnapshot(ikey.sequence,
compact->existing_snapshots,
&prev_snapshot);
if (visible_in_snapshot == visible) {
// If the earliest snapshot is which this key is visible in
// is the same as the visibily of a previous instance of the
// same key, then this kv is not visible in any snapshot.
// Hidden by an newer entry for same user key
// TODO: why not > ?
assert(last_sequence_for_key >= ikey.sequence);
drop = true; // (A)
RecordTick(options_.statistics, COMPACTION_KEY_DROP_NEWER_ENTRY);
} else if (ikey.type == kTypeDeletion &&
ikey.sequence <= earliest_snapshot &&
compact->compaction->IsBaseLevelForKey(ikey.user_key)) {
// For this user key:
// (1) there is no data in higher levels
// (2) data in lower levels will have larger sequence numbers
// (3) data in layers that are being compacted here and have
// smaller sequence numbers will be dropped in the next
// few iterations of this loop (by rule (A) above).
// Therefore this deletion marker is obsolete and can be dropped.
drop = true;
RecordTick(options_.statistics, COMPACTION_KEY_DROP_OBSOLETE);
} else if (ikey.type == kTypeMerge) {
// We know the merge type entry is not hidden, otherwise we would
// have hit (A)
// We encapsulate the merge related state machine in a different
// object to minimize change to the existing flow. Turn out this
// logic could also be nicely re-used for memtable flush purge
// optimization in BuildTable.
merge.MergeUntil(input.get(), prev_snapshot, bottommost_level);
current_entry_is_merged = true;
// get the merge result
key = merge.key();
ParseInternalKey(key, &ikey);
value = merge.value();
}
last_sequence_for_key = ikey.sequence;
visible_in_snapshot = visible;
}
#if 0
Log(options_.info_log,
" Compact: %s, seq %d, type: %d %d, drop: %d, is_base: %d, "
"%d smallest_snapshot: %d level: %d bottommost %d",
ikey.user_key.ToString().c_str(),
(int)ikey.sequence, ikey.type, kTypeValue, drop,
compact->compaction->IsBaseLevelForKey(ikey.user_key),
(int)last_sequence_for_key, (int)earliest_snapshot,
compact->compaction->level(), bottommost_level);
#endif
if (!drop) {
char* kptr = (char*)key.data();
std::string kstr;
// Zeroing out the sequence number leads to better compression.
// If this is the bottommost level (no files in lower levels)
// and the earliest snapshot is larger than this seqno
// then we can squash the seqno to zero.
if (bottommost_level && ikey.sequence < earliest_snapshot &&
ikey.type != kTypeMerge) {
assert(ikey.type != kTypeDeletion);
// make a copy because updating in place would cause problems
// with the priority queue that is managing the input key iterator
kstr.assign(key.data(), key.size());
kptr = (char *)kstr.c_str();
UpdateInternalKey(kptr, key.size(), (uint64_t)0, ikey.type);
}
Slice newkey(kptr, key.size());
assert((key.clear(), 1)); // we do not need 'key' anymore
// Open output file if necessary
if (compact->builder == nullptr) {
status = OpenCompactionOutputFile(compact);
if (!status.ok()) {
break;
}
}
if (compact->builder->NumEntries() == 0) {
compact->current_output()->smallest.DecodeFrom(newkey);
}
compact->current_output()->largest.DecodeFrom(newkey);
compact->builder->Add(newkey, value);
// Close output file if it is big enough
if (compact->builder->FileSize() >=
compact->compaction->MaxOutputFileSize()) {
status = FinishCompactionOutputFile(compact, input.get());
if (!status.ok()) {
break;
}
}
}
// MergeUntil has moved input to the next entry
if (!current_entry_is_merged) {
input->Next();
}
}
if (status.ok() && shutting_down_.Acquire_Load()) {
status = Status::IOError("Database shutdown started during compaction");
}
if (status.ok() && compact->builder != nullptr) {
status = FinishCompactionOutputFile(compact, input.get());
}
if (status.ok()) {
status = input->status();
}
input.reset();
CompactionStats stats;
stats.micros = env_->NowMicros() - start_micros - imm_micros;
if (options_.statistics) {
options_.statistics->measureTime(COMPACTION_TIME, stats.micros);
}
stats.files_in_leveln = compact->compaction->num_input_files(0);
stats.files_in_levelnp1 = compact->compaction->num_input_files(1);
int num_output_files = compact->outputs.size();
if (compact->builder != nullptr) {
// An error occured so ignore the last output.
assert(num_output_files > 0);
--num_output_files;
}
stats.files_out_levelnp1 = num_output_files;
for (int i = 0; i < compact->compaction->num_input_files(0); i++)
stats.bytes_readn += compact->compaction->input(0, i)->file_size;
for (int i = 0; i < compact->compaction->num_input_files(1); i++)
stats.bytes_readnp1 += compact->compaction->input(1, i)->file_size;
for (int i = 0; i < num_output_files; i++) {
stats.bytes_written += compact->outputs[i].file_size;
}
mutex_.Lock();
stats_[compact->compaction->level() + 1].Add(stats);
// if there were any unused file number (mostly in case of
// compaction error), free up the entry from pending_putputs
ReleaseCompactionUnusedFileNumbers(compact);
if (status.ok()) {
status = InstallCompactionResults(compact);
}
VersionSet::LevelSummaryStorage tmp;
Log(options_.info_log,
"compacted to: %s, %.1f MB/sec, level %d, files in(%d, %d) out(%d) "
"MB in(%.1f, %.1f) out(%.1f), amplify(%.1f) %s\n",
versions_->LevelSummary(&tmp),
(stats.bytes_readn + stats.bytes_readnp1 + stats.bytes_written) /
(double) stats.micros,
compact->compaction->level() + 1,
stats.files_in_leveln, stats.files_in_levelnp1, stats.files_out_levelnp1,
stats.bytes_readn / 1048576.0,
stats.bytes_readnp1 / 1048576.0,
stats.bytes_written / 1048576.0,
(stats.bytes_written + stats.bytes_readnp1) /
(double) stats.bytes_readn,
status.ToString().c_str());
return status;
}
namespace {
struct IterState {
port::Mutex* mu;
Version* version;
std::vector<MemTable*> mem; // includes both mem_ and imm_
};
static void CleanupIteratorState(void* arg1, void* arg2) {
IterState* state = reinterpret_cast<IterState*>(arg1);
state->mu->Lock();
for (unsigned int i = 0; i < state->mem.size(); i++) {
state->mem[i]->Unref();
}
state->version->Unref();
state->mu->Unlock();
delete state;
}
} // namespace
Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
SequenceNumber* latest_snapshot) {
IterState* cleanup = new IterState;
mutex_.Lock();
*latest_snapshot = versions_->LastSequence();
// Collect together all needed child iterators for mem
std::vector<Iterator*> list;
mem_->Ref();
list.push_back(mem_->NewIterator());
cleanup->mem.push_back(mem_);
// Collect together all needed child iterators for imm_
std::vector<MemTable*> immutables;
imm_.GetMemTables(&immutables);
for (unsigned int i = 0; i < immutables.size(); i++) {
MemTable* m = immutables[i];
m->Ref();
list.push_back(m->NewIterator());
cleanup->mem.push_back(m);
}
// Collect iterators for files in L0 - Ln
versions_->current()->AddIterators(options, storage_options_, &list);
Iterator* internal_iter =
NewMergingIterator(&internal_comparator_, &list[0], list.size());
versions_->current()->Ref();
cleanup->mu = &mutex_;
cleanup->version = versions_->current();
internal_iter->RegisterCleanup(CleanupIteratorState, cleanup, nullptr);
mutex_.Unlock();
return internal_iter;
}
Iterator* DBImpl::TEST_NewInternalIterator() {
SequenceNumber ignored;
return NewInternalIterator(ReadOptions(), &ignored);
}
int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes() {
MutexLock l(&mutex_);
return versions_->MaxNextLevelOverlappingBytes();
}
Status DBImpl::Get(const ReadOptions& options,
const Slice& key,
std::string* value) {
Status s;
StopWatch sw(env_, options_.statistics, DB_GET);
SequenceNumber snapshot;
MutexLock l(&mutex_);
if (options.snapshot != nullptr) {
snapshot = reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_;
} else {
snapshot = versions_->LastSequence();
}
MemTable* mem = mem_;
MemTableList imm = imm_;
Version* current = versions_->current();
mem->Ref();
imm.RefAll();
current->Ref();
// Unlock while reading from files and memtables
mutex_.Unlock();
bool have_stat_update = false;
Version::GetStats stats;
// First look in the memtable, then in the immutable memtable (if any).
// s is both in/out. When in, s could either be OK or MergeInProgress.
// value will contain the current merge operand in the latter case.
LookupKey lkey(key, snapshot);
if (mem->Get(lkey, value, &s, options_)) {
// Done
} else if (imm.Get(lkey, value, &s, options_)) {
// Done
} else {
current->Get(options, lkey, value, &s, &stats, options_);
have_stat_update = true;
}
mutex_.Lock();
if (!options_.disable_seek_compaction &&
have_stat_update && current->UpdateStats(stats)) {
MaybeScheduleCompaction();
}
mem->Unref();
imm.UnrefAll();
current->Unref();
RecordTick(options_.statistics, NUMBER_KEYS_READ);
RecordTick(options_.statistics, BYTES_READ, value->size());
return s;
}
std::vector<Status> DBImpl::MultiGet(const ReadOptions& options,
const std::vector<Slice>& keys,
std::vector<std::string>* values) {
StopWatch sw(env_, options_.statistics, DB_MULTIGET);
SequenceNumber snapshot;
MutexLock l(&mutex_);
if (options.snapshot != nullptr) {
snapshot = reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_;
} else {
snapshot = versions_->LastSequence();
}
MemTable* mem = mem_;
MemTableList imm = imm_;
Version* current = versions_->current();
mem->Ref();
imm.RefAll();
current->Ref();
// Unlock while reading from files and memtables
mutex_.Unlock();
bool have_stat_update = false;
Version::GetStats stats;
// Note: this always resizes the values array
int numKeys = keys.size();
std::vector<Status> statList(numKeys);
values->resize(numKeys);
// Keep track of bytes that we read for statistics-recording later
uint64_t bytesRead = 0;
// For each of the given keys, apply the entire "get" process as follows:
// First look in the memtable, then in the immutable memtable (if any).
// s is both in/out. When in, s could either be OK or MergeInProgress.
// value will contain the current merge operand in the latter case.
for(int i=0; i<numKeys; ++i) {
Status& s = statList[i];
std::string* value = &(*values)[i];
LookupKey lkey(keys[i], snapshot);
if (mem->Get(lkey, value, &s, options_)) {
// Done
} else if (imm.Get(lkey, value, &s, options_)) {
// Done
} else {
current->Get(options, lkey, value, &s, &stats, options_);
have_stat_update = true;
}
if (s.ok()) {
bytesRead += value->size();
}
}
// Post processing (decrement reference counts and record statistics)
mutex_.Lock();
if (!options_.disable_seek_compaction &&
have_stat_update && current->UpdateStats(stats)) {
MaybeScheduleCompaction();
}
mem->Unref();
imm.UnrefAll();
current->Unref();
RecordTick(options_.statistics, NUMBER_MULTIGET_CALLS);
RecordTick(options_.statistics, NUMBER_MULTIGET_KEYS_READ, numKeys);
RecordTick(options_.statistics, NUMBER_MULTIGET_BYTES_READ, bytesRead);
return statList;
}
Iterator* DBImpl::NewIterator(const ReadOptions& options) {
SequenceNumber latest_snapshot;
Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot);
return NewDBIterator(
&dbname_, env_, options_, user_comparator(), internal_iter,
(options.snapshot != nullptr
? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
: latest_snapshot));
}
const Snapshot* DBImpl::GetSnapshot() {
MutexLock l(&mutex_);
return snapshots_.New(versions_->LastSequence());
}
void DBImpl::ReleaseSnapshot(const Snapshot* s) {
MutexLock l(&mutex_);
snapshots_.Delete(reinterpret_cast<const SnapshotImpl*>(s));
}
// Convenience methods
Status DBImpl::Put(const WriteOptions& o, const Slice& key, const Slice& val) {
return DB::Put(o, key, val);
}
Status DBImpl::Merge(const WriteOptions& o, const Slice& key,
const Slice& val) {
if (!options_.merge_operator) {
return Status::NotSupported("Provide a merge_operator when opening DB");
} else {
return DB::Merge(o, key, val);
}
}
Status DBImpl::Delete(const WriteOptions& options, const Slice& key) {
return DB::Delete(options, key);
}
Status DBImpl::Write(const WriteOptions& options, WriteBatch* my_batch) {
Writer w(&mutex_);
w.batch = my_batch;
w.sync = options.sync;
w.disableWAL = options.disableWAL;
w.done = false;
StopWatch sw(env_, options_.statistics, DB_WRITE);
MutexLock l(&mutex_);
writers_.push_back(&w);
while (!w.done && &w != writers_.front()) {
w.cv.Wait();
}
if (w.done) {
return w.status;
}
// May temporarily unlock and wait.
Status status = MakeRoomForWrite(my_batch == nullptr);
uint64_t last_sequence = versions_->LastSequence();
Writer* last_writer = &w;
if (status.ok() && my_batch != nullptr) { // nullptr batch is for compactions
WriteBatch* updates = BuildBatchGroup(&last_writer);
const SequenceNumber current_sequence = last_sequence + 1;
WriteBatchInternal::SetSequence(updates, current_sequence);
int my_batch_count = WriteBatchInternal::Count(updates);
last_sequence += my_batch_count;
// Record statistics
RecordTick(options_.statistics, NUMBER_KEYS_WRITTEN, my_batch_count);
RecordTick(options_.statistics,
BYTES_WRITTEN,
WriteBatchInternal::ByteSize(updates));
// Add to log and apply to memtable. We can release the lock
// during this phase since &w is currently responsible for logging
// and protects against concurrent loggers and concurrent writes
// into mem_.
{
mutex_.Unlock();
if (options.disableWAL) {
flush_on_destroy_ = true;
}
if (!options.disableWAL) {
status = log_->AddRecord(WriteBatchInternal::Contents(updates));
if (status.ok() && options.sync) {
if (options_.use_fsync) {
StopWatch(env_, options_.statistics, WAL_FILE_SYNC_MICROS);
status = log_->file()->Fsync();
} else {
StopWatch(env_, options_.statistics, WAL_FILE_SYNC_MICROS);
status = log_->file()->Sync();
}
}
}
if (status.ok()) {
status = WriteBatchInternal::InsertInto(updates, mem_);
}
mutex_.Lock();
}
last_flushed_sequence_ = current_sequence;
if (updates == &tmp_batch_) tmp_batch_.Clear();
versions_->SetLastSequence(last_sequence);
}
while (true) {
Writer* ready = writers_.front();
writers_.pop_front();
if (ready != &w) {
ready->status = status;
ready->done = true;
ready->cv.Signal();
}
if (ready == last_writer) break;
}
// Notify new head of write queue
if (!writers_.empty()) {
writers_.front()->cv.Signal();
}
return status;
}
// REQUIRES: Writer list must be non-empty
// REQUIRES: First writer must have a non-nullptr batch
WriteBatch* DBImpl::BuildBatchGroup(Writer** last_writer) {
assert(!writers_.empty());
Writer* first = writers_.front();
WriteBatch* result = first->batch;
assert(result != nullptr);
size_t size = WriteBatchInternal::ByteSize(first->batch);
// Allow the group to grow up to a maximum size, but if the
// original write is small, limit the growth so we do not slow
// down the small write too much.
size_t max_size = 1 << 20;
if (size <= (128<<10)) {
max_size = size + (128<<10);
}
*last_writer = first;
std::deque<Writer*>::iterator iter = writers_.begin();
++iter; // Advance past "first"
for (; iter != writers_.end(); ++iter) {
Writer* w = *iter;
if (w->sync && !first->sync) {
// Do not include a sync write into a batch handled by a non-sync write.
break;
}
if (!w->disableWAL && first->disableWAL) {
// Do not include a write that needs WAL into a batch that has
// WAL disabled.
break;
}
if (w->batch != nullptr) {
size += WriteBatchInternal::ByteSize(w->batch);
if (size > max_size) {
// Do not make batch too big
break;
}
// Append to *reuslt
if (result == first->batch) {
// Switch to temporary batch instead of disturbing caller's batch
result = &tmp_batch_;
assert(WriteBatchInternal::Count(result) == 0);
WriteBatchInternal::Append(result, first->batch);
}
WriteBatchInternal::Append(result, w->batch);
}
*last_writer = w;
}
return result;
}
// REQUIRES: mutex_ is held
// REQUIRES: this thread is currently at the front of the writer queue
Status DBImpl::MakeRoomForWrite(bool force) {
mutex_.AssertHeld();
assert(!writers_.empty());
bool allow_delay = !force;
bool allow_rate_limit_delay = !force;
uint64_t rate_limit_delay_millis = 0;
Status s;
double score;
while (true) {
if (!bg_error_.ok()) {
// Yield previous error
s = bg_error_;
break;
} else if (
allow_delay &&
versions_->NumLevelFiles(0) >=
options_.level0_slowdown_writes_trigger) {
// We are getting close to hitting a hard limit on the number of
// L0 files. Rather than delaying a single write by several
// seconds when we hit the hard limit, start delaying each
// individual write by 1ms to reduce latency variance. Also,
// this delay hands over some CPU to the compaction thread in
// case it is sharing the same core as the writer.
mutex_.Unlock();
uint64_t t1 = env_->NowMicros();
env_->SleepForMicroseconds(1000);
uint64_t delayed = env_->NowMicros() - t1;
RecordTick(options_.statistics, STALL_L0_SLOWDOWN_MICROS, delayed);
stall_level0_slowdown_ += delayed;
allow_delay = false; // Do not delay a single write more than once
//Log(options_.info_log,
// "delaying write %llu usecs for level0_slowdown_writes_trigger\n",
// (long long unsigned int)delayed);
mutex_.Lock();
delayed_writes_++;
} else if (!force &&
(mem_->ApproximateMemoryUsage() <= options_.write_buffer_size)) {
// There is room in current memtable
if (allow_delay) {
DelayLoggingAndReset();
}
break;
} else if (imm_.size() == options_.max_write_buffer_number - 1) {
// We have filled up the current memtable, but the previous
// ones are still being compacted, so we wait.
DelayLoggingAndReset();
Log(options_.info_log, "wait for memtable compaction...\n");
uint64_t t1 = env_->NowMicros();
bg_cv_.Wait();
const uint64_t stall = env_->NowMicros() -t1;
RecordTick(options_.statistics, STALL_MEMTABLE_COMPACTION_MICROS, stall);
stall_memtable_compaction_ += stall;
} else if (versions_->NumLevelFiles(0) >=
options_.level0_stop_writes_trigger) {
// There are too many level-0 files.
DelayLoggingAndReset();
uint64_t t1 = env_->NowMicros();
Log(options_.info_log, "wait for fewer level0 files...\n");
bg_cv_.Wait();
const uint64_t stall = env_->NowMicros() - t1;
RecordTick(options_.statistics, STALL_L0_NUM_FILES_MICROS, stall);
stall_level0_num_files_ += stall;
} else if (
allow_rate_limit_delay &&
options_.rate_limit > 1.0 &&
(score = versions_->MaxCompactionScore()) > options_.rate_limit) {
// Delay a write when the compaction score for any level is too large.
int max_level = versions_->MaxCompactionScoreLevel();
mutex_.Unlock();
uint64_t t1 = env_->NowMicros();
env_->SleepForMicroseconds(1000);
uint64_t delayed = env_->NowMicros() - t1;
stall_leveln_slowdown_[max_level] += delayed;
// Make sure the following value doesn't round to zero.
uint64_t rate_limit = std::max((delayed / 1000), (uint64_t) 1);
rate_limit_delay_millis += rate_limit;
RecordTick(options_.statistics, RATE_LIMIT_DELAY_MILLIS, rate_limit);
if (rate_limit_delay_millis >=
(unsigned)options_.rate_limit_delay_milliseconds) {
allow_rate_limit_delay = false;
}
// Log(options_.info_log,
// "delaying write %llu usecs for rate limits with max score %.2f\n",
// (long long unsigned int)delayed, score);
mutex_.Lock();
} else {
// Attempt to switch to a new memtable and trigger compaction of old
DelayLoggingAndReset();
assert(versions_->PrevLogNumber() == 0);
uint64_t new_log_number = versions_->NewFileNumber();
unique_ptr<WritableFile> lfile;
EnvOptions soptions(storage_options_);
soptions.use_mmap_writes = false;
s = env_->NewWritableFile(
LogFileName(dbname_, new_log_number),
&lfile,
soptions
);
if (!s.ok()) {
// Avoid chewing through file number space in a tight loop.
versions_->ReuseFileNumber(new_log_number);
break;
}
// Our final size should be less than write_buffer_size
// (compression, etc) but err on the side of caution.
lfile->SetPreallocationBlockSize(1.1 * options_.write_buffer_size);
logfile_number_ = new_log_number;
log_.reset(new log::Writer(std::move(lfile)));
imm_.Add(mem_);
mem_ = new MemTable(internal_comparator_, NumberLevels());
mem_->Ref();
force = false; // Do not force another compaction if have room
MaybeScheduleCompaction();
}
}
return s;
}
bool DBImpl::GetProperty(const Slice& property, std::string* value) {
value->clear();
MutexLock l(&mutex_);
Slice in = property;
Slice prefix("leveldb.");
if (!in.starts_with(prefix)) return false;
in.remove_prefix(prefix.size());
if (in.starts_with("num-files-at-level")) {
in.remove_prefix(strlen("num-files-at-level"));
uint64_t level;
bool ok = ConsumeDecimalNumber(&in, &level) && in.empty();
if (!ok || (int)level >= NumberLevels()) {
return false;
} else {
char buf[100];
snprintf(buf, sizeof(buf), "%d",
versions_->NumLevelFiles(static_cast<int>(level)));
*value = buf;
return true;
}
} else if (in == "levelstats") {
char buf[1000];
snprintf(buf, sizeof(buf),
"Level Files Size(MB)\n"
"--------------------\n");
value->append(buf);
for (int level = 0; level < NumberLevels(); level++) {
snprintf(buf, sizeof(buf),
"%3d %8d %8.0f\n",
level,
versions_->NumLevelFiles(level),
versions_->NumLevelBytes(level) / 1048576.0);
value->append(buf);
}
return true;
} else if (in == "stats") {
char buf[1000];
uint64_t total_bytes_written = 0;
uint64_t total_bytes_read = 0;
uint64_t micros_up = env_->NowMicros() - started_at_;
// Add "+1" to make sure seconds_up is > 0 and avoid NaN later
double seconds_up = (micros_up + 1) / 1000000.0;
uint64_t total_slowdown = 0;
uint64_t interval_bytes_written = 0;
uint64_t interval_bytes_read = 0;
uint64_t interval_bytes_new = 0;
double interval_seconds_up = 0;
// Pardon the long line but I think it is easier to read this way.
snprintf(buf, sizeof(buf),
" Compactions\n"
"Level Files Size(MB) Score Time(sec) Read(MB) Write(MB) Rn(MB) Rnp1(MB) Wnew(MB) Amplify Read(MB/s) Write(MB/s) Rn Rnp1 Wnp1 NewW Count Ln-stall\n"
"----------------------------------------------------------------------------------------------------------------------------------------------------------------------------\n"
);
value->append(buf);
for (int level = 0; level < NumberLevels(); level++) {
int files = versions_->NumLevelFiles(level);
if (stats_[level].micros > 0 || files > 0) {
int64_t bytes_read = stats_[level].bytes_readn +
stats_[level].bytes_readnp1;
int64_t bytes_new = stats_[level].bytes_written -
stats_[level].bytes_readnp1;
double amplify = (stats_[level].bytes_readn == 0)
? 0.0
: (stats_[level].bytes_written + stats_[level].bytes_readnp1) /
(double) stats_[level].bytes_readn;
total_bytes_read += bytes_read;
total_bytes_written += stats_[level].bytes_written;
snprintf(
buf, sizeof(buf),
"%3d %8d %8.0f %5.1f %9.0f %9.0f %9.0f %9.0f %9.0f %9.0f %7.1f %9.1f %11.1f %8d %8d %8d %8d %8d %9.1f\n",
level,
files,
versions_->NumLevelBytes(level) / 1048576.0,
versions_->NumLevelBytes(level) /
versions_->MaxBytesForLevel(level),
stats_[level].micros / 1e6,
bytes_read / 1048576.0,
stats_[level].bytes_written / 1048576.0,
stats_[level].bytes_readn / 1048576.0,
stats_[level].bytes_readnp1 / 1048576.0,
bytes_new / 1048576.0,
amplify,
// +1 to avoid division by 0
(bytes_read / 1048576.0) / ((stats_[level].micros+1) / 1000000.0),
(stats_[level].bytes_written / 1048576.0) /
((stats_[level].micros+1) / 1000000.0),
stats_[level].files_in_leveln,
stats_[level].files_in_levelnp1,
stats_[level].files_out_levelnp1,
stats_[level].files_out_levelnp1 - stats_[level].files_in_levelnp1,
stats_[level].count,
stall_leveln_slowdown_[level] / 1000000.0);
total_slowdown += stall_leveln_slowdown_[level];
value->append(buf);
}
}
interval_bytes_new = stats_[0].bytes_written - last_stats_.bytes_new_;
interval_bytes_read = total_bytes_read - last_stats_.bytes_read_;
interval_bytes_written = total_bytes_written - last_stats_.bytes_written_;
interval_seconds_up = seconds_up - last_stats_.seconds_up_;
snprintf(buf, sizeof(buf), "Uptime(secs): %.1f total, %.1f interval\n",
seconds_up, interval_seconds_up);
value->append(buf);
snprintf(buf, sizeof(buf),
"Compaction IO cumulative (GB): "
"%.2f new, %.2f read, %.2f write, %.2f read+write\n",
stats_[0].bytes_written / (1048576.0 * 1024),
total_bytes_read / (1048576.0 * 1024),
total_bytes_written / (1048576.0 * 1024),
(total_bytes_read + total_bytes_written) / (1048576.0 * 1024));
value->append(buf);
snprintf(buf, sizeof(buf),
"Compaction IO cumulative (MB/sec): "
"%.1f new, %.1f read, %.1f write, %.1f read+write\n",
stats_[0].bytes_written / 1048576.0 / seconds_up,
total_bytes_read / 1048576.0 / seconds_up,
total_bytes_written / 1048576.0 / seconds_up,
(total_bytes_read + total_bytes_written) / 1048576.0 / seconds_up);
value->append(buf);
// +1 to avoid divide by 0 and NaN
snprintf(buf, sizeof(buf),
"Amplification cumulative: %.1f write, %.1f compaction\n",
(double) total_bytes_written / (stats_[0].bytes_written+1),
(double) (total_bytes_written + total_bytes_read)
/ (stats_[0].bytes_written+1));
value->append(buf);
snprintf(buf, sizeof(buf),
"Compaction IO interval (MB): "
"%.2f new, %.2f read, %.2f write, %.2f read+write\n",
interval_bytes_new / 1048576.0,
interval_bytes_read/ 1048576.0,
interval_bytes_written / 1048576.0,
(interval_bytes_read + interval_bytes_written) / 1048576.0);
value->append(buf);
snprintf(buf, sizeof(buf),
"Compaction IO interval (MB/sec): "
"%.1f new, %.1f read, %.1f write, %.1f read+write\n",
interval_bytes_new / 1048576.0 / interval_seconds_up,
interval_bytes_read / 1048576.0 / interval_seconds_up,
interval_bytes_written / 1048576.0 / interval_seconds_up,
(interval_bytes_read + interval_bytes_written)
/ 1048576.0 / interval_seconds_up);
value->append(buf);
// +1 to avoid divide by 0 and NaN
snprintf(buf, sizeof(buf),
"Amplification interval: %.1f write, %.1f compaction\n",
(double) interval_bytes_written / (interval_bytes_new+1),
(double) (interval_bytes_written + interval_bytes_read) /
(interval_bytes_new+1));
value->append(buf);
snprintf(buf, sizeof(buf),
"Stalls(secs): %.3f level0_slowdown, %.3f level0_numfiles, "
"%.3f memtable_compaction, %.3f leveln_slowdown\n",
stall_level0_slowdown_ / 1000000.0,
stall_level0_num_files_ / 1000000.0,
stall_memtable_compaction_ / 1000000.0,
total_slowdown / 1000000.0);
value->append(buf);
last_stats_.bytes_read_ = total_bytes_read;
last_stats_.bytes_written_ = total_bytes_written;
last_stats_.bytes_new_ = stats_[0].bytes_written;
last_stats_.seconds_up_ = seconds_up;
return true;
} else if (in == "sstables") {
*value = versions_->current()->DebugString();
return true;
}
return false;
}
void DBImpl::GetApproximateSizes(
const Range* range, int n,
uint64_t* sizes) {
// TODO(opt): better implementation
Version* v;
{
MutexLock l(&mutex_);
versions_->current()->Ref();
v = versions_->current();
}
for (int i = 0; i < n; i++) {
// Convert user_key into a corresponding internal key.
InternalKey k1(range[i].start, kMaxSequenceNumber, kValueTypeForSeek);
InternalKey k2(range[i].limit, kMaxSequenceNumber, kValueTypeForSeek);
uint64_t start = versions_->ApproximateOffsetOf(v, k1);
uint64_t limit = versions_->ApproximateOffsetOf(v, k2);
sizes[i] = (limit >= start ? limit - start : 0);
}
{
MutexLock l(&mutex_);
v->Unref();
}
}
inline void DBImpl::DelayLoggingAndReset() {
if (delayed_writes_ > 0) {
Log(options_.info_log, "delayed %d write...\n", delayed_writes_ );
delayed_writes_ = 0;
}
}
// Default implementations of convenience methods that subclasses of DB
// can call if they wish
Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value) {
WriteBatch batch;
batch.Put(key, value);
return Write(opt, &batch);
}
Status DB::Delete(const WriteOptions& opt, const Slice& key) {
WriteBatch batch;
batch.Delete(key);
return Write(opt, &batch);
}
Status DB::Merge(const WriteOptions& opt, const Slice& key,
const Slice& value) {
WriteBatch batch;
batch.Merge(key, value);
return Write(opt, &batch);
}
DB::~DB() { }
Status DB::Open(const Options& options, const std::string& dbname,
DB** dbptr) {
*dbptr = nullptr;
EnvOptions soptions;
if (options.block_cache != nullptr && options.no_block_cache) {
return Status::InvalidArgument(
"no_block_cache is true while block_cache is not nullptr");
}
DBImpl* impl = new DBImpl(options, dbname);
Status s = impl->CreateArchivalDirectory();
if (!s.ok()) {
delete impl;
return s;
}
impl->mutex_.Lock();
VersionEdit edit(impl->NumberLevels());
s = impl->Recover(&edit); // Handles create_if_missing, error_if_exists
if (s.ok()) {
uint64_t new_log_number = impl->versions_->NewFileNumber();
unique_ptr<WritableFile> lfile;
soptions.use_mmap_writes = false;
s = options.env->NewWritableFile(LogFileName(dbname, new_log_number),
&lfile, soptions);
if (s.ok()) {
lfile->SetPreallocationBlockSize(1.1 * options.write_buffer_size);
edit.SetLogNumber(new_log_number);
impl->logfile_number_ = new_log_number;
impl->log_.reset(new log::Writer(std::move(lfile)));
s = impl->versions_->LogAndApply(&edit, &impl->mutex_);
}
if (s.ok()) {
impl->DeleteObsoleteFiles();
impl->MaybeScheduleCompaction();
impl->MaybeScheduleLogDBDeployStats();
}
}
impl->mutex_.Unlock();
if (s.ok()) {
*dbptr = impl;
} else {
delete impl;
}
return s;
}
Snapshot::~Snapshot() {
}
Status DestroyDB(const std::string& dbname, const Options& options) {
Env* env = options.env;
std::vector<std::string> filenames;
std::vector<std::string> archiveFiles;
// Ignore error in case directory does not exist
env->GetChildren(dbname, &filenames);
env->GetChildren(ArchivalDirectory(dbname), &archiveFiles);
if (filenames.empty()) {
return Status::OK();
}
FileLock* lock;
const std::string lockname = LockFileName(dbname);
Status result = env->LockFile(lockname, &lock);
if (result.ok()) {
uint64_t number;
FileType type;
for (size_t i = 0; i < filenames.size(); i++) {
if (ParseFileName(filenames[i], &number, &type) &&
type != kDBLockFile) { // Lock file will be deleted at end
Status del;
if (type == kMetaDatabase) {
del = DestroyDB(dbname + "/" + filenames[i], options);
} else {
del = env->DeleteFile(dbname + "/" + filenames[i]);
}
if (result.ok() && !del.ok()) {
result = del;
}
}
}
// Delete archival files.
for (size_t i = 0; i < archiveFiles.size(); ++i) {
ParseFileName(archiveFiles[i], &number, &type);
if (type == kLogFile) {
Status del = env->DeleteFile(ArchivalDirectory(dbname) + "/" +
archiveFiles[i]);
if (result.ok() && !del.ok()) {
result = del;
}
}
}
// ignore case where no archival directory is present.
env->DeleteDir(ArchivalDirectory(dbname));
env->UnlockFile(lock); // Ignore error since state is already gone
env->DeleteFile(lockname);
env->DeleteDir(dbname); // Ignore error in case dir contains other files
}
return result;
}
//
// A global method that can dump out the build version
void dumpLeveldbBuildVersion(Logger * log) {
Log(log, "Git sha %s", leveldb_build_git_sha);
Log(log, "Compile time %s %s",
leveldb_build_compile_time, leveldb_build_compile_date);
}
} // namespace leveldb
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