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rocksdb/table/get_context.cc
Andrew Kryczka b7fbcefda8 Add API to limit blast radius of merge operator failure (#11092) 
Summary:
Prior to this PR, `FullMergeV2()` can only return `false` to indicate failure, which causes any operation invoking it to fail. During a compaction, such a failure causes the compaction to fail and causes the DB to irreversibly enter read-only mode. Some users asked for a way to allow the merge operator to fail without such widespread damage.

To limit the blast radius of merge operator failures, this PR introduces the `MergeOperationOutput::op_failure_scope` API. When unpopulated (`kDefault`) or set to `kTryMerge`, the merge operator failure handling is the same as before. When set to `kMustMerge`, merge operator failure still causes failure to operations that must merge (`Get()`, iterator, `MultiGet()`, etc.). However, under `kMustMerge`, flushes/compactions can survive merge operator failures by outputting the unmerged input operands.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/11092

Reviewed By: siying

Differential Revision: D42525673

Pulled By: ajkr

fbshipit-source-id: 951dc3bf190f86347dccf3381be967565cda52ee
2023-01-20 14:40:30 -08:00

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#include "table/get_context.h"
#include "db/blob//blob_fetcher.h"
#include "db/merge_helper.h"
#include "db/pinned_iterators_manager.h"
#include "db/read_callback.h"
#include "db/wide/wide_column_serialization.h"
#include "monitoring/file_read_sample.h"
#include "monitoring/perf_context_imp.h"
#include "monitoring/statistics.h"
#include "rocksdb/merge_operator.h"
#include "rocksdb/statistics.h"
#include "rocksdb/system_clock.h"
namespace ROCKSDB_NAMESPACE {
namespace {
void appendToReplayLog(std::string* replay_log, ValueType type, Slice value) {
#ifndef ROCKSDB_LITE
if (replay_log) {
if (replay_log->empty()) {
// Optimization: in the common case of only one operation in the
// log, we allocate the exact amount of space needed.
replay_log->reserve(1 + VarintLength(value.size()) + value.size());
}
replay_log->push_back(type);
PutLengthPrefixedSlice(replay_log, value);
}
#else
(void)replay_log;
(void)type;
(void)value;
#endif // ROCKSDB_LITE
}
} // namespace
GetContext::GetContext(
const Comparator* ucmp, const MergeOperator* merge_operator, Logger* logger,
Statistics* statistics, GetState init_state, const Slice& user_key,
PinnableSlice* pinnable_val, PinnableWideColumns* columns,
std::string* timestamp, bool* value_found, MergeContext* merge_context,
bool do_merge, SequenceNumber* _max_covering_tombstone_seq,
SystemClock* clock, SequenceNumber* seq,
PinnedIteratorsManager* _pinned_iters_mgr, ReadCallback* callback,
bool* is_blob_index, uint64_t tracing_get_id, BlobFetcher* blob_fetcher)
: ucmp_(ucmp),
merge_operator_(merge_operator),
logger_(logger),
statistics_(statistics),
state_(init_state),
user_key_(user_key),
pinnable_val_(pinnable_val),
columns_(columns),
timestamp_(timestamp),
value_found_(value_found),
merge_context_(merge_context),
max_covering_tombstone_seq_(_max_covering_tombstone_seq),
clock_(clock),
seq_(seq),
replay_log_(nullptr),
pinned_iters_mgr_(_pinned_iters_mgr),
callback_(callback),
do_merge_(do_merge),
is_blob_index_(is_blob_index),
tracing_get_id_(tracing_get_id),
blob_fetcher_(blob_fetcher) {
if (seq_) {
*seq_ = kMaxSequenceNumber;
}
sample_ = should_sample_file_read();
}
GetContext::GetContext(const Comparator* ucmp,
const MergeOperator* merge_operator, Logger* logger,
Statistics* statistics, GetState init_state,
const Slice& user_key, PinnableSlice* pinnable_val,
PinnableWideColumns* columns, bool* value_found,
MergeContext* merge_context, bool do_merge,
SequenceNumber* _max_covering_tombstone_seq,
SystemClock* clock, SequenceNumber* seq,
PinnedIteratorsManager* _pinned_iters_mgr,
ReadCallback* callback, bool* is_blob_index,
uint64_t tracing_get_id, BlobFetcher* blob_fetcher)
: GetContext(ucmp, merge_operator, logger, statistics, init_state, user_key,
pinnable_val, columns, /*timestamp=*/nullptr, value_found,
merge_context, do_merge, _max_covering_tombstone_seq, clock,
seq, _pinned_iters_mgr, callback, is_blob_index,
tracing_get_id, blob_fetcher) {}
// Called from TableCache::Get and Table::Get when file/block in which
// key may exist are not there in TableCache/BlockCache respectively. In this
// case we can't guarantee that key does not exist and are not permitted to do
// IO to be certain.Set the status=kFound and value_found=false to let the
// caller know that key may exist but is not there in memory
void GetContext::MarkKeyMayExist() {
state_ = kFound;
if (value_found_ != nullptr) {
*value_found_ = false;
}
}
void GetContext::SaveValue(const Slice& value, SequenceNumber /*seq*/) {
assert(state_ == kNotFound);
appendToReplayLog(replay_log_, kTypeValue, value);
state_ = kFound;
if (LIKELY(pinnable_val_ != nullptr)) {
pinnable_val_->PinSelf(value);
}
}
void GetContext::ReportCounters() {
if (get_context_stats_.num_cache_hit > 0) {
RecordTick(statistics_, BLOCK_CACHE_HIT, get_context_stats_.num_cache_hit);
}
if (get_context_stats_.num_cache_index_hit > 0) {
RecordTick(statistics_, BLOCK_CACHE_INDEX_HIT,
get_context_stats_.num_cache_index_hit);
}
if (get_context_stats_.num_cache_data_hit > 0) {
RecordTick(statistics_, BLOCK_CACHE_DATA_HIT,
get_context_stats_.num_cache_data_hit);
}
if (get_context_stats_.num_cache_filter_hit > 0) {
RecordTick(statistics_, BLOCK_CACHE_FILTER_HIT,
get_context_stats_.num_cache_filter_hit);
}
if (get_context_stats_.num_cache_compression_dict_hit > 0) {
RecordTick(statistics_, BLOCK_CACHE_COMPRESSION_DICT_HIT,
get_context_stats_.num_cache_compression_dict_hit);
}
if (get_context_stats_.num_cache_index_miss > 0) {
RecordTick(statistics_, BLOCK_CACHE_INDEX_MISS,
get_context_stats_.num_cache_index_miss);
}
if (get_context_stats_.num_cache_filter_miss > 0) {
RecordTick(statistics_, BLOCK_CACHE_FILTER_MISS,
get_context_stats_.num_cache_filter_miss);
}
if (get_context_stats_.num_cache_data_miss > 0) {
RecordTick(statistics_, BLOCK_CACHE_DATA_MISS,
get_context_stats_.num_cache_data_miss);
}
if (get_context_stats_.num_cache_compression_dict_miss > 0) {
RecordTick(statistics_, BLOCK_CACHE_COMPRESSION_DICT_MISS,
get_context_stats_.num_cache_compression_dict_miss);
}
if (get_context_stats_.num_cache_bytes_read > 0) {
RecordTick(statistics_, BLOCK_CACHE_BYTES_READ,
get_context_stats_.num_cache_bytes_read);
}
if (get_context_stats_.num_cache_miss > 0) {
RecordTick(statistics_, BLOCK_CACHE_MISS,
get_context_stats_.num_cache_miss);
}
if (get_context_stats_.num_cache_add > 0) {
RecordTick(statistics_, BLOCK_CACHE_ADD, get_context_stats_.num_cache_add);
}
if (get_context_stats_.num_cache_add_redundant > 0) {
RecordTick(statistics_, BLOCK_CACHE_ADD_REDUNDANT,
get_context_stats_.num_cache_add_redundant);
}
if (get_context_stats_.num_cache_bytes_write > 0) {
RecordTick(statistics_, BLOCK_CACHE_BYTES_WRITE,
get_context_stats_.num_cache_bytes_write);
}
if (get_context_stats_.num_cache_index_add > 0) {
RecordTick(statistics_, BLOCK_CACHE_INDEX_ADD,
get_context_stats_.num_cache_index_add);
}
if (get_context_stats_.num_cache_index_add_redundant > 0) {
RecordTick(statistics_, BLOCK_CACHE_INDEX_ADD_REDUNDANT,
get_context_stats_.num_cache_index_add_redundant);
}
if (get_context_stats_.num_cache_index_bytes_insert > 0) {
RecordTick(statistics_, BLOCK_CACHE_INDEX_BYTES_INSERT,
get_context_stats_.num_cache_index_bytes_insert);
}
if (get_context_stats_.num_cache_data_add > 0) {
RecordTick(statistics_, BLOCK_CACHE_DATA_ADD,
get_context_stats_.num_cache_data_add);
}
if (get_context_stats_.num_cache_data_add_redundant > 0) {
RecordTick(statistics_, BLOCK_CACHE_DATA_ADD_REDUNDANT,
get_context_stats_.num_cache_data_add_redundant);
}
if (get_context_stats_.num_cache_data_bytes_insert > 0) {
RecordTick(statistics_, BLOCK_CACHE_DATA_BYTES_INSERT,
get_context_stats_.num_cache_data_bytes_insert);
}
if (get_context_stats_.num_cache_filter_add > 0) {
RecordTick(statistics_, BLOCK_CACHE_FILTER_ADD,
get_context_stats_.num_cache_filter_add);
}
if (get_context_stats_.num_cache_filter_add_redundant > 0) {
RecordTick(statistics_, BLOCK_CACHE_FILTER_ADD_REDUNDANT,
get_context_stats_.num_cache_filter_add_redundant);
}
if (get_context_stats_.num_cache_filter_bytes_insert > 0) {
RecordTick(statistics_, BLOCK_CACHE_FILTER_BYTES_INSERT,
get_context_stats_.num_cache_filter_bytes_insert);
}
if (get_context_stats_.num_cache_compression_dict_add > 0) {
RecordTick(statistics_, BLOCK_CACHE_COMPRESSION_DICT_ADD,
get_context_stats_.num_cache_compression_dict_add);
}
if (get_context_stats_.num_cache_compression_dict_add_redundant > 0) {
RecordTick(statistics_, BLOCK_CACHE_COMPRESSION_DICT_ADD_REDUNDANT,
get_context_stats_.num_cache_compression_dict_add_redundant);
}
if (get_context_stats_.num_cache_compression_dict_bytes_insert > 0) {
RecordTick(statistics_, BLOCK_CACHE_COMPRESSION_DICT_BYTES_INSERT,
get_context_stats_.num_cache_compression_dict_bytes_insert);
}
}
bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
const Slice& value, bool* matched,
Cleanable* value_pinner) {
assert(matched);
assert((state_ != kMerge && parsed_key.type != kTypeMerge) ||
merge_context_ != nullptr);
if (ucmp_->EqualWithoutTimestamp(parsed_key.user_key, user_key_)) {
*matched = true;
// If the value is not in the snapshot, skip it
if (!CheckCallback(parsed_key.sequence)) {
return true; // to continue to the next seq
}
appendToReplayLog(replay_log_, parsed_key.type, value);
if (seq_ != nullptr) {
// Set the sequence number if it is uninitialized
if (*seq_ == kMaxSequenceNumber) {
*seq_ = parsed_key.sequence;
}
if (max_covering_tombstone_seq_) {
*seq_ = std::max(*seq_, *max_covering_tombstone_seq_);
}
}
size_t ts_sz = ucmp_->timestamp_size();
if (ts_sz > 0 && timestamp_ != nullptr) {
if (!timestamp_->empty()) {
assert(ts_sz == timestamp_->size());
// `timestamp` can be set before `SaveValue` is ever called
// when max_covering_tombstone_seq_ was set.
// If this key has a higher sequence number than range tombstone,
// then timestamp should be updated. `ts_from_rangetombstone_` is
// set to false afterwards so that only the key with highest seqno
// updates the timestamp.
if (ts_from_rangetombstone_) {
assert(max_covering_tombstone_seq_);
if (parsed_key.sequence > *max_covering_tombstone_seq_) {
Slice ts = ExtractTimestampFromUserKey(parsed_key.user_key, ts_sz);
timestamp_->assign(ts.data(), ts.size());
ts_from_rangetombstone_ = false;
}
}
}
// TODO optimize for small size ts
const std::string kMaxTs(ts_sz, '\xff');
if (timestamp_->empty() ||
ucmp_->CompareTimestamp(*timestamp_, kMaxTs) == 0) {
Slice ts = ExtractTimestampFromUserKey(parsed_key.user_key, ts_sz);
timestamp_->assign(ts.data(), ts.size());
}
}
auto type = parsed_key.type;
// Key matches. Process it
if ((type == kTypeValue || type == kTypeMerge || type == kTypeBlobIndex ||
type == kTypeWideColumnEntity || type == kTypeDeletion ||
type == kTypeDeletionWithTimestamp || type == kTypeSingleDeletion) &&
max_covering_tombstone_seq_ != nullptr &&
*max_covering_tombstone_seq_ > parsed_key.sequence) {
// Note that deletion types are also considered, this is for the case
// when we need to return timestamp to user. If a range tombstone has a
// higher seqno than point tombstone, its timestamp should be returned.
type = kTypeRangeDeletion;
}
switch (type) {
case kTypeValue:
case kTypeBlobIndex:
case kTypeWideColumnEntity:
assert(state_ == kNotFound || state_ == kMerge);
if (type == kTypeBlobIndex) {
if (is_blob_index_ == nullptr) {
// Blob value not supported. Stop.
state_ = kUnexpectedBlobIndex;
return false;
}
}
if (is_blob_index_ != nullptr) {
*is_blob_index_ = (type == kTypeBlobIndex);
}
if (kNotFound == state_) {
state_ = kFound;
if (do_merge_) {
if (LIKELY(pinnable_val_ != nullptr)) {
Slice value_to_use = value;
if (type == kTypeWideColumnEntity) {
Slice value_copy = value;
if (!WideColumnSerialization::GetValueOfDefaultColumn(
value_copy, value_to_use)
.ok()) {
state_ = kCorrupt;
return false;
}
}
if (LIKELY(value_pinner != nullptr)) {
// If the backing resources for the value are provided, pin them
pinnable_val_->PinSlice(value_to_use, value_pinner);
} else {
TEST_SYNC_POINT_CALLBACK("GetContext::SaveValue::PinSelf",
this);
// Otherwise copy the value
pinnable_val_->PinSelf(value_to_use);
}
} else if (columns_ != nullptr) {
if (type == kTypeWideColumnEntity) {
if (!columns_->SetWideColumnValue(value, value_pinner).ok()) {
state_ = kCorrupt;
return false;
}
} else {
columns_->SetPlainValue(value, value_pinner);
}
}
} else {
// It means this function is called as part of DB GetMergeOperands
// API and the current value should be part of
// merge_context_->operand_list
if (type == kTypeBlobIndex) {
PinnableSlice pin_val;
if (GetBlobValue(value, &pin_val) == false) {
return false;
}
Slice blob_value(pin_val);
push_operand(blob_value, nullptr);
} else if (type == kTypeWideColumnEntity) {
Slice value_copy = value;
Slice value_of_default;
if (!WideColumnSerialization::GetValueOfDefaultColumn(
value_copy, value_of_default)
.ok()) {
state_ = kCorrupt;
return false;
}
push_operand(value_of_default, value_pinner);
} else {
assert(type == kTypeValue);
push_operand(value, value_pinner);
}
}
} else if (kMerge == state_) {
assert(merge_operator_ != nullptr);
if (type == kTypeBlobIndex) {
PinnableSlice pin_val;
if (GetBlobValue(value, &pin_val) == false) {
return false;
}
Slice blob_value(pin_val);
state_ = kFound;
if (do_merge_) {
Merge(&blob_value);
} else {
// It means this function is called as part of DB GetMergeOperands
// API and the current value should be part of
// merge_context_->operand_list
push_operand(blob_value, nullptr);
}
} else if (type == kTypeWideColumnEntity) {
state_ = kFound;
if (do_merge_) {
MergeWithEntity(value);
} else {
// It means this function is called as part of DB GetMergeOperands
// API and the current value should be part of
// merge_context_->operand_list
Slice value_copy = value;
Slice value_of_default;
if (!WideColumnSerialization::GetValueOfDefaultColumn(
value_copy, value_of_default)
.ok()) {
state_ = kCorrupt;
return false;
}
push_operand(value_of_default, value_pinner);
}
} else {
assert(type == kTypeValue);
state_ = kFound;
if (do_merge_) {
Merge(&value);
} else {
// It means this function is called as part of DB GetMergeOperands
// API and the current value should be part of
// merge_context_->operand_list
push_operand(value, value_pinner);
}
}
}
return false;
case kTypeDeletion:
case kTypeDeletionWithTimestamp:
case kTypeSingleDeletion:
case kTypeRangeDeletion:
// TODO(noetzli): Verify correctness once merge of single-deletes
// is supported
assert(state_ == kNotFound || state_ == kMerge);
if (kNotFound == state_) {
state_ = kDeleted;
} else if (kMerge == state_) {
state_ = kFound;
if (do_merge_) {
Merge(nullptr);
}
// If do_merge_ = false then the current value shouldn't be part of
// merge_context_->operand_list
}
return false;
case kTypeMerge:
assert(state_ == kNotFound || state_ == kMerge);
state_ = kMerge;
// value_pinner is not set from plain_table_reader.cc for example.
push_operand(value, value_pinner);
if (do_merge_ && merge_operator_ != nullptr &&
merge_operator_->ShouldMerge(
merge_context_->GetOperandsDirectionBackward())) {
state_ = kFound;
Merge(nullptr);
return false;
}
return true;
default:
assert(false);
break;
}
}
// state_ could be Corrupt, merge or notfound
return false;
}
void GetContext::Merge(const Slice* value) {
assert(do_merge_);
assert(!pinnable_val_ || !columns_);
std::string result;
// `op_failure_scope` (an output parameter) is not provided (set to nullptr)
// since a failure must be propagated regardless of its value.
const Status s = MergeHelper::TimedFullMerge(
merge_operator_, user_key_, value, merge_context_->GetOperands(), &result,
logger_, statistics_, clock_, /* result_operand */ nullptr,
/* update_num_ops_stats */ true,
/* op_failure_scope */ nullptr);
if (!s.ok()) {
state_ = kCorrupt;
return;
}
if (LIKELY(pinnable_val_ != nullptr)) {
*(pinnable_val_->GetSelf()) = std::move(result);
pinnable_val_->PinSelf();
return;
}
assert(columns_);
columns_->SetPlainValue(result);
}
void GetContext::MergeWithEntity(Slice entity) {
assert(do_merge_);
assert(!pinnable_val_ || !columns_);
if (LIKELY(pinnable_val_ != nullptr)) {
Slice value_of_default;
{
const Status s = WideColumnSerialization::GetValueOfDefaultColumn(
entity, value_of_default);
if (!s.ok()) {
state_ = kCorrupt;
return;
}
}
{
// `op_failure_scope` (an output parameter) is not provided (set to
// nullptr) since a failure must be propagated regardless of its value.
const Status s = MergeHelper::TimedFullMerge(
merge_operator_, user_key_, &value_of_default,
merge_context_->GetOperands(), pinnable_val_->GetSelf(), logger_,
statistics_, clock_, /* result_operand */ nullptr,
/* update_num_ops_stats */ true,
/* op_failure_scope */ nullptr);
if (!s.ok()) {
state_ = kCorrupt;
return;
}
}
pinnable_val_->PinSelf();
return;
}
std::string result;
{
// `op_failure_scope` (an output parameter) is not provided (set to nullptr)
// since a failure must be propagated regardless of its value.
const Status s = MergeHelper::TimedFullMergeWithEntity(
merge_operator_, user_key_, entity, merge_context_->GetOperands(),
&result, logger_, statistics_, clock_, /* update_num_ops_stats */ true,
/* op_failure_scope */ nullptr);
if (!s.ok()) {
state_ = kCorrupt;
return;
}
}
{
assert(columns_);
const Status s = columns_->SetWideColumnValue(result);
if (!s.ok()) {
state_ = kCorrupt;
return;
}
}
}
bool GetContext::GetBlobValue(const Slice& blob_index,
PinnableSlice* blob_value) {
constexpr FilePrefetchBuffer* prefetch_buffer = nullptr;
constexpr uint64_t* bytes_read = nullptr;
Status status = blob_fetcher_->FetchBlob(
user_key_, blob_index, prefetch_buffer, blob_value, bytes_read);
if (!status.ok()) {
if (status.IsIncomplete()) {
// FIXME: this code is not covered by unit tests
MarkKeyMayExist();
return false;
}
state_ = kCorrupt;
return false;
}
*is_blob_index_ = false;
return true;
}
void GetContext::push_operand(const Slice& value, Cleanable* value_pinner) {
// TODO(yanqin) preserve timestamps information in merge_context
if (pinned_iters_mgr() && pinned_iters_mgr()->PinningEnabled() &&
value_pinner != nullptr) {
value_pinner->DelegateCleanupsTo(pinned_iters_mgr());
merge_context_->PushOperand(value, true /*value_pinned*/);
} else {
merge_context_->PushOperand(value, false);
}
}
void replayGetContextLog(const Slice& replay_log, const Slice& user_key,
GetContext* get_context, Cleanable* value_pinner) {
#ifndef ROCKSDB_LITE
Slice s = replay_log;
while (s.size()) {
auto type = static_cast<ValueType>(*s.data());
s.remove_prefix(1);
Slice value;
bool ret = GetLengthPrefixedSlice(&s, &value);
assert(ret);
(void)ret;
bool dont_care __attribute__((__unused__));
// Since SequenceNumber is not stored and unknown, we will use
// kMaxSequenceNumber.
get_context->SaveValue(
ParsedInternalKey(user_key, kMaxSequenceNumber, type), value,
&dont_care, value_pinner);
}
#else // ROCKSDB_LITE
(void)replay_log;
(void)user_key;
(void)get_context;
(void)value_pinner;
assert(false);
#endif // ROCKSDB_LITE
}
} // namespace ROCKSDB_NAMESPACE
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