From dc277f0ab7087a75eee1bba53668aa824c0034f6 Mon Sep 17 00:00:00 2001
From: Igor Canadi <icanadi@fb.com>
Date: Tue, 25 Feb 2014 13:16:59 -0800
Subject: [PATCH] [CF] Adaptation of GetLiveFiles for CF

Summary: Even if user flushes the memtables before getting live files, we still can't guarantee that new data didn't come in (to already-flushed memtables). If we want backups to provide consistent view of the database, we still need to get WAL files.

Test Plan: backupable_db_test

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16299
---
 db/db_filesnapshot.cc                 | 24 +++++++++++++++++++++---
 include/rocksdb/db.h                  |  9 ++++++---
 utilities/backupable/backupable_db.cc |  3 +--
 3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/db/db_filesnapshot.cc b/db/db_filesnapshot.cc
index 4b388accf1..bf5132dc96 100644
--- a/db/db_filesnapshot.cc
+++ b/db/db_filesnapshot.cc
@@ -60,18 +60,35 @@ Status DBImpl::GetLiveFiles(std::vector<std::string>& ret,
 
   *manifest_file_size = 0;
 
+  mutex_.Lock();
+
   if (flush_memtable) {
     // flush all dirty data to disk.
-    Status status =  Flush(FlushOptions());
+    autovector<ColumnFamilyData*> to_delete;
+    Status status;
+    for (auto cfd : *versions_->GetColumnFamilySet()) {
+      cfd->Ref();
+      mutex_.Unlock();
+      status = FlushMemTable(cfd, FlushOptions());
+      mutex_.Lock();
+      if (cfd->Unref()) {
+        to_delete.push_back(cfd);
+      }
+      if (!status.ok()) {
+        break;
+      }
+    }
+    for (auto cfd : to_delete) {
+      delete cfd;
+    }
     if (!status.ok()) {
+      mutex_.Unlock();
       Log(options_.info_log, "Cannot Flush data %s\n",
           status.ToString().c_str());
       return status;
     }
   }
 
-  MutexLock l(&mutex_);
-
   // Make a set of all of the live *.sst files
   std::set<uint64_t> live;
   for (auto cfd : *versions_->GetColumnFamilySet()) {
@@ -93,6 +110,7 @@ Status DBImpl::GetLiveFiles(std::vector<std::string>& ret,
   // find length of manifest file while holding the mutex lock
   *manifest_file_size = versions_->ManifestFileSize();
 
+  mutex_.Unlock();
   return Status::OK();
 }
 
diff --git a/include/rocksdb/db.h b/include/rocksdb/db.h
index 4d2e0ac79b..9773fe3f34 100644
--- a/include/rocksdb/db.h
+++ b/include/rocksdb/db.h
@@ -394,9 +394,12 @@ class DB {
   // Setting flush_memtable to true does Flush before recording the live files.
   // Setting flush_memtable to false is useful when we don't want to wait for
   // flush which may have to wait for compaction to complete taking an
-  // indeterminate time. But this will have to use GetSortedWalFiles after
-  // GetLiveFiles to compensate for memtables missed in this snapshot due to the
-  // absence of Flush, by WAL files to recover the database consistently later
+  // indeterminate time.
+  //
+  // In case you have multiple column families, even if flush_memtable is true,
+  // you still need to call GetSortedWalFiles after GetLiveFiles to compensate
+  // for new data that arrived to already-flushed column families while other
+  // column families were flushing
   virtual Status GetLiveFiles(std::vector<std::string>&,
                               uint64_t* manifest_file_size,
                               bool flush_memtable = true) = 0;
diff --git a/utilities/backupable/backupable_db.cc b/utilities/backupable/backupable_db.cc
index 89051f25aa..833140209b 100644
--- a/utilities/backupable/backupable_db.cc
+++ b/utilities/backupable/backupable_db.cc
@@ -311,8 +311,7 @@ Status BackupEngineImpl::CreateNewBackup(DB* db, bool flush_before_backup) {
     // this will return live_files prefixed with "/"
     s = db->GetLiveFiles(live_files, &manifest_file_size, flush_before_backup);
   }
-  // if we didn't flush before backup, we need to also get WAL files
-  if (s.ok() && !flush_before_backup) {
+  if (s.ok()) {
     // returns file names prefixed with "/"
     s = db->GetSortedWalFiles(live_wal_files);
   }