Rocksdb manual flush code changes

apple · Dec 19, 2024 · 002638a · 002638a
1 parent 9fb460b
commit 002638a
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Showing 2 changed files with 15 additions and 4 deletions.
diff --git a/fdbclient/ServerKnobs.cpp b/fdbclient/ServerKnobs.cpp
@@ -573,8 +573,8 @@ void ServerKnobs::initialize(Randomize randomize, ClientKnobs* clientKnobs, IsSi
 	init( ROCKSDB_CF_METRICS_DELAY,                            900.0 );
 	init( ROCKSDB_MAX_LOG_FILE_SIZE,                        10485760 ); // 10MB.
 	init( ROCKSDB_KEEP_LOG_FILE_NUM,                             100 ); // Keeps 1GB log per storage server.
-	// Does manual flushes at regular intervals(seconds), incase rocksdb did not flush. Feature disable if the value is 0.
-	init( ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL,                      0 ); if( randomize && BUGGIFY ) ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL = deterministicRandom()->randomInt(4, 10);
+	// Does manual flushes at regular intervals(seconds), incase rocksdb did not flush. Feature disabled if the value is 0.
+	init( ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL,                    600 ); if( randomize && BUGGIFY ) ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL = deterministicRandom()->randomInt(60, 1200);
 	init( ROCKSDB_SKIP_STATS_UPDATE_ON_OPEN,                    true );
 	init( ROCKSDB_SKIP_FILE_SIZE_CHECK_ON_OPEN,                 true );
 	init( ROCKSDB_FULLFILE_CHECKSUM,                           false ); if ( randomize && BUGGIFY ) ROCKSDB_FULLFILE_CHECKSUM = true;

diff --git a/fdbserver/KeyValueStoreRocksDB.actor.cpp b/fdbserver/KeyValueStoreRocksDB.actor.cpp
@@ -378,6 +378,9 @@ class RocksDBEventListener : public rocksdb::EventListener {
 	void OnFlushCompleted(rocksdb::DB* db, const rocksdb::FlushJobInfo& info) override { *lastFlushTime = now(); }
 
 private:
+	// lastFlushTime is used by two threads. One Thread is reading the value and the other thread is updating the value.
+	// If the reader thread gets a wrong value due to race, that will be still fine in this case(probably an extra flush
+	// or no flush). Considering the cost of atomic, avoided it here in this case.
 	std::shared_ptr<double> lastFlushTime;
 };
 
@@ -992,12 +995,20 @@ ACTOR Future<Void> manualFlush(UID id,
                                CF cf) {
 	if (SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL) {
 		state rocksdb::FlushOptions fOptions = sharedState->getFlushOptions();
+		state double waitTime = SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL;
+		state double currTime = 0;
+		state double timeElapsedAfterLastFlush = 0;
 		loop {
-			wait(delay(SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL));
+			wait(delay(waitTime));
 
-			if ((now() - *lastFlushTime) > SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL) {
+			currTime = now();
+			timeElapsedAfterLastFlush = currTime - *lastFlushTime;
+			if (timeElapsedAfterLastFlush >= SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL) {
 				db->Flush(fOptions, cf);
 				TraceEvent e("RocksDBManualFlush", id);
+				waitTime = SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL;
+			} else {
+				waitTime = SERVER_KNOBS->ROCKSDB_MANUAL_FLUSH_TIME_INTERVAL - timeElapsedAfterLastFlush;
 			}
 		}
 	}