added option `--rocksdb.use-file-logging` (#6308)

CHANGELOG

@@ -9,6 +9,12 @@ devel
   on path (vertices and edges) have not been applied. In SmartGraphs the checks
   have been executed properly.
 
+* added option `--rocksdb.use-file-logging` to enable writing of RocksDB's own
+  informational LOG files into RocksDB's database directory.
+
+  This option is turned off by default, but can be enabled for debugging RocksDB
+  internals and performance.
+
 * improved error messages when managing Foxx services
 
   Install/replace/upgrade will now provide additional information when an error

Documentation/Books/Manual/Administration/Configuration/RocksDB.md

@@ -240,3 +240,20 @@ have been executed without the *waitForSync* attribute.
 
 Note: this option is not supported on Windows platforms. Setting the option to
 a value greater 0 will produce a startup warning.
+
+`--rocksdb.use-file-logging`
+
+When set to *true*, enables writing of RocksDB's own informational LOG files into 
+RocksDB's database directory.
+
+This option is turned off by default, but can be enabled for debugging RocksDB
+internals and performance.
+
+`--rocksdb.debug-logging`
+
+When set to *true*, enables verbose logging of RocksDB's actions into the logfile
+written by ArangoDB (if option `--rocksdb.use-file-logging` is off) or RocksDB's
+own log (if option `--rocksdb.use-file-logging` is on).
+
+This option is turned off by default, but can be enabled for debugging RocksDB
+internals and performance.

arangod/RocksDBEngine/RocksDBEngine.cpp

@@ -420,18 +420,28 @@ void RocksDBEngine::start() {
 
   // intentionally set the RocksDB logger to warning because it will
   // log lots of things otherwise
-  if (!_debugLogging) {
-    _options.info_log_level = rocksdb::InfoLogLevel::ERROR_LEVEL;
-  } else {
+  if (_debugLogging) {
     _options.info_log_level = rocksdb::InfoLogLevel::DEBUG_LEVEL;
-  } // else
+  } else {
+    if (!opts->_useFileLogging) {
+      // if we don't use file logging but log into ArangoDB's logfile,
+      // we only want real errors
+      _options.info_log_level = rocksdb::InfoLogLevel::ERROR_LEVEL;
+    }
+  } 
 
-  auto logger = std::make_shared<RocksDBLogger>(_options.info_log_level);
-  _options.info_log = logger;
+  std::shared_ptr<RocksDBLogger> logger;
+ 
+  if (!opts->_useFileLogging) {
+    // if option "--rocksdb.use-file-logging" is set to false, we will use
+    // our own logger that logs to ArangoDB's logfile 
+    logger = std::make_shared<RocksDBLogger>(_options.info_log_level);
+    _options.info_log = logger;
 
-  if (!_debugLogging) {
-    logger->disable();
-  } // if
+    if (!_debugLogging) {
+      logger->disable();
+    } // if
+  }
 
   if (opts->_enableStatistics) {
     _options.statistics = rocksdb::CreateDBStatistics();
@@ -629,7 +639,9 @@ void RocksDBEngine::start() {
   arangodb::rocksdbStartupVersionCheck(_db, dbExisted);
 
   // only enable logger after RocksDB start
-  logger->enable();
+  if (logger != nullptr) {
+    logger->enable();
+  }
 
   if (_syncInterval > 0) {
     _syncThread.reset(

lib/ApplicationFeatures/RocksDBOptionFeature.cpp

@@ -79,7 +79,8 @@ RocksDBOptionFeature::RocksDBOptionFeature(
       _useFSync(rocksDBDefaults.use_fsync),
       _skipCorrupted(false),
       _dynamicLevelBytes(true),
-      _enableStatistics(false) {
+      _enableStatistics(false),
+      _useFileLogging(false) {
   // setting the number of background jobs to
   _maxBackgroundJobs = static_cast<int32_t>(std::max((size_t)2,
                                                      std::min(TRI_numberProcessors(), (size_t)8)));
@@ -261,6 +262,10 @@ void RocksDBOptionFeature::collectOptions(
       "that way RocksDB's compaction is doing sequential instead of random "
       "reads.",
       new UInt64Parameter(&_compactionReadaheadSize));
+  
+  options->addHiddenOption("--rocksdb.use-file-logging",
+                           "use a file-base logger for RocksDB's own logs",
+                           new BooleanParameter(&_useFileLogging));
 
   options->addHiddenOption("--rocksdb.wal-recovery-skip-corrupted",
                            "skip corrupted records in WAL recovery",

lib/ApplicationFeatures/RocksDBOptionFeature.h

@@ -80,6 +80,7 @@ class RocksDBOptionFeature final
   bool _skipCorrupted;
   bool _dynamicLevelBytes;
   bool _enableStatistics;
+  bool _useFileLogging;
 };
 
 }  // namespace arangodb