Introduce a new method Env->Fsync() that issues fsync (instead of fdatasync).

Summary:
Introduce a new method Env->Fsync() that issues fsync (instead of fdatasync).
This is needed for data durability when running on ext3 filesystems.
Added options to the benchmark db_bench to generate performance numbers
with either fsync or fdatasync enabled.

Cleaned up Makefile to build leveldb_shell only when building the thrift
leveldb server.

Test Plan: build and run benchmark

Reviewers: heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D4911

Makefile

@@ -58,7 +58,6 @@ TESTS = \
 
 TOOLS = \
 	manifest_dump \
-	leveldb_shell \
         sst_dump
 
 PROGRAMS = db_bench $(TESTS) $(TOOLS)
@@ -171,7 +170,7 @@ $(MEMENVLIBRARY) : $(MEMENVOBJECTS)
 memenv_test : helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS)
 	$(CXX) helpers/memenv/memenv_test.o $(MEMENVLIBRARY) $(LIBRARY) $(TESTHARNESS) -o $@ $(LDFLAGS)
 
-leveldb_server: thrift/server.o $(LIBRARY) 
+leveldb_server: thrift/server.o leveldb_shell $(LIBRARY) 
 	$(CXX) thrift/server.o $(LIBRARY) $(EXEC_LDFLAGS) -o $@  $(LDFLAGS) 
 
 leveldb_server_test: thrift/test/simpletest.o $(LIBRARY) 
@@ -196,9 +195,6 @@ sst_dump: tools/sst_dump.o $(LIBOBJECTS)
 $(VERSIONFILE):	build_detect_version
 	$(shell ./build_detect_platform build_config.mk)
 
-filelock_test: util/filelock_test.o $(LIBOBJECTS) $(TESTHARNESS)
-	$(CXX) util/filelock_test.o $(LIBOBJECTS) $(TESTHARNESS) -o $@ $(LDFLAGS)
-
 # recreate the version file with the latest git revision
 $(VERSIONFILE):	build_detect_version
 	$(shell ./build_detect_platform build_config.mk)

db/builder.cc

@@ -54,8 +54,12 @@ Status BuildTable(const std::string& dbname,
 
     // Finish and check for file errors
     if (s.ok() && !options.disableDataSync) {
+      if (options.use_fsync) {
+        s = file->Fsync();
+      } else {
         s = file->Sync();
       }
+    }
     if (s.ok()) {
       s = file->Close();
     }

db/db_bench.cc

@@ -128,6 +128,9 @@ static bool FLAGS_sync = false;
 // If true, do not wait until data is synced to disk.
 static bool FLAGS_disable_data_sync = false;
 
+// If true, issue fsync instead of fdatasync
+static bool FLAGS_use_fsync = false;
+
 // If true, do not write WAL for write.
 static bool FLAGS_disable_wal = false;
 
@@ -774,6 +777,7 @@ class Benchmark {
     options.statistics = dbstats;
     options.env = FLAGS_env;
     options.disableDataSync = FLAGS_disable_data_sync;
+    options.use_fsync = FLAGS_use_fsync;
     options.target_file_size_base = FLAGS_target_file_size_base;
     options.target_file_size_multiplier = FLAGS_target_file_size_multiplier;
     options.max_bytes_for_level_base = FLAGS_max_bytes_for_level_base;
@@ -1070,6 +1074,9 @@ int main(int argc, char** argv) {
     } else if (sscanf(argv[i], "--disable_data_sync=%d%c", &n, &junk) == 1 &&
         (n == 0 || n == 1)) {
       FLAGS_disable_data_sync = n;
+    } else if (sscanf(argv[i], "--use_fsync=%d%c", &n, &junk) == 1 &&
+        (n == 0 || n == 1)) {
+      FLAGS_use_fsync = n;
     } else if (sscanf(argv[i], "--disable_wal=%d%c", &n, &junk) == 1 &&
         (n == 0 || n == 1)) {
       FLAGS_disable_wal = n;

db/db_impl.cc

@@ -858,8 +858,12 @@ Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
 
   // Finish and check for file errors
   if (s.ok() && !options_.disableDataSync) {
+    if (options_.use_fsync) {
+      s = compact->outfile->Fsync();
+    } else {
       s = compact->outfile->Sync();
     }
+  }
   if (s.ok()) {
     s = compact->outfile->Close();
   }
@@ -1235,9 +1239,13 @@ Status DBImpl::Write(const WriteOptions& options, WriteBatch* my_batch) {
       if (!options.disableWAL) {
         status = log_->AddRecord(WriteBatchInternal::Contents(updates));
         if (status.ok() && options.sync) {
+          if (options_.use_fsync) {
+            status = logfile_->Fsync();
+          } else {
             status = logfile_->Sync();
           }
         }
+      }
       if (status.ok()) {
         status = WriteBatchInternal::InsertInto(updates, mem_);
       }

db/version_set.cc

@@ -793,9 +793,13 @@ Status VersionSet::LogAndApply(VersionEdit* edit, port::Mutex* mu) {
       edit->EncodeTo(&record);
       s = descriptor_log_->AddRecord(record);
       if (s.ok()) {
+        if (options_->use_fsync) {
+          s = descriptor_file_->Fsync();
+        } else {
           s = descriptor_file_->Sync();
         }
       }
+    }
 
     // If we just created a new descriptor file, install it by writing a
     // new CURRENT file that points to it.

include/leveldb/env.h

@@ -217,7 +217,17 @@ class WritableFile {
   virtual Status Append(const Slice& data) = 0;
   virtual Status Close() = 0;
   virtual Status Flush() = 0;
-  virtual Status Sync() = 0;
+  virtual Status Sync() = 0; // sync data
+
+  /* 
+   * Sync data and/or metadata as well.
+   * By default, sync only metadata. 
+   * Override this method for environments where we need to sync
+   * metadata as well.
+   */
+  virtual Status Fsync() {
+    return Sync();
+  }
 
  private:
   // No copying allowed

include/leveldb/options.h

@@ -198,6 +198,13 @@ struct Options {
   // Default: false
   bool disableDataSync;
 
+  // If true, then every store to stable storage will issue a fsync.
+  // If false, then every store to stable storage will issue a fdatasync.
+  // This parameter should be set to true while storing data to
+  // filesystem like ext3 which can lose files after a reboot.
+  // Default: false
+  bool use_fsync;
+
   // This number controls how often a new scribe log about
   // db deploy stats is written out.
   // -1 indicates no logging at all.

util/env_posix.cc

@@ -294,6 +294,22 @@ class PosixMmapFile : public WritableFile {
 
     return s;
   }
+
+  /**
+   * Flush data as well as metadata to stable storage.
+   */
+  virtual Status Fsync() {
+    if (pending_sync_) {
+      // Some unmapped data was not synced
+      pending_sync_ = false;
+      if (fsync(fd_) < 0) {
+        return IOError(filename_, errno);
+      }
+    }
+    // This invocation to Sync will not issue the call to
+    // fdatasync because pending_sync_ has already been cleared.
+    return Sync();
+  }
 };
 
 static int LockOrUnlock(const std::string& fname, int fd, bool lock) {

util/options.cc

@@ -37,6 +37,7 @@ Options::Options()
       filter_policy(NULL),
       statistics(NULL),
       disableDataSync(false),
+      use_fsync(false),
       db_stats_log_interval(1800) {
 }
 
@@ -56,7 +57,33 @@ Options::Dump(
     Log(log,"            Options.block_size: %zd", block_size);
     Log(log,"Options.block_restart_interval: %d", block_restart_interval);
     Log(log,"           Options.compression: %d", compression);
-    Log(log,"         Options.filter_policy: %s", filter_policy == NULL ? "NULL" : filter_policy->Name());
+    Log(log,"         Options.filter_policy: %s",
+        filter_policy == NULL ? "NULL" : filter_policy->Name());
+    Log(log,"            Options.num_levels: %d", num_levels);
+    Log(log,"       Options.disableDataSync: %d", disableDataSync);
+    Log(log,"             Options.use_fsync: %d", use_fsync);
+    Log(log," Options.db_stats_log_interval: %d", 
+        db_stats_log_interval);
+    Log(log,"     Options.level0_file_num_compaction_trigger: %d",
+        level0_file_num_compaction_trigger);
+    Log(log,"         Options.level0_slowdown_writes_trigger: %d",
+        level0_slowdown_writes_trigger);
+    Log(log,"             Options.level0_stop_writes_trigger: %d",
+        level0_stop_writes_trigger);
+    Log(log,"               Options.max_mem_compaction_level: %d",
+        max_mem_compaction_level);
+    Log(log,"                  Options.target_file_size_base: %d",
+        target_file_size_base);
+    Log(log,"            Options.target_file_size_multiplier: %d",
+        target_file_size_multiplier);
+    Log(log,"               Options.max_bytes_for_level_base: %d",
+        max_bytes_for_level_base);
+    Log(log,"         Options.max_bytes_for_level_multiplier: %d",
+        max_bytes_for_level_multiplier);
+    Log(log,"             Options.expanded_compaction_factor: %d",
+        expanded_compaction_factor);
+    Log(log,"         Options.max_grandparent_overlap_factor: %d",
+        max_grandparent_overlap_factor);
 
 }   // Options::Dump