Sync blob files before closing them (#7160)

Summary:
BlobDB currently syncs each blob file periodically after writing a certain amount of
data (as specified by the configuration option `BlobDBOptions::bytes_per_sync`)
and all open blob files when the base DB's memtables are flushed. With the patch,
in addition to the above, blob files are also synced right before being closed, after
the footer has been written. This will be beneficial for the new integrated blob file
write path as well.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7160

Test Plan: `make check`

Reviewed By: riversand963

Differential Revision: D22672646

Pulled By: ltamasi

fbshipit-source-id: 62b34263543a7e74abcbb7adf011daa1e699998f

db/blob/blob_log_writer.cc

@@ -13,6 +13,7 @@
 #include "file/writable_file_writer.h"
 #include "monitoring/statistics.h"
 #include "rocksdb/env.h"
+#include "test_util/sync_point.h"
 #include "util/coding.h"
 #include "util/stop_watch.h"
 
@@ -30,6 +31,8 @@ BlobLogWriter::BlobLogWriter(std::unique_ptr<WritableFileWriter>&& dest,
       last_elem_type_(kEtNone) {}
 
 Status BlobLogWriter::Sync() {
+  TEST_SYNC_POINT("BlobLogWriter::Sync");
+
   StopWatch sync_sw(env_, statistics_, BLOB_DB_BLOB_FILE_SYNC_MICROS);
   Status s = dest_->Sync(use_fsync_);
   RecordTick(statistics_, BLOB_DB_BLOB_FILE_SYNCED);
@@ -63,7 +66,10 @@ Status BlobLogWriter::AppendFooter(BlobLogFooter& footer) {
   Status s = dest_->Append(Slice(str));
   if (s.ok()) {
     block_offset_ += str.size();
-    s = dest_->Close();
+    s = Sync();
+    if (s.ok()) {
+      s = dest_->Close();
+    }
     dest_.reset();
   }
 

utilities/blob_db/blob_db_test.cc

@@ -2127,6 +2127,57 @@ TEST_F(BlobDBTest, ShutdownWait) {
   SyncPoint::GetInstance()->DisableProcessing();
 }
 
+TEST_F(BlobDBTest, SyncBlobFileBeforeClose) {
+  Options options;
+  options.statistics = CreateDBStatistics();
+
+  BlobDBOptions blob_options;
+  blob_options.min_blob_size = 0;
+  blob_options.bytes_per_sync = 1 << 20;
+  blob_options.disable_background_tasks = true;
+
+  Open(blob_options, options);
+
+  Put("foo", "bar");
+
+  auto blob_files = blob_db_impl()->TEST_GetBlobFiles();
+  ASSERT_EQ(blob_files.size(), 1);
+
+  ASSERT_OK(blob_db_impl()->TEST_CloseBlobFile(blob_files[0]));
+  ASSERT_EQ(options.statistics->getTickerCount(BLOB_DB_BLOB_FILE_SYNCED), 1);
+}
+
+TEST_F(BlobDBTest, SyncBlobFileBeforeCloseIOError) {
+  Options options;
+  options.env = fault_injection_env_.get();
+
+  BlobDBOptions blob_options;
+  blob_options.min_blob_size = 0;
+  blob_options.bytes_per_sync = 1 << 20;
+  blob_options.disable_background_tasks = true;
+
+  Open(blob_options, options);
+
+  Put("foo", "bar");
+
+  auto blob_files = blob_db_impl()->TEST_GetBlobFiles();
+  ASSERT_EQ(blob_files.size(), 1);
+
+  SyncPoint::GetInstance()->SetCallBack(
+      "BlobLogWriter::Sync", [this](void * /* arg */) {
+        fault_injection_env_->SetFilesystemActive(false, Status::IOError());
+      });
+  SyncPoint::GetInstance()->EnableProcessing();
+
+  const Status s = blob_db_impl()->TEST_CloseBlobFile(blob_files[0]);
+
+  fault_injection_env_->SetFilesystemActive(true);
+  SyncPoint::GetInstance()->DisableProcessing();
+  SyncPoint::GetInstance()->ClearAllCallBacks();
+
+  ASSERT_TRUE(s.IsIOError());
+}
+
 }  //  namespace blob_db
 }  // namespace ROCKSDB_NAMESPACE