Encode min_log_number_to_keep and delete_wals_before in one version edit (#9766)

Summary:
min_log_number_to_keep denotes that the WALs whose numbers are below
this value **will** be deleted by RocksDB.
delete_wals_before will be used by RocksDB if
track_and_verify_wals_in_manifest is set to true. During recovery,
RocksDB uses the info encoded in delete_wals_before to reconstruct its
knowledge about what WALs to expect existing.
If these two tags are not encoded in the same VersionEdit, then it's
possible for min_log_number_to_keep=100 to exist, but
delete_wals_before=100 to be lost due to power failure. Subsequent
recovery will delete 99.log. If the db crashes again, the following
recovery will expect to see 99.log since there is no
delete_wals_before=100 in the MANIFEST, but the WAL is already deleted.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9766

Test Plan:
First of all, make check.
Second, format compatibility.
SHORT_TEST=1 ./tools/check_format_compatible.sh

Reviewed By: ltamasi

Differential Revision: D35203623

Pulled By: riversand963

fbshipit-source-id: 45623fc4b4b50d299d5e0f9559a3a4c5e9522c8f

HISTORY.md

@@ -6,6 +6,7 @@
 * Fixed a heap use-after-free race with DropColumnFamily.
 * Fixed a bug that `rocksdb.read.block.compaction.micros` cannot track compaction stats (#9722).
 * Fixed `file_type`, `relative_filename` and `directory` fields returned by `GetLiveFilesMetaData()`, which were added in inheriting from `FileStorageInfo`.
+* Fixed a bug affecting `track_and_verify_wals_in_manifest`. Without the fix, application may see "open error: Corruption: Missing WAL with log number" while trying to open the db. The corruption is a false alarm but prevents DB open (#9766).
 
 ### New Features
 * For db_bench when --seed=0 or --seed is not set then it uses the current time as the seed value. Previously it used the value 1000.

db/db_flush_test.cc

@@ -2271,7 +2271,7 @@ TEST_P(DBAtomicFlushTest, ManualFlushUnder2PC) {
 
   // The recovered min log number with prepared data should be non-zero.
   // In 2pc mode, MinLogNumberToKeep returns the
-  // VersionSet::min_log_number_to_keep_2pc recovered from MANIFEST, if it's 0,
+  // VersionSet::min_log_number_to_keep recovered from MANIFEST, if it's 0,
   // it means atomic flush didn't write the min_log_number_to_keep to MANIFEST.
   cfs.push_back(kDefaultColumnFamilyName);
   ASSERT_OK(TryReopenWithColumnFamilies(cfs, options));

db/memtable_list.cc

@@ -505,21 +505,20 @@ Status MemTableList::TryInstallMemtableFlushResults(
         min_wal_number_to_keep =
             PrecomputeMinLogNumberToKeepNon2PC(vset, *cfd, edit_list);
       }
-      edit_list.back()->SetMinLogNumberToKeep(min_wal_number_to_keep);
 
-      std::unique_ptr<VersionEdit> wal_deletion;
+      VersionEdit wal_deletion;
+      wal_deletion.SetMinLogNumberToKeep(min_wal_number_to_keep);
       if (vset->db_options()->track_and_verify_wals_in_manifest) {
         if (min_wal_number_to_keep >
             vset->GetWalSet().GetMinWalNumberToKeep()) {
-          wal_deletion.reset(new VersionEdit);
-          wal_deletion->DeleteWalsBefore(min_wal_number_to_keep);
-          edit_list.push_back(wal_deletion.get());
+          wal_deletion.DeleteWalsBefore(min_wal_number_to_keep);
         }
         TEST_SYNC_POINT_CALLBACK(
             "MemTableList::TryInstallMemtableFlushResults:"
             "AfterComputeMinWalToKeep",
             nullptr);
       }
+      edit_list.push_back(&wal_deletion);
 
       const auto manifest_write_cb = [this, cfd, batch_count, log_buffer,
                                       to_delete, mu](const Status& status) {
@@ -805,17 +804,15 @@ Status InstallMemtableAtomicFlushResults(
     min_wal_number_to_keep =
         PrecomputeMinLogNumberToKeepNon2PC(vset, cfds, edit_lists);
   }
-  edit_lists.back().back()->SetMinLogNumberToKeep(min_wal_number_to_keep);
 
-  std::unique_ptr<VersionEdit> wal_deletion;
-  if (vset->db_options()->track_and_verify_wals_in_manifest) {
-    if (min_wal_number_to_keep > vset->GetWalSet().GetMinWalNumberToKeep()) {
-      wal_deletion.reset(new VersionEdit);
-      wal_deletion->DeleteWalsBefore(min_wal_number_to_keep);
-      edit_lists.back().push_back(wal_deletion.get());
-      ++num_entries;
-    }
+  VersionEdit wal_deletion;
+  wal_deletion.SetMinLogNumberToKeep(min_wal_number_to_keep);
+  if (vset->db_options()->track_and_verify_wals_in_manifest &&
+      min_wal_number_to_keep > vset->GetWalSet().GetMinWalNumberToKeep()) {
+    wal_deletion.DeleteWalsBefore(min_wal_number_to_keep);
   }
+  edit_lists.back().push_back(&wal_deletion);
+  ++num_entries;
 
   // Mark the version edits as an atomic group if the number of version edits
   // exceeds 1.

db/version_edit.cc

@@ -120,6 +120,9 @@ bool VersionEdit::EncodeTo(std::string* dst) const {
   if (has_max_column_family_) {
     PutVarint32Varint32(dst, kMaxColumnFamily, max_column_family_);
   }
+  if (has_min_log_number_to_keep_) {
+    PutVarint32Varint64(dst, kMinLogNumberToKeep, min_log_number_to_keep_);
+  }
   if (has_last_sequence_) {
     PutVarint32Varint64(dst, kLastSequence, last_sequence_);
   }