Add an option to prevent DB::Open() from querying sizes of all sst files (#6353)

Summary:
When paranoid_checks is on, DBImpl::CheckConsistency() iterates over all sst files and calls Env::GetFileSize() for each of them. As far as I could understand, this is pretty arbitrary and doesn't affect correctness - if filesystem doesn't corrupt fsynced files, the file sizes will always match; if it does, it may as well corrupt contents as well as sizes, and rocksdb doesn't check contents on open.

If there are thousands of sst files, getting all their sizes takes a while. If, on top of that, Env is overridden to use some remote storage instead of local filesystem, it can be *really* slow and overload the remote storage service. This PR adds an option to not do GetFileSize(); instead it does GetChildren() for parent directory to check that all the expected sst files are at least present, but doesn't check their sizes.

We can't just disable paranoid_checks instead because paranoid_checks do a few other important things: make the DB read-only on write errors, print error messages on read errors, etc.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6353

Test Plan: ran the added sanity check unit test. Will try it out in a LogDevice test cluster where the GetFileSize() calls are causing a lot of trouble.

Differential Revision: D19656425

Pulled By: al13n321

fbshipit-source-id: c2c421b367633033760d1f56747bad206d1fbf82

HISTORY.md

@@ -7,6 +7,7 @@
 * Fix incorrect results while block-based table uses kHashSearch, together with Prev()/SeekForPrev().
 * Fix a bug that prevents opening a DB after two consecutive crash with TransactionDB, where the first crash recovers from a corrupted WAL with kPointInTimeRecovery but the second cannot.
 * Fixed issue #6316 that can cause a corruption of the MANIFEST file in the middle when writing to it fails due to no disk space.
+* Add DBOptions::skip_checking_sst_file_sizes_on_db_open. It disables potentially expensive checking of all sst file sizes in DB::Open().
 
 ### Public API Change
 * The BlobDB garbage collector now emits the statistics `BLOB_DB_GC_NUM_FILES` (number of blob files obsoleted during GC), `BLOB_DB_GC_NUM_NEW_FILES` (number of new blob files generated during GC), `BLOB_DB_GC_FAILURES` (number of failed GC passes), `BLOB_DB_GC_NUM_KEYS_RELOCATED` (number of blobs relocated during GC), and `BLOB_DB_GC_BYTES_RELOCATED` (total size of blobs relocated during GC). On the other hand, the following statistics, which are not relevant for the new GC implementation, are now deprecated: `BLOB_DB_GC_NUM_KEYS_OVERWRITTEN`, `BLOB_DB_GC_NUM_KEYS_EXPIRED`, `BLOB_DB_GC_BYTES_OVERWRITTEN`, `BLOB_DB_GC_BYTES_EXPIRED`, and `BLOB_DB_GC_MICROS`.

db/c.cc

@@ -2320,6 +2320,11 @@ void rocksdb_options_set_skip_stats_update_on_db_open(rocksdb_options_t* opt,
   opt->rep.skip_stats_update_on_db_open = val;
 }
 
+void rocksdb_options_set_skip_checking_sst_file_sizes_on_db_open(
+    rocksdb_options_t* opt, unsigned char val) {
+  opt->rep.skip_checking_sst_file_sizes_on_db_open = val;
+}
+
 void rocksdb_options_set_num_levels(rocksdb_options_t* opt, int n) {
   opt->rep.num_levels = n;
 }

db/db_impl/db_impl.cc

@@ -3318,6 +3318,44 @@ Status DBImpl::CheckConsistency() {
   TEST_SYNC_POINT("DBImpl::CheckConsistency:AfterGetLiveFilesMetaData");
 
   std::string corruption_messages;
+
+  if (immutable_db_options_.skip_checking_sst_file_sizes_on_db_open) {
+    // Instead of calling GetFileSize() for each expected file, call
+    // GetChildren() for the DB directory and check that all expected files
+    // are listed, without checking their sizes.
+    // Since sst files might be in different directories, do it for each
+    // directory separately.
+    std::map<std::string, std::vector<std::string>> files_by_directory;
+    for (const auto& md : metadata) {
+      // md.name has a leading "/". Remove it.
+      std::string fname = md.name;
+      if (!fname.empty() && fname[0] == '/') {
+        fname = fname.substr(1);
+      }
+      files_by_directory[md.db_path].push_back(fname);
+    }
+    for (const auto& dir_files : files_by_directory) {
+      std::string directory = dir_files.first;
+      std::vector<std::string> existing_files;
+      Status s = env_->GetChildren(directory, &existing_files);
+      if (!s.ok()) {
+        corruption_messages +=
+            "Can't list files in " + directory + ": " + s.ToString() + "\n";
+        continue;
+      }
+      std::sort(existing_files.begin(), existing_files.end());
+
+      for (const std::string& fname : dir_files.second) {
+        if (!std::binary_search(existing_files.begin(), existing_files.end(),
+                                fname) &&
+            !std::binary_search(existing_files.begin(), existing_files.end(),
+                                Rocks2LevelTableFileName(fname))) {
+          corruption_messages +=
+              "Missing sst file " + fname + " in " + directory + "\n";
+        }
+      }
+    }
+  } else {
     for (const auto& md : metadata) {
       // md.name has a leading "/".
       std::string file_path = md.db_path + md.name;
@@ -3339,6 +3377,8 @@ Status DBImpl::CheckConsistency() {
                                ToString(fsize) + "\n";
       }
     }
+  }
+
   if (corruption_messages.size() == 0) {
     return Status::OK();
   } else {

db/db_impl/db_impl_open.cc

@@ -172,6 +172,13 @@ DBOptions SanitizeOptions(const std::string& dbname, const DBOptions& src) {
     result.sst_file_manager = sst_file_manager;
   }
 #endif
+
+  if (!result.paranoid_checks) {
+    result.skip_checking_sst_file_sizes_on_db_open = true;
+    ROCKS_LOG_INFO(result.info_log,
+                   "file size check will be skipped during open.");
+  }
+
   return result;
 }
 

db/db_impl/db_impl_secondary.cc

@@ -468,6 +468,11 @@ Status DBImplSecondary::CheckConsistency() {
   // approach and just proceed.
   TEST_SYNC_POINT_CALLBACK(
       "DBImplSecondary::CheckConsistency:AfterFirstAttempt", &s);
+
+  if (immutable_db_options_.skip_checking_sst_file_sizes_on_db_open) {
+    return Status::OK();
+  }
+
   std::vector<LiveFileMetaData> metadata;
   versions_->GetLiveFilesMetaData(&metadata);
 

db/db_sst_test.cc

@@ -124,6 +124,20 @@ TEST_F(DBSSTTest, SSTsWithLdbSuffixHandling) {
   Destroy(options);
 }
 
+// Check that we don't crash when opening DB with
+// DBOptions::skip_checking_sst_file_sizes_on_db_open = true.
+TEST_F(DBSSTTest, SkipCheckingSSTFileSizesOnDBOpen) {
+  ASSERT_OK(Put("pika", "choo"));
+  ASSERT_OK(Flush());
+
+  // Just open the DB with the option set to true and check that we don't crash.
+  Options options;
+  options.skip_checking_sst_file_sizes_on_db_open = true;
+  Reopen(options);
+
+  ASSERT_EQ("choo", Get("pika"));
+}
+
 #ifndef ROCKSDB_LITE
 TEST_F(DBSSTTest, DontDeleteMovedFile) {
   // This test triggers move compaction and verifies that the file is not

include/rocksdb/c.h

@@ -854,6 +854,9 @@ extern ROCKSDB_LIBRARY_API void rocksdb_options_enable_statistics(
 extern ROCKSDB_LIBRARY_API void
 rocksdb_options_set_skip_stats_update_on_db_open(rocksdb_options_t* opt,
                                                  unsigned char val);
+extern ROCKSDB_LIBRARY_API void
+rocksdb_options_set_skip_checking_sst_file_sizes_on_db_open(
+    rocksdb_options_t* opt, unsigned char val);
 
 /* returns a pointer to a malloc()-ed, null terminated string */
 extern ROCKSDB_LIBRARY_API char* rocksdb_options_statistics_get_string(

include/rocksdb/options.h

@@ -985,6 +985,16 @@ struct DBOptions {
   // Default: false
   bool skip_stats_update_on_db_open = false;
 
+  // If true, then DB::Open() will not fetch and check sizes of all sst files.
+  // This may significantly speed up startup if there are many sst files,
+  // especially when using non-default Env with expensive GetFileSize().
+  // We'll still check that all required sst files exist.
+  // If paranoid_checks is false, this option is ignored, and sst files are
+  // not checked at all.
+  //
+  // Default: false
+  bool skip_checking_sst_file_sizes_on_db_open = false;
+
   // Recovery mode to control the consistency while replaying WAL
   // Default: kPointInTimeRecovery
   WALRecoveryMode wal_recovery_mode = WALRecoveryMode::kPointInTimeRecovery;

java/rocksjni/options.cc

@@ -1738,6 +1738,30 @@ jboolean Java_org_rocksdb_Options_skipStatsUpdateOnDbOpen(
   return static_cast<jboolean>(opt->skip_stats_update_on_db_open);
 }
 
+/*
+ * Class:     org_rocksdb_Options
+ * Method:    setSkipCheckingSstFileSizesOnDbOpen
+ * Signature: (JZ)V
+ */
+void Java_org_rocksdb_Options_setSkipCheckingSstFileSizesOnDbOpen(
+    JNIEnv*, jobject, jlong jhandle,
+    jboolean jskip_checking_sst_file_sizes_on_db_open) {
+  auto* opt = reinterpret_cast<rocksdb::Options*>(jhandle);
+  opt->skip_checking_sst_file_sizes_on_db_open =
+      static_cast<bool>(jskip_checking_sst_file_sizes_on_db_open);
+}
+
+/*
+ * Class:     org_rocksdb_Options
+ * Method:    skipCheckingSstFileSizesOnDbOpen
+ * Signature: (J)Z
+ */
+jboolean Java_org_rocksdb_Options_skipCheckingSstFileSizesOnDbOpen(
+    JNIEnv*, jobject, jlong jhandle) {
+  auto* opt = reinterpret_cast<rocksdb::Options*>(jhandle);
+  return static_cast<jboolean>(opt->skip_checking_sst_file_sizes_on_db_open);
+}
+
 /*
  * Class:     org_rocksdb_Options
  * Method:    setWalRecoveryMode
@@ -6010,6 +6034,30 @@ jboolean Java_org_rocksdb_DBOptions_skipStatsUpdateOnDbOpen(
   return static_cast<jboolean>(opt->skip_stats_update_on_db_open);
 }
 
+/*
+ * Class:     org_rocksdb_DBOptions
+ * Method:    setSkipCheckingSstFileSizesOnDbOpen
+ * Signature: (JZ)V
+ */
+void Java_org_rocksdb_DBOptions_setSkipCheckingSstFileSizesOnDbOpen(
+    JNIEnv*, jobject, jlong jhandle,
+    jboolean jskip_checking_sst_file_sizes_on_db_open) {
+  auto* opt = reinterpret_cast<rocksdb::DBOptions*>(jhandle);
+  opt->skip_checking_sst_file_sizes_on_db_open =
+      static_cast<bool>(jskip_checking_sst_file_sizes_on_db_open);
+}
+
+/*
+ * Class:     org_rocksdb_DBOptions
+ * Method:    skipCheckingSstFileSizesOnDbOpen
+ * Signature: (J)Z
+ */
+jboolean Java_org_rocksdb_DBOptions_skipCheckingSstFileSizesOnDbOpen(
+    JNIEnv*, jobject, jlong jhandle) {
+  auto* opt = reinterpret_cast<rocksdb::DBOptions*>(jhandle);
+  return static_cast<jboolean>(opt->skip_checking_sst_file_sizes_on_db_open);
+}
+
 /*
  * Class:     org_rocksdb_DBOptions
  * Method:    setWalRecoveryMode

options/db_options.cc

@@ -74,6 +74,8 @@ ImmutableDBOptions::ImmutableDBOptions(const DBOptions& options)
       write_thread_max_yield_usec(options.write_thread_max_yield_usec),
       write_thread_slow_yield_usec(options.write_thread_slow_yield_usec),
       skip_stats_update_on_db_open(options.skip_stats_update_on_db_open),
+      skip_checking_sst_file_sizes_on_db_open(
+          options.skip_checking_sst_file_sizes_on_db_open),
       wal_recovery_mode(options.wal_recovery_mode),
       allow_2pc(options.allow_2pc),
       row_cache(options.row_cache),

options/db_options.h

@@ -68,6 +68,7 @@ struct ImmutableDBOptions {
   uint64_t write_thread_max_yield_usec;
   uint64_t write_thread_slow_yield_usec;
   bool skip_stats_update_on_db_open;
+  bool skip_checking_sst_file_sizes_on_db_open;
   WALRecoveryMode wal_recovery_mode;
   bool allow_2pc;
   std::shared_ptr<Cache> row_cache;

options/options_helper.cc

@@ -119,6 +119,8 @@ DBOptions BuildDBOptions(const ImmutableDBOptions& immutable_db_options,
       immutable_db_options.write_thread_slow_yield_usec;
   options.skip_stats_update_on_db_open =
       immutable_db_options.skip_stats_update_on_db_open;
+  options.skip_checking_sst_file_sizes_on_db_open =
+      immutable_db_options.skip_checking_sst_file_sizes_on_db_open;
   options.wal_recovery_mode = immutable_db_options.wal_recovery_mode;
   options.allow_2pc = immutable_db_options.allow_2pc;
   options.row_cache = immutable_db_options.row_cache;
@@ -1473,6 +1475,9 @@ std::unordered_map<std::string, OptionTypeInfo>
         {"skip_stats_update_on_db_open",
          {offsetof(struct DBOptions, skip_stats_update_on_db_open),
           OptionType::kBoolean, OptionVerificationType::kNormal, false, 0}},
+        {"skip_checking_sst_file_sizes_on_db_open",
+         {offsetof(struct DBOptions, skip_checking_sst_file_sizes_on_db_open),
+          OptionType::kBoolean, OptionVerificationType::kNormal, false, 0}},
         {"new_table_reader_for_compaction_inputs",
          {offsetof(struct DBOptions, new_table_reader_for_compaction_inputs),
           OptionType::kBoolean, OptionVerificationType::kNormal, false, 0}},

options/options_settable_test.cc

@@ -248,6 +248,7 @@ TEST_F(OptionsSettableTest, DBOptionsAllFieldsSettable) {
                              "new_table_reader_for_compaction_inputs=false;"
                              "keep_log_file_num=4890;"
                              "skip_stats_update_on_db_open=false;"
+                             "skip_checking_sst_file_sizes_on_db_open=false;"
                              "max_manifest_file_size=4295009941;"
                              "db_log_dir=path/to/db_log_dir;"
                              "skip_log_error_on_recovery=true;"

test_util/testutil.cc

@@ -265,6 +265,7 @@ void RandomInitDBOptions(DBOptions* db_opt, Random* rnd) {
   db_opt->paranoid_checks = rnd->Uniform(2);
   db_opt->skip_log_error_on_recovery = rnd->Uniform(2);
   db_opt->skip_stats_update_on_db_open = rnd->Uniform(2);
+  db_opt->skip_checking_sst_file_sizes_on_db_open = rnd->Uniform(2);
   db_opt->use_adaptive_mutex = rnd->Uniform(2);
   db_opt->use_fsync = rnd->Uniform(2);
   db_opt->recycle_log_file_num = rnd->Uniform(2);