Blob storage helper methods

Summary:
Split out interfaces needed for blob storage from #1560, including
* CompactionEventListener and OnFlushBegin listener interfaces.
* Blob filename support.
Closes https://github.com/facebook/rocksdb/pull/2169

Differential Revision: D4905463

Pulled By: yiwu-arbug

fbshipit-source-id: 564e73448f1b7a367e5e46216a521e57ea9011b5

HISTORY.md

@@ -9,6 +9,7 @@
     * PinnableSlice releases the pinned resources that contain the value when it is destructed or when ::Reset() is called on it.
     * The old API that accepts std::string, although discouraged, is still supported.
 * Replace Options::use_direct_writes with Options::use_direct_io_for_flush_and_compaction. Read Direct IO wiki for details.
+* Added CompactionEventListener and EventListener::OnFlushBegin interfaces.
 
 ### New Features
 * Memtable flush can be avoided during checkpoint creation if total log file size is smaller than a threshold specified by the user.

db/compaction_iterator.cc

@@ -10,12 +10,34 @@
 
 namespace rocksdb {
 
+CompactionEventListener::CompactionListenerValueType fromInternalValueType(
+    ValueType vt) {
+  switch (vt) {
+    case kTypeDeletion:
+      return CompactionEventListener::CompactionListenerValueType::kDelete;
+    case kTypeValue:
+      return CompactionEventListener::CompactionListenerValueType::kValue;
+    case kTypeMerge:
+      return CompactionEventListener::CompactionListenerValueType::
+          kMergeOperand;
+    case kTypeSingleDeletion:
+      return CompactionEventListener::CompactionListenerValueType::
+          kSingleDelete;
+    case kTypeRangeDeletion:
+      return CompactionEventListener::CompactionListenerValueType::kRangeDelete;
+    default:
+      assert(false);
+      return CompactionEventListener::CompactionListenerValueType::kInvalid;
+  }
+}
+
 CompactionIterator::CompactionIterator(
     InternalIterator* input, const Comparator* cmp, MergeHelper* merge_helper,
     SequenceNumber last_sequence, std::vector<SequenceNumber>* snapshots,
     SequenceNumber earliest_write_conflict_snapshot, Env* env,
     bool expect_valid_internal_key, RangeDelAggregator* range_del_agg,
     const Compaction* compaction, const CompactionFilter* compaction_filter,
+    CompactionEventListener* compaction_listener,
     const std::atomic<bool>* shutting_down)
     : CompactionIterator(
           input, cmp, merge_helper, last_sequence, snapshots,
@@ -23,7 +45,7 @@ CompactionIterator::CompactionIterator(
           range_del_agg,
           std::unique_ptr<CompactionProxy>(
               compaction ? new CompactionProxy(compaction) : nullptr),
-          compaction_filter, shutting_down) {}
+          compaction_filter, compaction_listener, shutting_down) {}
 
 CompactionIterator::CompactionIterator(
     InternalIterator* input, const Comparator* cmp, MergeHelper* merge_helper,
@@ -32,6 +54,7 @@ CompactionIterator::CompactionIterator(
     bool expect_valid_internal_key, RangeDelAggregator* range_del_agg,
     std::unique_ptr<CompactionProxy> compaction,
     const CompactionFilter* compaction_filter,
+    CompactionEventListener* compaction_listener,
     const std::atomic<bool>* shutting_down)
     : input_(input),
       cmp_(cmp),
@@ -43,7 +66,9 @@ CompactionIterator::CompactionIterator(
       range_del_agg_(range_del_agg),
       compaction_(std::move(compaction)),
       compaction_filter_(compaction_filter),
+      compaction_listener_(compaction_listener),
       shutting_down_(shutting_down),
+      ignore_snapshots_(false),
       merge_out_iter_(merge_helper_) {
   assert(compaction_filter_ == nullptr || compaction_ != nullptr);
   bottommost_level_ =
@@ -62,8 +87,8 @@ CompactionIterator::CompactionIterator(
     earliest_snapshot_ = snapshots_->at(0);
     latest_snapshot_ = snapshots_->back();
   }
-  if (compaction_filter_ != nullptr && compaction_filter_->IgnoreSnapshots()) {
-    ignore_snapshots_ = true;
+  if (compaction_filter_ != nullptr) {
+    if (compaction_filter_->IgnoreSnapshots()) ignore_snapshots_ = true;
   } else {
     ignore_snapshots_ = false;
   }
@@ -188,6 +213,12 @@ void CompactionIterator::NextFromInput() {
       current_user_key_sequence_ = kMaxSequenceNumber;
       current_user_key_snapshot_ = 0;
 
+      if (compaction_listener_) {
+        compaction_listener_->OnCompaction(compaction_->level(), ikey_.user_key,
+                                           fromInternalValueType(ikey_.type),
+                                           value_, ikey_.sequence, true);
+      }
+
       // apply the compaction filter to the first occurrence of the user key
       if (compaction_filter_ != nullptr && ikey_.type == kTypeValue &&
           (visible_at_tip_ || ikey_.sequence > latest_snapshot_ ||
@@ -235,6 +266,12 @@ void CompactionIterator::NextFromInput() {
         }
       }
     } else {
+      if (compaction_listener_) {
+        compaction_listener_->OnCompaction(compaction_->level(), ikey_.user_key,
+                                           fromInternalValueType(ikey_.type),
+                                           value_, ikey_.sequence, false);
+      }
+
       // Update the current key to reflect the new sequence number/type without
       // copying the user key.
       // TODO(rven): Compaction filter does not process keys in this path
@@ -394,7 +431,7 @@ void CompactionIterator::NextFromInput() {
       // is the same as the visibility of a previous instance of the
       // same key, then this kv is not visible in any snapshot.
       // Hidden by an newer entry for same user key
-      // TODO: why not > ?
+      // TODO(noetzli): why not > ?
       //
       // Note: Dropping this key will not affect TransactionDB write-conflict
       // checking since there has already been a record returned for this key

db/compaction_iterator.h

@@ -20,6 +20,8 @@
 
 namespace rocksdb {
 
+class CompactionEventListener;
+
 class CompactionIterator {
  public:
   // A wrapper around Compaction. Has a much smaller interface, only what
@@ -60,6 +62,7 @@ class CompactionIterator {
                      RangeDelAggregator* range_del_agg,
                      const Compaction* compaction = nullptr,
                      const CompactionFilter* compaction_filter = nullptr,
+                     CompactionEventListener* compaction_listener = nullptr,
                      const std::atomic<bool>* shutting_down = nullptr);
 
   // Constructor with custom CompactionProxy, used for tests.
@@ -71,6 +74,7 @@ class CompactionIterator {
                      RangeDelAggregator* range_del_agg,
                      std::unique_ptr<CompactionProxy> compaction,
                      const CompactionFilter* compaction_filter = nullptr,
+                     CompactionEventListener* compaction_listener = nullptr,
                      const std::atomic<bool>* shutting_down = nullptr);
 
   ~CompactionIterator();
@@ -124,6 +128,7 @@ class CompactionIterator {
   RangeDelAggregator* range_del_agg_;
   std::unique_ptr<CompactionProxy> compaction_;
   const CompactionFilter* compaction_filter_;
+  CompactionEventListener* compaction_listener_;
   const std::atomic<bool>* shutting_down_;
   bool bottommost_level_;
   bool valid_ = false;

db/compaction_iterator_test.cc

@@ -189,7 +189,7 @@ class CompactionIteratorTest : public testing::Test {
     c_iter_.reset(new CompactionIterator(
         iter_.get(), cmp_, merge_helper_.get(), last_sequence, &snapshots_,
         kMaxSequenceNumber, Env::Default(), false, range_del_agg_.get(),
-        std::move(compaction), filter, &shutting_down_));
+        std::move(compaction), filter, nullptr, &shutting_down_));
   }
 
   void AddSnapshot(SequenceNumber snapshot) { snapshots_.push_back(snapshot); }

db/compaction_job.cc

@@ -739,12 +739,21 @@ void CompactionJob::ProcessKeyValueCompaction(SubcompactionState* sub_compact) {
     input->SeekToFirst();
   }
 
+  // we allow only 1 compaction event listener. Used by blob storage
+  CompactionEventListener* comp_event_listener = nullptr;
+  for (auto& celitr : cfd->ioptions()->listeners) {
+    comp_event_listener = celitr->GetCompactionEventListener();
+    if (comp_event_listener != nullptr) {
+      break;
+    }
+  }
+
   Status status;
   sub_compact->c_iter.reset(new CompactionIterator(
       input.get(), cfd->user_comparator(), &merge, versions_->LastSequence(),
       &existing_snapshots_, earliest_write_conflict_snapshot_, env_, false,
       range_del_agg.get(), sub_compact->compaction, compaction_filter,
-      shutting_down_));
+      comp_event_listener, shutting_down_));
   auto c_iter = sub_compact->c_iter.get();
   c_iter->SeekToFirst();
   if (c_iter->Valid() &&

db/db_impl.h

@@ -557,6 +557,10 @@ class DBImpl : public DB {
   Status RenameTempFileToOptionsFile(const std::string& file_name);
   Status DeleteObsoleteOptionsFiles();
 
+  void NotifyOnFlushBegin(ColumnFamilyData* cfd, FileMetaData* file_meta,
+                          const MutableCFOptions& mutable_cf_options,
+                          int job_id, TableProperties prop);
+
   void NotifyOnFlushCompleted(ColumnFamilyData* cfd, FileMetaData* file_meta,
                               const MutableCFOptions& mutable_cf_options,
                               int job_id, TableProperties prop);
@@ -1095,13 +1099,6 @@ class DBImpl : public DB {
   DBImpl(const DBImpl&);
   void operator=(const DBImpl&);
 
-  // Return the earliest snapshot where seqno is visible.
-  // Store the snapshot right before that, if any, in prev_snapshot
-  inline SequenceNumber findEarliestVisibleSnapshot(
-    SequenceNumber in,
-    std::vector<SequenceNumber>& snapshots,
-    SequenceNumber* prev_snapshot);
-
   // Background threads call this function, which is just a wrapper around
   // the InstallSuperVersion() function. Background threads carry
   // job_context which can have new_superversion already

db/db_impl_compaction_flush.cc

@@ -90,6 +90,12 @@ Status DBImpl::FlushMemTableToOutputFile(
 
   flush_job.PickMemTable();
 
+#ifndef ROCKSDB_LITE
+  // may temporarily unlock and lock the mutex.
+  NotifyOnFlushBegin(cfd, &file_meta, mutable_cf_options, job_context->job_id,
+                     flush_job.GetTableProperties());
+#endif  // ROCKSDB_LITE
+
   Status s;
   if (logfile_number_ > 0 &&
       versions_->GetColumnFamilySet()->NumberOfColumnFamilies() > 0) {
@@ -156,6 +162,49 @@ Status DBImpl::FlushMemTableToOutputFile(
   return s;
 }
 
+void DBImpl::NotifyOnFlushBegin(ColumnFamilyData* cfd, FileMetaData* file_meta,
+                                const MutableCFOptions& mutable_cf_options,
+                                int job_id, TableProperties prop) {
+#ifndef ROCKSDB_LITE
+  if (immutable_db_options_.listeners.size() == 0U) {
+    return;
+  }
+  mutex_.AssertHeld();
+  if (shutting_down_.load(std::memory_order_acquire)) {
+    return;
+  }
+  bool triggered_writes_slowdown =
+      (cfd->current()->storage_info()->NumLevelFiles(0) >=
+       mutable_cf_options.level0_slowdown_writes_trigger);
+  bool triggered_writes_stop =
+      (cfd->current()->storage_info()->NumLevelFiles(0) >=
+       mutable_cf_options.level0_stop_writes_trigger);
+  // release lock while notifying events
+  mutex_.Unlock();
+  {
+    FlushJobInfo info;
+    info.cf_name = cfd->GetName();
+    // TODO(yhchiang): make db_paths dynamic in case flush does not
+    //                 go to L0 in the future.
+    info.file_path = MakeTableFileName(immutable_db_options_.db_paths[0].path,
+                                       file_meta->fd.GetNumber());
+    info.thread_id = env_->GetThreadID();
+    info.job_id = job_id;
+    info.triggered_writes_slowdown = triggered_writes_slowdown;
+    info.triggered_writes_stop = triggered_writes_stop;
+    info.smallest_seqno = file_meta->smallest_seqno;
+    info.largest_seqno = file_meta->largest_seqno;
+    info.table_properties = prop;
+    for (auto listener : immutable_db_options_.listeners) {
+      listener->OnFlushBegin(this, info);
+    }
+  }
+  mutex_.Lock();
+// no need to signal bg_cv_ as it will be signaled at the end of the
+// flush process.
+#endif  // ROCKSDB_LITE
+}
+
 void DBImpl::NotifyOnFlushCompleted(ColumnFamilyData* cfd,
                                     FileMetaData* file_meta,
                                     const MutableCFOptions& mutable_cf_options,

db/db_impl_files.cc

@@ -444,6 +444,7 @@ void DBImpl::PurgeObsoleteFiles(const JobContext& state, bool schedule_only) {
       case kIdentityFile:
       case kMetaDatabase:
       case kOptionsFile:
+      case kBlobFile:
         keep = true;
         break;
     }

db/log_format.h

@@ -34,8 +34,8 @@ static const int kMaxRecordType = kRecyclableLastType;
 
 static const unsigned int kBlockSize = 32768;
 
-// Header is checksum (4 bytes), type (1 byte), length (2 bytes).
-static const int kHeaderSize = 4 + 1 + 2;
+// Header is checksum (4 bytes), length (2 bytes), type (1 byte)
+static const int kHeaderSize = 4 + 2 + 1;
 
 // Recyclable header is checksum (4 bytes), type (1 byte), log number
 // (4 bytes), length (2 bytes).

db/memtable.cc

@@ -725,8 +725,8 @@ void MemTable::Update(SequenceNumber seq,
 
         // Update value, if new value size  <= previous value size
         if (new_size <= prev_size) {
-          char* p = EncodeVarint32(const_cast<char*>(key_ptr) + key_length,
-                                   new_size);
+          char* p =
+              EncodeVarint32(const_cast<char*>(key_ptr) + key_length, new_size);
           WriteLock wl(GetLock(lkey.user_key()));
           memcpy(p, value.data(), value.size());
           assert((unsigned)((p + value.size()) - entry) ==

include/rocksdb/env.h

@@ -163,6 +163,20 @@ class Env {
                                  unique_ptr<WritableFile>* result,
                                  const EnvOptions& options) = 0;
 
+  // Create an object that writes to a new file with the specified
+  // name.  Deletes any existing file with the same name and creates a
+  // new file.  On success, stores a pointer to the new file in
+  // *result and returns OK.  On failure stores nullptr in *result and
+  // returns non-OK.
+  //
+  // The returned file will only be accessed by one thread at a time.
+  virtual Status ReopenWritableFile(const std::string& fname,
+                                    unique_ptr<WritableFile>* result,
+                                    const EnvOptions& options) {
+    Status s;
+    return s;
+  }
+
   // Reuse an existing file by renaming it and opening it as writable.
   virtual Status ReuseWritableFile(const std::string& fname,
                                    const std::string& old_fname,
@@ -454,6 +468,8 @@ class SequentialFile {
   // aligned buffer for Direct I/O
   virtual size_t GetRequiredBufferAlignment() const { return kDefaultPageSize; }
 
+  virtual void Rewind() {}
+
   // Remove any kind of caching of data from the offset to offset+length
   // of this file. If the length is 0, then it refers to the end of file.
   // If the system is not caching the file contents, then this is a noop.
@@ -918,6 +934,11 @@ class EnvWrapper : public Env {
                          const EnvOptions& options) override {
     return target_->NewWritableFile(f, r, options);
   }
+  Status ReopenWritableFile(const std::string& fname,
+                            unique_ptr<WritableFile>* result,
+                            const EnvOptions& options) override {
+    return target_->ReopenWritableFile(fname, result, options);
+  }
   Status ReuseWritableFile(const std::string& fname,
                            const std::string& old_fname,
                            unique_ptr<WritableFile>* r,

include/rocksdb/listener.h

@@ -183,6 +183,28 @@ struct ExternalFileIngestionInfo {
   TableProperties table_properties;
 };
 
+// A call-back function to RocksDB which will be called when the compaction
+// iterator is compacting values. It is mean to be returned from
+// EventListner::GetCompactionEventListner() at the beginning of compaction
+// job.
+class CompactionEventListener {
+ public:
+  enum CompactionListenerValueType {
+    kValue,
+    kMergeOperand,
+    kDelete,
+    kSingleDelete,
+    kRangeDelete,
+    kInvalid,
+  };
+
+  virtual void OnCompaction(int level, const Slice& key,
+                            CompactionListenerValueType value_type,
+                            const Slice& existing_value,
+                            const SequenceNumber& sn, bool is_new) = 0;
+
+  virtual ~CompactionEventListener() = default;
+};
 
 // EventListener class contains a set of call-back functions that will
 // be called when specific RocksDB event happens such as flush.  It can
@@ -225,6 +247,16 @@ class EventListener {
   virtual void OnFlushCompleted(DB* /*db*/,
                                 const FlushJobInfo& /*flush_job_info*/) {}
 
+  // A call-back function to RocksDB which will be called before a
+  // RocksDB starts to flush memtables.  The default implementation is
+  // no-op.
+  //
+  // Note that the this function must be implemented in a way such that
+  // it should not run for an extended period of time before the function
+  // returns.  Otherwise, RocksDB may be blocked.
+  virtual void OnFlushBegin(DB* /*db*/,
+                            const FlushJobInfo& /*flush_job_info*/) {}
+
   // A call-back function for RocksDB which will be called whenever
   // a SST file is deleted.  Different from OnCompactionCompleted and
   // OnFlushCompleted, this call-back is designed for external logging
@@ -314,6 +346,12 @@ class EventListener {
   virtual void OnExternalFileIngested(
       DB* /*db*/, const ExternalFileIngestionInfo& /*info*/) {}
 
+  // Factory method to return CompactionEventListener. If multiple listeners
+  // provides CompactionEventListner, only the first one will be used.
+  virtual CompactionEventListener* GetCompactionEventListener() {
+    return nullptr;
+  }
+
   virtual ~EventListener() {}
 };
 

util/coding.h

@@ -48,6 +48,7 @@ extern void PutLengthPrefixedSliceParts(std::string* dst,
 // Standard Get... routines parse a value from the beginning of a Slice
 // and advance the slice past the parsed value.
 extern bool GetFixed64(Slice* input, uint64_t* value);
+extern bool GetFixed32(Slice* input, uint32_t* value);
 extern bool GetVarint32(Slice* input, uint32_t* value);
 extern bool GetVarint64(Slice* input, uint64_t* value);
 extern bool GetLengthPrefixedSlice(Slice* input, Slice* result);
@@ -271,6 +272,15 @@ inline bool GetFixed64(Slice* input, uint64_t* value) {
   return true;
 }
 
+inline bool GetFixed32(Slice* input, uint32_t* value) {
+  if (input->size() < sizeof(uint32_t)) {
+    return false;
+  }
+  *value = DecodeFixed32(input->data());
+  input->remove_prefix(sizeof(uint32_t));
+  return true;
+}
+
 inline bool GetVarint32(Slice* input, uint32_t* value) {
   const char* p = input->data();
   const char* limit = p + input->size();

util/filename.cc

@@ -27,6 +27,7 @@ namespace rocksdb {
 
 static const std::string kRocksDbTFileExt = "sst";
 static const std::string kLevelDbTFileExt = "ldb";
+static const std::string kRocksDBBlobFileExt = "blob";
 
 // Given a path, flatten the path name by replacing all chars not in
 // {[0-9,a-z,A-Z,-,_,.]} with _. And append '_LOG\0' at the end.
@@ -74,6 +75,11 @@ std::string LogFileName(const std::string& name, uint64_t number) {
   return MakeFileName(name, number, "log");
 }
 
+std::string BlobFileName(const std::string& blobdirname, uint64_t number) {
+  assert(number > 0);
+  return MakeFileName(blobdirname, number, kRocksDBBlobFileExt.c_str());
+}
+
 std::string ArchivalDirectory(const std::string& dir) {
   return dir + "/" + ARCHIVAL_DIR;
 }
@@ -220,7 +226,7 @@ std::string IdentityFileName(const std::string& dbname) {
 //    dbname/<info_log_name_prefix>
 //    dbname/<info_log_name_prefix>.old.[0-9]+
 //    dbname/MANIFEST-[0-9]+
-//    dbname/[0-9]+.(log|sst)
+//    dbname/[0-9]+.(log|sst|blob)
 //    dbname/METADB-[0-9]+
 //    dbname/OPTIONS-[0-9]+
 //    dbname/OPTIONS-[0-9]+.dbtmp
@@ -335,6 +341,8 @@ bool ParseFileName(const std::string& fname, uint64_t* number,
     } else if (suffix == Slice(kRocksDbTFileExt) ||
                suffix == Slice(kLevelDbTFileExt)) {
       *type = kTableFile;
+    } else if (suffix == Slice(kRocksDBBlobFileExt)) {
+      *type = kBlobFile;
     } else if (suffix == Slice(kTempFileNameSuffix)) {
       *type = kTempFile;
     } else {

util/filename.h

@@ -38,7 +38,8 @@ enum FileType {
   kInfoLogFile,  // Either the current one, or an old one
   kMetaDatabase,
   kIdentityFile,
-  kOptionsFile
+  kOptionsFile,
+  kBlobFile
 };
 
 // Return the name of the log file with the specified number
@@ -46,6 +47,8 @@ enum FileType {
 // "dbname".
 extern std::string LogFileName(const std::string& dbname, uint64_t number);
 
+extern std::string BlobFileName(const std::string& bdirname, uint64_t number);
+
 static const std::string ARCHIVAL_DIR = "archive";
 
 extern std::string ArchivalDirectory(const std::string& dbname);