text: // Copyright (c) 2014 The LevelDB Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file. See the AUTHORS file for names of contributors.
  //
  // The following only applies to changes made to this file as part of YugaByte development.
  //
  // Portions Copyright (c) YugaByte, Inc.
  //
  // Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
  // in compliance with the License.  You may obtain a copy of the License at
  //
  // http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software distributed under the License
  // is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
  // or implied.  See the License for the specific language governing permissions and limitations
  // under the License.
  //
  #ifndef YB_ROCKSDB_LISTENER_H
  #define YB_ROCKSDB_LISTENER_H
  
  #pragma once
  
  #include <memory>
  #include <string>
  #include <unordered_map>
  #include <vector>
  #include "yb/rocksdb/compaction_job_stats.h"
  #include "yb/rocksdb/status.h"
  #include "yb/rocksdb/table_properties.h"
  
  namespace rocksdb {
  
  typedef std::unordered_map<std::string, std::shared_ptr<const TableProperties>>
      TablePropertiesCollection;
  
  class DB;
  struct CompactionJobStats;
  
  struct TableFileCreationInfo {
    TableFileCreationInfo() = default;
    explicit TableFileCreationInfo(TableProperties&& prop) :
        table_properties(prop) {}
    // the name of the database where the file was created
    std::string db_name;
    // the name of the column family where the file was created.
    std::string cf_name;
    // the path to the created file.
    std::string file_path;
    // the size of the file.
    uint64_t file_size;
    // the id of the job (which could be flush or compaction) that
    // created the file.
    int job_id;
    // Detailed properties of the created file.
    TableProperties table_properties;
  };
  
  enum class CompactionReason {
    kUnknown,
    // [Level] number of L0 files > level0_file_num_compaction_trigger
    kLevelL0FilesNum,
    // [Level] total size of level > MaxBytesForLevel()
    kLevelMaxLevelSize,
    // [Universal] Compacting for size amplification
    kUniversalSizeAmplification,
    // [Universal] Compacting for size ratio
    kUniversalSizeRatio,
    // [Universal] number of sorted runs > level0_file_num_compaction_trigger
    kUniversalSortedRunNum,
    // [FIFO] total size > max_table_files_size
    kFIFOMaxSize,
    // Manual compaction
    kManualCompaction,
    // DB::SuggestCompactRange() marked files for compaction
    kFilesMarkedForCompaction,
  };
  
  #ifndef ROCKSDB_LITE
  
  struct TableFileDeletionInfo {
    // The name of the database where the file was deleted.
    std::string db_name;
    // The path to the deleted file.
    std::string file_path;
    // The id of the job which deleted the file.
    int job_id;
    // The status indicating whether the deletion was successful or not.
    Status status;
  };
  
  struct FlushJobInfo {
    // the name of the column family
    std::string cf_name;
    // the path to the newly created file
    std::string file_path;
    // the id of the thread that completed this flush job.
    uint64_t thread_id;
    // the job id, which is unique in the same thread.
    int job_id;
    // If true, then rocksdb is currently slowing-down all writes to prevent
    // creating too many Level 0 files as compaction seems not able to
    // catch up the write request speed.  This indicates that there are
    // too many files in Level 0.
    bool triggered_writes_slowdown;
    // If true, then rocksdb is currently blocking any writes to prevent
    // creating more L0 files.  This indicates that there are too many
    // files in level 0.  Compactions should try to compact L0 files down
    // to lower levels as soon as possible.
    bool triggered_writes_stop;
    // The smallest sequence number in the newly created file
    SequenceNumber smallest_seqno;
    // The largest sequence number in the newly created file
    SequenceNumber largest_seqno;
    // Table properties of the table being flushed
    TableProperties table_properties;
  };
  
  struct CompactionJobInfo {
    CompactionJobInfo() = default;
    explicit CompactionJobInfo(const CompactionJobStats& _stats) :
        stats(_stats) {}
  
    // the name of the column family where the compaction happened.
    std::string cf_name;
    // the status indicating whether the compaction was successful or not.
    Status status;
    // the id of the thread that completed this compaction job.
    uint64_t thread_id;
    // the job id, which is unique in the same thread.
    int job_id;
    // the smallest input level of the compaction.
    int base_input_level;
    // the output level of the compaction.
    int output_level;
    // the names of the compaction input files.
    std::vector<std::string> input_files;
  
    // the names of the compaction output files.
    std::vector<std::string> output_files;
    // Table properties for input and output tables.
    // The map is keyed by values from input_files and output_files.
    TablePropertiesCollection table_properties;
  
    // Reason to run the compaction
    CompactionReason compaction_reason;
  
    // If non-null, this variable stores detailed information
    // about this compaction.
    CompactionJobStats stats;
  };
  
  // EventListener class contains a set of call-back functions that will
  // be called when specific RocksDB event happens such as flush.  It can
  // be used as a building block for developing custom features such as
  // stats-collector or external compaction algorithm.
  //
  // Note that call-back functions should not run for an extended period of
  // time before the function returns, otherwise RocksDB may be blocked.
  // For example, it is not suggested to do DB::CompactFiles() (as it may
  // run for a long while) or issue many of DB::Put() (as Put may be blocked
  // in certain cases) in the same thread in the EventListener callback.
  // However, doing DB::CompactFiles() and DB::Put() in another thread is
  // considered safe.
  //
  // [Threading] All EventListener callback will be called using the
  // actual thread that involves in that specific event.   For example, it
  // is the RocksDB background flush thread that does the actual flush to
  // call EventListener::OnFlushCompleted().
  //
  // [Locking] All EventListener callbacks are designed to be called without
  // the current thread holding any DB mutex. This is to prevent potential
  // deadlock and performance issue when using EventListener callback
  // in a complex way. However, all EventListener call-back functions
  // should not run for an extended period of time before the function
  // returns, otherwise RocksDB may be blocked. For example, it is not
  // suggested to do DB::CompactFiles() (as it may run for a long while)
  // or issue many of DB::Put() (as Put may be blocked in certain cases)
  // in the same thread in the EventListener callback. However, doing
  // DB::CompactFiles() and DB::Put() in a thread other than the
  // EventListener callback thread is considered safe.
  class EventListener {
   public:
  
    // A call-back function which will be called whenever a RocksDB
    // memstore flush is scheduled.
    //
    // 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 OnFlushScheduled(DB* db) {}
  
    // A call-back function to RocksDB which will be called whenever a
    // registered RocksDB flushes a file.  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 OnFlushCompleted(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
    // service and thus only provide string parameters instead
    // of a pointer to DB.  Applications that build logic basic based
    // on file creations and deletions is suggested to implement
    // OnFlushCompleted and OnCompactionCompleted.
    //
    // Note that if applications would like to use the passed reference
    // outside this function call, they should make copies from the
    // returned value.
    virtual void OnTableFileDeleted(const TableFileDeletionInfo& /*info*/) {}
  
    // A call-back function for RocksDB which will be called whenever a compaction has been started.
    virtual void OnCompactionStarted() {}
  
    // A call-back function for RocksDB which will be called whenever
    // a registered RocksDB compacts a file. The default implementation
    // is a no-op.
    //
    // Note that 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.
    //
    // @param db a pointer to the rocksdb instance which just compacted
    //   a file.
    // @param ci a reference to a CompactionJobInfo struct. 'ci' is released
    //  after this function is returned, and must be copied if it is needed
    //  outside of this function.
    virtual void OnCompactionCompleted(DB* /*db*/,
                                       const CompactionJobInfo& /*ci*/) {}
  
    // A call-back function for RocksDB which will be called whenever
    // a SST file is created.  Different from OnCompactionCompleted and
    // OnFlushCompleted, this call-back is designed for external logging
    // service and thus only provide string parameters instead
    // of a pointer to DB.  Applications that build logic basic based
    // on file creations and deletions is suggested to implement
    // OnFlushCompleted and OnCompactionCompleted.
    //
    // Note that if applications would like to use the passed reference
    // outside this function call, they should make copies from these
    // returned value.
    virtual void OnTableFileCreated(const TableFileCreationInfo& /*info*/) {}
  
    virtual ~EventListener() {}
  };
  
  #else
  
  class EventListener {
  };
  
  #endif  // ROCKSDB_LITE
  
  }  // namespace rocksdb
  
  #endif // YB_ROCKSDB_LISTENER_H
  