thread_status.h

// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).
//
// This file defines the structures for exposing run-time status of any
// rocksdb-related thread.  Such run-time status can be obtained via
// GetThreadList() API.
//
// Note that all thread-status features are still under-development, and
// thus APIs and class definitions might subject to change at this point.
// Will remove this comment once the APIs have been finalized.

#pragma once

#include <cstddef>
#include <cstdint>
#include <map>
#include <string>
#include <utility>
#include <vector>

#include "rocksdb/rocksdb_namespace.h"

#if !defined(NROCKSDB_THREAD_STATUS)
#define ROCKSDB_USING_THREAD_STATUS
#endif

namespace ROCKSDB_NAMESPACE {

// TODO(yhchiang): remove this function once c++14 is available
//                 as std::max will be able to cover this.
// Current MS compiler does not support constexpr
template <int A, int B>
struct constexpr_max {
  static const int result = (A > B) ? A : B;
};

// A structure that describes the current status of a thread.
// The status of active threads can be fetched using
// ROCKSDB_NAMESPACE::GetThreadList().
struct ThreadStatus {
  // The type of a thread.
  enum ThreadType : int {
    HIGH_PRIORITY = 0,  // RocksDB BG thread in high-pri thread pool
    LOW_PRIORITY,       // RocksDB BG thread in low-pri thread pool
    USER,               // User thread (Non-RocksDB BG thread)
    BOTTOM_PRIORITY,    // RocksDB BG thread in bottom-pri thread pool
    NUM_THREAD_TYPES
  };

  // The type used to refer to a thread operation.
  // A thread operation describes high-level action of a thread.
  // Examples include compaction and flush.
  enum OperationType : int {
    OP_UNKNOWN = 0,
    OP_COMPACTION,
    OP_FLUSH,
    NUM_OP_TYPES
  };

  enum OperationStage : int {
    STAGE_UNKNOWN = 0,
    STAGE_FLUSH_RUN,
    STAGE_FLUSH_WRITE_L0,
    STAGE_COMPACTION_PREPARE,
    STAGE_COMPACTION_RUN,
    STAGE_COMPACTION_PROCESS_KV,
    STAGE_COMPACTION_INSTALL,
    STAGE_COMPACTION_SYNC_FILE,
    STAGE_PICK_MEMTABLES_TO_FLUSH,
    STAGE_MEMTABLE_ROLLBACK,
    STAGE_MEMTABLE_INSTALL_FLUSH_RESULTS,
    NUM_OP_STAGES
  };

  enum CompactionPropertyType : int {
    COMPACTION_JOB_ID = 0,
    COMPACTION_INPUT_OUTPUT_LEVEL,
    COMPACTION_PROP_FLAGS,
    COMPACTION_TOTAL_INPUT_BYTES,
    COMPACTION_BYTES_READ,
    COMPACTION_BYTES_WRITTEN,
    NUM_COMPACTION_PROPERTIES
  };

  enum FlushPropertyType : int {
    FLUSH_JOB_ID = 0,
    FLUSH_BYTES_MEMTABLES,
    FLUSH_BYTES_WRITTEN,
    NUM_FLUSH_PROPERTIES
  };

  // The maximum number of properties of an operation.
  // This number should be set to the biggest NUM_XXX_PROPERTIES.
  static const int kNumOperationProperties =
      constexpr_max<NUM_COMPACTION_PROPERTIES, NUM_FLUSH_PROPERTIES>::result;

  // The type used to refer to a thread state.
  // A state describes lower-level action of a thread
  // such as reading / writing a file or waiting for a mutex.
  enum StateType : int {
    STATE_UNKNOWN = 0,
    STATE_MUTEX_WAIT = 1,
    NUM_STATE_TYPES
  };

  ThreadStatus(const uint64_t _id, const ThreadType _thread_type,
               const std::string& _db_name, const std::string& _cf_name,
               const OperationType _operation_type,
               const uint64_t _op_elapsed_micros,
               const OperationStage _operation_stage,
               const uint64_t _op_props[], const StateType _state_type)
      : thread_id(_id),
        thread_type(_thread_type),
        db_name(_db_name),
        cf_name(_cf_name),
        operation_type(_operation_type),
        op_elapsed_micros(_op_elapsed_micros),
        operation_stage(_operation_stage),
        state_type(_state_type) {
    for (int i = 0; i < kNumOperationProperties; ++i) {
      op_properties[i] = _op_props[i];
    }
  }

  // An unique ID for the thread.
  const uint64_t thread_id;

  // The type of the thread, it could be HIGH_PRIORITY,
  // LOW_PRIORITY, and USER
  const ThreadType thread_type;

  // The name of the DB instance where the thread is currently
  // involved with.  It would be set to empty string if the thread
  // does not involve in any DB operation.
  const std::string db_name;

  // The name of the column family where the thread is currently
  // It would be set to empty string if the thread does not involve
  // in any column family.
  const std::string cf_name;

  // The operation (high-level action) that the current thread is involved.
  const OperationType operation_type;

  // The elapsed time of the current thread operation in microseconds.
  const uint64_t op_elapsed_micros;

  // An integer showing the current stage where the thread is involved
  // in the current operation.
  const OperationStage operation_stage;

  // A list of properties that describe some details about the current
  // operation.  Same field in op_properties[] might have different
  // meanings for different operations.
  uint64_t op_properties[kNumOperationProperties];

  // The state (lower-level action) that the current thread is involved.
  const StateType state_type;

  // The followings are a set of utility functions for interpreting
  // the information of ThreadStatus

  static std::string GetThreadTypeName(ThreadType thread_type);

  // Obtain the name of an operation given its type.
  static const std::string& GetOperationName(OperationType op_type);

  static const std::string MicrosToString(uint64_t op_elapsed_time);

  // Obtain a human-readable string describing the specified operation stage.
  static const std::string& GetOperationStageName(OperationStage stage);

  // Obtain the name of the "i"th operation property of the
  // specified operation.
  static const std::string& GetOperationPropertyName(OperationType op_type,
                                                     int i);

  // Translate the "i"th property of the specified operation given
  // a property value.
  static std::map<std::string, uint64_t> InterpretOperationProperties(
      OperationType op_type, const uint64_t* op_properties);

  // Obtain the name of a state given its type.
  static const std::string& GetStateName(StateType state_type);
};

}  // namespace ROCKSDB_NAMESPACE