rocksdb/util/thread_status_util.h

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#pragma once
#include "db/column_family.h"
#include "rocksdb/env.h"
#include "rocksdb/thread_status.h"
#include "util/thread_status_updater.h"
namespace rocksdb {
// The static utility class for updating thread-local status.
//
// The thread-local status is updated via the thread-local cached
// pointer thread_updater_local_cache_. During each function call,
// when ThreadStatusUtil finds thread_updater_local_cache_ is
// left uninitialized (determined by thread_updater_initialized_),
// it will tries to initialize it using the return value of
// Env::GetThreadStatusUpdater(). When thread_updater_local_cache_
// is initialized by a non-null pointer, each function call will
// then update the status of the current thread. Otherwise,
// all function calls to ThreadStatusUtil will be no-op.
class ThreadStatusUtil {
public:
// Set the thread type of the current thread.
static void SetThreadType(
const Env* env, ThreadStatus::ThreadType thread_type);
// Unregister the current thread.
static void UnregisterThread();
// Create an entry in the global ColumnFamilyInfo table for the
// specified column family. This function should be called only
// when the current thread does not hold db_mutex.
static void NewColumnFamilyInfo(
const DB* db, const ColumnFamilyData* cfd);
// Erase the ConstantColumnFamilyInfo that is associated with the
// specified ColumnFamilyData. This function should be called only
// when the current thread does not hold db_mutex.
static void EraseColumnFamilyInfo(const ColumnFamilyData* cfd);
// Erase all ConstantColumnFamilyInfo that is associated with the
// specified db instance. This function should be called only when
// the current thread does not hold db_mutex.
static void EraseDatabaseInfo(const DB* db);
// Update the thread status to indicate the current thread is doing
// something related to the specified column family.
static void SetColumnFamily(const ColumnFamilyData* cfd);
protected:
// Initialize the thread-local ThreadStatusUpdater when it finds
// the cached value is nullptr. Returns true if it has cached
// a non-null pointer.
static bool MaybeInitThreadLocalUpdater(const Env* env);
#if ROCKSDB_USING_THREAD_STATUS
// A boolean flag indicating whether thread_updater_local_cache_
// is initialized. It is set to true when an Env uses any
// ThreadStatusUtil functions using the current thread other
// than UnregisterThread(). It will be set to false when
// UnregisterThread() is called.
//
// When this variable is set to true, thread_updater_local_cache_
// will not be updated until this variable is again set to false
// in UnregisterThread().
static __thread bool thread_updater_initialized_;
// The thread-local cached ThreadStatusUpdater that caches the
// thread_status_updater_ of the first Env that uses any ThreadStatusUtil
// function other than UnregisterThread(). This variable will
// be cleared when UnregisterThread() is called.
//
// When this variable is set to a non-null pointer, then the status
// of the current thread will be updated when a function of
// ThreadStatusUtil is called. Otherwise, all functions of
// ThreadStatusUtil will be no-op.
//
// When thread_updater_initialized_ is set to true, this variable
// will not be updated until this thread_updater_initialized_ is
// again set to false in UnregisterThread().
static __thread ThreadStatusUpdater* thread_updater_local_cache_;
#else
static bool thread_updater_initialized_;
static ThreadStatusUpdater* thread_updater_local_cache_;
#endif
};
} // namespace rocksdb