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rocksdb/util/thread_status_impl.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.
//
// The implementation of ThreadStatus. It is implemented via combination
// of macros and thread-local variables.
//
// Note that we make get and set access to ThreadStatusData lockless.
// As a result, ThreadStatusData as a whole is not atomic. However,
// we guarantee consistent ThreadStatusData all the time whenever
// user call GetThreadList(). This consistency guarantee is done
// by having the following constraint in the internal implementation
// of set and get order:
//
// 1. When reset any information in ThreadStatusData, always start from
// clearing up the lower-level information first.
// 2. When setting any information in ThreadStatusData, always start from
// setting the higher-level information.
// 3. When returning ThreadStatusData to the user, fields are fetched from
// higher-level to lower-level. In addition, where there's a nullptr
// in one field, then all fields that has lower-level than that field
// should be ignored.
//
// The high to low level information would be:
// thread_id > thread_type > db > cf > event > event_count > event_details
//
// This means user might not always get full information, but whenever
// returned by the GetThreadList() is guaranteed to be consistent.
#pragma once
#include <unordered_set>
#include <atomic>
#include <string>
#include <unordered_map>
#include <mutex>
#include <list>
#include <vector>
#include "rocksdb/status.h"
#include "rocksdb/thread_status.h"
#include "port/port_posix.h"
namespace rocksdb {
class ColumnFamilyHandle;
// The mutable version of ThreadStatus. It has a static set maintaining
// the set of current registered threades.
//
// Note that it is suggested to call the above macros.
struct ConstantColumnFamilyInfo {
#if ROCKSDB_USING_THREAD_STATUS
public:
ConstantColumnFamilyInfo(
const void* _db_key,
const std::string& _db_name,
const std::string& _cf_name) :
db_key(_db_key), db_name(_db_name), cf_name(_cf_name) {}
const void* db_key;
const std::string db_name;
const std::string cf_name;
#endif // ROCKSDB_USING_THREAD_STATUS
};
struct ThreadEventInfo {
#if ROCKSDB_USING_THREAD_STATUS
public:
const std::string event_name;
#endif // ROCKSDB_USING_THREAD_STATUS
};
// the internal data-structure that is used to reflect the current
// status of a thread using a set of atomic pointers.
struct ThreadStatusData {
#if ROCKSDB_USING_THREAD_STATUS
explicit ThreadStatusData() : thread_id(0) {
thread_type.store(ThreadStatus::ThreadType::USER_THREAD);
cf_key.store(0);
event_info.store(nullptr);
}
uint64_t thread_id;
std::atomic<ThreadStatus::ThreadType> thread_type;
std::atomic<const void*> cf_key;
std::atomic<const ThreadEventInfo*> event_info;
#endif // ROCKSDB_USING_THREAD_STATUS
};
class ThreadStatusImpl {
public:
ThreadStatusImpl() {}
// Releases all ThreadStatusData of all active threads.
~ThreadStatusImpl();
void UnregisterThread();
// Set the thread type of the current thread.
void SetThreadType(ThreadStatus::ThreadType ttype);
// Update the column-family info of the current thread by setting
// its thread-local pointer of ThreadEventInfo to the correct entry.
void SetColumnFamilyInfoKey(const void* cf_key);
// Update the event info of the current thread by setting
// its thread-local pointer of ThreadEventInfo to the correct entry.
void SetEventInfoPtr(const ThreadEventInfo* event_info);
Status GetThreadList(
std::vector<ThreadStatus>* thread_list) const;
// 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 void* db_key, const std::string& db_name,
const void* cf_key, const std::string& cf_name);
// 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 void* db_key);
// 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 void* cf_key);
// Verifies whether the input ColumnFamilyHandles matches
// the information stored in the current cf_info_map.
static void TEST_VerifyColumnFamilyInfoMap(
const std::vector<ColumnFamilyHandle*>& handles,
bool check_exist);
protected:
#if ROCKSDB_USING_THREAD_STATUS
// The thread-local variable for storing thread status.
static __thread ThreadStatusData* thread_status_data_;
// Obtain the pointer to the thread status data. It also performs
// initialization when necessary.
ThreadStatusData* InitAndGet();
// The mutex that protects cf_info_map and db_key_map.
static std::mutex thread_list_mutex_;
// The current status data of all active threads.
static std::unordered_set<ThreadStatusData*> thread_data_set_;
// A global map that keeps the column family information. It is stored
// globally instead of inside DB is to avoid the situation where DB is
// closing while GetThreadList function already get the pointer to its
// CopnstantColumnFamilyInfo.
static std::unordered_map<
const void*, std::unique_ptr<ConstantColumnFamilyInfo>> cf_info_map_;
// A db_key to cf_key map that allows erasing elements in cf_info_map
// associated to the same db_key faster.
static std::unordered_map<
const void*, std::unordered_set<const void*>> db_key_map_;
#else
static ThreadStatusData* thread_status_data_;
#endif // ROCKSDB_USING_THREAD_STATUS
};
extern ThreadStatusImpl thread_local_status;
} // namespace rocksdb