rocksdb/db/periodic_task_scheduler.h
Jay Zhuang d9e71fb2c5 Fix periodic_task unable to re-register the same task type (#10379)
Summary:
Timer has a limitation that it cannot re-register a task with the same name,
because the cancel only mark the task as invalid and wait for the Timer thread
to clean it up later, before the task is cleaned up, the same task name cannot
be added. Which makes the task option update likely to fail, which basically
cancel and re-register the same task name. Change the periodic task name to a
random unique id and store it in periodic_task_scheduler.

Also refactor the `periodic_work` to `periodic_task` to make each job function
as a `task`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10379

Test Plan: unittests

Reviewed By: ajkr

Differential Revision: D38000615

Pulled By: jay-zhuang

fbshipit-source-id: e4135f9422e3b53aaec8eda54f4e18ce633a279e
2022-08-25 18:52:37 -07:00

111 lines
3.4 KiB
C++

// Copyright (c) Meta Platforms, Inc. and affiliates.
//
// 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).
#pragma once
#ifndef ROCKSDB_LITE
#include "util/timer.h"
namespace ROCKSDB_NAMESPACE {
class SystemClock;
using PeriodicTaskFunc = std::function<void()>;
constexpr uint64_t kInvalidPeriodSec = 0;
// List of task types
enum class PeriodicTaskType : uint8_t {
kDumpStats = 0,
kPersistStats,
kFlushInfoLog,
kRecordSeqnoTime,
kMax,
};
// PeriodicTaskScheduler contains the periodic task scheduled from the DB
// instance. It's used to schedule/unschedule DumpStats(), PersistStats(),
// FlushInfoLog(), etc. Each type of the task can only have one instance,
// re-register the same task type would only update the repeat period.
//
// Internally, it uses a global single threaded timer object to run the periodic
// task functions. Timer thread will always be started since the info log
// flushing cannot be disabled.
class PeriodicTaskScheduler {
public:
explicit PeriodicTaskScheduler() = default;
PeriodicTaskScheduler(const PeriodicTaskScheduler&) = delete;
PeriodicTaskScheduler(PeriodicTaskScheduler&&) = delete;
PeriodicTaskScheduler& operator=(const PeriodicTaskScheduler&) = delete;
PeriodicTaskScheduler& operator=(PeriodicTaskScheduler&&) = delete;
// Register a task with its default repeat period
Status Register(PeriodicTaskType task_type, const PeriodicTaskFunc& fn);
// Register a task with specified repeat period. 0 is an invalid argument
// (kInvalidPeriodSec). To stop the task, please use Unregister() specifically
Status Register(PeriodicTaskType task_type, const PeriodicTaskFunc& fn,
uint64_t repeat_period_seconds);
// Unregister the task
Status Unregister(PeriodicTaskType task_type);
#ifndef NDEBUG
// Override the timer for the unittest
void TEST_OverrideTimer(SystemClock* clock);
// Call Timer TEST_WaitForRun() which wait until Timer starting waiting.
void TEST_WaitForRun(const std::function<void()>& callback) const {
if (timer_ != nullptr) {
timer_->TEST_WaitForRun(callback);
}
}
// Get global valid task number in the Timer
size_t TEST_GetValidTaskNum() const {
if (timer_ != nullptr) {
return timer_->TEST_GetPendingTaskNum();
}
return 0;
}
// If it has the specified task type registered
bool TEST_HasTask(PeriodicTaskType task_type) const {
auto it = tasks_map_.find(task_type);
return it != tasks_map_.end();
}
#endif // NDEBUG
private:
// default global Timer instance
static Timer* Default();
// Internal structure to store task information
struct TaskInfo {
TaskInfo(std::string _name, uint64_t _repeat_every_sec)
: name(std::move(_name)), repeat_every_sec(_repeat_every_sec) {}
std::string name;
uint64_t repeat_every_sec;
};
// Internal tasks map
std::map<PeriodicTaskType, TaskInfo> tasks_map_;
// Global timer pointer, which doesn't support synchronous add/cancel tasks
// so having a global `timer_mutex` for add/cancel task.
Timer* timer_ = Default();
// Global task id, protected by the global `timer_mutex`
inline static uint64_t id_;
static constexpr uint64_t kMicrosInSecond = 1000U * 1000U;
};
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE