fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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261 lines
6.9 KiB
261 lines
6.9 KiB
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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#pragma once
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#include <functional>
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#include <memory>
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#include <queue>
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#include <unordered_map>
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#include <utility>
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#include <vector>
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#include "monitoring/instrumented_mutex.h"
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#include "rocksdb/env.h"
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#include "test_util/sync_point.h"
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#include "util/mutexlock.h"
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namespace ROCKSDB_NAMESPACE {
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// A Timer class to handle repeated work.
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//
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// A single timer instance can handle multiple functions via a single thread.
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// It is better to leave long running work to a dedicated thread pool.
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//
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// Timer can be started by calling `Start()`, and ended by calling `Shutdown()`.
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// Work (in terms of a `void function`) can be scheduled by calling `Add` with
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// a unique function name and de-scheduled by calling `Cancel`.
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// Many functions can be added.
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//
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// Impl Details:
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// A heap is used to keep track of when the next timer goes off.
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// A map from a function name to the function keeps track of all the functions.
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class Timer {
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public:
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explicit Timer(Env* env)
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: env_(env),
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mutex_(env),
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cond_var_(&mutex_),
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running_(false),
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executing_task_(false) {}
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~Timer() {}
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// repeat_every_us == 0 means do not repeat
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void Add(std::function<void()> fn,
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const std::string& fn_name,
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uint64_t start_after_us,
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uint64_t repeat_every_us) {
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std::unique_ptr<FunctionInfo> fn_info(new FunctionInfo(
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std::move(fn),
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fn_name,
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env_->NowMicros() + start_after_us,
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repeat_every_us));
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InstrumentedMutexLock l(&mutex_);
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heap_.push(fn_info.get());
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map_.emplace(std::make_pair(fn_name, std::move(fn_info)));
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cond_var_.Signal();
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}
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void Cancel(const std::string& fn_name) {
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InstrumentedMutexLock l(&mutex_);
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// Mark the function with fn_name as invalid so that it will not be
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// requeued.
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auto it = map_.find(fn_name);
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if (it != map_.end() && it->second) {
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it->second->Cancel();
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}
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// If the currently running function is fn_name, then we need to wait
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// until it finishes before returning to caller.
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while (!heap_.empty() && executing_task_) {
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FunctionInfo* func_info = heap_.top();
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assert(func_info);
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if (func_info->name == fn_name) {
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WaitForTaskCompleteIfNecessary();
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} else {
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break;
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}
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}
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}
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void CancelAll() {
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InstrumentedMutexLock l(&mutex_);
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CancelAllWithLock();
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}
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// Start the Timer
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bool Start() {
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InstrumentedMutexLock l(&mutex_);
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if (running_) {
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return false;
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}
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running_ = true;
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thread_.reset(new port::Thread(&Timer::Run, this));
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return true;
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}
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// Shutdown the Timer
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bool Shutdown() {
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{
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InstrumentedMutexLock l(&mutex_);
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if (!running_) {
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return false;
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}
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running_ = false;
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CancelAllWithLock();
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cond_var_.SignalAll();
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}
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if (thread_) {
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thread_->join();
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}
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return true;
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}
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private:
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void Run() {
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InstrumentedMutexLock l(&mutex_);
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while (running_) {
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if (heap_.empty()) {
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// wait
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TEST_SYNC_POINT("Timer::Run::Waiting");
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cond_var_.Wait();
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continue;
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}
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FunctionInfo* current_fn = heap_.top();
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assert(current_fn);
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if (!current_fn->IsValid()) {
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heap_.pop();
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map_.erase(current_fn->name);
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continue;
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}
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if (current_fn->next_run_time_us <= env_->NowMicros()) {
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executing_task_ = true;
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mutex_.Unlock();
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// Execute the work
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current_fn->fn();
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mutex_.Lock();
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executing_task_ = false;
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cond_var_.SignalAll();
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// Remove the work from the heap once it is done executing.
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// Note that we are just removing the pointer from the heap. Its
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// memory is still managed in the map (as it holds a unique ptr).
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// So current_fn is still a valid ptr.
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heap_.pop();
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// current_fn may be cancelled already.
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if (current_fn->IsValid() && current_fn->repeat_every_us > 0) {
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assert(running_);
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current_fn->next_run_time_us = env_->NowMicros() +
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current_fn->repeat_every_us;
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// Schedule new work into the heap with new time.
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heap_.push(current_fn);
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}
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} else {
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cond_var_.TimedWait(current_fn->next_run_time_us);
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}
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}
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}
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void CancelAllWithLock() {
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mutex_.AssertHeld();
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if (map_.empty() && heap_.empty()) {
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return;
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}
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// With mutex_ held, set all tasks to invalid so that they will not be
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// re-queued.
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for (auto& elem : map_) {
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auto& func_info = elem.second;
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assert(func_info);
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func_info->Cancel();
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}
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// WaitForTaskCompleteIfNecessary() may release mutex_
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WaitForTaskCompleteIfNecessary();
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while (!heap_.empty()) {
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heap_.pop();
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}
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map_.clear();
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}
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// A wrapper around std::function to keep track when it should run next
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// and at what frequency.
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struct FunctionInfo {
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// the actual work
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std::function<void()> fn;
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// name of the function
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std::string name;
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// when the function should run next
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uint64_t next_run_time_us;
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// repeat interval
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uint64_t repeat_every_us;
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// controls whether this function is valid.
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// A function is valid upon construction and until someone explicitly
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// calls `Cancel()`.
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bool valid;
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FunctionInfo(std::function<void()>&& _fn, const std::string& _name,
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const uint64_t _next_run_time_us, uint64_t _repeat_every_us)
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: fn(std::move(_fn)),
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name(_name),
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next_run_time_us(_next_run_time_us),
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repeat_every_us(_repeat_every_us),
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valid(true) {}
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void Cancel() {
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valid = false;
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}
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bool IsValid() const { return valid; }
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};
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void WaitForTaskCompleteIfNecessary() {
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mutex_.AssertHeld();
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while (executing_task_) {
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TEST_SYNC_POINT("Timer::WaitForTaskCompleteIfNecessary:TaskExecuting");
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cond_var_.Wait();
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}
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}
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struct RunTimeOrder {
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bool operator()(const FunctionInfo* f1,
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const FunctionInfo* f2) {
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return f1->next_run_time_us > f2->next_run_time_us;
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}
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};
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Env* const env_;
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// This mutex controls both the heap_ and the map_. It needs to be held for
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// making any changes in them.
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InstrumentedMutex mutex_;
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InstrumentedCondVar cond_var_;
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std::unique_ptr<port::Thread> thread_;
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bool running_;
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bool executing_task_;
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std::priority_queue<FunctionInfo*,
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std::vector<FunctionInfo*>,
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RunTimeOrder> heap_;
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// In addition to providing a mapping from a function name to a function,
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// it is also responsible for memory management.
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std::unordered_map<std::string, std::unique_ptr<FunctionInfo>> map_;
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};
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} // namespace ROCKSDB_NAMESPACE
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