2 * Copyright 2016 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 #include <folly/Function.h>
20 #include <folly/Range.h>
22 #include <condition_variable>
30 * Schedules any number of functions to run at various intervals. E.g.,
32 * FunctionScheduler fs;
34 * fs.addFunction([&] { LOG(INFO) << "tick..."; }, seconds(1), "ticker");
35 * fs.addFunction(std::bind(&TestClass::doStuff, this), minutes(5), "stuff");
38 * fs.cancelFunction("ticker");
39 * fs.addFunction([&] { LOG(INFO) << "tock..."; }, minutes(3), "tocker");
44 * Note: the class uses only one thread - if you want to use more than one
45 * thread use multiple FunctionScheduler objects
47 * start() schedules the functions, while shutdown() terminates further
50 class FunctionScheduler {
56 * By default steady is false, meaning schedules may lag behind overtime.
57 * This could be due to long running tasks or time drift because of randomness
58 * in thread wakeup time.
59 * By setting steady to true, FunctionScheduler will attempt to catch up.
60 * i.e. more like a cronjob
62 * NOTE: it's only safe to set this before calling start()
64 void setSteady(bool steady) { steady_ = steady; }
67 * Parameters to control the function interval.
69 * If isPoisson is true, then use std::poisson_distribution to pick the
70 * interval between each invocation of the function.
72 * If isPoisson os false, then always use fixed the interval specified to
75 struct LatencyDistribution {
79 LatencyDistribution(bool poisson, double mean)
86 * Adds a new function to the FunctionScheduler.
88 * Functions will not be run until start() is called. When start() is
89 * called, each function will be run after its specified startDelay.
90 * Functions may also be added after start() has been called, in which case
91 * startDelay is still honored.
93 * Throws an exception on error. In particular, each function must have a
94 * unique name--two functions cannot be added with the same name.
96 void addFunction(Function<void()>&& cb,
97 std::chrono::milliseconds interval,
98 StringPiece nameID = StringPiece(),
99 std::chrono::milliseconds startDelay =
100 std::chrono::milliseconds(0));
103 * Add a new function to the FunctionScheduler with a specified
104 * LatencyDistribution
107 Function<void()>&& cb,
108 std::chrono::milliseconds interval,
109 const LatencyDistribution& latencyDistr,
110 StringPiece nameID = StringPiece(),
111 std::chrono::milliseconds startDelay = std::chrono::milliseconds(0));
114 * Adds a new function to the FunctionScheduler to run only once.
116 void addFunctionOnce(
117 Function<void()>&& cb,
118 StringPiece nameID = StringPiece(),
119 std::chrono::milliseconds startDelay = std::chrono::milliseconds(0));
122 * Add a new function to the FunctionScheduler with the time
123 * interval being distributed uniformly within the given interval
124 * [minInterval, maxInterval].
126 void addFunctionUniformDistribution(Function<void()>&& cb,
127 std::chrono::milliseconds minInterval,
128 std::chrono::milliseconds maxInterval,
130 std::chrono::milliseconds startDelay);
133 * A type alias for function that is called to determine the time
134 * interval for the next scheduled run.
136 using IntervalDistributionFunc = Function<std::chrono::milliseconds()>;
139 * Add a new function to the FunctionScheduler. The scheduling interval
140 * is determined by the interval distribution functor, which is called
141 * every time the next function execution is scheduled. This allows
142 * for supporting custom interval distribution algorithms in addition
143 * to built in constant interval; and Poisson and jitter distributions
144 * (@see FunctionScheduler::addFunction and
145 * @see FunctionScheduler::addFunctionJitterInterval).
147 void addFunctionGenericDistribution(
148 Function<void()>&& cb,
149 IntervalDistributionFunc&& intervalFunc,
150 const std::string& nameID,
151 const std::string& intervalDescr,
152 std::chrono::milliseconds startDelay);
155 * Cancels the function with the specified name, so it will no longer be run.
157 * Returns false if no function exists with the specified name.
159 bool cancelFunction(StringPiece nameID);
162 * All functions registered will be canceled.
164 void cancelAllFunctions();
167 * Resets the specified function's timer.
168 * When resetFunctionTimer is called, the specified function's timer will
169 * be reset with the same parameters it was passed initially, including
170 * its startDelay. If the startDelay was 0, the function will be invoked
173 * Returns false if no function exists with the specified name.
175 bool resetFunctionTimer(StringPiece nameID);
178 * Starts the scheduler.
180 * Returns false if the scheduler was already running.
185 * Stops the FunctionScheduler.
187 * It may be restarted later by calling start() again.
188 * Returns false if the scheduler was not running.
193 * Set the name of the worker thread.
195 void setThreadName(StringPiece threadName);
200 IntervalDistributionFunc intervalFunc;
201 std::chrono::steady_clock::time_point nextRunTime;
203 std::chrono::milliseconds startDelay;
204 std::string intervalDescr;
208 Function<void()>&& cback,
209 IntervalDistributionFunc&& intervalFn,
210 const std::string& nameID,
211 const std::string& intervalDistDescription,
212 std::chrono::milliseconds delay,
214 : cb(std::move(cback)),
215 intervalFunc(std::move(intervalFn)),
219 intervalDescr(intervalDistDescription),
222 std::chrono::steady_clock::time_point getNextRunTime() const {
225 void setNextRunTimeStrict(std::chrono::steady_clock::time_point curTime) {
226 nextRunTime = curTime + intervalFunc();
228 void setNextRunTimeSteady() { nextRunTime += intervalFunc(); }
229 void resetNextRunTime(std::chrono::steady_clock::time_point curTime) {
230 nextRunTime = curTime + startDelay;
233 // Simply reset cb to an empty function.
236 bool isValid() const { return bool(cb); }
239 struct RunTimeOrder {
240 bool operator()(const RepeatFunc& f1, const RepeatFunc& f2) const {
241 return f1.getNextRunTime() > f2.getNextRunTime();
245 typedef std::vector<RepeatFunc> FunctionHeap;
248 void runOneFunction(std::unique_lock<std::mutex>& lock,
249 std::chrono::steady_clock::time_point now);
250 void cancelFunction(const std::unique_lock<std::mutex>& lock,
251 FunctionHeap::iterator it);
252 void addFunctionToHeap(const std::unique_lock<std::mutex>& lock,
255 void addFunctionInternal(
256 Function<void()>&& cb,
257 IntervalDistributionFunc&& intervalFunc,
258 const std::string& nameID,
259 const std::string& intervalDescr,
260 std::chrono::milliseconds startDelay,
265 // Mutex to protect our member variables.
267 bool running_{false};
269 // The functions to run.
270 // This is a heap, ordered by next run time.
271 FunctionHeap functions_;
274 // The function currently being invoked by the running thread.
275 // This is null when the running thread is idle
276 RepeatFunc* currentFunction_{nullptr};
278 // Condition variable that is signalled whenever a new function is added
279 // or when the FunctionScheduler is stopped.
280 std::condition_variable runningCondvar_;
282 std::string threadName_;