Browse Source

CScheduler class for lightweight task scheduling

Simple class to manage a task queue that is serviced by one or
more threads.
pull/1/head
Gavin Andresen 8 years ago
parent
commit
928b950e3b
No known key found for this signature in database
GPG Key ID: 7588242FBE38D3A8
  1. 2
      src/Makefile.am
  2. 102
      src/scheduler.cpp
  3. 70
      src/scheduler.h

2
src/Makefile.am

@ -115,6 +115,7 @@ BITCOIN_CORE_H = \ @@ -115,6 +115,7 @@ BITCOIN_CORE_H = \
rpcclient.h \
rpcprotocol.h \
rpcserver.h \
scheduler.h \
script/interpreter.h \
script/script_error.h \
script/script.h \
@ -257,6 +258,7 @@ libbitcoin_common_a_SOURCES = \ @@ -257,6 +258,7 @@ libbitcoin_common_a_SOURCES = \
netbase.cpp \
protocol.cpp \
pubkey.cpp \
scheduler.cpp \
script/interpreter.cpp \
script/script.cpp \
script/sign.cpp \

102
src/scheduler.cpp

@ -0,0 +1,102 @@ @@ -0,0 +1,102 @@
// Copyright (c) 2015 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "scheduler.h"
#include <assert.h>
#include <boost/bind.hpp>
#include <utility>
CScheduler::CScheduler() : nThreadsServicingQueue(0)
{
}
CScheduler::~CScheduler()
{
assert(nThreadsServicingQueue == 0);
}
#if BOOST_VERSION < 105000
static boost::system_time toPosixTime(const boost::chrono::system_clock::time_point& t)
{
boost::chrono::system_clock::duration d = t.time_since_epoch();
boost::chrono::microseconds usecs = boost::chrono::duration_cast<boost::chrono::microseconds>(d);
boost::system_time result = boost::posix_time::from_time_t(0) +
boost::posix_time::microseconds(usecs.count());
return result;
}
#endif
void CScheduler::serviceQueue()
{
boost::unique_lock<boost::mutex> lock(newTaskMutex);
++nThreadsServicingQueue;
// newTaskMutex is locked throughout this loop EXCEPT
// when the thread is waiting or when the user's function
// is called.
while (1) {
try {
while (taskQueue.empty()) {
// Wait until there is something to do.
newTaskScheduled.wait(lock);
}
// Wait until either there is a new task, or until
// the time of the first item on the queue:
// wait_until needs boost 1.50 or later; older versions have timed_wait:
#if BOOST_VERSION < 105000
while (!taskQueue.empty() && newTaskScheduled.timed_wait(lock, toPosixTime(taskQueue.begin()->first))) {
// Keep waiting until timeout
}
#else
while (!taskQueue.empty() && newTaskScheduled.wait_until(lock, taskQueue.begin()->first) != boost::cv_status::timeout) {
// Keep waiting until timeout
}
#endif
// If there are multiple threads, the queue can empty while we're waiting (another
// thread may service the task we were waiting on).
if (taskQueue.empty())
continue;
Function f = taskQueue.begin()->second;
taskQueue.erase(taskQueue.begin());
// Unlock before calling f, so it can reschedule itself or another task
// without deadlocking:
lock.unlock();
f();
lock.lock();
} catch (...) {
--nThreadsServicingQueue;
throw;
}
}
}
void CScheduler::schedule(CScheduler::Function f, boost::chrono::system_clock::time_point t)
{
{
boost::unique_lock<boost::mutex> lock(newTaskMutex);
taskQueue.insert(std::make_pair(t, f));
}
newTaskScheduled.notify_one();
}
void CScheduler::scheduleFromNow(CScheduler::Function f, int64_t deltaSeconds)
{
schedule(f, boost::chrono::system_clock::now() + boost::chrono::seconds(deltaSeconds));
}
static void Repeat(CScheduler* s, CScheduler::Function f, int64_t deltaSeconds)
{
f();
s->scheduleFromNow(boost::bind(&Repeat, s, f, deltaSeconds), deltaSeconds);
}
void CScheduler::scheduleEvery(CScheduler::Function f, int64_t deltaSeconds)
{
scheduleFromNow(boost::bind(&Repeat, this, f, deltaSeconds), deltaSeconds);
}

70
src/scheduler.h

@ -0,0 +1,70 @@ @@ -0,0 +1,70 @@
// Copyright (c) 2015 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_SCHEDULER_H
#define BITCOIN_SCHEDULER_H
//
// NOTE:
// boost::thread / boost::function / boost::chrono should be ported to
// std::thread / std::function / std::chrono when we support C++11.
//
#include <boost/function.hpp>
#include <boost/chrono/chrono.hpp>
#include <boost/thread.hpp>
#include <map>
//
// Simple class for background tasks that should be run
// periodically or once "after a while"
//
// Usage:
//
// CScheduler* s = new CScheduler();
// s->scheduleFromNow(doSomething, 11); // Assuming a: void doSomething() { }
// s->scheduleFromNow(boost::bind(Class::func, this, argument), 3);
// boost::thread* t = new boost::thread(boost::bind(CScheduler::serviceQueue, s));
//
// ... then at program shutdown, clean up the thread running serviceQueue:
// t->interrupt();
// t->join();
// delete t;
// delete s; // Must be done after thread is interrupted/joined.
//
class CScheduler
{
public:
CScheduler();
~CScheduler();
typedef boost::function<void(void)> Function;
// Call func at/after time t
void schedule(Function f, boost::chrono::system_clock::time_point t);
// Convenience method: call f once deltaSeconds from now
void scheduleFromNow(Function f, int64_t deltaSeconds);
// Another convenience method: call f approximately
// every deltaSeconds forever, starting deltaSeconds from now.
// To be more precise: every time f is finished, it
// is rescheduled to run deltaSeconds later. If you
// need more accurate scheduling, don't use this method.
void scheduleEvery(Function f, int64_t deltaSeconds);
// To keep things as simple as possible, there is no unschedule.
// Services the queue 'forever'. Should be run in a thread,
// and interrupted using boost::interrupt_thread
void serviceQueue();
private:
std::multimap<boost::chrono::system_clock::time_point, Function> taskQueue;
boost::condition_variable newTaskScheduled;
boost::mutex newTaskMutex;
int nThreadsServicingQueue;
};
#endif
Loading…
Cancel
Save