4 // Fraunhofer Institute for Open Communication Systems (FOKUS)
5 // Competence Center NETwork research (NET), St. Augustin, GERMANY
6 // Stefan Bund <g0dil@berlios.de>
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 2 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the
20 // Free Software Foundation, Inc.,
21 // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 \brief Scheduler public header
27 #ifndef HH_SENF_Scheduler_Scheduler_
28 #define HH_SENF_Scheduler_Scheduler_ 1
31 #include <boost/utility.hpp>
32 #include "../Utils/Logger/SenfLog.hh"
34 #include "TimerEvent.hh"
35 #include "SignalEvent.hh"
36 #include "EventHook.hh"
38 //#include "scheduler.mpp"
39 ///////////////////////////////hh.p////////////////////////////////////////
43 /** \brief The Scheduler interface
45 The %scheduler API is comprised of two parts:
47 \li Specific \ref sched_objects, one for each type of event.
48 \li Some <a href="#autotoc-7.">generic functions</a> implemented in the \ref senf::scheduler
51 Events are registered via the respective event class. The (global) functions are used to enter
52 the application main-loop or query for global information.
57 \section sched_objects Event classes
59 The Scheduler is based on the RAII principle: Every event is represented by a class
60 instance. The event is registered in the constructor and removed by the destructor of that
61 instance. This implementation automatically links the lifetime of an event with the lifetime of
62 the object resposible for it's creation.
64 Every event registration is represented by an instance of an event specific class:
66 \li senf::scheduler::FdEvent for file descriptor events
67 \li senf::scheduler::TimerEvent for single-shot deadline timer events
68 \li senf::scheduler::SignalEvent for UNIX signal events
69 \li senf::scheduler::EventHook for a special event hook
71 These instance are owned and managed by the user of the scheduler \e not by the scheduler so the
72 RAII concept can be used.
77 SomeSocketHandle handle_;
78 senf::scheduler::FdEvent event_;
81 SomeServer(SomeSocketHandle handle)
83 event_ ("SomeServer handler", senf::membind(&SomeServer::readData, this),
84 handle, senf::scheduler::FdEvent::EV_READ)
87 void readData(int events)
89 // read data from handle_, check for eof and so on.
94 The event is defined as a class member variable. When the event member is initialized in the
95 constructor, the event is automatically registered (except if the optional \a initiallyEnabled
96 flag argument is set to \c false). The Destructor will automatically remove the event from the
97 scheduler and ensure, that no dead code is called accidentally.
99 The process is the same for the other event types or when registering multiple events. For
100 detailed information on the constructor arguments and other features see the event class
101 documentation referenced below.
104 \section sched_handlers Specifying handlers
106 All handlers are specified as generic <a
107 href="http://www.boost.org/doc/html/function.html">Boost.Function</a> objects. This allows to
108 pass any callable as a handler. Depending on the type of handler, some additional arguments may
109 be passed to the handler by the %scheduler.
111 If you need to pass additional information to your handler, use <a
112 href="http://www.boost.org/libs/bind/bind.html">Boost.Bind</a>:
114 // Handle callback function
115 void callback(UDPv4ClientSocketHandle handle, senf::Scheduler::EventId event) {..}
116 // Pass 'handle' as additional first argument to callback()
117 senf::scheduler::FdEvent event ("name", boost::bind(&callback, handle, _1),
118 handle, senf::scheduler::FdEvent::EV_READ);
120 void timeout( int n) {..}
121 // Call timeout() handler with argument 'n'
122 senf::scheduler::TimerEvent timer ("name", boost::bind(&timeout, n),
123 senf::ClockService::now() + senf::ClockService::seconds(1));
126 To use member-functions as callbacks, use either <a
127 href="http://www.boost.org/libs/bind/bind.html">Boost.Bind</a> or senf::membind()
129 // e.g. in Foo::Foo() constructor:
132 readevent_ ("Foo read", senf::membind(&Foo::callback, this),
133 handle_, senf::scheduler::FdEvent::EV_READ)
137 The handler is identified by an arbitrary, user specified name. This name is used in error
138 messages to identify the failing handler.
141 \section sched_exec Executing the Scheduler
143 To enter the scheduler main-loop, call
146 senf::scheduler::process();
149 This call will only return in two cases:
151 \li When a handler calls senf::scheduler::terminate()
152 \li When there is no active file descriptor or timer event.
154 Additional <a href="#autotoc-7.">generic functions</a> provide information and %scheduler
157 \section sched_container Event objects and container classes
159 As the event objects are \e not copyable, they cannot be placed into ordinary
160 containers. However, it is quite simple to use pointer containers to hold event instances:
163 #include <boost/ptr_container/ptr_map.hpp>
164 #include <boost/bind.hpp>
173 new senf::scheduler::FdEvent("foo", boost::bind(&callback, this, fd, _1), fd,
174 senf::scheduler::FdEvent::EV_READ) );
177 void callback(int fd, int events)
179 FdEvent & event (fdEvents_[fd]);
188 boost::ptr_map<int, FdEvent> fdEvents_;
192 The pointer container API is (almost) completely identical to the corresponding standard library
193 container API. The only difference is, that all elements added to the container \e must be
194 created via \c new and that the pointer containers themselves are \e not copyable (ok, they are,
195 if the elements are cloneable ...). See <a
196 href="http://www.boost.org/doc/libs/1_36_0/libs/ptr_container/doc/ptr_container.html">Boost.PointerContainer</a>
197 for the pointer container library reference.
200 \section sched_signals Signals and the Watchdog
202 To secure against blocking callbacks, the %scheduler implementation includes a watchdog
203 timer. This timer will produce a warning message on the standard error stream when a single
204 callback is executing for more than the watchdog timeout value. Since the scheduler
205 implementation is completely single threaded, we cannot terminate the callback but at least we
206 can produce an informative message and optionally the program can be aborted.
208 The watchdog is controlled using the watchdogTimeout(), watchdogEvents() and watchdogAbort().
211 The watchdog is implemented using a free running interval timer. The watchdog signal (\c SIGURG)
212 must \e not be blocked. If signals need to be blocked for some reason, those regions will not be
213 checked by the watchdog. If a callback blocks, the watchdog has no chance to interrupt the
216 \warning Since the watchdog is free running for performance reasons, every callback must expect
217 signals to happen. Signals \e will certainly happen since the watchdog signal is generated
218 periodically (which does not necessarily generate a watchdog event ...)
220 Additional signals (\c SIGALRM) may occur when using using hires timers on kernel/glibc
221 combinations which do not support timerfd(). On such systems, hires timers are implemented using
222 POSIX timers which generate a considerable number of additional signals.
224 \todo Fix the file support to use threads (?) fork (?) and a pipe so it works reliably even
227 namespace scheduler {
229 /** \brief Event handler main loop
231 This member must be called at some time to enter the event handler main loop. Only while
232 this function is running any events are handled. The call will return if
233 \li a callback calls terminate()
234 \li the run queue becomes empty.
238 /** \brief \c true, if scheduler is running, \c false otherwise */
241 /** \brief Called by callbacks to terminate the main loop
243 This member may be called by any callback to tell the main loop to terminate. The main loop
244 will return to it's caller after the currently running callback returns.
248 /** \brief Immediately rescheduler
250 Calling yield() will cause the scheduler to terminate the current queue run and immediately
251 rescheduler all pending tasks.
255 /** \brief Return timestamp of last event
257 This is the timestamp, the last event has been signaled. This is the real time at which the
258 event is delivered \e not the time it should have been delivered (in the case of timers).
260 ClockService::clock_type eventTime();
262 /** \brief Return (approximate) current time
264 This call will return the current time as far as it is already known to the scheduler. If
265 the scheduler is running, this will return eventTime(), otherwise it will return
266 ClockService::now(). While the scheduler is running, this will reduce the number of system
269 ClockService::clock_type now();
271 /** \brief Set watchdog timeout to \a ms milliseconds.
273 Setting the watchdog timeout to 0 will disable the watchdog.
275 void watchdogTimeout(unsigned ms);
277 /** \brief Current watchdog timeout in milliseconds */
278 unsigned watchdogTimeout();
280 /** \brief Number of watchdog events
282 calling watchtogEvents() will reset the counter to 0
284 unsigned watchdogEvents();
286 /** \brief Enable/disable abort on watchdog event.
288 Calling watchdogAbort(\c true) will enable aborting the program execution on a watchdog
291 void watchdogAbort(bool flag);
293 /** \brief Get current watchdog abort on event status */
294 bool watchdogAbort();
296 /** \brief Switch to using hi resolution timers
298 By default, timers are implemented directly using epoll. This however restricts the timer
299 resolution to that of the kernel HZ value.
301 High resolution timers are implemented either using POSIX timers or, when available, using
302 the Linux special \c timerfd() syscall.
304 POSIX timers are delivered using signals. A high timer load this increases the signal load
305 considerably. \c timerfd()'s are delivered on a file descriptor and thus don't have such a
308 \warning The timer source must not be switched from a scheduler callback
312 /** \brief Switch back to using epoll for timing
317 /** \brief return \c true, if \c timerfd() timing is available, \c false otherwise
320 bool haveScalableHiresTimers();
322 /** \brief Return \c true, if using hires times, \c false otherwise
323 \see hiresTimers() */
324 bool usingHiresTimers();
326 /** \brief Restart scheduler
328 This call will restart all scheduler dispatchers (timers, signals, file descriptors). This
329 is necessary after a fork().
330 \warning This call will \e remove all registered events from the scheduler
334 /** \brief Return \c true, if no event is registered, \c false otherwise. */
337 /** \brief %scheduler specific time source for Utils/Logger framework
339 This time source may be used to provide timing information for log messages within the
340 Utils/Logger framework. This time source will use Scheduler::eventTime() to provide timing
344 senf::log::timeSource<senf::scheduler::LogTimeSource>();
347 Using this information reduces the number of necessary ClockService::now() calls and thus
348 the number of system calls.
350 struct LogTimeSource : public senf::log::TimeSource
352 senf::log::time_type operator()() const;
355 /** \brief Temporarily block all signals
357 This class is used to temporarily block all signals in a critical section.
360 // Begin critical section
362 senf::scheduler::BlockSignals signalBlocker;
364 // critical code executed with all signals blocked
366 // End critical section
369 You need to take care not to block since even the watchdog timer will be disabled while
370 executing within a critical section.
376 BlockSignals(bool initiallyBlocked=true);
377 ///< Block signals until end of scope
378 /**< \param[in] initiallyBlocked set to \c false to not
379 automatically block signals initially */
380 ~BlockSignals(); ///< Release all signal blocks
382 void block(); ///< Block signals if not blocked
383 void unblock(); ///< Unblock signals if blocked
384 bool blocked() const; ///< \c true, if signals currently blocked, \c false
395 ///////////////////////////////hh.e////////////////////////////////////////
396 #include "Scheduler.cci"
397 //#include "Scheduler.ct"
398 //#include "Scheduler.cti"
405 // c-file-style: "senf"
406 // indent-tabs-mode: nil
407 // ispell-local-dictionary: "american"
408 // compile-command: "scons -u test"
409 // comment-column: 40