X-Git-Url: http://g0dil.de/git?a=blobdiff_plain;f=Scheduler%2FScheduler.hh;h=62a687ce5f39cea447d7228642a5abff0069b5f8;hb=bd9f9d3fd6fbcff0112a7bf48ab9284da9576b11;hp=8916723181261819df9eb2e84d03feb1003216b3;hpb=1835b928b179302ecb716d697fbf3fa24b415ba4;p=senf.git diff --git a/Scheduler/Scheduler.hh b/Scheduler/Scheduler.hh index 8916723..62a687c 100644 --- a/Scheduler/Scheduler.hh +++ b/Scheduler/Scheduler.hh @@ -1,9 +1,9 @@ // $Id$ // -// Copyright (C) 2006 -// Fraunhofer Institut fuer offene Kommunikationssysteme (FOKUS) -// Kompetenzzentrum fuer Satelitenkommunikation (SatCom) -// Stefan Bund +// Copyright (C) 2006 +// Fraunhofer Institute for Open Communication Systems (FOKUS) +// Competence Center NETwork research (NET), St. Augustin, GERMANY +// Stefan Bund // // This program is free software; you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by @@ -20,112 +20,391 @@ // Free Software Foundation, Inc., // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. -#ifndef HH_Scheduler_ -#define HH_Scheduler_ 1 +/** \file + \brief Scheduler public header + */ + +#ifndef HH_SENF_Scheduler_Scheduler_ +#define HH_SENF_Scheduler_Scheduler_ 1 // Custom includes -#include -#include #include -#include +#include "../Utils/Logger/SenfLog.hh" +#include "FdEvent.hh" +#include "TimerEvent.hh" +#include "SignalEvent.hh" +#include "EventHook.hh" //#include "scheduler.mpp" ///////////////////////////////hh.p//////////////////////////////////////// -namespace satcom { -namespace lib { +namespace senf { - /** \brief Singleton class to manage the event loop +/** \brief The Scheduler interface - This class manages a single select() type event loop. A - customer of this class may register any number of file - descriptiors with this class and pass callback functions to be - called on input, output or error. This functions are specified - using boost::function objects - */ - class Scheduler - : boost::noncopyable + The %scheduler API is comprised of two parts: + + \li Specific \ref sched_objects, one for each type of event. + \li Some generic functions implemented in the \ref senf::scheduler + namespace. + + Events are registered via the respective event class. The (global) functions are used to enter + the application main-loop or query for global information. + + \autotoc + + + \section sched_objects Event classes + + The Scheduler is based on the RAII principle: Every event is represented by a class + instance. The event is registered in the constructor and removed by the destructor of that + instance. This implementation automatically links the lifetime of an event with the lifetime of + the object resposible for it's creation. + + Every event registration is represented by an instance of an event specific class: + + \li senf::scheduler::FdEvent for file descriptor events + \li senf::scheduler::TimerEvent for single-shot deadline timer events + \li senf::scheduler::SignalEvent for UNIX signal events + \li senf::scheduler::EventHook for a special event hook + + These instance are owned and managed by the user of the scheduler \e not by the scheduler so the + RAII concept can be used. + + \code + class SomeServer { + SomeSocketHandle handle_; + senf::scheduler::FdEvent event_; + public: - /////////////////////////////////////////////////////////////////////////// - // Types + SomeServer(SomeSocketHandle handle) + : handle_ (handle), + event_ ("SomeServer handler", senf::membind(&SomeServer::readData, this), + handle, senf::scheduler::FdEvent::EV_READ) + {} + + void readData(int events) + { + // read data from handle_, check for eof and so on. + } + }; + \endcode - enum EventId { EV_NONE=0, - EV_READ=1, EV_PRIO=2, EV_WRITE=4, EV_HUP=8, EV_ERR=16, - EV_ALL=31 }; + The event is defined as a class member variable. When the event member is initialized in the + constructor, the event is automatically registered (except if the optional \a initiallyEnabled + flag argument is set to \c false). The Destructor will automatically remove the event from the + scheduler and ensure, that no dead code is called accidentally. - template - struct GenericCallback { - typedef boost::function::param_type, - EventId) > Callback; - }; + The process is the same for the other event types or when registering multiple events. For + detailed information on the constructor arguments and other features see the event class + documentation referenced below. - /////////////////////////////////////////////////////////////////////////// - ///\name Structors and default members - ///@{ - // private default constructor - // no copy constructor - // no copy assignment - // default destructor - // no conversion constructors + \section sched_handlers Specifying handlers - static Scheduler & instance(); + All handlers are specified as generic Boost.Function objects. This allows to + pass any callable as a handler. Depending on the type of handler, some additional arguments may + be passed to the handler by the %scheduler. - ///@} - /////////////////////////////////////////////////////////////////////////// + If you need to pass additional information to your handler, use Boost.Bind: + \code + // Handle callback function + void callback(UDPv4ClientSocketHandle handle, senf::Scheduler::EventId event) {..} + // Pass 'handle' as additional first argument to callback() + senf::scheduler::FdEvent event ("name", boost::bind(&callback, handle, _1), + handle, senf::scheduler::FdEvent::EV_READ); + // Timeout function + void timeout( int n) {..} + // Call timeout() handler with argument 'n' + senf::scheduler::TimerEvent timer ("name", boost::bind(&timeout, n), + senf::ClockService::now() + senf::ClockService::seconds(1)); + \endcode - template - void add(Handle const & handle, - typename GenericCallback::Callback const & cb, - EventId eventMask = EV_ALL); - template - void remove(Handle const & handle, EventId eventMask = EV_ALL); + To use member-functions as callbacks, use either Boost.Bind or senf::membind() + \code + // e.g. in Foo::Foo() constructor: + Foo::Foo() + : handle_ (...), + readevent_ ("Foo read", senf::membind(&Foo::callback, this), + handle_, senf::scheduler::FdEvent::EV_READ) + { ... } + \endcode - void process(); + The handler is identified by an arbitrary, user specified name. This name is used in error + messages to identify the failing handler. - void terminate(); - protected: + \section sched_exec Executing the Scheduler - private: - Scheduler(); - - typedef boost::function InternalCallback; - - void do_add(int fd, InternalCallback const & cb, EventId eventMask = EV_ALL); - void do_remove(int fd, EventId eventMask = EV_ALL); - - struct EventSpec + To enter the scheduler main-loop, call + + \code + senf::scheduler::process(); + \endcode + + This call will only return in two cases: + + \li When a handler calls senf::scheduler::terminate() + \li When there is no active file descriptor or timer event. + + Additional generic functions provide information and %scheduler + parameters. + + \section sched_container Event objects and container classes + + As the event objects are \e not copyable, they cannot be placed into ordinary + containers. However, it is quite simple to use pointer containers to hold event instances: + + \code + #include + #include + + class Foo + { + public: + void add(int fd) { - InternalCallback cb_read; - InternalCallback cb_prio; - InternalCallback cb_write; - InternalCallback cb_hup; - InternalCallback cb_err; - - int epollMask() const; - }; + fdEvents.insert( + fd, + new senf::scheduler::FdEvent("foo", boost::bind(&callback, this, fd, _1), fd, + senf::scheduler::FdEvent::EV_READ) ); + } + + void callback(int fd, int events) + { + FdEvent & event (fdEvents_[fd]); + + // ... + + if (complete) + fdEvents_.remove(fd) + } + + private: + boost::ptr_map fdEvents_; + }; + \endcode + + The pointer container API is (almost) completely identical to the corresponding standard library + container API. The only difference is, that all elements added to the container \e must be + created via \c new and that the pointer containers themselves are \e not copyable (ok, they are, + if the elements are cloneable ...). See Boost.PointerContainer + for the pointer container library reference. + + + \section sched_signals Signals and the Watchdog + + To secure against blocking callbacks, the %scheduler implementation includes a watchdog + timer. This timer will produce a warning message on the standard error stream when a single + callback is executing for more than the watchdog timeout value. Since the scheduler + implementation is completely single threaded, we cannot terminate the callback but at least we + can produce an informative message and optionally the program can be aborted. + + The watchdog is controlled using the watchdogTimeout(), watchdogEvents() and watchdogAbort(). + functions. + + The watchdog is implemented using a free running interval timer. The watchdog signal (\c SIGURG) + must \e not be blocked. If signals need to be blocked for some reason, those regions will not be + checked by the watchdog. If a callback blocks, the watchdog has no chance to interrupt the + process. + + \warning Since the watchdog is free running for performance reasons, every callback must expect + signals to happen. Signals \e will certainly happen since the watchdog signal is generated + periodically (which does not necessarily generate a watchdog event ...) + + Additional signals (\c SIGALRM) may occur when using using hires timers on kernel/glibc + combinations which do not support timerfd(). On such systems, hires timers are implemented using + POSIX timers which generate a considerable number of additional signals. + + \todo Fix the file support to use threads (?) fork (?) and a pipe so it works reliably even + over e.g. NFS. + */ +namespace scheduler { + + /** \brief Event handler main loop + + This member must be called at some time to enter the event handler main loop. Only while + this function is running any events are handled. The call will return if + \li a callback calls terminate() + \li the run queue becomes empty. + */ + void process(); + + /** \brief \c true, if scheduler is running, \c false otherwise */ + bool running(); + + /** \brief Called by callbacks to terminate the main loop + + This member may be called by any callback to tell the main loop to terminate. The main loop + will return to it's caller after the currently running callback returns. + */ + void terminate(); + + /** \brief Immediately rescheduler + + Calling yield() will cause the scheduler to terminate the current queue run and immediately + rescheduler all pending tasks. + */ + void yield(); + + /** \brief Return timestamp of last event + + This is the timestamp, the last event has been signaled. This is the real time at which the + event is delivered \e not the time it should have been delivered (in the case of timers). + */ + ClockService::clock_type eventTime(); + + /** \brief Return (approximate) current time + + This call will return the current time as far as it is already known to the scheduler. If + the scheduler is running, this will return eventTime(), otherwise it will return + ClockService::now(). While the scheduler is running, this will reduce the number of system + calls. + */ + ClockService::clock_type now(); + + /** \brief Set watchdog timeout to \a ms milliseconds. + + Setting the watchdog timeout to 0 will disable the watchdog. + */ + void watchdogTimeout(unsigned ms); + + /** \brief Current watchdog timeout in milliseconds */ + unsigned watchdogTimeout(); + + /** \brief Number of watchdog events + + calling watchtogEvents() will reset the counter to 0 + */ + unsigned watchdogEvents(); + + /** \brief Enable/disable abort on watchdog event. - typedef std::map FdTable; + Calling watchdogAbort(\c true) will enable aborting the program execution on a watchdog + event. + */ + void watchdogAbort(bool flag); + + /** \brief Get current watchdog abort on event status */ + bool watchdogAbort(); + + /** \brief Switch to using hi resolution timers + + By default, timers are implemented directly using epoll. This however restricts the timer + resolution to that of the kernel HZ value. + + High resolution timers are implemented either using POSIX timers or, when available, using + the Linux special \c timerfd() syscall. + + POSIX timers are delivered using signals. A high timer load this increases the signal load + considerably. \c timerfd()'s are delivered on a file descriptor and thus don't have such a + scalability issue. + + \warning The timer source must not be switched from a scheduler callback + */ + void hiresTimers(); + + /** \brief Switch back to using epoll for timing + \see hiresTimers() + */ + void loresTimers(); - FdTable fdTable_; - int epollFd_; - bool terminate_; + /** \brief return \c true, if \c timerfd() timing is available, \c false otherwise + \see hiresTimers() + */ + bool haveScalableHiresTimers(); + + /** \brief Return \c true, if using hires times, \c false otherwise + \see hiresTimers() */ + bool usingHiresTimers(); + + /** \brief Restart scheduler + + This call will restart all scheduler dispatchers (timers, signals, file descriptors). This + is necessary after a fork(). + \warning This call will \e remove all registered events from the scheduler + */ + void restart(); + + /** \brief Return \c true, if no event is registered, \c false otherwise. */ + bool empty(); + + /** \brief %scheduler specific time source for Utils/Logger framework + + This time source may be used to provide timing information for log messages within the + Utils/Logger framework. This time source will use Scheduler::eventTime() to provide timing + information. + + \code + senf::log::timeSource(); + \endcode + + Using this information reduces the number of necessary ClockService::now() calls and thus + the number of system calls. + */ + struct LogTimeSource : public senf::log::TimeSource + { + senf::log::time_type operator()() const; }; - int retrieve_filehandle(int fd); + /** \brief Temporarily block all signals + + This class is used to temporarily block all signals in a critical section. + + \code + // Begin critical section + { + senf::scheduler::BlockSignals signalBlocker; + + // critical code executed with all signals blocked + } + // End critical section + \endcode + + You need to take care not to block since even the watchdog timer will be disabled while + executing within a critical section. + */ + class BlockSignals + : boost::noncopyable + { + public: + BlockSignals(bool initiallyBlocked=true); + ///< Block signals until end of scope + /**< \param[in] initiallyBlocked set to \c false to not + automatically block signals initially */ + ~BlockSignals(); ///< Release all signal blocks + + void block(); ///< Block signals if not blocked + void unblock(); ///< Unblock signals if blocked + bool blocked() const; ///< \c true, if signals currently blocked, \c false + ///< otherwise + + private: + bool blocked_; + sigset_t allSigs_; + sigset_t savedSigs_; + }; }} ///////////////////////////////hh.e//////////////////////////////////////// #include "Scheduler.cci" -#include "Scheduler.ct" -#include "Scheduler.cti" +//#include "Scheduler.ct" +//#include "Scheduler.cti" #endif // Local Variables: // mode: c++ -// c-file-style: "satcom" +// fill-column: 100 +// c-file-style: "senf" +// indent-tabs-mode: nil +// ispell-local-dictionary: "american" +// compile-command: "scons -u test" +// comment-column: 40 // End: