X-Git-Url: http://g0dil.de/git?a=blobdiff_plain;f=Scheduler%2FScheduler.hh;h=9f3d3cd2f3715f9c0156a9c5c1c9d8409c62c955;hb=3863d46dd898b7bc35ea8c6ccd8563b18762a6b6;hp=fb1aebf2f07e5a4d1855c1f4da8aa6e411e4777d;hpb=31d85cd6b8e03c5ecc924ca8892906be1bab702f;p=senf.git diff --git a/Scheduler/Scheduler.hh b/Scheduler/Scheduler.hh index fb1aebf..9f3d3cd 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 +// 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 @@ -24,206 +24,371 @@ \brief Scheduler public header */ -#ifndef HH_Scheduler_ -#define HH_Scheduler_ 1 +#ifndef HH_SENF_Scheduler_Scheduler_ +#define HH_SENF_Scheduler_Scheduler_ 1 // Custom includes -#include -#include -#include #include -#include - -#include "Utils/MicroTime.hh" +#include "../Utils/Logger/SenfLog.hh" +#include "FdEvent.hh" +#include "TimerEvent.hh" +#include "SignalEvent.hh" +#include "EventHook.hh" //#include "scheduler.mpp" ///////////////////////////////hh.p//////////////////////////////////////// -/** \brief SENF Project namespace */ 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 descriptors with this class and pass callback functions to be called on - input, output or error. This functions are specified using boost::function objects (See Boost.Function) + The %scheduler API is comprised of two parts: - The Scheduler is based on a generic handle representation. The only information needed from - a handle, is the intrinsic file descriptor. Any object for which the statement - \code - int fd = retrieve_filehandle(object); - \endcode - is valid and places the relevant file descriptor into fd can be used as a Handle type. There - is an implementation of retrieve_filehandle(int) within the library to handle explicit file - descriptors. The Socket library provides an - implementation of retrieve_filehandle(FileHandle handle). If you want to support - some other handle type, just define an appropriate \c retrieve_filehandle function in - that types namespace. - - It is important to note, that for every combination of file descriptor and event, only a \e - single handler may be installed. Installing more handlers does not make sense. If you need - to distribute data to several interested parties, you must take care of this yourself. - - \todo Fix EventId parameter (probably to int) to allow |-ing without casting ... - */ - class Scheduler - : boost::noncopyable + \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: + 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 + + 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. + + 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. + + + \section sched_handlers Specifying handlers + + 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 + + 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 + + The handler is identified by an arbitrary, user specified name. This name is used in error + messages to identify the failing handler. + + + \section sched_exec Executing the Scheduler + + 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: - /////////////////////////////////////////////////////////////////////////// - // Types - - /// \brief Types of file descriptor events */ - enum EventId { EV_NONE=0, - EV_READ=1, EV_PRIO=2, EV_WRITE=4, - EV_ALL=7, - EV_HUP=8, EV_ERR=16 }; - - /** \brief Template typedef for Callback type - - This is a template typedef (which does not exist in C++) that is, a template class whose - sole member is a typedef symbol defining the callback type given the handle type. - - The Callback is any callable object taking a \c Handle and an \c EventId as argument. - */ - template - struct GenericCallback { - typedef boost::function::param_type, - EventId) > Callback; - }; - /** \brief Callback type for timer events */ - typedef boost::function TimerCallback; - - /////////////////////////////////////////////////////////////////////////// - ///\name Structors and default members - ///@{ - - // private default constructor - // no copy constructor - // no copy assignment - // default destructor - // no conversion constructors - - /** \brief Return Scheduler instance - - This static member is used to access the singleton instance. This member is save to - return a correctly initialized Scheduler instance even if called at global construction - time - - \implementation This static member just defines the Scheduler as a static method - variable. The C++ standard then provides above guarantee. The instance will be - initialized the first time, the code flow passes the variable declaration found in - the instance() body. - */ - static Scheduler & instance(); - - ///@} - /////////////////////////////////////////////////////////////////////////// - - template - void add(Handle const & handle, - typename GenericCallback::Callback const & cb, - int eventMask = EV_ALL); ///< Add file handle event callback - /**< add() will add a callback to the Scheduler. The - callback will be called for the given type of event on - the given arbitrary file-descriptor or - handle-like object. If there already is a Callback - registered for one of the events requested, the new - handler will replace the old one. - \param[in] handle file descriptor or handle providing - the Handle interface defined above. - \param[in] cb callback - \param[in] eventMask arbitrary combination via '|' - operator of EventId designators. */ - template - void remove(Handle const & handle, int eventMask = EV_ALL); ///< Remove event callback - /**< remove() will remove any callback registered for any of - the given events on the given file descriptor or handle - like object. - \param[in] handle file descriptor or handle providing - the Handle interface defined above. - \param[in] eventMask arbitrary combination via '|' - operator of EventId designators. */ - - void timeout(unsigned long timeout, TimerCallback const & cb); ///< Add timeout event - /**< \param[in] timeout timeout in milliseconds - \param[in] cb callback to call after \a timeout - milliseconds - \todo Return some kind of handle/pointer and add - support to update or revoke a timeout */ - - void process(); ///< 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 - only, if any callback calls terminate(). */ - void terminate(); ///< 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. */ - - protected: + void add(int fd) + { + 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: - typedef boost::function SimpleCallback; + boost::ptr_map fdEvents_; + }; + \endcode - Scheduler(); + 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. - void do_add(int fd, SimpleCallback const & cb, int eventMask = EV_ALL); - void do_remove(int fd, int eventMask = EV_ALL); - /** \brief Descriptor event specification - \internal */ - struct EventSpec - { - SimpleCallback cb_read; - SimpleCallback cb_prio; - SimpleCallback cb_write; + \section sched_signals Signals and the Watchdog - int epollMask() const; - }; + 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. - /** \brief Timer event specification - \internal */ - struct TimerSpec - { - TimerSpec() : timeout(), cb() {} - TimerSpec(unsigned long long timeout_, TimerCallback cb_) - : timeout(timeout_), cb(cb_) {} + 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 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(); - bool operator< (TimerSpec const & other) const - { return timeout > other.timeout; } + /** \brief Return (approximate) current time - unsigned long long timeout; - TimerCallback cb; - }; + 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. + + 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(); - typedef std::map FdTable; - typedef std::priority_queue TimerQueue; + /** \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. - FdTable fdTable_; - TimerQueue timerQueue_; - int epollFd_; - bool terminate_; + 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(); + + /** \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; }; - /** \brief Default file descriptor accessor + /** \brief Temporarily block all signals - retrieve_filehandle() provides the Scheduler with support for explicit file descriptors as - file handle argument. + 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 - \relates Scheduler + You need to take care not to block since even the watchdog timer will be disabled while + executing within a critical section. */ - int retrieve_filehandle(int fd); + 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.cti" #endif @@ -234,4 +399,5 @@ namespace senf { // indent-tabs-mode: nil // ispell-local-dictionary: "american" // compile-command: "scons -u test" +// comment-column: 40 // End: