… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
|
|
68 | |
|
|
69 | This document documents the libev software package. |
68 | |
70 | |
69 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
70 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
71 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
|
74 | |
|
|
75 | While this document tries to be as complete as possible in documenting |
|
|
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
|
|
78 | with libev. |
|
|
79 | |
|
|
80 | Familarity with event based programming techniques in general is assumed |
|
|
81 | throughout this document. |
|
|
82 | |
|
|
83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
74 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
111 | this argument. |
123 | this argument. |
112 | |
124 | |
113 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
114 | |
126 | |
115 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
118 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
119 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
120 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
121 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
122 | throughout libev. |
134 | throughout libev. |
123 | |
135 | |
124 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
125 | |
137 | |
… | |
… | |
460 | |
472 | |
461 | While nominally embeddable in other event loops, this doesn't work |
473 | While nominally embeddable in other event loops, this doesn't work |
462 | everywhere, so you might need to test for this. And since it is broken |
474 | everywhere, so you might need to test for this. And since it is broken |
463 | almost everywhere, you should only use it when you have a lot of sockets |
475 | almost everywhere, you should only use it when you have a lot of sockets |
464 | (for which it usually works), by embedding it into another event loop |
476 | (for which it usually works), by embedding it into another event loop |
465 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
477 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
466 | using it only for sockets. |
478 | also broken on OS X)) and, did I mention it, using it only for sockets. |
467 | |
479 | |
468 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
480 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
469 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
481 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
470 | C<NOTE_EOF>. |
482 | C<NOTE_EOF>. |
471 | |
483 | |
… | |
… | |
632 | |
644 | |
633 | This function is rarely useful, but when some event callback runs for a |
645 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
646 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
647 | the current time is a good idea. |
636 | |
648 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
649 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
650 | |
|
|
651 | =item ev_suspend (loop) |
|
|
652 | |
|
|
653 | =item ev_resume (loop) |
|
|
654 | |
|
|
655 | These two functions suspend and resume a loop, for use when the loop is |
|
|
656 | not used for a while and timeouts should not be processed. |
|
|
657 | |
|
|
658 | A typical use case would be an interactive program such as a game: When |
|
|
659 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
660 | would be best to handle timeouts as if no time had actually passed while |
|
|
661 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
662 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
663 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
664 | |
|
|
665 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
666 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
667 | will be rescheduled (that is, they will lose any events that would have |
|
|
668 | occured while suspended). |
|
|
669 | |
|
|
670 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
671 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
672 | without a previous call to C<ev_suspend>. |
|
|
673 | |
|
|
674 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
675 | event loop time (see C<ev_now_update>). |
638 | |
676 | |
639 | =item ev_loop (loop, int flags) |
677 | =item ev_loop (loop, int flags) |
640 | |
678 | |
641 | Finally, this is it, the event handler. This function usually is called |
679 | Finally, this is it, the event handler. This function usually is called |
642 | after you initialised all your watchers and you want to start handling |
680 | after you initialised all your watchers and you want to start handling |
… | |
… | |
726 | |
764 | |
727 | If you have a watcher you never unregister that should not keep C<ev_loop> |
765 | If you have a watcher you never unregister that should not keep C<ev_loop> |
728 | from returning, call ev_unref() after starting, and ev_ref() before |
766 | from returning, call ev_unref() after starting, and ev_ref() before |
729 | stopping it. |
767 | stopping it. |
730 | |
768 | |
731 | As an example, libev itself uses this for its internal signal pipe: It is |
769 | As an example, libev itself uses this for its internal signal pipe: It |
732 | not visible to the libev user and should not keep C<ev_loop> from exiting |
770 | is not visible to the libev user and should not keep C<ev_loop> from |
733 | if no event watchers registered by it are active. It is also an excellent |
771 | exiting if no event watchers registered by it are active. It is also an |
734 | way to do this for generic recurring timers or from within third-party |
772 | excellent way to do this for generic recurring timers or from within |
735 | libraries. Just remember to I<unref after start> and I<ref before stop> |
773 | third-party libraries. Just remember to I<unref after start> and I<ref |
736 | (but only if the watcher wasn't active before, or was active before, |
774 | before stop> (but only if the watcher wasn't active before, or was active |
737 | respectively). |
775 | before, respectively. Note also that libev might stop watchers itself |
|
|
776 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
777 | in the callback). |
738 | |
778 | |
739 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
779 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
740 | running when nothing else is active. |
780 | running when nothing else is active. |
741 | |
781 | |
742 | ev_signal exitsig; |
782 | ev_signal exitsig; |
… | |
… | |
771 | |
811 | |
772 | By setting a higher I<io collect interval> you allow libev to spend more |
812 | By setting a higher I<io collect interval> you allow libev to spend more |
773 | time collecting I/O events, so you can handle more events per iteration, |
813 | time collecting I/O events, so you can handle more events per iteration, |
774 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
814 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
775 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
815 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
776 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
816 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
817 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
818 | once per this interval, on average. |
777 | |
819 | |
778 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
820 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
779 | to spend more time collecting timeouts, at the expense of increased |
821 | to spend more time collecting timeouts, at the expense of increased |
780 | latency/jitter/inexactness (the watcher callback will be called |
822 | latency/jitter/inexactness (the watcher callback will be called |
781 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
823 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
783 | |
825 | |
784 | Many (busy) programs can usually benefit by setting the I/O collect |
826 | Many (busy) programs can usually benefit by setting the I/O collect |
785 | interval to a value near C<0.1> or so, which is often enough for |
827 | interval to a value near C<0.1> or so, which is often enough for |
786 | interactive servers (of course not for games), likewise for timeouts. It |
828 | interactive servers (of course not for games), likewise for timeouts. It |
787 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
829 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
788 | as this approaches the timing granularity of most systems. |
830 | as this approaches the timing granularity of most systems. Note that if |
|
|
831 | you do transactions with the outside world and you can't increase the |
|
|
832 | parallelity, then this setting will limit your transaction rate (if you |
|
|
833 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
834 | then you can't do more than 100 transations per second). |
789 | |
835 | |
790 | Setting the I<timeout collect interval> can improve the opportunity for |
836 | Setting the I<timeout collect interval> can improve the opportunity for |
791 | saving power, as the program will "bundle" timer callback invocations that |
837 | saving power, as the program will "bundle" timer callback invocations that |
792 | are "near" in time together, by delaying some, thus reducing the number of |
838 | are "near" in time together, by delaying some, thus reducing the number of |
793 | times the process sleeps and wakes up again. Another useful technique to |
839 | times the process sleeps and wakes up again. Another useful technique to |
794 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
840 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
795 | they fire on, say, one-second boundaries only. |
841 | they fire on, say, one-second boundaries only. |
|
|
842 | |
|
|
843 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
844 | more often than 100 times per second: |
|
|
845 | |
|
|
846 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
847 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
796 | |
848 | |
797 | =item ev_loop_verify (loop) |
849 | =item ev_loop_verify (loop) |
798 | |
850 | |
799 | This function only does something when C<EV_VERIFY> support has been |
851 | This function only does something when C<EV_VERIFY> support has been |
800 | compiled in, which is the default for non-minimal builds. It tries to go |
852 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
926 | |
978 | |
927 | =item C<EV_ASYNC> |
979 | =item C<EV_ASYNC> |
928 | |
980 | |
929 | The given async watcher has been asynchronously notified (see C<ev_async>). |
981 | The given async watcher has been asynchronously notified (see C<ev_async>). |
930 | |
982 | |
|
|
983 | =item C<EV_CUSTOM> |
|
|
984 | |
|
|
985 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
986 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
987 | |
931 | =item C<EV_ERROR> |
988 | =item C<EV_ERROR> |
932 | |
989 | |
933 | An unspecified error has occurred, the watcher has been stopped. This might |
990 | An unspecified error has occurred, the watcher has been stopped. This might |
934 | happen because the watcher could not be properly started because libev |
991 | happen because the watcher could not be properly started because libev |
935 | ran out of memory, a file descriptor was found to be closed or any other |
992 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1050 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1107 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1051 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1108 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1052 | before watchers with lower priority, but priority will not keep watchers |
1109 | before watchers with lower priority, but priority will not keep watchers |
1053 | from being executed (except for C<ev_idle> watchers). |
1110 | from being executed (except for C<ev_idle> watchers). |
1054 | |
1111 | |
1055 | This means that priorities are I<only> used for ordering callback |
|
|
1056 | invocation after new events have been received. This is useful, for |
|
|
1057 | example, to reduce latency after idling, or more often, to bind two |
|
|
1058 | watchers on the same event and make sure one is called first. |
|
|
1059 | |
|
|
1060 | If you need to suppress invocation when higher priority events are pending |
1112 | If you need to suppress invocation when higher priority events are pending |
1061 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1113 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1062 | |
1114 | |
1063 | You I<must not> change the priority of a watcher as long as it is active or |
1115 | You I<must not> change the priority of a watcher as long as it is active or |
1064 | pending. |
1116 | pending. |
1065 | |
|
|
1066 | The default priority used by watchers when no priority has been set is |
|
|
1067 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1068 | |
1117 | |
1069 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1118 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1070 | fine, as long as you do not mind that the priority value you query might |
1119 | fine, as long as you do not mind that the priority value you query might |
1071 | or might not have been clamped to the valid range. |
1120 | or might not have been clamped to the valid range. |
|
|
1121 | |
|
|
1122 | The default priority used by watchers when no priority has been set is |
|
|
1123 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1124 | |
|
|
1125 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1126 | priorities. |
1072 | |
1127 | |
1073 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1128 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1074 | |
1129 | |
1075 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1130 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1076 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1131 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1141 | #include <stddef.h> |
1196 | #include <stddef.h> |
1142 | |
1197 | |
1143 | static void |
1198 | static void |
1144 | t1_cb (EV_P_ ev_timer *w, int revents) |
1199 | t1_cb (EV_P_ ev_timer *w, int revents) |
1145 | { |
1200 | { |
1146 | struct my_biggy big = (struct my_biggy * |
1201 | struct my_biggy big = (struct my_biggy *) |
1147 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1202 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1148 | } |
1203 | } |
1149 | |
1204 | |
1150 | static void |
1205 | static void |
1151 | t2_cb (EV_P_ ev_timer *w, int revents) |
1206 | t2_cb (EV_P_ ev_timer *w, int revents) |
1152 | { |
1207 | { |
1153 | struct my_biggy big = (struct my_biggy * |
1208 | struct my_biggy big = (struct my_biggy *) |
1154 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1209 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1155 | } |
1210 | } |
|
|
1211 | |
|
|
1212 | =head2 WATCHER PRIORITY MODELS |
|
|
1213 | |
|
|
1214 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1215 | integers that influence the ordering of event callback invocation |
|
|
1216 | between watchers in some way, all else being equal. |
|
|
1217 | |
|
|
1218 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1219 | description for the more technical details such as the actual priority |
|
|
1220 | range. |
|
|
1221 | |
|
|
1222 | There are two common ways how these these priorities are being interpreted |
|
|
1223 | by event loops: |
|
|
1224 | |
|
|
1225 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1226 | of lower priority watchers, which means as long as higher priority |
|
|
1227 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1228 | |
|
|
1229 | The less common only-for-ordering model uses priorities solely to order |
|
|
1230 | callback invocation within a single event loop iteration: Higher priority |
|
|
1231 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1232 | before polling for new events. |
|
|
1233 | |
|
|
1234 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1235 | except for idle watchers (which use the lock-out model). |
|
|
1236 | |
|
|
1237 | The rationale behind this is that implementing the lock-out model for |
|
|
1238 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1239 | libraries will just poll for the same events again and again as long as |
|
|
1240 | their callbacks have not been executed, which is very inefficient in the |
|
|
1241 | common case of one high-priority watcher locking out a mass of lower |
|
|
1242 | priority ones. |
|
|
1243 | |
|
|
1244 | Static (ordering) priorities are most useful when you have two or more |
|
|
1245 | watchers handling the same resource: a typical usage example is having an |
|
|
1246 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1247 | timeouts. Under load, data might be received while the program handles |
|
|
1248 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1249 | handler will be executed before checking for data. In that case, giving |
|
|
1250 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1251 | handled first even under adverse conditions (which is usually, but not |
|
|
1252 | always, what you want). |
|
|
1253 | |
|
|
1254 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1255 | will only be executed when no same or higher priority watchers have |
|
|
1256 | received events, they can be used to implement the "lock-out" model when |
|
|
1257 | required. |
|
|
1258 | |
|
|
1259 | For example, to emulate how many other event libraries handle priorities, |
|
|
1260 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1261 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1262 | processing is done in the idle watcher callback. This causes libev to |
|
|
1263 | continously poll and process kernel event data for the watcher, but when |
|
|
1264 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1265 | workable. |
|
|
1266 | |
|
|
1267 | Usually, however, the lock-out model implemented that way will perform |
|
|
1268 | miserably under the type of load it was designed to handle. In that case, |
|
|
1269 | it might be preferable to stop the real watcher before starting the |
|
|
1270 | idle watcher, so the kernel will not have to process the event in case |
|
|
1271 | the actual processing will be delayed for considerable time. |
|
|
1272 | |
|
|
1273 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1274 | priority than the default, and which should only process data when no |
|
|
1275 | other events are pending: |
|
|
1276 | |
|
|
1277 | ev_idle idle; // actual processing watcher |
|
|
1278 | ev_io io; // actual event watcher |
|
|
1279 | |
|
|
1280 | static void |
|
|
1281 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1282 | { |
|
|
1283 | // stop the I/O watcher, we received the event, but |
|
|
1284 | // are not yet ready to handle it. |
|
|
1285 | ev_io_stop (EV_A_ w); |
|
|
1286 | |
|
|
1287 | // start the idle watcher to ahndle the actual event. |
|
|
1288 | // it will not be executed as long as other watchers |
|
|
1289 | // with the default priority are receiving events. |
|
|
1290 | ev_idle_start (EV_A_ &idle); |
|
|
1291 | } |
|
|
1292 | |
|
|
1293 | static void |
|
|
1294 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1295 | { |
|
|
1296 | // actual processing |
|
|
1297 | read (STDIN_FILENO, ...); |
|
|
1298 | |
|
|
1299 | // have to start the I/O watcher again, as |
|
|
1300 | // we have handled the event |
|
|
1301 | ev_io_start (EV_P_ &io); |
|
|
1302 | } |
|
|
1303 | |
|
|
1304 | // initialisation |
|
|
1305 | ev_idle_init (&idle, idle_cb); |
|
|
1306 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1307 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1308 | |
|
|
1309 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1310 | low-priority connections can not be locked out forever under load. This |
|
|
1311 | enables your program to keep a lower latency for important connections |
|
|
1312 | during short periods of high load, while not completely locking out less |
|
|
1313 | important ones. |
1156 | |
1314 | |
1157 | |
1315 | |
1158 | =head1 WATCHER TYPES |
1316 | =head1 WATCHER TYPES |
1159 | |
1317 | |
1160 | This section describes each watcher in detail, but will not repeat |
1318 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1186 | descriptors to non-blocking mode is also usually a good idea (but not |
1344 | descriptors to non-blocking mode is also usually a good idea (but not |
1187 | required if you know what you are doing). |
1345 | required if you know what you are doing). |
1188 | |
1346 | |
1189 | If you cannot use non-blocking mode, then force the use of a |
1347 | If you cannot use non-blocking mode, then force the use of a |
1190 | known-to-be-good backend (at the time of this writing, this includes only |
1348 | known-to-be-good backend (at the time of this writing, this includes only |
1191 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1349 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1350 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1351 | files) - libev doesn't guarentee any specific behaviour in that case. |
1192 | |
1352 | |
1193 | Another thing you have to watch out for is that it is quite easy to |
1353 | Another thing you have to watch out for is that it is quite easy to |
1194 | receive "spurious" readiness notifications, that is your callback might |
1354 | receive "spurious" readiness notifications, that is your callback might |
1195 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1355 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1196 | because there is no data. Not only are some backends known to create a |
1356 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1317 | year, it will still time out after (roughly) one hour. "Roughly" because |
1477 | year, it will still time out after (roughly) one hour. "Roughly" because |
1318 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1478 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1319 | monotonic clock option helps a lot here). |
1479 | monotonic clock option helps a lot here). |
1320 | |
1480 | |
1321 | The callback is guaranteed to be invoked only I<after> its timeout has |
1481 | The callback is guaranteed to be invoked only I<after> its timeout has |
1322 | passed, but if multiple timers become ready during the same loop iteration |
1482 | passed (not I<at>, so on systems with very low-resolution clocks this |
1323 | then order of execution is undefined. |
1483 | might introduce a small delay). If multiple timers become ready during the |
|
|
1484 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1485 | before ones with later time-out values (but this is no longer true when a |
|
|
1486 | callback calls C<ev_loop> recursively). |
1324 | |
1487 | |
1325 | =head3 Be smart about timeouts |
1488 | =head3 Be smart about timeouts |
1326 | |
1489 | |
1327 | Many real-world problems involve some kind of timeout, usually for error |
1490 | Many real-world problems involve some kind of timeout, usually for error |
1328 | recovery. A typical example is an HTTP request - if the other side hangs, |
1491 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1372 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1535 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1373 | member and C<ev_timer_again>. |
1536 | member and C<ev_timer_again>. |
1374 | |
1537 | |
1375 | At start: |
1538 | At start: |
1376 | |
1539 | |
1377 | ev_timer_init (timer, callback); |
1540 | ev_init (timer, callback); |
1378 | timer->repeat = 60.; |
1541 | timer->repeat = 60.; |
1379 | ev_timer_again (loop, timer); |
1542 | ev_timer_again (loop, timer); |
1380 | |
1543 | |
1381 | Each time there is some activity: |
1544 | Each time there is some activity: |
1382 | |
1545 | |
… | |
… | |
1444 | |
1607 | |
1445 | To start the timer, simply initialise the watcher and set C<last_activity> |
1608 | To start the timer, simply initialise the watcher and set C<last_activity> |
1446 | to the current time (meaning we just have some activity :), then call the |
1609 | to the current time (meaning we just have some activity :), then call the |
1447 | callback, which will "do the right thing" and start the timer: |
1610 | callback, which will "do the right thing" and start the timer: |
1448 | |
1611 | |
1449 | ev_timer_init (timer, callback); |
1612 | ev_init (timer, callback); |
1450 | last_activity = ev_now (loop); |
1613 | last_activity = ev_now (loop); |
1451 | callback (loop, timer, EV_TIMEOUT); |
1614 | callback (loop, timer, EV_TIMEOUT); |
1452 | |
1615 | |
1453 | And when there is some activity, simply store the current time in |
1616 | And when there is some activity, simply store the current time in |
1454 | C<last_activity>, no libev calls at all: |
1617 | C<last_activity>, no libev calls at all: |
… | |
… | |
1547 | If the timer is started but non-repeating, stop it (as if it timed out). |
1710 | If the timer is started but non-repeating, stop it (as if it timed out). |
1548 | |
1711 | |
1549 | If the timer is repeating, either start it if necessary (with the |
1712 | If the timer is repeating, either start it if necessary (with the |
1550 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1713 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1551 | |
1714 | |
1552 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1715 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1553 | usage example. |
1716 | usage example. |
1554 | |
1717 | |
1555 | =item ev_tstamp repeat [read-write] |
1718 | =item ev_tstamp repeat [read-write] |
1556 | |
1719 | |
1557 | The current C<repeat> value. Will be used each time the watcher times out |
1720 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1596 | =head2 C<ev_periodic> - to cron or not to cron? |
1759 | =head2 C<ev_periodic> - to cron or not to cron? |
1597 | |
1760 | |
1598 | Periodic watchers are also timers of a kind, but they are very versatile |
1761 | Periodic watchers are also timers of a kind, but they are very versatile |
1599 | (and unfortunately a bit complex). |
1762 | (and unfortunately a bit complex). |
1600 | |
1763 | |
1601 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1764 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1602 | but on wall clock time (absolute time). You can tell a periodic watcher |
1765 | relative time, the physical time that passes) but on wall clock time |
1603 | to trigger after some specific point in time. For example, if you tell a |
1766 | (absolute time, the thing you can read on your calender or clock). The |
1604 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1767 | difference is that wall clock time can run faster or slower than real |
1605 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1768 | time, and time jumps are not uncommon (e.g. when you adjust your |
1606 | clock to January of the previous year, then it will take more than year |
1769 | wrist-watch). |
1607 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1608 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1609 | |
1770 | |
|
|
1771 | You can tell a periodic watcher to trigger after some specific point |
|
|
1772 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1773 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1774 | not a delay) and then reset your system clock to January of the previous |
|
|
1775 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1776 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1777 | it, as it uses a relative timeout). |
|
|
1778 | |
1610 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1779 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1611 | such as triggering an event on each "midnight, local time", or other |
1780 | timers, such as triggering an event on each "midnight, local time", or |
1612 | complicated rules. |
1781 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1782 | those cannot react to time jumps. |
1613 | |
1783 | |
1614 | As with timers, the callback is guaranteed to be invoked only when the |
1784 | As with timers, the callback is guaranteed to be invoked only when the |
1615 | time (C<at>) has passed, but if multiple periodic timers become ready |
1785 | point in time where it is supposed to trigger has passed. If multiple |
1616 | during the same loop iteration, then order of execution is undefined. |
1786 | timers become ready during the same loop iteration then the ones with |
|
|
1787 | earlier time-out values are invoked before ones with later time-out values |
|
|
1788 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1617 | |
1789 | |
1618 | =head3 Watcher-Specific Functions and Data Members |
1790 | =head3 Watcher-Specific Functions and Data Members |
1619 | |
1791 | |
1620 | =over 4 |
1792 | =over 4 |
1621 | |
1793 | |
1622 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1794 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1623 | |
1795 | |
1624 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1796 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1625 | |
1797 | |
1626 | Lots of arguments, lets sort it out... There are basically three modes of |
1798 | Lots of arguments, let's sort it out... There are basically three modes of |
1627 | operation, and we will explain them from simplest to most complex: |
1799 | operation, and we will explain them from simplest to most complex: |
1628 | |
1800 | |
1629 | =over 4 |
1801 | =over 4 |
1630 | |
1802 | |
1631 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1803 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1632 | |
1804 | |
1633 | In this configuration the watcher triggers an event after the wall clock |
1805 | In this configuration the watcher triggers an event after the wall clock |
1634 | time C<at> has passed. It will not repeat and will not adjust when a time |
1806 | time C<offset> has passed. It will not repeat and will not adjust when a |
1635 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1807 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1636 | only run when the system clock reaches or surpasses this time. |
1808 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1809 | this point in time. |
1637 | |
1810 | |
1638 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1811 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1639 | |
1812 | |
1640 | In this mode the watcher will always be scheduled to time out at the next |
1813 | In this mode the watcher will always be scheduled to time out at the next |
1641 | C<at + N * interval> time (for some integer N, which can also be negative) |
1814 | C<offset + N * interval> time (for some integer N, which can also be |
1642 | and then repeat, regardless of any time jumps. |
1815 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1816 | argument is merely an offset into the C<interval> periods. |
1643 | |
1817 | |
1644 | This can be used to create timers that do not drift with respect to the |
1818 | This can be used to create timers that do not drift with respect to the |
1645 | system clock, for example, here is a C<ev_periodic> that triggers each |
1819 | system clock, for example, here is an C<ev_periodic> that triggers each |
1646 | hour, on the hour: |
1820 | hour, on the hour (with respect to UTC): |
1647 | |
1821 | |
1648 | ev_periodic_set (&periodic, 0., 3600., 0); |
1822 | ev_periodic_set (&periodic, 0., 3600., 0); |
1649 | |
1823 | |
1650 | This doesn't mean there will always be 3600 seconds in between triggers, |
1824 | This doesn't mean there will always be 3600 seconds in between triggers, |
1651 | but only that the callback will be called when the system time shows a |
1825 | but only that the callback will be called when the system time shows a |
1652 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1826 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1653 | by 3600. |
1827 | by 3600. |
1654 | |
1828 | |
1655 | Another way to think about it (for the mathematically inclined) is that |
1829 | Another way to think about it (for the mathematically inclined) is that |
1656 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1830 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1657 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1831 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1658 | |
1832 | |
1659 | For numerical stability it is preferable that the C<at> value is near |
1833 | For numerical stability it is preferable that the C<offset> value is near |
1660 | C<ev_now ()> (the current time), but there is no range requirement for |
1834 | C<ev_now ()> (the current time), but there is no range requirement for |
1661 | this value, and in fact is often specified as zero. |
1835 | this value, and in fact is often specified as zero. |
1662 | |
1836 | |
1663 | Note also that there is an upper limit to how often a timer can fire (CPU |
1837 | Note also that there is an upper limit to how often a timer can fire (CPU |
1664 | speed for example), so if C<interval> is very small then timing stability |
1838 | speed for example), so if C<interval> is very small then timing stability |
1665 | will of course deteriorate. Libev itself tries to be exact to be about one |
1839 | will of course deteriorate. Libev itself tries to be exact to be about one |
1666 | millisecond (if the OS supports it and the machine is fast enough). |
1840 | millisecond (if the OS supports it and the machine is fast enough). |
1667 | |
1841 | |
1668 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1842 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1669 | |
1843 | |
1670 | In this mode the values for C<interval> and C<at> are both being |
1844 | In this mode the values for C<interval> and C<offset> are both being |
1671 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1845 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1672 | reschedule callback will be called with the watcher as first, and the |
1846 | reschedule callback will be called with the watcher as first, and the |
1673 | current time as second argument. |
1847 | current time as second argument. |
1674 | |
1848 | |
1675 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1849 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1676 | ever, or make ANY event loop modifications whatsoever>. |
1850 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1851 | allowed by documentation here>. |
1677 | |
1852 | |
1678 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1853 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1679 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1854 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1680 | only event loop modification you are allowed to do). |
1855 | only event loop modification you are allowed to do). |
1681 | |
1856 | |
… | |
… | |
1711 | a different time than the last time it was called (e.g. in a crond like |
1886 | a different time than the last time it was called (e.g. in a crond like |
1712 | program when the crontabs have changed). |
1887 | program when the crontabs have changed). |
1713 | |
1888 | |
1714 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1889 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1715 | |
1890 | |
1716 | When active, returns the absolute time that the watcher is supposed to |
1891 | When active, returns the absolute time that the watcher is supposed |
1717 | trigger next. |
1892 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1893 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1894 | rescheduling modes. |
1718 | |
1895 | |
1719 | =item ev_tstamp offset [read-write] |
1896 | =item ev_tstamp offset [read-write] |
1720 | |
1897 | |
1721 | When repeating, this contains the offset value, otherwise this is the |
1898 | When repeating, this contains the offset value, otherwise this is the |
1722 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1899 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1900 | although libev might modify this value for better numerical stability). |
1723 | |
1901 | |
1724 | Can be modified any time, but changes only take effect when the periodic |
1902 | Can be modified any time, but changes only take effect when the periodic |
1725 | timer fires or C<ev_periodic_again> is being called. |
1903 | timer fires or C<ev_periodic_again> is being called. |
1726 | |
1904 | |
1727 | =item ev_tstamp interval [read-write] |
1905 | =item ev_tstamp interval [read-write] |
… | |
… | |
1836 | some child status changes (most typically when a child of yours dies or |
2014 | some child status changes (most typically when a child of yours dies or |
1837 | exits). It is permissible to install a child watcher I<after> the child |
2015 | exits). It is permissible to install a child watcher I<after> the child |
1838 | has been forked (which implies it might have already exited), as long |
2016 | has been forked (which implies it might have already exited), as long |
1839 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2017 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1840 | forking and then immediately registering a watcher for the child is fine, |
2018 | forking and then immediately registering a watcher for the child is fine, |
1841 | but forking and registering a watcher a few event loop iterations later is |
2019 | but forking and registering a watcher a few event loop iterations later or |
1842 | not. |
2020 | in the next callback invocation is not. |
1843 | |
2021 | |
1844 | Only the default event loop is capable of handling signals, and therefore |
2022 | Only the default event loop is capable of handling signals, and therefore |
1845 | you can only register child watchers in the default event loop. |
2023 | you can only register child watchers in the default event loop. |
1846 | |
2024 | |
1847 | =head3 Process Interaction |
2025 | =head3 Process Interaction |
… | |
… | |
2179 | |
2357 | |
2180 | =head3 Watcher-Specific Functions and Data Members |
2358 | =head3 Watcher-Specific Functions and Data Members |
2181 | |
2359 | |
2182 | =over 4 |
2360 | =over 4 |
2183 | |
2361 | |
2184 | =item ev_idle_init (ev_signal *, callback) |
2362 | =item ev_idle_init (ev_idle *, callback) |
2185 | |
2363 | |
2186 | Initialises and configures the idle watcher - it has no parameters of any |
2364 | Initialises and configures the idle watcher - it has no parameters of any |
2187 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2365 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2188 | believe me. |
2366 | believe me. |
2189 | |
2367 | |
… | |
… | |
2202 | // no longer anything immediate to do. |
2380 | // no longer anything immediate to do. |
2203 | } |
2381 | } |
2204 | |
2382 | |
2205 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2383 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2206 | ev_idle_init (idle_watcher, idle_cb); |
2384 | ev_idle_init (idle_watcher, idle_cb); |
2207 | ev_idle_start (loop, idle_cb); |
2385 | ev_idle_start (loop, idle_watcher); |
2208 | |
2386 | |
2209 | |
2387 | |
2210 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2388 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2211 | |
2389 | |
2212 | Prepare and check watchers are usually (but not always) used in pairs: |
2390 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2305 | struct pollfd fds [nfd]; |
2483 | struct pollfd fds [nfd]; |
2306 | // actual code will need to loop here and realloc etc. |
2484 | // actual code will need to loop here and realloc etc. |
2307 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2485 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2308 | |
2486 | |
2309 | /* the callback is illegal, but won't be called as we stop during check */ |
2487 | /* the callback is illegal, but won't be called as we stop during check */ |
2310 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2488 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2311 | ev_timer_start (loop, &tw); |
2489 | ev_timer_start (loop, &tw); |
2312 | |
2490 | |
2313 | // create one ev_io per pollfd |
2491 | // create one ev_io per pollfd |
2314 | for (int i = 0; i < nfd; ++i) |
2492 | for (int i = 0; i < nfd; ++i) |
2315 | { |
2493 | { |
… | |
… | |
2428 | some fds have to be watched and handled very quickly (with low latency), |
2606 | some fds have to be watched and handled very quickly (with low latency), |
2429 | and even priorities and idle watchers might have too much overhead. In |
2607 | and even priorities and idle watchers might have too much overhead. In |
2430 | this case you would put all the high priority stuff in one loop and all |
2608 | this case you would put all the high priority stuff in one loop and all |
2431 | the rest in a second one, and embed the second one in the first. |
2609 | the rest in a second one, and embed the second one in the first. |
2432 | |
2610 | |
2433 | As long as the watcher is active, the callback will be invoked every time |
2611 | As long as the watcher is active, the callback will be invoked every |
2434 | there might be events pending in the embedded loop. The callback must then |
2612 | time there might be events pending in the embedded loop. The callback |
2435 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2613 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2436 | their callbacks (you could also start an idle watcher to give the embedded |
2614 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2437 | loop strictly lower priority for example). You can also set the callback |
2615 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2438 | to C<0>, in which case the embed watcher will automatically execute the |
2616 | to give the embedded loop strictly lower priority for example). |
2439 | embedded loop sweep. |
|
|
2440 | |
2617 | |
2441 | As long as the watcher is started it will automatically handle events. The |
2618 | You can also set the callback to C<0>, in which case the embed watcher |
2442 | callback will be invoked whenever some events have been handled. You can |
2619 | will automatically execute the embedded loop sweep whenever necessary. |
2443 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2444 | interested in that. |
|
|
2445 | |
2620 | |
2446 | Also, there have not currently been made special provisions for forking: |
2621 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2447 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2622 | is active, i.e., the embedded loop will automatically be forked when the |
2448 | but you will also have to stop and restart any C<ev_embed> watchers |
2623 | embedding loop forks. In other cases, the user is responsible for calling |
2449 | yourself - but you can use a fork watcher to handle this automatically, |
2624 | C<ev_loop_fork> on the embedded loop. |
2450 | and future versions of libev might do just that. |
|
|
2451 | |
2625 | |
2452 | Unfortunately, not all backends are embeddable: only the ones returned by |
2626 | Unfortunately, not all backends are embeddable: only the ones returned by |
2453 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2627 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2454 | portable one. |
2628 | portable one. |
2455 | |
2629 | |
… | |
… | |
2549 | event loop blocks next and before C<ev_check> watchers are being called, |
2723 | event loop blocks next and before C<ev_check> watchers are being called, |
2550 | and only in the child after the fork. If whoever good citizen calling |
2724 | and only in the child after the fork. If whoever good citizen calling |
2551 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2725 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2552 | handlers will be invoked, too, of course. |
2726 | handlers will be invoked, too, of course. |
2553 | |
2727 | |
|
|
2728 | =head3 The special problem of life after fork - how is it possible? |
|
|
2729 | |
|
|
2730 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2731 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2732 | sequence should be handled by libev without any problems. |
|
|
2733 | |
|
|
2734 | This changes when the application actually wants to do event handling |
|
|
2735 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2736 | fork. |
|
|
2737 | |
|
|
2738 | The default mode of operation (for libev, with application help to detect |
|
|
2739 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2740 | when I<either> the parent I<or> the child process continues. |
|
|
2741 | |
|
|
2742 | When both processes want to continue using libev, then this is usually the |
|
|
2743 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2744 | supposed to continue with all watchers in place as before, while the other |
|
|
2745 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2746 | |
|
|
2747 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2748 | simply create a new event loop, which of course will be "empty", and |
|
|
2749 | use that for new watchers. This has the advantage of not touching more |
|
|
2750 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2751 | disadvantage of having to use multiple event loops (which do not support |
|
|
2752 | signal watchers). |
|
|
2753 | |
|
|
2754 | When this is not possible, or you want to use the default loop for |
|
|
2755 | other reasons, then in the process that wants to start "fresh", call |
|
|
2756 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2757 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2758 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2759 | also that in that case, you have to re-register any signal watchers. |
|
|
2760 | |
2554 | =head3 Watcher-Specific Functions and Data Members |
2761 | =head3 Watcher-Specific Functions and Data Members |
2555 | |
2762 | |
2556 | =over 4 |
2763 | =over 4 |
2557 | |
2764 | |
2558 | =item ev_fork_init (ev_signal *, callback) |
2765 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2686 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2893 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2687 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2894 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2688 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2895 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2689 | section below on what exactly this means). |
2896 | section below on what exactly this means). |
2690 | |
2897 | |
|
|
2898 | Note that, as with other watchers in libev, multiple events might get |
|
|
2899 | compressed into a single callback invocation (another way to look at this |
|
|
2900 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2901 | reset when the event loop detects that). |
|
|
2902 | |
2691 | This call incurs the overhead of a system call only once per loop iteration, |
2903 | This call incurs the overhead of a system call only once per event loop |
2692 | so while the overhead might be noticeable, it doesn't apply to repeated |
2904 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2693 | calls to C<ev_async_send>. |
2905 | repeated calls to C<ev_async_send> for the same event loop. |
2694 | |
2906 | |
2695 | =item bool = ev_async_pending (ev_async *) |
2907 | =item bool = ev_async_pending (ev_async *) |
2696 | |
2908 | |
2697 | Returns a non-zero value when C<ev_async_send> has been called on the |
2909 | Returns a non-zero value when C<ev_async_send> has been called on the |
2698 | watcher but the event has not yet been processed (or even noted) by the |
2910 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2701 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2913 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2702 | the loop iterates next and checks for the watcher to have become active, |
2914 | the loop iterates next and checks for the watcher to have become active, |
2703 | it will reset the flag again. C<ev_async_pending> can be used to very |
2915 | it will reset the flag again. C<ev_async_pending> can be used to very |
2704 | quickly check whether invoking the loop might be a good idea. |
2916 | quickly check whether invoking the loop might be a good idea. |
2705 | |
2917 | |
2706 | Not that this does I<not> check whether the watcher itself is pending, only |
2918 | Not that this does I<not> check whether the watcher itself is pending, |
2707 | whether it has been requested to make this watcher pending. |
2919 | only whether it has been requested to make this watcher pending: there |
|
|
2920 | is a time window between the event loop checking and resetting the async |
|
|
2921 | notification, and the callback being invoked. |
2708 | |
2922 | |
2709 | =back |
2923 | =back |
2710 | |
2924 | |
2711 | |
2925 | |
2712 | =head1 OTHER FUNCTIONS |
2926 | =head1 OTHER FUNCTIONS |
… | |
… | |
3016 | L<http://software.schmorp.de/pkg/EV>. |
3230 | L<http://software.schmorp.de/pkg/EV>. |
3017 | |
3231 | |
3018 | =item Python |
3232 | =item Python |
3019 | |
3233 | |
3020 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3234 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3021 | seems to be quite complete and well-documented. Note, however, that the |
3235 | seems to be quite complete and well-documented. |
3022 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
3023 | for everybody else, and therefore, should never be applied in an installed |
|
|
3024 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
3025 | libev). |
|
|
3026 | |
3236 | |
3027 | =item Ruby |
3237 | =item Ruby |
3028 | |
3238 | |
3029 | Tony Arcieri has written a ruby extension that offers access to a subset |
3239 | Tony Arcieri has written a ruby extension that offers access to a subset |
3030 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3240 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3031 | more on top of it. It can be found via gem servers. Its homepage is at |
3241 | more on top of it. It can be found via gem servers. Its homepage is at |
3032 | L<http://rev.rubyforge.org/>. |
3242 | L<http://rev.rubyforge.org/>. |
3033 | |
3243 | |
3034 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
3244 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
3035 | makes rev work even on mingw. |
3245 | makes rev work even on mingw. |
|
|
3246 | |
|
|
3247 | =item Haskell |
|
|
3248 | |
|
|
3249 | A haskell binding to libev is available at |
|
|
3250 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3036 | |
3251 | |
3037 | =item D |
3252 | =item D |
3038 | |
3253 | |
3039 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3254 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3040 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3255 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
… | |
… | |
3233 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3448 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3234 | |
3449 | |
3235 | =item EV_USE_REALTIME |
3450 | =item EV_USE_REALTIME |
3236 | |
3451 | |
3237 | If defined to be C<1>, libev will try to detect the availability of the |
3452 | If defined to be C<1>, libev will try to detect the availability of the |
3238 | real-time clock option at compile time (and assume its availability at |
3453 | real-time clock option at compile time (and assume its availability |
3239 | runtime if successful). Otherwise no use of the real-time clock option will |
3454 | at runtime if successful). Otherwise no use of the real-time clock |
3240 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3455 | option will be attempted. This effectively replaces C<gettimeofday> |
3241 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3456 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3242 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3457 | correctness. See the note about libraries in the description of |
|
|
3458 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3459 | C<EV_USE_CLOCK_SYSCALL>. |
3243 | |
3460 | |
3244 | =item EV_USE_CLOCK_SYSCALL |
3461 | =item EV_USE_CLOCK_SYSCALL |
3245 | |
3462 | |
3246 | If defined to be C<1>, libev will try to use a direct syscall instead |
3463 | If defined to be C<1>, libev will try to use a direct syscall instead |
3247 | of calling the system-provided C<clock_gettime> function. This option |
3464 | of calling the system-provided C<clock_gettime> function. This option |
… | |
… | |
3730 | way (note also that glib is the slowest event library known to man). |
3947 | way (note also that glib is the slowest event library known to man). |
3731 | |
3948 | |
3732 | There is no supported compilation method available on windows except |
3949 | There is no supported compilation method available on windows except |
3733 | embedding it into other applications. |
3950 | embedding it into other applications. |
3734 | |
3951 | |
|
|
3952 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3953 | tries its best, but under most conditions, signals will simply not work. |
|
|
3954 | |
3735 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3955 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3736 | accept large writes: instead of resulting in a partial write, windows will |
3956 | accept large writes: instead of resulting in a partial write, windows will |
3737 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3957 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3738 | so make sure you only write small amounts into your sockets (less than a |
3958 | so make sure you only write small amounts into your sockets (less than a |
3739 | megabyte seems safe, but this apparently depends on the amount of memory |
3959 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3743 | the abysmal performance of winsockets, using a large number of sockets |
3963 | the abysmal performance of winsockets, using a large number of sockets |
3744 | is not recommended (and not reasonable). If your program needs to use |
3964 | is not recommended (and not reasonable). If your program needs to use |
3745 | more than a hundred or so sockets, then likely it needs to use a totally |
3965 | more than a hundred or so sockets, then likely it needs to use a totally |
3746 | different implementation for windows, as libev offers the POSIX readiness |
3966 | different implementation for windows, as libev offers the POSIX readiness |
3747 | notification model, which cannot be implemented efficiently on windows |
3967 | notification model, which cannot be implemented efficiently on windows |
3748 | (Microsoft monopoly games). |
3968 | (due to Microsoft monopoly games). |
3749 | |
3969 | |
3750 | A typical way to use libev under windows is to embed it (see the embedding |
3970 | A typical way to use libev under windows is to embed it (see the embedding |
3751 | section for details) and use the following F<evwrap.h> header file instead |
3971 | section for details) and use the following F<evwrap.h> header file instead |
3752 | of F<ev.h>: |
3972 | of F<ev.h>: |
3753 | |
3973 | |
… | |
… | |
3789 | |
4009 | |
3790 | Early versions of winsocket's select only supported waiting for a maximum |
4010 | Early versions of winsocket's select only supported waiting for a maximum |
3791 | of C<64> handles (probably owning to the fact that all windows kernels |
4011 | of C<64> handles (probably owning to the fact that all windows kernels |
3792 | can only wait for C<64> things at the same time internally; Microsoft |
4012 | can only wait for C<64> things at the same time internally; Microsoft |
3793 | recommends spawning a chain of threads and wait for 63 handles and the |
4013 | recommends spawning a chain of threads and wait for 63 handles and the |
3794 | previous thread in each. Great). |
4014 | previous thread in each. Sounds great!). |
3795 | |
4015 | |
3796 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4016 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3797 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4017 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3798 | call (which might be in libev or elsewhere, for example, perl does its own |
4018 | call (which might be in libev or elsewhere, for example, perl and many |
3799 | select emulation on windows). |
4019 | other interpreters do their own select emulation on windows). |
3800 | |
4020 | |
3801 | Another limit is the number of file descriptors in the Microsoft runtime |
4021 | Another limit is the number of file descriptors in the Microsoft runtime |
3802 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4022 | libraries, which by default is C<64> (there must be a hidden I<64> |
3803 | or something like this inside Microsoft). You can increase this by calling |
4023 | fetish or something like this inside Microsoft). You can increase this |
3804 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4024 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3805 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4025 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3806 | libraries. |
|
|
3807 | |
|
|
3808 | This might get you to about C<512> or C<2048> sockets (depending on |
4026 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3809 | windows version and/or the phase of the moon). To get more, you need to |
4027 | (depending on windows version and/or the phase of the moon). To get more, |
3810 | wrap all I/O functions and provide your own fd management, but the cost of |
4028 | you need to wrap all I/O functions and provide your own fd management, but |
3811 | calling select (O(n²)) will likely make this unworkable. |
4029 | the cost of calling select (O(n²)) will likely make this unworkable. |
3812 | |
4030 | |
3813 | =back |
4031 | =back |
3814 | |
4032 | |
3815 | =head2 PORTABILITY REQUIREMENTS |
4033 | =head2 PORTABILITY REQUIREMENTS |
3816 | |
4034 | |
… | |
… | |
3937 | involves iterating over all running async watchers or all signal numbers. |
4155 | involves iterating over all running async watchers or all signal numbers. |
3938 | |
4156 | |
3939 | =back |
4157 | =back |
3940 | |
4158 | |
3941 | |
4159 | |
|
|
4160 | =head1 GLOSSARY |
|
|
4161 | |
|
|
4162 | =over 4 |
|
|
4163 | |
|
|
4164 | =item active |
|
|
4165 | |
|
|
4166 | A watcher is active as long as it has been started (has been attached to |
|
|
4167 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4168 | |
|
|
4169 | =item application |
|
|
4170 | |
|
|
4171 | In this document, an application is whatever is using libev. |
|
|
4172 | |
|
|
4173 | =item callback |
|
|
4174 | |
|
|
4175 | The address of a function that is called when some event has been |
|
|
4176 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4177 | received the event, and the actual event bitset. |
|
|
4178 | |
|
|
4179 | =item callback invocation |
|
|
4180 | |
|
|
4181 | The act of calling the callback associated with a watcher. |
|
|
4182 | |
|
|
4183 | =item event |
|
|
4184 | |
|
|
4185 | A change of state of some external event, such as data now being available |
|
|
4186 | for reading on a file descriptor, time having passed or simply not having |
|
|
4187 | any other events happening anymore. |
|
|
4188 | |
|
|
4189 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4190 | C<EV_TIMEOUT>). |
|
|
4191 | |
|
|
4192 | =item event library |
|
|
4193 | |
|
|
4194 | A software package implementing an event model and loop. |
|
|
4195 | |
|
|
4196 | =item event loop |
|
|
4197 | |
|
|
4198 | An entity that handles and processes external events and converts them |
|
|
4199 | into callback invocations. |
|
|
4200 | |
|
|
4201 | =item event model |
|
|
4202 | |
|
|
4203 | The model used to describe how an event loop handles and processes |
|
|
4204 | watchers and events. |
|
|
4205 | |
|
|
4206 | =item pending |
|
|
4207 | |
|
|
4208 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4209 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4210 | pending status is explicitly cleared by the application. |
|
|
4211 | |
|
|
4212 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4213 | its pending status. |
|
|
4214 | |
|
|
4215 | =item real time |
|
|
4216 | |
|
|
4217 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4218 | |
|
|
4219 | =item wall-clock time |
|
|
4220 | |
|
|
4221 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4222 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4223 | clock. |
|
|
4224 | |
|
|
4225 | =item watcher |
|
|
4226 | |
|
|
4227 | A data structure that describes interest in certain events. Watchers need |
|
|
4228 | to be started (attached to an event loop) before they can receive events. |
|
|
4229 | |
|
|
4230 | =item watcher invocation |
|
|
4231 | |
|
|
4232 | The act of calling the callback associated with a watcher. |
|
|
4233 | |
|
|
4234 | =back |
|
|
4235 | |
3942 | =head1 AUTHOR |
4236 | =head1 AUTHOR |
3943 | |
4237 | |
3944 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4238 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3945 | |
4239 | |