… | |
… | |
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 | |
… | |
… | |
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 |
… | |
… | |
1057 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1095 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1058 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1096 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1059 | before watchers with lower priority, but priority will not keep watchers |
1097 | before watchers with lower priority, but priority will not keep watchers |
1060 | from being executed (except for C<ev_idle> watchers). |
1098 | from being executed (except for C<ev_idle> watchers). |
1061 | |
1099 | |
1062 | This means that priorities are I<only> used for ordering callback |
|
|
1063 | invocation after new events have been received. This is useful, for |
|
|
1064 | example, to reduce latency after idling, or more often, to bind two |
|
|
1065 | watchers on the same event and make sure one is called first. |
|
|
1066 | |
|
|
1067 | If you need to suppress invocation when higher priority events are pending |
1100 | If you need to suppress invocation when higher priority events are pending |
1068 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1101 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1069 | |
1102 | |
1070 | You I<must not> change the priority of a watcher as long as it is active or |
1103 | You I<must not> change the priority of a watcher as long as it is active or |
1071 | pending. |
1104 | pending. |
1072 | |
|
|
1073 | The default priority used by watchers when no priority has been set is |
|
|
1074 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1075 | |
1105 | |
1076 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1106 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1077 | fine, as long as you do not mind that the priority value you query might |
1107 | fine, as long as you do not mind that the priority value you query might |
1078 | or might not have been clamped to the valid range. |
1108 | or might not have been clamped to the valid range. |
|
|
1109 | |
|
|
1110 | The default priority used by watchers when no priority has been set is |
|
|
1111 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1112 | |
|
|
1113 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1114 | priorities. |
1079 | |
1115 | |
1080 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1116 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1081 | |
1117 | |
1082 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1118 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1083 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1119 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1148 | #include <stddef.h> |
1184 | #include <stddef.h> |
1149 | |
1185 | |
1150 | static void |
1186 | static void |
1151 | t1_cb (EV_P_ ev_timer *w, int revents) |
1187 | t1_cb (EV_P_ ev_timer *w, int revents) |
1152 | { |
1188 | { |
1153 | struct my_biggy big = (struct my_biggy * |
1189 | struct my_biggy big = (struct my_biggy *) |
1154 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1190 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1155 | } |
1191 | } |
1156 | |
1192 | |
1157 | static void |
1193 | static void |
1158 | t2_cb (EV_P_ ev_timer *w, int revents) |
1194 | t2_cb (EV_P_ ev_timer *w, int revents) |
1159 | { |
1195 | { |
1160 | struct my_biggy big = (struct my_biggy * |
1196 | struct my_biggy big = (struct my_biggy *) |
1161 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1197 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1162 | } |
1198 | } |
|
|
1199 | |
|
|
1200 | =head2 WATCHER PRIORITY MODELS |
|
|
1201 | |
|
|
1202 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1203 | integers that influence the ordering of event callback invocation |
|
|
1204 | between watchers in some way, all else being equal. |
|
|
1205 | |
|
|
1206 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1207 | description for the more technical details such as the actual priority |
|
|
1208 | range. |
|
|
1209 | |
|
|
1210 | There are two common ways how these these priorities are being interpreted |
|
|
1211 | by event loops: |
|
|
1212 | |
|
|
1213 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1214 | of lower priority watchers, which means as long as higher priority |
|
|
1215 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1216 | |
|
|
1217 | The less common only-for-ordering model uses priorities solely to order |
|
|
1218 | callback invocation within a single event loop iteration: Higher priority |
|
|
1219 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1220 | before polling for new events. |
|
|
1221 | |
|
|
1222 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1223 | except for idle watchers (which use the lock-out model). |
|
|
1224 | |
|
|
1225 | The rationale behind this is that implementing the lock-out model for |
|
|
1226 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1227 | libraries will just poll for the same events again and again as long as |
|
|
1228 | their callbacks have not been executed, which is very inefficient in the |
|
|
1229 | common case of one high-priority watcher locking out a mass of lower |
|
|
1230 | priority ones. |
|
|
1231 | |
|
|
1232 | Static (ordering) priorities are most useful when you have two or more |
|
|
1233 | watchers handling the same resource: a typical usage example is having an |
|
|
1234 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1235 | timeouts. Under load, data might be received while the program handles |
|
|
1236 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1237 | handler will be executed before checking for data. In that case, giving |
|
|
1238 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1239 | handled first even under adverse conditions (which is usually, but not |
|
|
1240 | always, what you want). |
|
|
1241 | |
|
|
1242 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1243 | will only be executed when no same or higher priority watchers have |
|
|
1244 | received events, they can be used to implement the "lock-out" model when |
|
|
1245 | required. |
|
|
1246 | |
|
|
1247 | For example, to emulate how many other event libraries handle priorities, |
|
|
1248 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1249 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1250 | processing is done in the idle watcher callback. This causes libev to |
|
|
1251 | continously poll and process kernel event data for the watcher, but when |
|
|
1252 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1253 | workable. |
|
|
1254 | |
|
|
1255 | Usually, however, the lock-out model implemented that way will perform |
|
|
1256 | miserably under the type of load it was designed to handle. In that case, |
|
|
1257 | it might be preferable to stop the real watcher before starting the |
|
|
1258 | idle watcher, so the kernel will not have to process the event in case |
|
|
1259 | the actual processing will be delayed for considerable time. |
|
|
1260 | |
|
|
1261 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1262 | priority than the default, and which should only process data when no |
|
|
1263 | other events are pending: |
|
|
1264 | |
|
|
1265 | ev_idle idle; // actual processing watcher |
|
|
1266 | ev_io io; // actual event watcher |
|
|
1267 | |
|
|
1268 | static void |
|
|
1269 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1270 | { |
|
|
1271 | // stop the I/O watcher, we received the event, but |
|
|
1272 | // are not yet ready to handle it. |
|
|
1273 | ev_io_stop (EV_A_ w); |
|
|
1274 | |
|
|
1275 | // start the idle watcher to ahndle the actual event. |
|
|
1276 | // it will not be executed as long as other watchers |
|
|
1277 | // with the default priority are receiving events. |
|
|
1278 | ev_idle_start (EV_A_ &idle); |
|
|
1279 | } |
|
|
1280 | |
|
|
1281 | static void |
|
|
1282 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1283 | { |
|
|
1284 | // actual processing |
|
|
1285 | read (STDIN_FILENO, ...); |
|
|
1286 | |
|
|
1287 | // have to start the I/O watcher again, as |
|
|
1288 | // we have handled the event |
|
|
1289 | ev_io_start (EV_P_ &io); |
|
|
1290 | } |
|
|
1291 | |
|
|
1292 | // initialisation |
|
|
1293 | ev_idle_init (&idle, idle_cb); |
|
|
1294 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1295 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1296 | |
|
|
1297 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1298 | low-priority connections can not be locked out forever under load. This |
|
|
1299 | enables your program to keep a lower latency for important connections |
|
|
1300 | during short periods of high load, while not completely locking out less |
|
|
1301 | important ones. |
1163 | |
1302 | |
1164 | |
1303 | |
1165 | =head1 WATCHER TYPES |
1304 | =head1 WATCHER TYPES |
1166 | |
1305 | |
1167 | This section describes each watcher in detail, but will not repeat |
1306 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1193 | descriptors to non-blocking mode is also usually a good idea (but not |
1332 | descriptors to non-blocking mode is also usually a good idea (but not |
1194 | required if you know what you are doing). |
1333 | required if you know what you are doing). |
1195 | |
1334 | |
1196 | If you cannot use non-blocking mode, then force the use of a |
1335 | If you cannot use non-blocking mode, then force the use of a |
1197 | known-to-be-good backend (at the time of this writing, this includes only |
1336 | known-to-be-good backend (at the time of this writing, this includes only |
1198 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1337 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1338 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1339 | files) - libev doesn't guarentee any specific behaviour in that case. |
1199 | |
1340 | |
1200 | Another thing you have to watch out for is that it is quite easy to |
1341 | Another thing you have to watch out for is that it is quite easy to |
1201 | receive "spurious" readiness notifications, that is your callback might |
1342 | receive "spurious" readiness notifications, that is your callback might |
1202 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1343 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1203 | because there is no data. Not only are some backends known to create a |
1344 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1324 | year, it will still time out after (roughly) one hour. "Roughly" because |
1465 | year, it will still time out after (roughly) one hour. "Roughly" because |
1325 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1466 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1326 | monotonic clock option helps a lot here). |
1467 | monotonic clock option helps a lot here). |
1327 | |
1468 | |
1328 | The callback is guaranteed to be invoked only I<after> its timeout has |
1469 | The callback is guaranteed to be invoked only I<after> its timeout has |
1329 | passed, but if multiple timers become ready during the same loop iteration |
1470 | passed (not I<at>, so on systems with very low-resolution clocks this |
1330 | then order of execution is undefined. |
1471 | might introduce a small delay). If multiple timers become ready during the |
|
|
1472 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1473 | before ones with later time-out values (but this is no longer true when a |
|
|
1474 | callback calls C<ev_loop> recursively). |
1331 | |
1475 | |
1332 | =head3 Be smart about timeouts |
1476 | =head3 Be smart about timeouts |
1333 | |
1477 | |
1334 | Many real-world problems involve some kind of timeout, usually for error |
1478 | Many real-world problems involve some kind of timeout, usually for error |
1335 | recovery. A typical example is an HTTP request - if the other side hangs, |
1479 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1379 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1523 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1380 | member and C<ev_timer_again>. |
1524 | member and C<ev_timer_again>. |
1381 | |
1525 | |
1382 | At start: |
1526 | At start: |
1383 | |
1527 | |
1384 | ev_timer_init (timer, callback); |
1528 | ev_init (timer, callback); |
1385 | timer->repeat = 60.; |
1529 | timer->repeat = 60.; |
1386 | ev_timer_again (loop, timer); |
1530 | ev_timer_again (loop, timer); |
1387 | |
1531 | |
1388 | Each time there is some activity: |
1532 | Each time there is some activity: |
1389 | |
1533 | |
… | |
… | |
1451 | |
1595 | |
1452 | To start the timer, simply initialise the watcher and set C<last_activity> |
1596 | To start the timer, simply initialise the watcher and set C<last_activity> |
1453 | to the current time (meaning we just have some activity :), then call the |
1597 | to the current time (meaning we just have some activity :), then call the |
1454 | callback, which will "do the right thing" and start the timer: |
1598 | callback, which will "do the right thing" and start the timer: |
1455 | |
1599 | |
1456 | ev_timer_init (timer, callback); |
1600 | ev_init (timer, callback); |
1457 | last_activity = ev_now (loop); |
1601 | last_activity = ev_now (loop); |
1458 | callback (loop, timer, EV_TIMEOUT); |
1602 | callback (loop, timer, EV_TIMEOUT); |
1459 | |
1603 | |
1460 | And when there is some activity, simply store the current time in |
1604 | And when there is some activity, simply store the current time in |
1461 | C<last_activity>, no libev calls at all: |
1605 | C<last_activity>, no libev calls at all: |
… | |
… | |
1554 | If the timer is started but non-repeating, stop it (as if it timed out). |
1698 | If the timer is started but non-repeating, stop it (as if it timed out). |
1555 | |
1699 | |
1556 | If the timer is repeating, either start it if necessary (with the |
1700 | If the timer is repeating, either start it if necessary (with the |
1557 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1701 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1558 | |
1702 | |
1559 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1703 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1560 | usage example. |
1704 | usage example. |
1561 | |
1705 | |
1562 | =item ev_tstamp repeat [read-write] |
1706 | =item ev_tstamp repeat [read-write] |
1563 | |
1707 | |
1564 | The current C<repeat> value. Will be used each time the watcher times out |
1708 | The current C<repeat> value. Will be used each time the watcher times out |
… | |
… | |
1624 | timers, such as triggering an event on each "midnight, local time", or |
1768 | timers, such as triggering an event on each "midnight, local time", or |
1625 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1769 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
1626 | those cannot react to time jumps. |
1770 | those cannot react to time jumps. |
1627 | |
1771 | |
1628 | As with timers, the callback is guaranteed to be invoked only when the |
1772 | As with timers, the callback is guaranteed to be invoked only when the |
1629 | point in time where it is supposed to trigger has passed, but if multiple |
1773 | point in time where it is supposed to trigger has passed. If multiple |
1630 | periodic timers become ready during the same loop iteration, then order of |
1774 | timers become ready during the same loop iteration then the ones with |
1631 | execution is undefined. |
1775 | earlier time-out values are invoked before ones with later time-out values |
|
|
1776 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1632 | |
1777 | |
1633 | =head3 Watcher-Specific Functions and Data Members |
1778 | =head3 Watcher-Specific Functions and Data Members |
1634 | |
1779 | |
1635 | =over 4 |
1780 | =over 4 |
1636 | |
1781 | |
… | |
… | |
2223 | // no longer anything immediate to do. |
2368 | // no longer anything immediate to do. |
2224 | } |
2369 | } |
2225 | |
2370 | |
2226 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2371 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2227 | ev_idle_init (idle_watcher, idle_cb); |
2372 | ev_idle_init (idle_watcher, idle_cb); |
2228 | ev_idle_start (loop, idle_cb); |
2373 | ev_idle_start (loop, idle_watcher); |
2229 | |
2374 | |
2230 | |
2375 | |
2231 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2376 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2232 | |
2377 | |
2233 | Prepare and check watchers are usually (but not always) used in pairs: |
2378 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2326 | struct pollfd fds [nfd]; |
2471 | struct pollfd fds [nfd]; |
2327 | // actual code will need to loop here and realloc etc. |
2472 | // actual code will need to loop here and realloc etc. |
2328 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2473 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2329 | |
2474 | |
2330 | /* the callback is illegal, but won't be called as we stop during check */ |
2475 | /* the callback is illegal, but won't be called as we stop during check */ |
2331 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2476 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2332 | ev_timer_start (loop, &tw); |
2477 | ev_timer_start (loop, &tw); |
2333 | |
2478 | |
2334 | // create one ev_io per pollfd |
2479 | // create one ev_io per pollfd |
2335 | for (int i = 0; i < nfd; ++i) |
2480 | for (int i = 0; i < nfd; ++i) |
2336 | { |
2481 | { |
… | |
… | |
2566 | event loop blocks next and before C<ev_check> watchers are being called, |
2711 | event loop blocks next and before C<ev_check> watchers are being called, |
2567 | and only in the child after the fork. If whoever good citizen calling |
2712 | and only in the child after the fork. If whoever good citizen calling |
2568 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2713 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2569 | handlers will be invoked, too, of course. |
2714 | handlers will be invoked, too, of course. |
2570 | |
2715 | |
|
|
2716 | =head3 The special problem of life after fork - how is it possible? |
|
|
2717 | |
|
|
2718 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2719 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2720 | sequence should be handled by libev without any problems. |
|
|
2721 | |
|
|
2722 | This changes when the application actually wants to do event handling |
|
|
2723 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2724 | fork. |
|
|
2725 | |
|
|
2726 | The default mode of operation (for libev, with application help to detect |
|
|
2727 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2728 | when I<either> the parent I<or> the child process continues. |
|
|
2729 | |
|
|
2730 | When both processes want to continue using libev, then this is usually the |
|
|
2731 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2732 | supposed to continue with all watchers in place as before, while the other |
|
|
2733 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2734 | |
|
|
2735 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2736 | simply create a new event loop, which of course will be "empty", and |
|
|
2737 | use that for new watchers. This has the advantage of not touching more |
|
|
2738 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2739 | disadvantage of having to use multiple event loops (which do not support |
|
|
2740 | signal watchers). |
|
|
2741 | |
|
|
2742 | When this is not possible, or you want to use the default loop for |
|
|
2743 | other reasons, then in the process that wants to start "fresh", call |
|
|
2744 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2745 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2746 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2747 | also that in that case, you have to re-register any signal watchers. |
|
|
2748 | |
2571 | =head3 Watcher-Specific Functions and Data Members |
2749 | =head3 Watcher-Specific Functions and Data Members |
2572 | |
2750 | |
2573 | =over 4 |
2751 | =over 4 |
2574 | |
2752 | |
2575 | =item ev_fork_init (ev_signal *, callback) |
2753 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
3757 | way (note also that glib is the slowest event library known to man). |
3935 | way (note also that glib is the slowest event library known to man). |
3758 | |
3936 | |
3759 | There is no supported compilation method available on windows except |
3937 | There is no supported compilation method available on windows except |
3760 | embedding it into other applications. |
3938 | embedding it into other applications. |
3761 | |
3939 | |
|
|
3940 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
3941 | tries its best, but under most conditions, signals will simply not work. |
|
|
3942 | |
3762 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3943 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3763 | accept large writes: instead of resulting in a partial write, windows will |
3944 | accept large writes: instead of resulting in a partial write, windows will |
3764 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3945 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3765 | so make sure you only write small amounts into your sockets (less than a |
3946 | so make sure you only write small amounts into your sockets (less than a |
3766 | megabyte seems safe, but this apparently depends on the amount of memory |
3947 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3770 | the abysmal performance of winsockets, using a large number of sockets |
3951 | the abysmal performance of winsockets, using a large number of sockets |
3771 | is not recommended (and not reasonable). If your program needs to use |
3952 | is not recommended (and not reasonable). If your program needs to use |
3772 | more than a hundred or so sockets, then likely it needs to use a totally |
3953 | more than a hundred or so sockets, then likely it needs to use a totally |
3773 | different implementation for windows, as libev offers the POSIX readiness |
3954 | different implementation for windows, as libev offers the POSIX readiness |
3774 | notification model, which cannot be implemented efficiently on windows |
3955 | notification model, which cannot be implemented efficiently on windows |
3775 | (Microsoft monopoly games). |
3956 | (due to Microsoft monopoly games). |
3776 | |
3957 | |
3777 | A typical way to use libev under windows is to embed it (see the embedding |
3958 | A typical way to use libev under windows is to embed it (see the embedding |
3778 | section for details) and use the following F<evwrap.h> header file instead |
3959 | section for details) and use the following F<evwrap.h> header file instead |
3779 | of F<ev.h>: |
3960 | of F<ev.h>: |
3780 | |
3961 | |
… | |
… | |
3816 | |
3997 | |
3817 | Early versions of winsocket's select only supported waiting for a maximum |
3998 | Early versions of winsocket's select only supported waiting for a maximum |
3818 | of C<64> handles (probably owning to the fact that all windows kernels |
3999 | of C<64> handles (probably owning to the fact that all windows kernels |
3819 | can only wait for C<64> things at the same time internally; Microsoft |
4000 | can only wait for C<64> things at the same time internally; Microsoft |
3820 | recommends spawning a chain of threads and wait for 63 handles and the |
4001 | recommends spawning a chain of threads and wait for 63 handles and the |
3821 | previous thread in each. Great). |
4002 | previous thread in each. Sounds great!). |
3822 | |
4003 | |
3823 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4004 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3824 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4005 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3825 | call (which might be in libev or elsewhere, for example, perl does its own |
4006 | call (which might be in libev or elsewhere, for example, perl and many |
3826 | select emulation on windows). |
4007 | other interpreters do their own select emulation on windows). |
3827 | |
4008 | |
3828 | Another limit is the number of file descriptors in the Microsoft runtime |
4009 | Another limit is the number of file descriptors in the Microsoft runtime |
3829 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4010 | libraries, which by default is C<64> (there must be a hidden I<64> |
3830 | or something like this inside Microsoft). You can increase this by calling |
4011 | fetish or something like this inside Microsoft). You can increase this |
3831 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4012 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3832 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4013 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3833 | libraries. |
|
|
3834 | |
|
|
3835 | This might get you to about C<512> or C<2048> sockets (depending on |
4014 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3836 | windows version and/or the phase of the moon). To get more, you need to |
4015 | (depending on windows version and/or the phase of the moon). To get more, |
3837 | wrap all I/O functions and provide your own fd management, but the cost of |
4016 | you need to wrap all I/O functions and provide your own fd management, but |
3838 | calling select (O(n²)) will likely make this unworkable. |
4017 | the cost of calling select (O(n²)) will likely make this unworkable. |
3839 | |
4018 | |
3840 | =back |
4019 | =back |
3841 | |
4020 | |
3842 | =head2 PORTABILITY REQUIREMENTS |
4021 | =head2 PORTABILITY REQUIREMENTS |
3843 | |
4022 | |
… | |
… | |
3964 | involves iterating over all running async watchers or all signal numbers. |
4143 | involves iterating over all running async watchers or all signal numbers. |
3965 | |
4144 | |
3966 | =back |
4145 | =back |
3967 | |
4146 | |
3968 | |
4147 | |
|
|
4148 | =head1 GLOSSARY |
|
|
4149 | |
|
|
4150 | =over 4 |
|
|
4151 | |
|
|
4152 | =item active |
|
|
4153 | |
|
|
4154 | A watcher is active as long as it has been started (has been attached to |
|
|
4155 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4156 | |
|
|
4157 | =item application |
|
|
4158 | |
|
|
4159 | In this document, an application is whatever is using libev. |
|
|
4160 | |
|
|
4161 | =item callback |
|
|
4162 | |
|
|
4163 | The address of a function that is called when some event has been |
|
|
4164 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4165 | received the event, and the actual event bitset. |
|
|
4166 | |
|
|
4167 | =item callback invocation |
|
|
4168 | |
|
|
4169 | The act of calling the callback associated with a watcher. |
|
|
4170 | |
|
|
4171 | =item event |
|
|
4172 | |
|
|
4173 | A change of state of some external event, such as data now being available |
|
|
4174 | for reading on a file descriptor, time having passed or simply not having |
|
|
4175 | any other events happening anymore. |
|
|
4176 | |
|
|
4177 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4178 | C<EV_TIMEOUT>). |
|
|
4179 | |
|
|
4180 | =item event library |
|
|
4181 | |
|
|
4182 | A software package implementing an event model and loop. |
|
|
4183 | |
|
|
4184 | =item event loop |
|
|
4185 | |
|
|
4186 | An entity that handles and processes external events and converts them |
|
|
4187 | into callback invocations. |
|
|
4188 | |
|
|
4189 | =item event model |
|
|
4190 | |
|
|
4191 | The model used to describe how an event loop handles and processes |
|
|
4192 | watchers and events. |
|
|
4193 | |
|
|
4194 | =item pending |
|
|
4195 | |
|
|
4196 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4197 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4198 | pending status is explicitly cleared by the application. |
|
|
4199 | |
|
|
4200 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4201 | its pending status. |
|
|
4202 | |
|
|
4203 | =item real time |
|
|
4204 | |
|
|
4205 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4206 | |
|
|
4207 | =item wall-clock time |
|
|
4208 | |
|
|
4209 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4210 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4211 | clock. |
|
|
4212 | |
|
|
4213 | =item watcher |
|
|
4214 | |
|
|
4215 | A data structure that describes interest in certain events. Watchers need |
|
|
4216 | to be started (attached to an event loop) before they can receive events. |
|
|
4217 | |
|
|
4218 | =item watcher invocation |
|
|
4219 | |
|
|
4220 | The act of calling the callback associated with a watcher. |
|
|
4221 | |
|
|
4222 | =back |
|
|
4223 | |
3969 | =head1 AUTHOR |
4224 | =head1 AUTHOR |
3970 | |
4225 | |
3971 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
4226 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3972 | |
4227 | |