… | |
… | |
1174 | |
1174 | |
1175 | =item C<EV_PREPARE> |
1175 | =item C<EV_PREPARE> |
1176 | |
1176 | |
1177 | =item C<EV_CHECK> |
1177 | =item C<EV_CHECK> |
1178 | |
1178 | |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1180 | to gather new events, and all C<ev_check> watchers are invoked just after |
1180 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1181 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1181 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1182 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1183 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1184 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1185 | or lower priority within an event loop iteration. |
|
|
1186 | |
1182 | received events. Callbacks of both watcher types can start and stop as |
1187 | Callbacks of both watcher types can start and stop as many watchers as |
1183 | many watchers as they want, and all of them will be taken into account |
1188 | they want, and all of them will be taken into account (for example, a |
1184 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1189 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1185 | C<ev_run> from blocking). |
1190 | blocking). |
1186 | |
1191 | |
1187 | =item C<EV_EMBED> |
1192 | =item C<EV_EMBED> |
1188 | |
1193 | |
1189 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1194 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1190 | |
1195 | |
… | |
… | |
2842 | Apart from keeping your process non-blocking (which is a useful |
2847 | Apart from keeping your process non-blocking (which is a useful |
2843 | effect on its own sometimes), idle watchers are a good place to do |
2848 | effect on its own sometimes), idle watchers are a good place to do |
2844 | "pseudo-background processing", or delay processing stuff to after the |
2849 | "pseudo-background processing", or delay processing stuff to after the |
2845 | event loop has handled all outstanding events. |
2850 | event loop has handled all outstanding events. |
2846 | |
2851 | |
|
|
2852 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2853 | |
|
|
2854 | As long as there is at least one active idle watcher, libev will never |
|
|
2855 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2856 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2857 | lowest priority will do. |
|
|
2858 | |
|
|
2859 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2860 | to do something on each event loop iteration - for example to balance load |
|
|
2861 | between different connections. |
|
|
2862 | |
|
|
2863 | See L<Abusing an C<ev_check> watcher for its side-effect> for a longer |
|
|
2864 | example. |
|
|
2865 | |
2847 | =head3 Watcher-Specific Functions and Data Members |
2866 | =head3 Watcher-Specific Functions and Data Members |
2848 | |
2867 | |
2849 | =over 4 |
2868 | =over 4 |
2850 | |
2869 | |
2851 | =item ev_idle_init (ev_idle *, callback) |
2870 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2874 | ev_idle_start (loop, idle_watcher); |
2893 | ev_idle_start (loop, idle_watcher); |
2875 | |
2894 | |
2876 | |
2895 | |
2877 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2896 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2878 | |
2897 | |
2879 | Prepare and check watchers are usually (but not always) used in pairs: |
2898 | Prepare and check watchers are often (but not always) used in pairs: |
2880 | prepare watchers get invoked before the process blocks and check watchers |
2899 | prepare watchers get invoked before the process blocks and check watchers |
2881 | afterwards. |
2900 | afterwards. |
2882 | |
2901 | |
2883 | You I<must not> call C<ev_run> or similar functions that enter |
2902 | You I<must not> call C<ev_run> or similar functions that enter |
2884 | the current event loop from either C<ev_prepare> or C<ev_check> |
2903 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2912 | with priority higher than or equal to the event loop and one coroutine |
2931 | with priority higher than or equal to the event loop and one coroutine |
2913 | of lower priority, but only once, using idle watchers to keep the event |
2932 | of lower priority, but only once, using idle watchers to keep the event |
2914 | loop from blocking if lower-priority coroutines are active, thus mapping |
2933 | loop from blocking if lower-priority coroutines are active, thus mapping |
2915 | low-priority coroutines to idle/background tasks). |
2934 | low-priority coroutines to idle/background tasks). |
2916 | |
2935 | |
2917 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2936 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2918 | priority, to ensure that they are being run before any other watchers |
2937 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2919 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2938 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2939 | watchers). |
2920 | |
2940 | |
2921 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2941 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2922 | activate ("feed") events into libev. While libev fully supports this, they |
2942 | activate ("feed") events into libev. While libev fully supports this, they |
2923 | might get executed before other C<ev_check> watchers did their job. As |
2943 | might get executed before other C<ev_check> watchers did their job. As |
2924 | C<ev_check> watchers are often used to embed other (non-libev) event |
2944 | C<ev_check> watchers are often used to embed other (non-libev) event |
2925 | loops those other event loops might be in an unusable state until their |
2945 | loops those other event loops might be in an unusable state until their |
2926 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2946 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2927 | others). |
2947 | others). |
|
|
2948 | |
|
|
2949 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2950 | |
|
|
2951 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2952 | useful because they are called once per event loop iteration. For |
|
|
2953 | example, if you want to handle a large number of connections fairly, you |
|
|
2954 | normally only do a bit of work for each active connection, and if there |
|
|
2955 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2956 | connections have a chance of making progress. |
|
|
2957 | |
|
|
2958 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2959 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2960 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2961 | |
|
|
2962 | |
|
|
2963 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2964 | single global idle watcher that is active as long as you have one active |
|
|
2965 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2966 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2967 | invoked. Neither watcher alone can do that. |
2928 | |
2968 | |
2929 | =head3 Watcher-Specific Functions and Data Members |
2969 | =head3 Watcher-Specific Functions and Data Members |
2930 | |
2970 | |
2931 | =over 4 |
2971 | =over 4 |
2932 | |
2972 | |