… | |
… | |
2847 | Apart from keeping your process non-blocking (which is a useful |
2847 | Apart from keeping your process non-blocking (which is a useful |
2848 | 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 |
2849 | "pseudo-background processing", or delay processing stuff to after the |
2849 | "pseudo-background processing", or delay processing stuff to after the |
2850 | event loop has handled all outstanding events. |
2850 | event loop has handled all outstanding events. |
2851 | |
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 | |
2852 | =head3 Watcher-Specific Functions and Data Members |
2866 | =head3 Watcher-Specific Functions and Data Members |
2853 | |
2867 | |
2854 | =over 4 |
2868 | =over 4 |
2855 | |
2869 | |
2856 | =item ev_idle_init (ev_idle *, callback) |
2870 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2879 | ev_idle_start (loop, idle_watcher); |
2893 | ev_idle_start (loop, idle_watcher); |
2880 | |
2894 | |
2881 | |
2895 | |
2882 | =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! |
2883 | |
2897 | |
2884 | 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: |
2885 | prepare watchers get invoked before the process blocks and check watchers |
2899 | prepare watchers get invoked before the process blocks and check watchers |
2886 | afterwards. |
2900 | afterwards. |
2887 | |
2901 | |
2888 | 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 |
2889 | 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> |
… | |
… | |
2917 | 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 |
2918 | 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 |
2919 | loop from blocking if lower-priority coroutines are active, thus mapping |
2933 | loop from blocking if lower-priority coroutines are active, thus mapping |
2920 | low-priority coroutines to idle/background tasks). |
2934 | low-priority coroutines to idle/background tasks). |
2921 | |
2935 | |
2922 | 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 |
2923 | 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 |
2924 | 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). |
2925 | |
2940 | |
2926 | 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 |
2927 | activate ("feed") events into libev. While libev fully supports this, they |
2942 | activate ("feed") events into libev. While libev fully supports this, they |
2928 | 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 |
2929 | 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 |
2930 | 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 |
2931 | 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 |
2932 | 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. |
2933 | |
2968 | |
2934 | =head3 Watcher-Specific Functions and Data Members |
2969 | =head3 Watcher-Specific Functions and Data Members |
2935 | |
2970 | |
2936 | =over 4 |
2971 | =over 4 |
2937 | |
2972 | |