src/or/periodic.c

   1 /* Copyright (c) 2015-2016, The Tor Project, Inc. */
   2 /* See LICENSE for licensing information */
   3
   4 /**
   5  * \file periodic.c
   6  *
   7  * \brief Generic backend for handling periodic events.
   8  *
   9  * The events in this module are used by main.c to track items that need
  10  * to fire once every N seconds, possibly picking a new interval each time
  11  * that they fire.  See periodic_events[] in main.c for examples.
  12  */
  13
  14 #include "or.h"
  15 #include "compat_libevent.h"
  16 #include "config.h"
  17 #include "periodic.h"
  18
  19 #include <event2/event.h>
  20
  21 /** We disable any interval greater than this number of seconds, on the
  22  * grounds that it is probably an absolute time mistakenly passed in as a
  23  * relative time.
  24  */
  25 static const int MAX_INTERVAL = 10 * 365 * 86400;
  26
  27 /** Set the event <b>event</b> to run in <b>next_interval</b> seconds from
  28  * now. */
  29 static void
  30 periodic_event_set_interval(periodic_event_item_t *event,
  31                             time_t next_interval)
  32 {
  33   tor_assert(next_interval < MAX_INTERVAL);
  34   struct timeval tv;
  35   tv.tv_sec = next_interval;
  36   tv.tv_usec = 0;
  37   event_add(event->ev, &tv);
  38 }
  39
  40 /** Wraps dispatches for periodic events, <b>data</b> will be a pointer to the
  41  * event that needs to be called */
  42 static void
  43 periodic_event_dispatch(evutil_socket_t fd, short what, void *data)
  44 {
  45   (void)fd;
  46   (void)what;
  47   periodic_event_item_t *event = data;
  48
  49   time_t now = time(NULL);
  50   const or_options_t *options = get_options();
  51 //  log_debug(LD_GENERAL, "Dispatching %s", event->name);
  52   int r = event->fn(now, options);
  53   int next_interval = 0;
  54
  55   /* update the last run time if action was taken */
  56   if (r==0) {
  57     log_err(LD_BUG, "Invalid return value for periodic event from %s.",
  58                       event->name);
  59     tor_assert(r != 0);
  60   } else if (r > 0) {
  61     event->last_action_time = now;
  62     /* If the event is meant to happen after ten years, that's likely
  63      * a bug, and somebody gave an absolute time rather than an interval.
  64      */
  65     tor_assert(r < MAX_INTERVAL);
  66     next_interval = r;
  67   } else {
  68     /* no action was taken, it is likely a precondition failed,
  69      * we should reschedule for next second incase the precondition
  70      * passes then */
  71     next_interval = 1;
  72   }
  73
  74 //  log_debug(LD_GENERAL, "Scheduling %s for %d seconds", event->name,
  75 //           next_interval);
  76   struct timeval tv = { next_interval , 0 };
  77   event_add(event->ev, &tv);
  78 }
  79
  80 /** Schedules <b>event</b> to run as soon as possible from now. */
  81 void
  82 periodic_event_reschedule(periodic_event_item_t *event)
  83 {
  84   periodic_event_set_interval(event, 1);
  85 }
  86
  87 /** Initializes the libevent backend for a periodic event. */
  88 void
  89 periodic_event_setup(periodic_event_item_t *event)
  90 {
  91   if (event->ev) { /* Already setup? This is a bug */
  92     log_err(LD_BUG, "Initial dispatch should only be done once.");
  93     tor_assert(0);
  94   }
  95
  96   event->ev = tor_event_new(tor_libevent_get_base(),
  97                             -1, 0,
  98                             periodic_event_dispatch,
  99                             event);
 100   tor_assert(event->ev);
 101 }
 102
 103 /** Handles initial dispatch for periodic events. It should happen 1 second
 104  * after the events are created to mimic behaviour before #3199's refactor */
 105 void
 106 periodic_event_launch(periodic_event_item_t *event)
 107 {
 108   if (! event->ev) { /* Not setup? This is a bug */
 109     log_err(LD_BUG, "periodic_event_launch without periodic_event_setup");
 110     tor_assert(0);
 111   }
 112
 113   // Initial dispatch
 114   periodic_event_dispatch(-1, EV_TIMEOUT, event);
 115 }
 116
 117 /** Release all storage associated with <b>event</b> */
 118 void
 119 periodic_event_destroy(periodic_event_item_t *event)
 120 {
 121   if (!event)
 122     return;
 123   tor_event_free(event->ev);
 124   event->last_action_time = 0;
 125 }
 126