- Fix dnstap wakeup, a running wakeup timer is left to expire and not

increased, a timer is started when the dtio thread is sleeping,
  the timer set disabled when the dtio thread goes to sleep, and
  after sleep the thread checks to see if there are messages to log
  immediately.

dnstap/dtstream.c

@@ -176,10 +176,7 @@ void
 mq_wakeup_cb(void* arg)
 {
 	struct dt_msg_queue* mq = (struct dt_msg_queue*)arg;
-	/* even if the dtio is already active, because perhaps much
-	 * traffic suddenly, we leave the timer running to save on
-	 * managing it, the once a second timer is less work then
-	 * starting and stopping the timer frequently */
+
 	lock_basic_lock(&mq->dtio->wakeup_timer_lock);
 	mq->dtio->wakeup_timer_enabled = 0;
 	lock_basic_unlock(&mq->dtio->wakeup_timer_lock);
@@ -210,6 +207,8 @@ dt_msg_queue_start_timer(struct dt_msg_queue* mq, int wakeupnow)
 	lock_basic_lock(&mq->dtio->wakeup_timer_lock);
 	if(mq->dtio->wakeup_timer_enabled) {
 		if(wakeupnow) {
+			tv.tv_sec = 0;
+			tv.tv_usec = 0;
 			comm_timer_set(mq->wakeup_timer, &tv);
 		}
 		lock_basic_unlock(&mq->dtio->wakeup_timer_lock);
@@ -221,8 +220,14 @@ dt_msg_queue_start_timer(struct dt_msg_queue* mq, int wakeupnow)
 	if(!wakeupnow) {
 		tv.tv_sec = 1;
 		tv.tv_usec = 0;
+		/* If it is already set, keep it running. */
+		if(!comm_timer_is_set(mq->wakeup_timer))
+			comm_timer_set(mq->wakeup_timer, &tv);
+	} else {
+		tv.tv_sec = 0;
+		tv.tv_usec = 0;
+		comm_timer_set(mq->wakeup_timer, &tv);
 	}
-	comm_timer_set(mq->wakeup_timer, &tv);
 	lock_basic_unlock(&mq->dtio->wakeup_timer_lock);
 }
 
@@ -260,8 +265,9 @@ dt_msg_queue_submit(struct dt_msg_queue* mq, void* buf, size_t len)
 
 	/* acquire lock */
 	lock_basic_lock(&mq->lock);
-	/* if list was empty, start timer for (eventual) wakeup */
-	if(mq->first == NULL)
+	/* if list was empty, start timer for (eventual) wakeup,
+	 * or if dtio is not writing now an eventual wakeup is needed. */
+	if(mq->first == NULL || !mq->dtio->event_added_is_write)
 		wakeupstarttimer = 1;
 	/* if list contains more than wakeupnum elements, wakeup now,
 	 * or if list is (going to be) almost full */
@@ -1259,6 +1265,13 @@ static void dtio_sleep(struct dt_io_thread* dtio)
 	/* unregister the event polling for write, because there is
 	 * nothing to be written */
 	(void)dtio_add_output_event_read(dtio);
+
+	/* Set wakeuptimer enabled off; so that the next worker thread that
+	 * wants to log starts a timer if needed, since the writer thread
+	 * has gone to sleep. */
+	lock_basic_lock(&dtio->wakeup_timer_lock);
+	dtio->wakeup_timer_enabled = 0;
+	lock_basic_unlock(&dtio->wakeup_timer_lock);
 }
 
 #ifdef HAVE_SSL
@@ -1521,8 +1534,22 @@ void dtio_output_cb(int ATTR_UNUSED(fd), short bits, void* arg)
 					/* no messages on the first iteration,
 					 * the queues are all empty */
 					dtio_sleep(dtio);
+					/* After putting to sleep, see if
+					 * a message is in a message queue,
+					 * if so, resume service. Stops a
+					 * race condition where a thread could
+					 * have one message but the dtio
+					 * also just went to sleep. With the
+					 * message queued between the
+					 * dtio_find_msg and dtio_sleep
+					 * calls. */
+					if(dtio_find_msg(dtio)) {
+						if(!dtio_add_output_event_write(dtio))
+							return;
+					}
 				}
-				return; /* nothing to do */
+				if(!dtio->cur_msg)
+					return; /* nothing to do */
 			}
 		}
 

doc/Changelog

@@ -1,6 +1,11 @@
 19 July 2024: Wouter
 	- Add dnstap-sample-rate that logs only 1/N messages, for high volume
 	  server environments. Thanks Dan Luther.
+	- Fix dnstap wakeup, a running wakeup timer is left to expire and not
+	  increased, a timer is started when the dtio thread is sleeping,
+	  the timer set disabled when the dtio thread goes to sleep, and
+	  after sleep the thread checks to see if there are messages to log
+	  immediately.
 
 16 July 2024: Wouter
 	- For #1103: Fix to drop mesh state reference for the http2 stream

testcode/fake_event.c

@@ -1655,6 +1655,12 @@ void comm_timer_set(struct comm_timer* timer, struct timeval* tv)
 	timeval_add(&t->tv, &t->runtime->now_tv);
 }
 
+int comm_timer_is_set(struct comm_timer* timer)
+{
+	struct fake_timer* t = (struct fake_timer*)timer;
+	return t->enabled;
+}
+
 void comm_timer_delete(struct comm_timer* timer)
 {
 	struct fake_timer* t = (struct fake_timer*)timer;