output: delay reopen after device failure

When one of several output devices failed, MPD tried to reopen it
quite often, wasting a lot of resources.  This patch adds a delay:
wait 10 seconds before retrying.  This might be changed to exponential
delays later, but for now, it makes the problem go away.

src/audio.c

@@ -342,6 +342,7 @@ int enableAudioDevice(unsigned int device)
 	if (device >= audioOutputArraySize)
 		return -1;
 
+	audioOutputArray[device].reopen_after = 0;
 	audioOutputArray[device].enabled = true;
 	idle_add(IDLE_OUTPUT);
 

src/output_control.c

@@ -57,6 +57,8 @@ audio_output_open(struct audio_output *audioOutput,
 {
 	bool ret = true;
 
+	audioOutput->reopen_after = 0;
+
 	if (audioOutput->open &&
 	    audio_format_equals(audioFormat, &audioOutput->inAudioFormat)) {
 		return true;
@@ -93,9 +95,10 @@ void
 audio_output_update(struct audio_output *ao,
 		    const struct audio_format *audio_format)
 {
-	if (ao->enabled)
-		audio_output_open(ao, audio_format);
-	else if (audio_output_is_open(ao))
+	if (ao->enabled) {
+		if (ao->reopen_after == 0 || time(NULL) > ao->reopen_after)
+			audio_output_open(ao, audio_format);
+	} else if (audio_output_is_open(ao))
 		audio_output_close(ao);
 }
 

src/output_init.c

@@ -87,6 +87,7 @@ int audio_output_init(struct audio_output *ao, ConfigParam * param)
 	ao->plugin = plugin;
 	ao->enabled = true;
 	ao->open = false;
+	ao->reopen_after = 0;
 
 	ao->convBuffer = NULL;
 	ao->convBufferLen = 0;

src/output_internal.h

@@ -23,6 +23,8 @@
 #include "pcm_utils.h"
 #include "notify.h"
 
+#include <time.h>
+
 struct audio_output {
 	/**
 	 * The device's configured display name.
@@ -50,6 +52,12 @@ struct audio_output {
 	 */
 	bool open;
 
+	/**
+	 * If not zero, the device has failed, and should not be
+	 * reopened automatically before this time stamp.
+	 */
+	time_t reopen_after;
+
 	/**
 	 * The audio_format in which audio data is received from the
 	 * player thread (which in turn receives it from the decoder).

src/output_thread.c

@@ -23,6 +23,12 @@
 
 #include <assert.h>
 
+enum {
+	/** after a failure, wait this number of seconds before
+	    automatically reopening the device */
+	REOPEN_AFTER = 10,
+};
+
 static void ao_command_finished(struct audio_output *ao)
 {
 	assert(ao->command != AO_COMMAND_NONE);
@@ -104,6 +110,8 @@ static void *audio_output_task(void *arg)
 			assert(!ao->open);
 			if (ao->result == true)
 				ao->open = true;
+			else
+				ao->reopen_after = time(NULL) + REOPEN_AFTER;
 
 			ao_command_finished(ao);
 			break;