devicestate: Don't create topic when change isn't cached.

When publishing a device state the change can be marked as being
cachable or not. If it is not cached the change is just published
to all interested and not stored away for later query. This was not
fully taken into account when publishing in stasis. The act of
publishing would create a topic for the device even if it may be
ephemeral.

This change makes it so messages which are not cached won't create
a topic for the device. If a topic does already exist it will be
published to but otherwise the change will only be published to
the device state all topic.

ASTERISK-27591

Change-Id: I18da0e8cbb18e79602e731020c46ba4101e59f0a

include/asterisk/stasis.h

@@ -744,6 +744,16 @@ struct stasis_topic_pool *stasis_topic_pool_create(struct stasis_topic *pooled_t
  */
 struct stasis_topic *stasis_topic_pool_get_topic(struct stasis_topic_pool *pool, const char *topic_name);
 
+/*!
+ * \brief Check if a topic exists in a pool
+ * \param pool Pool to check
+ * \param topic_name Name of the topic to check
+ * \retval 1 exists
+ * \retval 0 does not exist
+ * \since 13.23.0
+ */
+int stasis_topic_pool_topic_exists(const struct stasis_topic_pool *pool, const char *topic_name);
+
 /*! \addtogroup StasisTopicsAndMessages
  * @{
  */

main/devicestate.c

@@ -714,7 +714,7 @@ int ast_publish_device_state_full(
 {
 	RAII_VAR(struct ast_device_state_message *, device_state, NULL, ao2_cleanup);
 	RAII_VAR(struct stasis_message *, message, NULL, ao2_cleanup);
-	struct stasis_topic *device_specific_topic;
+	struct stasis_topic *topic;
 
 	ast_assert(!ast_strlen_zero(device));
 
@@ -733,12 +733,28 @@ int ast_publish_device_state_full(
 		return -1;
 	}
 
-	device_specific_topic = ast_device_state_topic(device);
-	if (!device_specific_topic) {
+	/* When a device state is to be cached it is likely that something
+	 * external will either be monitoring it or will want to pull the
+	 * information from the cache, so we always publish to the device
+	 * specific topic. Cachable updates traditionally come from such things
+	 * as a SIP or PJSIP device.
+	 * When a device state is not to be cached we only publish to its
+	 * specific topic if something has already created the topic. Publishing
+	 * to its topic otherwise would create the topic, which may not be
+	 * necessary as it could be an ephemeral device. Uncachable updates
+	 * traditionally come from such things as Local channels.
+	 */
+	if (cachable || stasis_topic_pool_topic_exists(device_state_topic_pool, device)) {
+		topic = ast_device_state_topic(device);
+	} else {
+		topic = ast_device_state_topic_all();
+	}
+
+	if (!topic) {
 		return -1;
 	}
 
-	stasis_publish(device_specific_topic, message);
+	stasis_publish(topic, message);
 	return 0;
 }
 

main/stasis.c

@@ -1196,6 +1196,19 @@ struct stasis_topic *stasis_topic_pool_get_topic(struct stasis_topic_pool *pool,
 	return topic_pool_entry->topic;
 }
 
+int stasis_topic_pool_topic_exists(const struct stasis_topic_pool *pool, const char *topic_name)
+{
+	struct topic_pool_entry *topic_pool_entry;
+
+	topic_pool_entry = ao2_find(pool->pool_container, topic_name, OBJ_SEARCH_KEY);
+	if (!topic_pool_entry) {
+		return 0;
+	}
+
+	ao2_ref(topic_pool_entry, -1);
+	return 1;
+}
+
 void stasis_log_bad_type_access(const char *name)
 {
 #ifdef AST_DEVMODE