endpoint/stasis: Eliminate duplicate events on endpoint status change

When an endpoint was created, it's messages were being forwarded to
both the tech endpoint topic and the all endpoints topic.  Since
the tech topic was also forwarded to all, this was resulting in
duplicate messages whenever an endpoint published.  This patch
causes the endpoint to only forward to the tech topic and lets
the tech topic forward to all.

To accomplish this, the existing stasis_cp_single_create function
(which both creates and forwards) was cloned and split into 2
functions, one that creates the topic and one that sets up the
forwarding.  This allows endpoint_internal_create to create
the topic from the endpoint_all cache without forwarding it there,
then allows it to do the forward to the tech's topic.

ASTERISK-25137 #close
Reported-by: Vitezslav Novy
ASTERISK-25116 #close
Reported-by: George Joseph <george.joseph@fairview5.com>
Tested-by: George Joseph <george.joseph@fairview5.com>

Change-Id: I26d7d4926a0861748fd3bdffe316b75b549a801c

3 files changed, 85 insertions, 20 deletions

diff --git a/include/asterisk/stasis_cache_pattern.h b/include/asterisk/stasis_cache_pattern.h
index 2ea643e19..27761351a 100644
--- a/include/asterisk/stasis_cache_pattern.h
+++ b/include/asterisk/stasis_cache_pattern.h
@@ -109,6 +109,8 @@ struct stasis_cp_single;
 /*!
  * \brief Create the 'one' side of the cache pattern.
  *
+ * Create the 'one' and forward to all's topic and topic_cached.
+ *
  * Dispose of using stasis_cp_single_unsubscribe().
  *
  * \param all Corresponding all side.
@@ -119,6 +121,32 @@ struct stasis_cp_single *stasis_cp_single_create(struct stasis_cp_all *all,
 	const char *name);
 
 /*!
+ * \brief Create the 'one' side of the cache pattern.
+ *
+ * Create the 'one' but do not automatically forward.
+ *
+ * Dispose of using stasis_cp_single_unsubscribe().
+ *
+ * \param all Corresponding all side.
+ * \param name Base name for the topics.
+ * \return One side instance
+ */
+struct stasis_cp_single *stasis_cp_single_create_only(struct stasis_cp_all *all,
+	const char *name);
+
+/*!
+ * \brief Set up a topic and topic cache forward.
+ *
+ * Forward 'from' to 'to'.
+ *
+ * \param from Source 'one' side instance.
+ * \param to Destination 'one' side instance.
+ * \retval 0 Success
+ * \retval -1 Failure
+ */
+int stasis_cp_single_forward(struct stasis_cp_single *from, struct stasis_cp_single *to);
+
+/*!
  * \brief Stops caching and forwarding messages.
  *
  * \param one One side of the cache pattern.
diff --git a/main/endpoints.c b/main/endpoints.c
index ce0ab0292..a64001403 100644
--- a/main/endpoints.c
+++ b/main/endpoints.c
@@ -74,8 +74,6 @@ struct ast_endpoint {
 	struct stasis_message_router *router;
 	/*! ast_str_container of channels associated with this endpoint */
 	struct ao2_container *channel_ids;
-	/*! Forwarding subscription from an endpoint to its tech endpoint */
-	struct stasis_forward *tech_forward;
 };
 
 static int endpoint_hash(const void *obj, int flags)
@@ -303,13 +301,14 @@ static struct ast_endpoint *endpoint_internal_create(const char *tech, const cha
 		return NULL;
 	}
 
-	endpoint->topics = stasis_cp_single_create(ast_endpoint_cache_all(),
-		endpoint->id);
-	if (!endpoint->topics) {
-		return NULL;
-	}
-
 	if (!ast_strlen_zero(resource)) {
+
+		endpoint->topics = stasis_cp_single_create_only(ast_endpoint_cache_all(),
+			endpoint->id);
+		if (!endpoint->topics) {
+			return NULL;
+		}
+
 		endpoint->router = stasis_message_router_create_pool(ast_endpoint_topic(endpoint));
 		if (!endpoint->router) {
 			return NULL;
@@ -323,11 +322,19 @@ static struct ast_endpoint *endpoint_internal_create(const char *tech, const cha
 			return NULL;
 		}
 
-		endpoint->tech_forward = stasis_forward_all(stasis_cp_single_topic(endpoint->topics),
-			stasis_cp_single_topic(tech_endpoint->topics));
+		if (stasis_cp_single_forward(endpoint->topics, tech_endpoint->topics)) {
+			return NULL;
+		}
+
 		endpoint_publish_snapshot(endpoint);
 		ao2_link(endpoints, endpoint);
 	} else {
+		endpoint->topics = stasis_cp_single_create(ast_endpoint_cache_all(),
+			endpoint->id);
+		if (!endpoint->topics) {
+			return NULL;
+		}
+
 		ao2_link(tech_endpoints, endpoint);
 	}
 
@@ -375,7 +382,6 @@ void ast_endpoint_shutdown(struct ast_endpoint *endpoint)
 	}
 
 	ao2_unlink(endpoints, endpoint);
-	endpoint->tech_forward = stasis_forward_cancel(endpoint->tech_forward);
 
 	clear_msg = create_endpoint_snapshot_message(endpoint);
 	if (clear_msg) {
diff --git a/main/stasis_cache_pattern.c b/main/stasis_cache_pattern.c
index 9e3de367a..ccc9ebf08 100644
--- a/main/stasis_cache_pattern.c
+++ b/main/stasis_cache_pattern.c
@@ -138,6 +138,30 @@ struct stasis_cp_single *stasis_cp_single_create(struct stasis_cp_all *all,
 {
 	RAII_VAR(struct stasis_cp_single *, one, NULL, ao2_cleanup);
 
+	one = stasis_cp_single_create_only(all, name);
+	if (!one) {
+		return NULL;
+	}
+
+	one->forward_topic_to_all = stasis_forward_all(one->topic, all->topic);
+	if (!one->forward_topic_to_all) {
+		return NULL;
+	}
+	one->forward_cached_to_all = stasis_forward_all(
+		stasis_caching_get_topic(one->topic_cached), all->topic_cached);
+	if (!one->forward_cached_to_all) {
+		return NULL;
+	}
+
+	ao2_ref(one, +1);
+	return one;
+}
+
+struct stasis_cp_single *stasis_cp_single_create_only(struct stasis_cp_all *all,
+	const char *name)
+{
+	RAII_VAR(struct stasis_cp_single *, one, NULL, ao2_cleanup);
+
 	one = ao2_t_alloc(sizeof(*one), one_dtor, name);
 	if (!one) {
 		return NULL;
@@ -152,18 +176,25 @@ struct stasis_cp_single *stasis_cp_single_create(struct stasis_cp_all *all,
 		return NULL;
 	}
 
-	one->forward_topic_to_all = stasis_forward_all(one->topic, all->topic);
-	if (!one->forward_topic_to_all) {
-		return NULL;
+	ao2_ref(one, +1);
+	return one;
+}
+
+int stasis_cp_single_forward(struct stasis_cp_single *from, struct stasis_cp_single *to)
+{
+	from->forward_topic_to_all = stasis_forward_all(from->topic, to->topic);
+	if (!from->forward_topic_to_all) {
+		return -1;;
 	}
-	one->forward_cached_to_all = stasis_forward_all(
-		stasis_caching_get_topic(one->topic_cached), all->topic_cached);
-	if (!one->forward_cached_to_all) {
-		return NULL;
+
+	from->forward_cached_to_all = stasis_forward_all(
+		stasis_caching_get_topic(from->topic_cached),
+		stasis_caching_get_topic(to->topic_cached));
+	if (!from->forward_cached_to_all) {
+		return -1;
 	}
 
-	ao2_ref(one, +1);
-	return one;
+	return 0;
 }
 
 void stasis_cp_single_unsubscribe(struct stasis_cp_single *one)