stasis: Add internal filtering of messages.

This change adds the ability for subscriptions to indicate
which message types they are interested in accepting. By
doing so the filtering is done before being dispatched
to the subscriber, reducing the amount of work that has
to be done.

This is optional and if a subscriber does not add
message types they wish to accept and set the subscription
to selective filtering the previous behavior is preserved
and they receive all messages.

There is also the ability to explicitly force the reception
of all messages for cases such as AMI or ARI where a large
number of messages are expected that are then generically
converted into a different format.

ASTERISK-28103

Change-Id: I99bee23895baa0a117985d51683f7963b77aa190

apps/app_queue.c

@@ -11336,6 +11336,8 @@ static int load_module(void)
 	if (!device_state_sub) {
 		err = -1;
 	}
+	stasis_subscription_accept_message_type(device_state_sub, ast_device_state_message_type());
+	stasis_subscription_set_filter(device_state_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	manager_topic = ast_manager_get_topic();
 	queue_topic = ast_queue_topic_all();

channels/chan_dahdi.c

@@ -12594,6 +12594,8 @@ static struct dahdi_pvt *mkintf(int channel, const struct dahdi_chan_conf *conf,
 				 * knows that we care about it.  Then, chan_dahdi will get the MWI from the
 				 * event cache instead of checking the mailbox directly. */
 				tmp->mwi_event_sub = stasis_subscribe_pool(mailbox_specific_topic, stasis_subscription_cb_noop, NULL);
+				stasis_subscription_accept_message_type(tmp->mwi_event_sub, ast_mwi_state_type());
+				stasis_subscription_set_filter(tmp->mwi_event_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 			}
 		}
 #ifdef HAVE_DAHDI_LINEREVERSE_VMWI

channels/chan_iax2.c

@@ -1456,6 +1456,8 @@ static void network_change_stasis_subscribe(void)
 	if (!network_change_sub) {
 		network_change_sub = stasis_subscribe(ast_system_topic(),
 			network_change_stasis_cb, NULL);
+		stasis_subscription_accept_message_type(network_change_sub, ast_network_change_type());
+		stasis_subscription_set_filter(network_change_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 }
 
@@ -1469,6 +1471,8 @@ static void acl_change_stasis_subscribe(void)
 	if (!acl_change_sub) {
 		acl_change_sub = stasis_subscribe(ast_security_topic(),
 			acl_change_stasis_cb, NULL);
+		stasis_subscription_accept_message_type(acl_change_sub, ast_named_acl_change_type());
+		stasis_subscription_set_filter(acl_change_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 }
 
@@ -13072,6 +13076,8 @@ static struct iax2_peer *build_peer(const char *name, struct ast_variable *v, st
 			 * mailboxes.  However, we just grab the events out of the cache when it
 			 * is time to send MWI, since it is only sent with a REGACK. */
 			peer->mwi_event_sub = stasis_subscribe_pool(mailbox_specific_topic, stasis_subscription_cb_noop, NULL);
+			stasis_subscription_accept_message_type(peer->mwi_event_sub, ast_mwi_state_type());
+			stasis_subscription_set_filter(peer->mwi_event_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 		}
 	}
 

channels/chan_mgcp.c

@@ -4242,6 +4242,8 @@ static struct mgcp_gateway *build_gateway(char *cat, struct ast_variable *v)
 						 * knows that we care about it.  Then, chan_mgcp will get the MWI from the
 						 * event cache instead of checking the mailbox directly. */
 						e->mwi_event_sub = stasis_subscribe_pool(mailbox_specific_topic, stasis_subscription_cb_noop, NULL);
+						stasis_subscription_accept_message_type(e->mwi_event_sub, ast_mwi_state_type());
+						stasis_subscription_set_filter(e->mwi_event_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 					}
 				}
 				snprintf(e->rqnt_ident, sizeof(e->rqnt_ident), "%08lx", (unsigned long)ast_random());

channels/chan_sip.c

@@ -17494,6 +17494,8 @@ static void network_change_stasis_subscribe(void)
 	if (!network_change_sub) {
 		network_change_sub = stasis_subscribe(ast_system_topic(),
 			network_change_stasis_cb, NULL);
+		stasis_subscription_accept_message_type(network_change_sub, ast_network_change_type());
+		stasis_subscription_set_filter(network_change_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 }
 
@@ -17507,6 +17509,8 @@ static void acl_change_stasis_subscribe(void)
 	if (!acl_change_sub) {
 		acl_change_sub = stasis_subscribe(ast_security_topic(),
 			acl_change_stasis_cb, NULL);
+		stasis_subscription_accept_message_type(acl_change_sub, ast_named_acl_change_type());
+		stasis_subscription_set_filter(acl_change_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 
 }
@@ -28385,6 +28389,9 @@ static void add_peer_mwi_subs(struct sip_peer *peer)
 		mailbox_specific_topic = ast_mwi_topic(mailbox->id);
 		if (mailbox_specific_topic) {
 			mailbox->event_sub = stasis_subscribe_pool(mailbox_specific_topic, mwi_event_cb, peer);
+			stasis_subscription_accept_message_type(mailbox->event_sub, ast_mwi_state_type());
+			stasis_subscription_accept_message_type(mailbox->event_sub, stasis_subscription_change_type());
+			stasis_subscription_set_filter(mailbox->event_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 		}
 	}
 }

channels/chan_skinny.c

@@ -8334,6 +8334,8 @@ static struct skinny_line *config_line(const char *lname, struct ast_variable *v
 		mailbox_specific_topic = ast_mwi_topic(l->mailbox);
 		if (mailbox_specific_topic) {
 			l->mwi_event_sub = stasis_subscribe_pool(mailbox_specific_topic, mwi_event_cb, l);
+			stasis_subscription_accept_message_type(l->mwi_event_sub, ast_mwi_state_type());
+			stasis_subscription_set_filter(l->mwi_event_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 		}
 	}
 

channels/sig_pri.c

@@ -9130,6 +9130,9 @@ int sig_pri_start_pri(struct sig_pri_span *pri)
 		if (!pri->mbox[i].sub) {
 			ast_log(LOG_ERROR, "%s span %d could not subscribe to MWI events for %s(%s).\n",
 				sig_pri_cc_type_name, pri->span, pri->mbox[i].vm_box, mbox_id);
+		} else {
+			stasis_subscription_accept_message_type(pri->mbox[i].sub, ast_mwi_state_type());
+			stasis_subscription_set_filter(pri->mbox[i].sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 		}
 #if defined(HAVE_PRI_MWI_V2)
 		if (ast_strlen_zero(pri->mbox[i].vm_number)) {

include/asterisk/stasis.h

@@ -291,6 +291,15 @@ enum stasis_message_type_result {
 	STASIS_MESSAGE_TYPE_DECLINED,	/*!< Message type was not created due to configuration */
 };
 
+/*!
+ * \brief Stasis subscription message filters
+ */
+enum stasis_subscription_message_filter {
+	STASIS_SUBSCRIPTION_FILTER_NONE = 0,    /*!< No filter is in place, all messages are raised */
+	STASIS_SUBSCRIPTION_FILTER_FORCED_NONE, /*!< No filter is in place or can be set, all messages are raised */
+	STASIS_SUBSCRIPTION_FILTER_SELECTIVE,   /*!< Only messages of allowed message types are raised */
+};
+
 /*!
  * \brief Create a new message type.
  *
@@ -326,6 +335,14 @@ const char *stasis_message_type_name(const struct stasis_message_type *type);
  */
 unsigned int stasis_message_type_hash(const struct stasis_message_type *type);
 
+/*!
+ * \brief Gets the id of a given message type
+ * \param type The type to get the id of.
+ * \return The id
+ * \since 17.0.0
+ */
+int stasis_message_type_id(const struct stasis_message_type *type);
+
 /*!
  * \brief Check whether a message type is declined
  *
@@ -494,6 +511,14 @@ struct stasis_topic *stasis_topic_create(const char *name);
  */
 const char *stasis_topic_name(const struct stasis_topic *topic);
 
+/*!
+ * \brief Return the number of subscribers of a topic.
+ * \param topic Topic.
+ * \return Number of subscribers of the topic.
+ * \since 17.0.0
+ */
+size_t stasis_topic_subscribers(const struct stasis_topic *topic);
+
 /*!
  * \brief Publish a message to a topic's subscribers.
  * \param topic Topic.
@@ -559,6 +584,10 @@ void stasis_subscription_cb_noop(void *data, struct stasis_subscription *sub, st
  * \return New \ref stasis_subscription object.
  * \return \c NULL on error.
  * \since 12
+ *
+ * \note This callback will receive a callback with a message indicating it
+ * has been subscribed. This occurs immediately before accepted message
+ * types can be set and the callback must expect to receive it.
  */
 struct stasis_subscription *stasis_subscribe(struct stasis_topic *topic,
 	stasis_subscription_cb callback, void *data);
@@ -584,10 +613,68 @@ struct stasis_subscription *stasis_subscribe(struct stasis_topic *topic,
  * \return New \ref stasis_subscription object.
  * \return \c NULL on error.
  * \since 12.8.0
+ *
+ * \note This callback will receive a callback with a message indicating it
+ * has been subscribed. This occurs immediately before accepted message
+ * types can be set and the callback must expect to receive it.
  */
 struct stasis_subscription *stasis_subscribe_pool(struct stasis_topic *topic,
 	stasis_subscription_cb callback, void *data);
 
+/*!
+ * \brief Indicate to a subscription that we are interested in a message type.
+ *
+ * This will cause the subscription to allow the given message type to be
+ * raised to our subscription callback. This enables internal filtering in
+ * the stasis message bus to reduce messages.
+ *
+ * \param subscription Subscription to add message type to.
+ * \param type The message type we wish to receive.
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ *
+ * \note If you are wanting to use stasis_final_message you will need to accept
+ * \ref stasis_subscription_change_type as a message type.
+ *
+ * \note Until the subscription is set to selective filtering it is possible for it
+ * to receive messages of message types that would not normally be accepted.
+ */
+int stasis_subscription_accept_message_type(struct stasis_subscription *subscription,
+	const struct stasis_message_type *type);
+
+/*!
+ * \brief Indicate to a subscription that we are not interested in a message type.
+ *
+ * \param subscription Subscription to remove message type from.
+ * \param type The message type we don't wish to receive.
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ */
+int stasis_subscription_decline_message_type(struct stasis_subscription *subscription,
+	const struct stasis_message_type *type);
+
+/*!
+ * \brief Set the message type filtering level on a subscription
+ *
+ * This will cause the subscription to filter messages according to the
+ * provided filter level. For example if selective is used then only
+ * messages matching those provided to \ref stasis_subscription_accept_message_type
+ * will be raised to the subscription callback.
+ *
+ * \param subscription Subscription that should receive all messages.
+ * \param filter What filter to use
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ */
+int stasis_subscription_set_filter(struct stasis_subscription *subscription,
+	enum stasis_subscription_message_filter filter);
+
 /*!
  * \brief Cancel a subscription.
  *
@@ -1036,6 +1123,41 @@ struct stasis_caching_topic *stasis_caching_unsubscribe_and_join(
 struct stasis_topic *stasis_caching_get_topic(
 	struct stasis_caching_topic *caching_topic);
 
+/*!
+ * \brief Indicate to a caching topic that we are interested in a message type.
+ *
+ * This will cause the caching topic to receive messages of the given message
+ * type. This enables internal filtering in the stasis message bus to reduce
+ * messages.
+ *
+ * \param caching_topic The caching topic.
+ * \param type The message type we wish to receive.
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ */
+int stasis_caching_accept_message_type(struct stasis_caching_topic *caching_topic,
+	struct stasis_message_type *type);
+
+/*!
+ * \brief Set the message type filtering level on a cache
+ *
+ * This will cause the underlying subscription to filter messages according to the
+ * provided filter level. For example if selective is used then only
+ * messages matching those provided to \ref stasis_subscription_accept_message_type
+ * will be raised to the subscription callback.
+ *
+ * \param caching_topic The caching topic.
+ * \param filter What filter to use
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ */
+int stasis_caching_set_filter(struct stasis_caching_topic *caching_topic,
+	enum stasis_subscription_message_filter filter);
+
 /*!
  * \brief A message which instructs the caching topic to remove an entry from
  * its cache.

include/asterisk/stasis_cache_pattern.h

@@ -169,4 +169,39 @@ struct stasis_topic *stasis_cp_single_topic(struct stasis_cp_single *one);
 struct stasis_topic *stasis_cp_single_topic_cached(
 	struct stasis_cp_single *one);
 
+/*!
+ * \brief Indicate to an instance that we are interested in a message type.
+ *
+ * This will cause the caching topic to receive messages of the given message
+ * type. This enables internal filtering in the stasis message bus to reduce
+ * messages.
+ *
+ * \param one One side of the cache pattern.
+ * \param type The message type we wish to receive.
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ */
+int stasis_cp_single_accept_message_type(struct stasis_cp_single *one,
+	struct stasis_message_type *type);
+
+/*!
+ * \brief Set the message type filtering level on a cache
+ *
+ * This will cause the underlying subscription to filter messages according to the
+ * provided filter level. For example if selective is used then only
+ * messages matching those provided to \ref stasis_subscription_accept_message_type
+ * will be raised to the subscription callback.
+ *
+ * \param one One side of the cache pattern.
+ * \param filter What filter to use
+ * \retval 0 on success
+ * \retval -1 failure
+ *
+ * \since 17.0.0
+ */
+int stasis_cp_single_set_filter(struct stasis_cp_single *one,
+	enum stasis_subscription_message_filter filter);
+
 #endif /* _ASTERISK_STASIS_CACHE_PATTERN_H */

include/asterisk/stasis_message_router.h

@@ -233,6 +233,10 @@ void stasis_message_router_remove_cache_update(
  * \retval -1 on failure
  *
  * \since 12
+ *
+ * \note Setting a default callback will automatically cause the underlying
+ * subscription to receive all messages and not be filtered. If filtering is
+ * desired then a specific route for each message type should be provided.
  */
 int stasis_message_router_set_default(struct stasis_message_router *router,
 				      stasis_subscription_cb callback,

main/ccss.c

@@ -1433,6 +1433,8 @@ static struct generic_monitor_instance_list *create_new_generic_list(struct ast_
 		cc_unref(generic_list, "Failed to subscribe to device state");
 		return NULL;
 	}
+	stasis_subscription_accept_message_type(generic_list->sub, ast_device_state_message_type());
+	stasis_subscription_set_filter(generic_list->sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	generic_list->current_state = ast_device_state(monitor->interface->device_name);
 	ao2_t_link(generic_monitors, generic_list, "linking new generic monitor instance list");
 	return generic_list;
@@ -2804,6 +2806,9 @@ static int cc_generic_agent_start_monitoring(struct ast_cc_agent *agent)
 	if (!(generic_pvt->sub = stasis_subscribe(device_specific_topic, generic_agent_devstate_cb, agent))) {
 		return -1;
 	}
+	stasis_subscription_accept_message_type(generic_pvt->sub, ast_device_state_message_type());
+	stasis_subscription_accept_message_type(generic_pvt->sub, stasis_subscription_change_type());
+	stasis_subscription_set_filter(generic_pvt->sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	cc_ref(agent, "Ref agent for subscription");
 	return 0;
 }

main/devicestate.c

@@ -920,6 +920,8 @@ int devstate_init(void)
 	if (!device_state_topic_cached) {
 		return -1;
 	}
+	stasis_caching_accept_message_type(device_state_topic_cached, ast_device_state_message_type());
+	stasis_caching_set_filter(device_state_topic_cached, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	devstate_message_sub = stasis_subscribe(ast_device_state_topic_all(),
 		devstate_change_cb, NULL);
@@ -927,6 +929,8 @@ int devstate_init(void)
 		ast_log(LOG_ERROR, "Failed to create subscription creating uncached device state aggregate events.\n");
 		return -1;
 	}
+	stasis_subscription_accept_message_type(devstate_message_sub, ast_device_state_message_type());
+	stasis_subscription_set_filter(devstate_message_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	return 0;
 }

main/endpoints.c

@@ -202,7 +202,7 @@ static void endpoint_cache_clear(void *data,
 	endpoint_publish_snapshot(endpoint);
 }
 
-static void endpoint_default(void *data,
+static void endpoint_subscription_change(void *data,
 	struct stasis_subscription *sub,
 	struct stasis_message *message)
 {
@@ -263,6 +263,8 @@ static struct ast_endpoint *endpoint_internal_create(const char *tech, const cha
 		if (!endpoint->topics) {
 			return NULL;
 		}
+		stasis_cp_single_accept_message_type(endpoint->topics, ast_endpoint_snapshot_type());
+		stasis_cp_single_set_filter(endpoint->topics, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 		endpoint->router = stasis_message_router_create_pool(ast_endpoint_topic(endpoint));
 		if (!endpoint->router) {
@@ -271,8 +273,9 @@ static struct ast_endpoint *endpoint_internal_create(const char *tech, const cha
 		r |= stasis_message_router_add(endpoint->router,
 			stasis_cache_clear_type(), endpoint_cache_clear,
 			endpoint);
-		r |= stasis_message_router_set_default(endpoint->router,
+		r |= stasis_message_router_add(endpoint->router,
-			endpoint_default, endpoint);
+			stasis_subscription_change_type(), endpoint_subscription_change,
+			endpoint);
 		if (r) {
 			return NULL;
 		}
@@ -288,6 +291,8 @@ static struct ast_endpoint *endpoint_internal_create(const char *tech, const cha
 		if (!endpoint->topics) {
 			return NULL;
 		}
+		stasis_cp_single_accept_message_type(endpoint->topics, ast_endpoint_snapshot_type());
+		stasis_cp_single_set_filter(endpoint->topics, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 		ao2_link(tech_endpoints, endpoint);
 	}

main/manager.c

@@ -1527,6 +1527,8 @@ static void acl_change_stasis_subscribe(void)
 	if (!acl_change_sub) {
 		acl_change_sub = stasis_subscribe(ast_security_topic(),
 			acl_change_stasis_cb, NULL);
+		stasis_subscription_accept_message_type(acl_change_sub, ast_named_acl_change_type());
+		stasis_subscription_set_filter(acl_change_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 }
 

main/pbx.c

@@ -8416,10 +8416,15 @@ int load_pbx(void)
 	if (!(device_state_sub = stasis_subscribe(ast_device_state_topic_all(), device_state_cb, NULL))) {
 		return -1;
 	}
+	stasis_subscription_accept_message_type(device_state_sub, ast_device_state_message_type());
+	stasis_subscription_accept_message_type(device_state_sub, hint_change_message_type());
+	stasis_subscription_set_filter(device_state_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	if (!(presence_state_sub = stasis_subscribe(ast_presence_state_topic_all(), presence_state_cb, NULL))) {
 		return -1;
 	}
+	stasis_subscription_accept_message_type(presence_state_sub, ast_presence_state_message_type());
+	stasis_subscription_set_filter(presence_state_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	return 0;
 }

main/presencestate.c

@@ -514,6 +514,8 @@ int ast_presence_state_engine_init(void)
 	if (!presence_state_topic_cached) {
 		return -1;
 	}
+	stasis_caching_accept_message_type(presence_state_topic_cached, ast_presence_state_message_type());
+	stasis_caching_set_filter(presence_state_topic_cached, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	AST_TEST_REGISTER(test_presence_chan);
 

main/stasis.c

@@ -370,6 +370,11 @@ const char *stasis_topic_name(const struct stasis_topic *topic)
 	return topic->name;
 }
 
+size_t stasis_topic_subscribers(const struct stasis_topic *topic)
+{
+	return AST_VECTOR_SIZE(&topic->subscribers);
+}
+
 /*! \internal */
 struct stasis_subscription {
 	/*! Unique ID for this subscription */
@@ -391,6 +396,11 @@ struct stasis_subscription {
 	/*! Flag set when final message for sub has been processed.
 	 *  Be sure join_lock is held before reading/setting. */
 	int final_message_processed;
+
+	/*! The message types this subscription is accepting */
+	AST_VECTOR(, char) accepted_message_types;
+	/*! The message filter currently in use */
+	enum stasis_subscription_message_filter filter;
 };
 
 static void subscription_dtor(void *obj)
@@ -409,6 +419,8 @@ static void subscription_dtor(void *obj)
 	ast_taskprocessor_unreference(sub->mailbox);
 	sub->mailbox = NULL;
 	ast_cond_destroy(&sub->join_cond);
+
+	AST_VECTOR_FREE(&sub->accepted_message_types);
 }
 
 /*!
@@ -420,19 +432,25 @@ static void subscription_dtor(void *obj)
 static void subscription_invoke(struct stasis_subscription *sub,
 				  struct stasis_message *message)
 {
+	unsigned int final = stasis_subscription_final_message(sub, message);
+	int message_type_id = stasis_message_type_id(stasis_subscription_change_type());
+
 	/* Notify that the final message has been received */
-	if (stasis_subscription_final_message(sub, message)) {
+	if (final) {
 		ao2_lock(sub);
 		sub->final_message_rxed = 1;
 		ast_cond_signal(&sub->join_cond);
 		ao2_unlock(sub);
 	}
 
-	/* Since sub is mostly immutable, no need to lock sub */
+	if (!final || sub->filter != STASIS_SUBSCRIPTION_FILTER_SELECTIVE ||
-	sub->callback(sub->data, sub, message);
+		(message_type_id < AST_VECTOR_SIZE(&sub->accepted_message_types) && AST_VECTOR_GET(&sub->accepted_message_types, message_type_id))) {
+		/* Since sub is mostly immutable, no need to lock sub */
+		sub->callback(sub->data, sub, message);
+	}
 
 	/* Notify that the final message has been processed */
-	if (stasis_subscription_final_message(sub, message)) {
+	if (final) {
 		ao2_lock(sub);
 		sub->final_message_processed = 1;
 		ast_cond_signal(&sub->join_cond);
@@ -500,6 +518,8 @@ struct stasis_subscription *internal_stasis_subscribe(
 	sub->callback = callback;
 	sub->data = data;
 	ast_cond_init(&sub->join_cond, NULL);
+	sub->filter = STASIS_SUBSCRIPTION_FILTER_NONE;
+	AST_VECTOR_INIT(&sub->accepted_message_types, 0);
 
 	if (topic_add_subscription(topic, sub) != 0) {
 		ao2_ref(sub, -1);
@@ -586,6 +606,76 @@ int stasis_subscription_set_congestion_limits(struct stasis_subscription *subscr
 	return res;
 }
 
+int stasis_subscription_accept_message_type(struct stasis_subscription *subscription,
+	const struct stasis_message_type *type)
+{
+	if (!subscription) {
+		return -1;
+	}
+
+	ast_assert(type != NULL);
+	ast_assert(stasis_message_type_name(type) != NULL);
+
+	if (!type || !stasis_message_type_name(type)) {
+		/* Filtering is unreliable as this message type is not yet initialized
+		 * so force all messages through.
+		 */
+		subscription->filter = STASIS_SUBSCRIPTION_FILTER_FORCED_NONE;
+		return 0;
+	}
+
+	ao2_lock(subscription->topic);
+	if (AST_VECTOR_REPLACE(&subscription->accepted_message_types, stasis_message_type_id(type), 1)) {
+		/* We do this for the same reason as above. The subscription can still operate, so allow
+		 * it to do so by forcing all messages through.
+		 */
+		subscription->filter = STASIS_SUBSCRIPTION_FILTER_FORCED_NONE;
+	}
+	ao2_unlock(subscription->topic);
+
+	return 0;
+}
+
+int stasis_subscription_decline_message_type(struct stasis_subscription *subscription,
+	const struct stasis_message_type *type)
+{
+	if (!subscription) {
+		return -1;
+	}
+
+	ast_assert(type != NULL);
+	ast_assert(stasis_message_type_name(type) != NULL);
+
+	if (!type || !stasis_message_type_name(type)) {
+		return 0;
+	}
+
+	ao2_lock(subscription->topic);
+	if (stasis_message_type_id(type) < AST_VECTOR_SIZE(&subscription->accepted_message_types)) {
+		/* The memory is already allocated so this can't fail */
+		AST_VECTOR_REPLACE(&subscription->accepted_message_types, stasis_message_type_id(type), 0);
+	}
+	ao2_unlock(subscription->topic);
+
+	return 0;
+}
+
+int stasis_subscription_set_filter(struct stasis_subscription *subscription,
+	enum stasis_subscription_message_filter filter)
+{
+	if (!subscription) {
+		return -1;
+	}
+
+	ao2_lock(subscription->topic);
+	if (subscription->filter != STASIS_SUBSCRIPTION_FILTER_FORCED_NONE) {
+		subscription->filter = filter;
+	}
+	ao2_unlock(subscription->topic);
+
+	return 0;
+}
+
 void stasis_subscription_join(struct stasis_subscription *subscription)
 {
 	if (subscription) {
@@ -781,6 +871,18 @@ static void dispatch_message(struct stasis_subscription *sub,
 	struct stasis_message *message,
 	int synchronous)
 {
+	/* Determine if this subscription is interested in this message. Note that final
+	 * messages are special and are always invoked on the subscription.
+	 */
+	if (sub->filter == STASIS_SUBSCRIPTION_FILTER_SELECTIVE) {
+		int message_type_id = stasis_message_type_id(stasis_message_type(message));
+		if ((message_type_id >= AST_VECTOR_SIZE(&sub->accepted_message_types) ||
+			!AST_VECTOR_GET(&sub->accepted_message_types, message_type_id)) &&
+			!stasis_subscription_final_message(sub, message)) {
+			return;
+		}
+	}
+
 	if (!sub->mailbox) {
 		/* Dispatch directly */
 		subscription_invoke(sub, message);
@@ -840,6 +942,11 @@ static void publish_msg(struct stasis_topic *topic,
 	ast_assert(topic != NULL);
 	ast_assert(message != NULL);
 
+	/* If there are no subscribers don't bother */
+	if (!stasis_topic_subscribers(topic)) {
+		return;
+	}
+
 	/*
 	 * The topic may be unref'ed by the subscription invocation.
 	 * Make sure we hold onto a reference while dispatching.

main/stasis_cache.c

@@ -87,6 +87,35 @@ struct stasis_topic *stasis_caching_get_topic(struct stasis_caching_topic *cachi
 	return caching_topic->topic;
 }
 
+int stasis_caching_accept_message_type(struct stasis_caching_topic *caching_topic,
+	struct stasis_message_type *type)
+{
+	int res;
+
+	if (!caching_topic) {
+		return -1;
+	}
+
+	/* We wait to accept the stasis specific message types until now so that by default everything
+	 * will flow to us.
+	 */
+	res = stasis_subscription_accept_message_type(caching_topic->sub, stasis_cache_clear_type());
+	res |= stasis_subscription_accept_message_type(caching_topic->sub, stasis_subscription_change_type());
+	res |= stasis_subscription_accept_message_type(caching_topic->sub, type);
+
+	return res;
+}
+
+int stasis_caching_set_filter(struct stasis_caching_topic *caching_topic,
+	enum stasis_subscription_message_filter filter)
+{
+	if (!caching_topic) {
+		return -1;
+	}
+	return stasis_subscription_set_filter(caching_topic->sub, filter);
+}
+
+
 struct stasis_caching_topic *stasis_caching_unsubscribe(struct stasis_caching_topic *caching_topic)
 {
 	if (!caching_topic) {
@@ -856,11 +885,13 @@ static void caching_topic_exec(void *data, struct stasis_subscription *sub,
 		/* Update the cache */
 		snapshots = cache_put(caching_topic->cache, msg_type, msg_id, msg_eid, msg_put);
 		if (snapshots.old || msg_put) {
-			update = update_create(snapshots.old, msg_put);
+			if (stasis_topic_subscribers(caching_topic->topic)) {
-			if (update) {
+				update = update_create(snapshots.old, msg_put);
-				stasis_publish(caching_topic->topic, update);
+				if (update) {
+					stasis_publish(caching_topic->topic, update);
+					ao2_ref(update, -1);
+				}
 			}
-			ao2_cleanup(update);
 		} else {
 			ast_debug(1,
 				"Attempting to remove an item from the %s cache that isn't there: %s %s\n",
@@ -873,11 +904,13 @@ static void caching_topic_exec(void *data, struct stasis_subscription *sub,
 				caching_topic->cache->aggregate_publish_fn(caching_topic->original_topic,
 					snapshots.aggregate_new);
 			}
-			update = update_create(snapshots.aggregate_old, snapshots.aggregate_new);
+			if (stasis_topic_subscribers(caching_topic->topic)) {
-			if (update) {
+				update = update_create(snapshots.aggregate_old, snapshots.aggregate_new);
-				stasis_publish(caching_topic->topic, update);
+				if (update) {
+					stasis_publish(caching_topic->topic, update);
+					ao2_ref(update, -1);
+				}
 			}
-			ao2_cleanup(update);
 		}
 
 		ao2_cleanup(snapshots.old);

main/stasis_cache_pattern.c

@@ -217,3 +217,21 @@ struct stasis_topic *stasis_cp_single_topic_cached(
 	}
 	return stasis_caching_get_topic(one->topic_cached);
 }
+
+int stasis_cp_single_accept_message_type(struct stasis_cp_single *one,
+	struct stasis_message_type *type)
+{
+	if (!one) {
+		return -1;
+	}
+	return stasis_caching_accept_message_type(one->topic_cached, type);
+}
+
+int stasis_cp_single_set_filter(struct stasis_cp_single *one,
+	enum stasis_subscription_message_filter filter)
+{
+	if (!one) {
+		return -1;
+	}
+	return stasis_caching_set_filter(one->topic_cached, filter);
+}

main/stasis_message.c

@@ -39,9 +39,11 @@ struct stasis_message_type {
 	struct stasis_message_vtable *vtable;
 	char *name;
 	unsigned int hash;
+	int id;
 };
 
 static struct stasis_message_vtable null_vtable = {};
+static int message_type_id;
 
 static void message_type_dtor(void *obj)
 {
@@ -78,6 +80,7 @@ int stasis_message_type_create(const char *name,
 	}
 	type->hash = ast_hashtab_hash_string(name);
 	type->vtable = vtable;
+	type->id = ast_atomic_fetchadd_int(&message_type_id, +1);
 	*result = type;
 
 	return STASIS_MESSAGE_TYPE_SUCCESS;
@@ -93,6 +96,11 @@ unsigned int stasis_message_type_hash(const struct stasis_message_type *type)
 	return type->hash;
 }
 
+int stasis_message_type_id(const struct stasis_message_type *type)
+{
+	return type->id;
+}
+
 /*! \internal */
 struct stasis_message {
 	/*! Time the message was created */

main/stasis_message_router.c

@@ -235,6 +235,9 @@ static struct stasis_message_router *stasis_message_router_create_internal(
 		return NULL;
 	}
 
+	/* We need to receive subscription change messages so we know when our subscription goes away */
+	stasis_subscription_accept_message_type(router->subscription, stasis_subscription_change_type());
+
 	return router;
 }
 
@@ -316,6 +319,14 @@ int stasis_message_router_add(struct stasis_message_router *router,
 	}
 	ao2_lock(router);
 	res = route_table_add(&router->routes, message_type, callback, data);
+	if (!res) {
+		stasis_subscription_accept_message_type(router->subscription, message_type);
+		/* Until a specific message type was added we would already drop the message, so being
+		 * selective now doesn't harm us. If we have a default route then we are already forced
+		 * to filter nothing and messages will come in regardless.
+		 */
+		stasis_subscription_set_filter(router->subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
+	}
 	ao2_unlock(router);
 	return res;
 }
@@ -334,6 +345,10 @@ int stasis_message_router_add_cache_update(struct stasis_message_router *router,
 	}
 	ao2_lock(router);
 	res = route_table_add(&router->cache_routes, message_type, callback, data);
+	if (!res) {
+		stasis_subscription_accept_message_type(router->subscription, stasis_cache_update_type());
+		stasis_subscription_set_filter(router->subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
+	}
 	ao2_unlock(router);
 	return res;
 }
@@ -378,6 +393,9 @@ int stasis_message_router_set_default(struct stasis_message_router *router,
 	router->default_route.callback = callback;
 	router->default_route.data = data;
 	ao2_unlock(router);
+
+	stasis_subscription_set_filter(router->subscription, STASIS_SUBSCRIPTION_FILTER_FORCED_NONE);
+
 	/* While this implementation can never fail, it used to be able to */
 	return 0;
 }

res/parking/parking_applications.c

@@ -868,6 +868,10 @@ static void park_announce_update_cb(void *data, struct stasis_subscription *sub,
 		return;
 	}
 
+	if (ast_parked_call_type() != stasis_message_type(message)) {
+		return;
+	}
+
 	if (payload->event_type != PARKED_CALL) {
 		/* We are only concerned with calls parked */
 		return;
@@ -954,6 +958,10 @@ static int park_and_announce_app_exec(struct ast_channel *chan, const char *data
 		return -1;
 	}
 
+	stasis_subscription_accept_message_type(parking_subscription, ast_parked_call_type());
+	stasis_subscription_accept_message_type(parking_subscription, stasis_subscription_change_type());
+	stasis_subscription_set_filter(parking_subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
+
 	/* Now for the fun part... park it! */
 	ast_bridge_join(parking_bridge, chan, NULL, &chan_features, NULL, 0);
 

res/parking/parking_bridge_features.c

@@ -213,6 +213,9 @@ static int create_parked_subscription_full(struct ast_channel *chan, const char
 	if (!(parked_datastore->parked_subscription = stasis_subscribe_pool(ast_parking_topic(), parker_update_cb, subscription_data))) {
 		return -1;
 	}
+	stasis_subscription_accept_message_type(parked_datastore->parked_subscription, ast_parked_call_type());
+	stasis_subscription_accept_message_type(parked_datastore->parked_subscription, stasis_subscription_change_type());
+	stasis_subscription_set_filter(parked_datastore->parked_subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	datastore->data = parked_datastore;
 

res/parking/parking_manager.c

@@ -686,6 +686,8 @@ static void parking_manager_enable_stasis(void)
 {
 	if (!parking_sub) {
 		parking_sub = stasis_subscribe(ast_parking_topic(), parking_event_cb, NULL);
+		stasis_subscription_accept_message_type(parking_sub, ast_parked_call_type());
+		stasis_subscription_set_filter(parking_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 }
 

res/res_hep_rtcp.c

@@ -167,6 +167,9 @@ static int load_module(void)
 	if (!stasis_rtp_subscription) {
 		return AST_MODULE_LOAD_DECLINE;
 	}
+	stasis_subscription_accept_message_type(stasis_rtp_subscription, ast_rtp_rtcp_sent_type());
+	stasis_subscription_accept_message_type(stasis_rtp_subscription, ast_rtp_rtcp_received_type());
+	stasis_subscription_set_filter(stasis_rtp_subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	return AST_MODULE_LOAD_SUCCESS;
 }

res/res_pjsip_mwi.c

@@ -269,6 +269,9 @@ static struct mwi_stasis_subscription *mwi_stasis_subscription_alloc(const char
 		ao2_ref(mwi_sub, -1);
 		mwi_stasis_sub = NULL;
 	}
+	stasis_subscription_accept_message_type(mwi_stasis_sub->stasis_sub, ast_mwi_state_type());
+	stasis_subscription_accept_message_type(mwi_stasis_sub->stasis_sub, stasis_subscription_change_type());
+	stasis_subscription_set_filter(mwi_stasis_sub->stasis_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	return mwi_stasis_sub;
 }
 
@@ -1364,7 +1367,11 @@ static int load_module(void)
 		if (ast_test_flag(&ast_options, AST_OPT_FLAG_FULLY_BOOTED)) {
 			ast_sip_push_task(NULL, send_initial_notify_all, NULL);
 		} else {
-			stasis_subscribe_pool(ast_manager_get_topic(), mwi_startup_event_cb, NULL);
+			struct stasis_subscription *sub;
+
+			sub = stasis_subscribe_pool(ast_manager_get_topic(), mwi_startup_event_cb, NULL);
+			stasis_subscription_accept_message_type(sub, ast_manager_get_generic_type());
+			stasis_subscription_set_filter(sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 		}
 	}
 

res/res_pjsip_outbound_registration.c

@@ -2534,6 +2534,8 @@ static int load_module(void)
 
 	network_change_sub = stasis_subscribe(ast_system_topic(),
 		network_change_stasis_cb, NULL);
+	stasis_subscription_accept_message_type(network_change_sub, ast_network_change_type());
+	stasis_subscription_set_filter(network_change_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	return AST_MODULE_LOAD_SUCCESS;
 }

res/res_pjsip_publish_asterisk.c

@@ -360,6 +360,9 @@ static int asterisk_start_devicestate_publishing(struct ast_sip_outbound_publish
 		ao2_ref(datastore, -1);
 		return -1;
 	}
+	stasis_subscription_accept_message_type(publisher_state->device_state_subscription, ast_device_state_message_type());
+	stasis_subscription_accept_message_type(publisher_state->device_state_subscription, stasis_subscription_change_type());
+	stasis_subscription_set_filter(publisher_state->device_state_subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	cached = stasis_cache_dump(ast_device_state_cache(), NULL);
 	ao2_callback(cached, OBJ_NODATA, cached_devstate_cb, datastore);
@@ -435,6 +438,9 @@ static int asterisk_start_mwi_publishing(struct ast_sip_outbound_publish *config
 		ao2_ref(datastore, -1);
 		return -1;
 	}
+	stasis_subscription_accept_message_type(publisher_state->mailbox_state_subscription, ast_mwi_state_type());
+	stasis_subscription_accept_message_type(publisher_state->mailbox_state_subscription, stasis_subscription_change_type());
+	stasis_subscription_set_filter(publisher_state->mailbox_state_subscription, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	cached = stasis_cache_dump(ast_mwi_state_cache(), NULL);
 	ao2_callback(cached, OBJ_NODATA, cached_mwistate_cb, datastore);

res/res_pjsip_pubsub.c

@@ -5567,7 +5567,11 @@ static int load_module(void)
 	if (ast_test_flag(&ast_options, AST_OPT_FLAG_FULLY_BOOTED)) {
 		ast_sip_push_task(NULL, subscription_persistence_load, NULL);
 	} else {
-		stasis_subscribe_pool(ast_manager_get_topic(), subscription_persistence_event_cb, NULL);
+		struct stasis_subscription *sub;
+
+		sub = stasis_subscribe_pool(ast_manager_get_topic(), subscription_persistence_event_cb, NULL);
+		stasis_subscription_accept_message_type(sub, ast_manager_get_generic_type());
+		stasis_subscription_set_filter(sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 	}
 
 	ast_manager_register_xml(AMI_SHOW_SUBSCRIPTIONS_INBOUND, EVENT_FLAG_SYSTEM,

res/res_pjsip_refer.c

@@ -686,6 +686,10 @@ static void refer_blind_callback(struct ast_channel *chan, struct transfer_chann
 			ast_channel_unlock(chan);
 
 			ao2_cleanup(refer->progress);
+		} else {
+			stasis_subscription_accept_message_type(refer->progress->bridge_sub, ast_channel_entered_bridge_type());
+			stasis_subscription_accept_message_type(refer->progress->bridge_sub, stasis_subscription_change_type());
+			stasis_subscription_set_filter(refer->progress->bridge_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 		}
 	}
 

res/res_security_log.c

@@ -141,6 +141,8 @@ static int load_module(void)
 		LOG_SECURITY = -1;
 		return AST_MODULE_LOAD_DECLINE;
 	}
+	stasis_subscription_accept_message_type(security_stasis_sub, ast_security_event_type());
+	stasis_subscription_set_filter(security_stasis_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	ast_verb(3, "Security Logging Enabled\n");
 

res/res_stasis_device_state.c

@@ -394,6 +394,9 @@ static int subscribe_device_state(struct stasis_app *app, void *obj)
 		ao2_ref(sub, -1);
 		return -1;
 	}
+	stasis_subscription_accept_message_type(sub->sub, ast_device_state_message_type());
+	stasis_subscription_accept_message_type(sub->sub, stasis_subscription_change_type());
+	stasis_subscription_set_filter(sub->sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	ao2_link_flags(device_state_subscriptions, sub, OBJ_NOLOCK);
 	ao2_unlock(device_state_subscriptions);

res/res_xmpp.c

@@ -1599,11 +1599,15 @@ static void xmpp_init_event_distribution(struct ast_xmpp_client *client)
 	if (!(client->mwi_sub = stasis_subscribe_pool(ast_mwi_topic_all(), xmpp_pubsub_mwi_cb, client))) {
 		return;
 	}
+	stasis_subscription_accept_message_type(client->mwi_sub, ast_mwi_state_type());
+	stasis_subscription_set_filter(client->mwi_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	if (!(client->device_state_sub = stasis_subscribe(ast_device_state_topic_all(), xmpp_pubsub_devstate_cb, client))) {
 		client->mwi_sub = stasis_unsubscribe(client->mwi_sub);
 		return;
 	}
+	stasis_subscription_accept_message_type(client->device_state_sub, ast_device_state_message_type());
+	stasis_subscription_set_filter(client->device_state_sub, STASIS_SUBSCRIPTION_FILTER_SELECTIVE);
 
 	cached = stasis_cache_dump(ast_device_state_cache(), NULL);
 	ao2_callback(cached, OBJ_NODATA, cached_devstate_cb, client);