Split caching out from the stasis_caching_topic.

In working with res_stasis, I discovered a significant limitation to
the current structure of stasis_caching_topics: you cannot subscribe
to cache updates for a single channel/bridge/endpoint/etc.

To address this, this patch splits the cache away from the
stasis_caching_topic, making it a first class object. The stasis_cache
object is shared amongst individual stasis_caching_topics that are
created per channel/endpoint/etc. These are still forwarded to global
whatever_all_cached topics, so their use from most of the code does
not change.

In making these changes, I noticed that we frequently used a similar
pattern for bridges, endpoints and channels:

     single_topic  ---------------->  all_topic
           ^
           |
     single_topic_cached  ----+---->  all_topic_cached
                              |
                              +---->  cache

This pattern was extracted as the 'Stasis Caching Pattern', defined in
stasis_caching_pattern.h. This avoids a lot of duplicate code between
the different domain objects.

Since the cache is now disassociated from its upstream caching topics,
this also necessitated a change to how the 'guaranteed' flag worked
for retrieving from a cache. The code for handling the caching
guarantee was extracted into a 'stasis_topic_wait' function, which
works for any stasis_topic.

(closes issue ASTERISK-22002)
Review: https://reviewboard.asterisk.org/r/2672/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@395954 65c4cc65-6c06-0410-ace0-fbb531ad65f3

9 files changed, 31 insertions, 35 deletions

diff --git a/res/ari/resource_bridges.c b/res/ari/resource_bridges.c
index 17a8bb132..7730d0cd9 100644
--- a/res/ari/resource_bridges.c
+++ b/res/ari/resource_bridges.c
@@ -448,22 +448,22 @@ void ast_ari_delete_bridge(struct ast_variable *headers, struct ast_delete_bridg
 
 void ast_ari_get_bridges(struct ast_variable *headers, struct ast_get_bridges_args *args, struct ast_ari_response *response)
 {
-	RAII_VAR(struct stasis_caching_topic *, caching_topic, NULL, ao2_cleanup);
+	RAII_VAR(struct stasis_cache *, cache, NULL, ao2_cleanup);
 	RAII_VAR(struct ao2_container *, snapshots, NULL, ao2_cleanup);
 	RAII_VAR(struct ast_json *, json, NULL, ast_json_unref);
 	struct ao2_iterator i;
 	void *obj;
 
-	caching_topic = ast_bridge_topic_all_cached();
-	if (!caching_topic) {
+	cache = ast_bridge_cache();
+	if (!cache) {
 		ast_ari_response_error(
 			response, 500, "Internal Server Error",
 			"Message bus not initialized");
 		return;
 	}
-	ao2_ref(caching_topic, +1);
+	ao2_ref(cache, +1);
 
-	snapshots = stasis_cache_dump(caching_topic, ast_bridge_snapshot_type());
+	snapshots = stasis_cache_dump(cache, ast_bridge_snapshot_type());
 	if (!snapshots) {
 		ast_ari_response_alloc_failed(response);
 		return;
diff --git a/res/ari/resource_channels.c b/res/ari/resource_channels.c
index 7f3a91fba..dd323bac5 100644
--- a/res/ari/resource_channels.c
+++ b/res/ari/resource_channels.c
@@ -466,18 +466,18 @@ void ast_ari_get_channel(struct ast_variable *headers,
 			     struct ast_ari_response *response)
 {
 	RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
-	struct stasis_caching_topic *caching_topic;
+	struct stasis_cache *cache;
 	struct ast_channel_snapshot *snapshot;
 
-	caching_topic = ast_channel_topic_all_cached();
-	if (!caching_topic) {
+	cache = ast_channel_cache();
+	if (!cache) {
 		ast_ari_response_error(
 			response, 500, "Internal Server Error",
 			"Message bus not initialized");
 		return;
 	}
 
-	msg = stasis_cache_get(caching_topic, ast_channel_snapshot_type(),
+	msg = stasis_cache_get(cache, ast_channel_snapshot_type(),
 			       args->channel_id);
 	if (!msg) {
 		ast_ari_response_error(
@@ -516,22 +516,22 @@ void ast_ari_get_channels(struct ast_variable *headers,
 			      struct ast_get_channels_args *args,
 			      struct ast_ari_response *response)
 {
-	RAII_VAR(struct stasis_caching_topic *, caching_topic, NULL, ao2_cleanup);
+	RAII_VAR(struct stasis_cache *, cache, NULL, ao2_cleanup);
 	RAII_VAR(struct ao2_container *, snapshots, NULL, ao2_cleanup);
 	RAII_VAR(struct ast_json *, json, NULL, ast_json_unref);
 	struct ao2_iterator i;
 	void *obj;
 
-	caching_topic = ast_channel_topic_all_cached();
-	if (!caching_topic) {
+	cache = ast_channel_cache();
+	if (!cache) {
 		ast_ari_response_error(
 			response, 500, "Internal Server Error",
 			"Message bus not initialized");
 		return;
 	}
-	ao2_ref(caching_topic, +1);
+	ao2_ref(cache, +1);
 
-	snapshots = stasis_cache_dump(caching_topic, ast_channel_snapshot_type());
+	snapshots = stasis_cache_dump(cache, ast_channel_snapshot_type());
 	if (!snapshots) {
 		ast_ari_response_alloc_failed(response);
 		return;
diff --git a/res/ari/resource_endpoints.c b/res/ari/resource_endpoints.c
index bb28df03c..35d8a45cc 100644
--- a/res/ari/resource_endpoints.c
+++ b/res/ari/resource_endpoints.c
@@ -37,22 +37,22 @@ void ast_ari_get_endpoints(struct ast_variable *headers,
 	struct ast_get_endpoints_args *args,
 	struct ast_ari_response *response)
 {
-	RAII_VAR(struct stasis_caching_topic *, caching_topic, NULL, ao2_cleanup);
+	RAII_VAR(struct stasis_cache *, cache, NULL, ao2_cleanup);
 	RAII_VAR(struct ao2_container *, snapshots, NULL, ao2_cleanup);
 	RAII_VAR(struct ast_json *, json, NULL, ast_json_unref);
 	struct ao2_iterator i;
 	void *obj;
 
-	caching_topic = ast_endpoint_topic_all_cached();
-	if (!caching_topic) {
+	cache = ast_endpoint_cache();
+	if (!cache) {
 		ast_ari_response_error(
 			response, 500, "Internal Server Error",
 			"Message bus not initialized");
 		return;
 	}
-	ao2_ref(caching_topic, +1);
+	ao2_ref(cache, +1);
 
-	snapshots = stasis_cache_dump(caching_topic, ast_endpoint_snapshot_type());
+	snapshots = stasis_cache_dump(cache, ast_endpoint_snapshot_type());
 	if (!snapshots) {
 		ast_ari_response_alloc_failed(response);
 		return;
@@ -83,7 +83,7 @@ void ast_ari_get_endpoints_by_tech(struct ast_variable *headers,
 	struct ast_get_endpoints_by_tech_args *args,
 	struct ast_ari_response *response)
 {
-	RAII_VAR(struct stasis_caching_topic *, caching_topic, NULL, ao2_cleanup);
+	RAII_VAR(struct stasis_cache *, cache, NULL, ao2_cleanup);
 	RAII_VAR(struct ao2_container *, snapshots, NULL, ao2_cleanup);
 	RAII_VAR(struct ast_json *, json, NULL, ast_json_unref);
 	struct ao2_iterator i;
@@ -91,16 +91,16 @@ void ast_ari_get_endpoints_by_tech(struct ast_variable *headers,
 
 	/* TODO - if tech isn't a recognized type of endpoint, it should 404 */
 
-	caching_topic = ast_endpoint_topic_all_cached();
-	if (!caching_topic) {
+	cache = ast_endpoint_cache();
+	if (!cache) {
 		ast_ari_response_error(
 			response, 500, "Internal Server Error",
 			"Message bus not initialized");
 		return;
 	}
-	ao2_ref(caching_topic, +1);
+	ao2_ref(cache, +1);
 
-	snapshots = stasis_cache_dump(caching_topic, ast_endpoint_snapshot_type());
+	snapshots = stasis_cache_dump(cache, ast_endpoint_snapshot_type());
 	if (!snapshots) {
 		ast_ari_response_alloc_failed(response);
 		return;
diff --git a/res/res_agi.c b/res/res_agi.c
index 07735130c..5c79ec27f 100644
--- a/res/res_agi.c
+++ b/res/res_agi.c
@@ -2771,7 +2771,7 @@ static int handle_channelstatus(struct ast_channel *chan, AGI *agi, int argc, co
 		RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
 
 		/* one argument: look for info on the specified channel */
-		if ((msg = stasis_cache_get(ast_channel_topic_all_cached_by_name(), ast_channel_snapshot_type(), argv[2]))) {
+		if ((msg = stasis_cache_get(ast_channel_cache_by_name(), ast_channel_snapshot_type(), argv[2]))) {
 			struct ast_channel_snapshot *snapshot = stasis_message_data(msg);
 
 			ast_agi_send(agi->fd, chan, "200 result=%d\n", snapshot->state);
diff --git a/res/res_chan_stats.c b/res/res_chan_stats.c
index 0f39f071f..a43c564b1 100644
--- a/res/res_chan_stats.c
+++ b/res/res_chan_stats.c
@@ -154,7 +154,7 @@ static int load_module(void)
 {
 	/* You can create a message router to route messages by type */
 	router = stasis_message_router_create(
-		stasis_caching_get_topic(ast_channel_topic_all_cached()));
+		ast_channel_topic_all_cached());
 	if (!router) {
 		return AST_MODULE_LOAD_FAILURE;
 	}
diff --git a/res/res_jabber.c b/res/res_jabber.c
index 7ca0bf81e..0e373e5e7 100644
--- a/res/res_jabber.c
+++ b/res/res_jabber.c
@@ -3310,7 +3310,7 @@ static void aji_init_event_distribution(struct aji_client *client)
 		RAII_VAR(struct ao2_container *, cached, NULL, ao2_cleanup);
 		device_state_sub = stasis_subscribe(ast_device_state_topic_all(),
 			aji_devstate_cb, client);
-		cached = stasis_cache_dump(ast_device_state_topic_cached(), NULL);
+		cached = stasis_cache_dump(ast_device_state_cache(), NULL);
 		ao2_callback(cached, OBJ_NODATA, cached_devstate_cb, client);
 	}
 
diff --git a/res/res_stasis.c b/res/res_stasis.c
index 624950399..e4ad97eae 100644
--- a/res/res_stasis.c
+++ b/res/res_stasis.c
@@ -993,7 +993,7 @@ static int load_module(void)
 		return AST_MODULE_LOAD_FAILURE;
 	}
 
-	channel_router = stasis_message_router_create(stasis_caching_get_topic(ast_channel_topic_all_cached()));
+	channel_router = stasis_message_router_create(ast_channel_topic_all_cached());
 	if (!channel_router) {
 		return AST_MODULE_LOAD_FAILURE;
 	}
@@ -1013,7 +1013,7 @@ static int load_module(void)
 		return AST_MODULE_LOAD_FAILURE;
 	}
 
-	bridge_router = stasis_message_router_create(stasis_caching_get_topic(ast_bridge_topic_all_cached()));
+	bridge_router = stasis_message_router_create(ast_bridge_topic_all_cached());
 	if (!bridge_router) {
 		return AST_MODULE_LOAD_FAILURE;
 	}
diff --git a/res/res_xmpp.c b/res/res_xmpp.c
index 89eb45d18..3be8aa458 100644
--- a/res/res_xmpp.c
+++ b/res/res_xmpp.c
@@ -1605,7 +1605,7 @@ static void xmpp_init_event_distribution(struct ast_xmpp_client *client)
 		return;
 	}
 
-	cached = stasis_cache_dump(ast_device_state_topic_cached(), NULL);
+	cached = stasis_cache_dump(ast_device_state_cache(), NULL);
 	ao2_callback(cached, OBJ_NODATA, cached_devstate_cb, client);
 
 	xmpp_pubsub_subscribe(client, "device_state");
diff --git a/res/stasis/control.c b/res/stasis/control.c
index 1fbae0c7c..94f1d700d 100644
--- a/res/stasis/control.c
+++ b/res/stasis/control.c
@@ -364,13 +364,9 @@ struct ast_channel_snapshot *stasis_app_control_get_snapshot(
 	const struct stasis_app_control *control)
 {
 	RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
-	struct stasis_caching_topic *caching_topic;
 	struct ast_channel_snapshot *snapshot;
 
-	caching_topic = ast_channel_topic_all_cached();
-	ast_assert(caching_topic != NULL);
-
-	msg = stasis_cache_get(caching_topic, ast_channel_snapshot_type(),
+	msg = stasis_cache_get(ast_channel_cache(), ast_channel_snapshot_type(),
 		stasis_app_control_get_channel_id(control));
 	if (!msg) {
 		return NULL;