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

1 files changed, 5 insertions, 5 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;