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, 9 insertions, 9 deletions

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;