stasis: Reduce creation of channel snapshots to improve performance

During some performance testing of Asterisk with AGI, ARI, and lots of Local
channels, we noticed that there's quite a hit in performance during channel
creation and releasing to the dialplan (ARI continue). After investigating
the performance spike that occurs during channel creation, we discovered
that we create a lot of channel snapshots that are technically unnecessary.
This includes creating snapshots during:
 * AGI execution
 * Returning objects for ARI commands
 * During some Local channel operations
 * During some dialling operations
 * During variable setting
 * During some bridging operations
And more.

This patch does the following:
 - It removes a number of fields from channel snapshots. These fields were
   rarely used, were expensive to have on the snapshot, and hurt performance.
   This included formats, translation paths, Log Call ID, callgroup, pickup
   group, and all channel variables. As a result, AMI Status,
   "core show channel", "core show channelvar", and "pjsip show channel" were
   modified to either hit the live channel or not show certain pieces of data.
   While this is unfortunate, the performance gain from this patch is worth
   the loss in behaviour.
 - It adds a mechanism to publish a cached snapshot + blob. A large number of
   publications were changed to use this, including:
   - During Dial begin
   - During Variable assignment (if no AMI variables are emitted - if AMI
     variables are set, we have to make snapshots when a variable is changed)
   - During channel pickup
   - When a channel is put on hold/unhold
   - When a DTMF digit is begun/ended
   - When creating a bridge snapshot
   - When an AOC event is raised
   - During Local channel optimization/Local bridging
   - When endpoint snapshots are generated
   - All AGI events
   - All ARI responses that return a channel
   - Events in the AgentPool, MeetMe, and some in Queue
 - Additionally, some extraneous channel snapshots were being made that were
   unnecessary. These were removed.
 - The result of ast_hashtab_hash_string is now cached in stasis_cache. This
   reduces a large number of calls to ast_hashtab_hash_string, which reduced
   the amount of time spent in this function in gprof by around 50%.

#ASTERISK-23811 #close
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/3568/
........

Merged revisions 416211 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@416216 65c4cc65-6c06-0410-ace0-fbb531ad65f3

15 files changed, 271 insertions, 217 deletions

diff --git a/main/aoc.c b/main/aoc.c
index 7dd888ec2..de43efcb5 100644
--- a/main/aoc.c
+++ b/main/aoc.c
@@ -1871,7 +1871,7 @@ int ast_aoc_manager_event(const struct ast_aoc_decoded *decoded, struct ast_chan
 		return 0;
 	}
 
-	ast_channel_publish_blob(chan, msg_type, blob);
+	ast_channel_publish_cached_blob(chan, msg_type, blob);
 	return 0;
 }
 
diff --git a/main/bridge_channel.c b/main/bridge_channel.c
index 9a1e40bba..9b1b5737e 100644
--- a/main/bridge_channel.c
+++ b/main/bridge_channel.c
@@ -838,18 +838,16 @@ int ast_bridge_channel_write_hold(struct ast_bridge_channel *bridge_channel, con
 		datalen = 0;
 	}
 
-	ast_channel_lock(bridge_channel->chan);
-	ast_channel_publish_blob(bridge_channel->chan, ast_channel_hold_type(), blob);
-	ast_channel_unlock(bridge_channel->chan);
+	ast_channel_publish_cached_blob(bridge_channel->chan, ast_channel_hold_type(), blob);
+
 	return ast_bridge_channel_write_control_data(bridge_channel, AST_CONTROL_HOLD,
 		moh_class, datalen);
 }
 
 int ast_bridge_channel_write_unhold(struct ast_bridge_channel *bridge_channel)
 {
-	ast_channel_lock(bridge_channel->chan);
-	ast_channel_publish_blob(bridge_channel->chan, ast_channel_unhold_type(), NULL);
-	ast_channel_unlock(bridge_channel->chan);
+	ast_channel_publish_cached_blob(bridge_channel->chan, ast_channel_unhold_type(), NULL);
+
 	return ast_bridge_channel_write_control_data(bridge_channel, AST_CONTROL_UNHOLD, NULL, 0);
 }
 
diff --git a/main/cel.c b/main/cel.c
index e61adfcec..c7f4fc366 100644
--- a/main/cel.c
+++ b/main/cel.c
@@ -1798,9 +1798,7 @@ void ast_cel_publish_event(struct ast_channel *chan,
 		"event_type", event_type,
 		"event_details", blob);
 
-	ast_channel_lock(chan);
-	message = ast_channel_blob_create(chan, cel_generic_type(), cel_blob);
-	ast_channel_unlock(chan);
+	message = ast_channel_blob_create_from_cache(ast_channel_uniqueid(chan), cel_generic_type(), cel_blob);
 	if (message) {
 		stasis_publish(ast_cel_topic(), message);
 	}
diff --git a/main/channel.c b/main/channel.c
index dd3539479..04c396a71 100644
--- a/main/channel.c
+++ b/main/channel.c
@@ -1270,7 +1270,6 @@ int ast_queue_hold(struct ast_channel *chan, const char *musicclass)
 	struct ast_frame f = { AST_FRAME_CONTROL, .subclass.integer = AST_CONTROL_HOLD };
 	int res;
 
-	ast_channel_lock(chan);
 	if (!ast_strlen_zero(musicclass)) {
 		f.data.ptr = (void *) musicclass;
 		f.datalen = strlen(musicclass) + 1;
@@ -1279,10 +1278,10 @@ int ast_queue_hold(struct ast_channel *chan, const char *musicclass)
 				     "musicclass", musicclass);
 	}
 
-	ast_channel_publish_blob(chan, ast_channel_hold_type(), blob);
+	ast_channel_publish_cached_blob(chan, ast_channel_hold_type(), blob);
 
 	res = ast_queue_frame(chan, &f);
-	ast_channel_unlock(chan);
+
 	return res;
 }
 
@@ -1291,11 +1290,10 @@ int ast_queue_unhold(struct ast_channel *chan)
 	struct ast_frame f = { AST_FRAME_CONTROL, .subclass.integer = AST_CONTROL_UNHOLD };
 	int res;
 
-	ast_channel_lock(chan);
-	ast_channel_publish_blob(chan, ast_channel_unhold_type(), NULL);
+	ast_channel_publish_cached_blob(chan, ast_channel_unhold_type(), NULL);
 
 	res = ast_queue_frame(chan, &f);
-	ast_channel_unlock(chan);
+
 	return res;
 }
 
@@ -3639,7 +3637,7 @@ static void send_dtmf_begin_event(struct ast_channel *chan,
 		return;
 	}
 
-	ast_channel_publish_blob(chan, ast_channel_dtmf_begin_type(), blob);
+	ast_channel_publish_cached_blob(chan, ast_channel_dtmf_begin_type(), blob);
 }
 
 static void send_dtmf_end_event(struct ast_channel *chan,
@@ -3656,7 +3654,7 @@ static void send_dtmf_end_event(struct ast_channel *chan,
 		return;
 	}
 
-	ast_channel_publish_blob(chan, ast_channel_dtmf_end_type(), blob);
+	ast_channel_publish_cached_blob(chan, ast_channel_dtmf_end_type(), blob);
 }
 
 static void ast_read_generator_actions(struct ast_channel *chan, struct ast_frame *f)
@@ -3988,7 +3986,6 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
 					ast_frfree(f);
 					f = &ast_null_frame;
 				} else {
-					/* Answer the CDR */
 					ast_setstate(chan, AST_STATE_UP);
 				}
 			} else if (f->subclass.integer == AST_CONTROL_READ_ACTION) {
@@ -5332,10 +5329,6 @@ static int set_format(struct ast_channel *chan,
 			generator_write_format_change(chan);
 		}
 
-		ast_channel_lock(chan);
-		ast_channel_publish_snapshot(chan);
-		ast_channel_unlock(chan);
-
 		return 0;
 	}
 
@@ -5415,10 +5408,6 @@ static int set_format(struct ast_channel *chan,
 		generator_write_format_change(chan);
 	}
 
-	ast_channel_lock(chan);
-	ast_channel_publish_snapshot(chan);
-	ast_channel_unlock(chan);
-
 	return res;
 }
 
@@ -7414,6 +7403,17 @@ static void free_channelvars(void)
 	AST_RWLIST_UNLOCK(&channelvars);
 }
 
+int ast_channel_has_manager_vars(void)
+{
+	int vars_present;
+
+	AST_RWLIST_RDLOCK(&channelvars);
+	vars_present = !AST_LIST_EMPTY(&channelvars);
+	AST_RWLIST_UNLOCK(&channelvars);
+
+	return vars_present;
+}
+
 void ast_channel_set_manager_vars(size_t varc, char **vars)
 {
 	size_t i;
@@ -7644,12 +7644,9 @@ void ast_set_variables(struct ast_channel *chan, struct ast_variable *vars)
 {
 	struct ast_variable *cur;
 
-	ast_channel_stage_snapshot(chan);
-
-	for (cur = vars; cur; cur = cur->next)
+	for (cur = vars; cur; cur = cur->next) {
 		pbx_builtin_setvar_helper(chan, cur->name, cur->value);
-
-	ast_channel_stage_snapshot_done(chan);
+	}
 }
 
 static void *silence_generator_alloc(struct ast_channel *chan, void *data)
diff --git a/main/channel_internal_api.c b/main/channel_internal_api.c
index 9cc99f3d5..0c5117e6d 100644
--- a/main/channel_internal_api.c
+++ b/main/channel_internal_api.c
@@ -943,9 +943,8 @@ void ast_channel_callid_set(struct ast_channel *chan, struct ast_callid *callid)
 		ast_channel_name(chan),
 		call_identifier_to,
 		call_identifier_from);
-
-	ast_channel_publish_snapshot(chan);
 }
+
 void ast_channel_state_set(struct ast_channel *chan, enum ast_channel_state value)
 {
 	chan->state = value;
@@ -1073,7 +1072,6 @@ void ast_channel_dtmf_tv_set(struct ast_channel *chan, struct timeval *value)
 void ast_channel_whentohangup_set(struct ast_channel *chan, struct timeval *value)
 {
 	chan->whentohangup = *value;
-	ast_channel_publish_snapshot(chan);
 }
 void ast_channel_varshead_set(struct ast_channel *chan, struct varshead *value)
 {
@@ -1131,7 +1129,6 @@ ast_group_t ast_channel_callgroup(const struct ast_channel *chan)
 void ast_channel_callgroup_set(struct ast_channel *chan, ast_group_t value)
 {
 	chan->callgroup = value;
-	ast_channel_publish_snapshot(chan);
 }
 ast_group_t ast_channel_pickupgroup(const struct ast_channel *chan)
 {
@@ -1140,7 +1137,6 @@ ast_group_t ast_channel_pickupgroup(const struct ast_channel *chan)
 void ast_channel_pickupgroup_set(struct ast_channel *chan, ast_group_t value)
 {
 	chan->pickupgroup = value;
-	ast_channel_publish_snapshot(chan);
 }
 struct ast_namedgroups *ast_channel_named_callgroups(const struct ast_channel *chan)
 {
diff --git a/main/cli.c b/main/cli.c
index 0fbdb69f6..bff58695d 100644
--- a/main/cli.c
+++ b/main/cli.c
@@ -1513,8 +1513,7 @@ static char *handle_nodebugchan_deprecated(struct ast_cli_entry *e, int cmd, str
 
 static char *handle_showchan(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
 {
-	RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
-	struct ast_channel_snapshot *snapshot;
+	struct ast_channel *chan;
 	struct timeval now;
 	char cdrtime[256];
 	struct ast_str *obuf;/*!< Buffer for CDR variables. */
@@ -1522,6 +1521,12 @@ static char *handle_showchan(struct ast_cli_entry *e, int cmd, struct ast_cli_ar
 	long elapsed_seconds=0;
 	int hour=0, min=0, sec=0;
 	struct ast_var_t *var;
+	char nativeformats[256];
+	struct ast_str *write_transpath = ast_str_alloca(256);
+	struct ast_str *read_transpath = ast_str_alloca(256);
+	struct ast_bridge *bridge;
+	struct ast_callid *callid;
+	char callid_buf[32];
 
 	switch (cmd) {
 	case CLI_INIT:
@@ -1538,25 +1543,27 @@ static char *handle_showchan(struct ast_cli_entry *e, int cmd, struct ast_cli_ar
 		return CLI_SHOWUSAGE;
 	}
 
-	now = ast_tvnow();
-
-	if (!(msg = stasis_cache_get(ast_channel_cache_by_name(), ast_channel_snapshot_type(), a->argv[3]))) {
-		ast_cli(a->fd, "%s is not a known channel\n", a->argv[3]);
-		return CLI_SUCCESS;
-	}
-	snapshot = stasis_message_data(msg);
-
 	obuf = ast_str_thread_get(&ast_str_thread_global_buf, 16);
 	if (!obuf) {
 		return CLI_FAILURE;
 	}
+
 	output = ast_str_create(8192);
 	if (!output) {
 		return CLI_FAILURE;
 	}
 
-	if (!ast_tvzero(snapshot->creationtime)) {
-		elapsed_seconds = now.tv_sec - snapshot->creationtime.tv_sec;
+	chan = ast_channel_get_by_name(a->argv[3]);
+	if (!chan) {
+		ast_cli(a->fd, "%s is not a known channel\n", a->argv[3]);
+		return CLI_SUCCESS;
+	}
+
+	now = ast_tvnow();
+	ast_channel_lock(chan);
+
+	if (!ast_tvzero(ast_channel_creationtime(chan))) {
+		elapsed_seconds = now.tv_sec - ast_channel_creationtime(chan).tv_sec;
 		hour = elapsed_seconds / 3600;
 		min = (elapsed_seconds % 3600) / 60;
 		sec = elapsed_seconds % 60;
@@ -1565,6 +1572,16 @@ static char *handle_showchan(struct ast_cli_entry *e, int cmd, struct ast_cli_ar
 		strcpy(cdrtime, "N/A");
 	}
 
+	ast_translate_path_to_str(ast_channel_writetrans(chan), &write_transpath);
+	ast_translate_path_to_str(ast_channel_readtrans(chan), &read_transpath);
+
+	bridge = ast_channel_get_bridge(chan);
+	callid = ast_channel_callid(chan);
+	if (callid) {
+		ast_callid_strnprint(callid_buf, sizeof(callid_buf), callid);
+		ast_callid_unref(callid);
+	}
+
 	ast_str_append(&output, 0,
 		" -- General --\n"
 		"           Name: %s\n"
@@ -1597,51 +1614,63 @@ static char *handle_showchan(struct ast_cli_entry *e, int cmd, struct ast_cli_ar
 		"    Application: %s\n"
 		"           Data: %s\n"
 		" Call Identifer: %s\n",
-		snapshot->name,
-		snapshot->type,
-		snapshot->uniqueid,
-		snapshot->linkedid,
-		S_OR(snapshot->caller_number, "(N/A)"),
-		S_OR(snapshot->caller_name, "(N/A)"),
-		S_OR(snapshot->connected_number, "(N/A)"),
-		S_OR(snapshot->connected_name, "(N/A)"),
-		S_OR(snapshot->effective_number, "(N/A)"),
-		S_OR(snapshot->effective_name, "(N/A)"),
-		S_OR(snapshot->caller_dnid, "(N/A)"),
-		snapshot->language,
-		ast_state2str(snapshot->state),
-		snapshot->state,
-		snapshot->nativeformats,
-		snapshot->writeformat,
-		snapshot->readformat,
-		!ast_strlen_zero(snapshot->writetrans) ? "Yes" : "No",
-		snapshot->writetrans,
-		!ast_strlen_zero(snapshot->readtrans) ? "Yes" : "No",
-		snapshot->readtrans,
-		(long) snapshot->hanguptime.tv_sec,
+		ast_channel_name(chan),
+		ast_channel_tech(chan)->type,
+		ast_channel_uniqueid(chan),
+		ast_channel_linkedid(chan),
+		S_COR(ast_channel_caller(chan)->id.number.valid,
+		      ast_channel_caller(chan)->id.number.str, "(N/A)"),
+		S_COR(ast_channel_caller(chan)->id.name.valid,
+		      ast_channel_caller(chan)->id.name.str, "(N/A)"),
+		S_COR(ast_channel_connected(chan)->id.number.valid,
+		      ast_channel_connected(chan)->id.number.str, "(N/A)"),
+		S_COR(ast_channel_connected(chan)->id.name.valid,
+		      ast_channel_connected(chan)->id.name.str, "(N/A)"),
+		S_COR(ast_channel_connected_effective_id(chan).number.valid,
+		      ast_channel_connected_effective_id(chan).number.str, "(N/A)"),
+		S_COR(ast_channel_connected_effective_id(chan).name.valid,
+		      ast_channel_connected_effective_id(chan).name.str, "(N/A)"),
+		S_OR(ast_channel_dialed(chan)->number.str, "(N/A)"),
+		ast_channel_language(chan),
+		ast_state2str(ast_channel_state(chan)),
+		ast_channel_state(chan),
+		ast_getformatname_multiple(nativeformats, sizeof(nativeformats), ast_channel_nativeformats(chan)),
+		ast_getformatname(ast_channel_writeformat(chan)),
+		ast_getformatname(ast_channel_readformat(chan)),
+		ast_str_strlen(write_transpath) ? "Yes" : "No",
+		ast_str_buffer(write_transpath),
+		ast_str_strlen(read_transpath) ? "Yes" : "No",
+		ast_str_buffer(read_transpath),
+		ast_channel_whentohangup(chan)->tv_sec,
 		cdrtime,
-		S_OR(snapshot->bridgeid, "(Not bridged)"),
-		snapshot->context,
-		snapshot->exten,
-		snapshot->priority,
-		snapshot->callgroup,
-		snapshot->pickupgroup,
-		S_OR(snapshot->appl, "(N/A)"),
-		S_OR(snapshot->data, "(Empty)"),
-		S_OR(snapshot->callid, "(None)"));
-
+		bridge ? bridge->uniqueid : "(Not bridged)",
+		ast_channel_context(chan),
+		ast_channel_exten(chan),
+		ast_channel_priority(chan),
+		ast_channel_callgroup(chan),
+		ast_channel_pickupgroup(chan),
+		S_OR(ast_channel_appl(chan), "(N/A)"),
+		S_OR(ast_channel_data(chan), "(Empty)"),
+		S_OR(callid_buf, "(None)")
+		);
 	ast_str_append(&output, 0, "      Variables:\n");
 
-	AST_LIST_TRAVERSE(snapshot->channel_vars, var, entries) {
+	AST_LIST_TRAVERSE(ast_channel_varshead(chan), var, entries) {
 		ast_str_append(&output, 0, "%s=%s\n", ast_var_name(var), ast_var_value(var));
 	}
 
-	if (ast_cdr_serialize_variables(snapshot->name, &obuf, '=', '\n')) {
+	if (ast_cdr_serialize_variables(ast_channel_name(chan), &obuf, '=', '\n')) {
 		ast_str_append(&output, 0, "  CDR Variables:\n%s\n", ast_str_buffer(obuf));
 	}
 
+	ast_channel_unlock(chan);
+
 	ast_cli(a->fd, "%s", ast_str_buffer(output));
 	ast_free(output);
+
+	ao2_cleanup(bridge);
+	ast_channel_unref(chan);
+
 	return CLI_SUCCESS;
 }
 
diff --git a/main/core_local.c b/main/core_local.c
index 98db5e575..e803f29ec 100644
--- a/main/core_local.c
+++ b/main/core_local.c
@@ -328,12 +328,12 @@ static struct ast_multi_channel_blob *local_channel_optimization_blob(struct loc
 	RAII_VAR(struct ast_channel_snapshot *, local_one_snapshot, NULL, ao2_cleanup);
 	RAII_VAR(struct ast_channel_snapshot *, local_two_snapshot, NULL, ao2_cleanup);
 
-	local_one_snapshot = ast_channel_snapshot_create(p->base.owner);
+	local_one_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(p->base.owner));
 	if (!local_one_snapshot) {
 		return NULL;
 	}
 
-	local_two_snapshot = ast_channel_snapshot_create(p->base.chan);
+	local_two_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(p->base.chan));
 	if (!local_two_snapshot) {
 		return NULL;
 	}
@@ -371,7 +371,7 @@ static void local_optimization_started_cb(struct ast_unreal_pvt *base, struct as
 
 	if (source) {
 		RAII_VAR(struct ast_channel_snapshot *, source_snapshot, NULL, ao2_cleanup);
-		source_snapshot = ast_channel_snapshot_create(source);
+		source_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(source));
 		if (!source_snapshot) {
 			return;
 		}
@@ -516,12 +516,12 @@ static void publish_local_bridge_message(struct local_pvt *p)
 		goto end;
 	}
 
-	one_snapshot = ast_channel_snapshot_create(owner);
+	one_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(owner));
 	if (!one_snapshot) {
 		goto end;
 	}
 
-	two_snapshot = ast_channel_snapshot_create(chan);
+	two_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(chan));
 	if (!two_snapshot) {
 		goto end;
 	}
diff --git a/main/dial.c b/main/dial.c
index 2563c707b..f03d43d25 100644
--- a/main/dial.c
+++ b/main/dial.c
@@ -323,7 +323,7 @@ static int begin_dial_prerun(struct ast_dial_channel *channel, struct ast_channe
 
 	ast_channel_appl_set(channel->owner, "AppDial2");
 	ast_channel_data_set(channel->owner, "(Outgoing Line)");
-	ast_publish_channel_state(channel->owner);
+
 	memset(ast_channel_whentohangup(channel->owner), 0, sizeof(*ast_channel_whentohangup(channel->owner)));
 
 	/* Inherit everything from he who spawned this dial */
diff --git a/main/endpoints.c b/main/endpoints.c
index 9cc0178e0..10b32e268 100644
--- a/main/endpoints.c
+++ b/main/endpoints.c
@@ -203,9 +203,6 @@ int ast_endpoint_add_channel(struct ast_endpoint *endpoint,
 	ast_str_container_add(endpoint->channel_ids, ast_channel_uniqueid(chan));
 	ao2_unlock(endpoint);
 
-	ast_channel_lock(chan);
-	ast_publish_channel_state(chan);
-	ast_channel_unlock(chan);
 	endpoint_publish_snapshot(endpoint);
 
 	return 0;
diff --git a/main/manager.c b/main/manager.c
index 7a7e8903a..6e056a163 100644
--- a/main/manager.c
+++ b/main/manager.c
@@ -99,6 +99,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 #include "asterisk/bridge.h"
 #include "asterisk/features_config.h"
 #include "asterisk/rtp_engine.h"
+#include "asterisk/translate.h"
 
 /*** DOCUMENTATION
 	<manager name="Ping" language="en_US">
@@ -3846,95 +3847,110 @@ static int action_getvar(struct mansession *s, const struct message *m)
 static int action_status(struct mansession *s, const struct message *m)
 {
 	const char *name = astman_get_header(m, "Channel");
-	const char *cvariables = astman_get_header(m, "Variables");
-	char *variables = ast_strdupa(S_OR(cvariables, ""));
-	RAII_VAR(struct ao2_container *, cached_channels, NULL, ao2_cleanup);
-	struct stasis_message *msg;
+	const char *chan_variables = astman_get_header(m, "Variables");
+	const char *id = astman_get_header(m, "ActionID");
+	char *variables = ast_strdupa(S_OR(chan_variables, ""));
+	struct ast_str *variable_str = ast_str_create(1024);
+	struct ast_str *write_transpath = ast_str_alloca(256);
+	struct ast_str *read_transpath = ast_str_alloca(256);
+	struct ast_channel *chan;
+	char nativeformats[256];
 	int channels = 0;
 	int all = ast_strlen_zero(name); /* set if we want all channels */
-	const char *id = astman_get_header(m, "ActionID");
-	char idText[256];
+	char id_text[256];
+	struct ast_channel_iterator *it_chans = NULL;
 	AST_DECLARE_APP_ARGS(vars,
 		AST_APP_ARG(name)[100];
 	);
-	struct ast_str *str = ast_str_create(1000);
-	struct ao2_iterator it_chans;
-	struct timeval now = ast_tvnow();
 
-	if (!ast_strlen_zero(id)) {
-		snprintf(idText, sizeof(idText), "ActionID: %s\r\n", id);
-	} else {
-		idText[0] = '\0';
+	if (!variable_str) {
+		astman_send_error(s, m, "Memory Allocation Failure");
+		return 1;
 	}
 
 	if (!(function_capable_string_allowed_with_auths(variables, s->session->writeperm))) {
+		ast_free(variable_str);
 		astman_send_error(s, m, "Status Access Forbidden: Variables");
 		return 0;
 	}
 
 	if (all) {
-		if (!(cached_channels = stasis_cache_dump(ast_channel_cache_by_name(), ast_channel_snapshot_type()))) {
-			ast_free(str);
+		if (!(it_chans = ast_channel_iterator_all_new())) {
+			ast_free(variable_str);
 			astman_send_error(s, m, "Memory Allocation Failure");
 			return 1;
 		}
-		it_chans = ao2_iterator_init(cached_channels, 0);
-		msg = ao2_iterator_next(&it_chans);
+		chan = ast_channel_iterator_next(it_chans);
 	} else {
-		if (!(msg = stasis_cache_get(ast_channel_cache_by_name(), ast_channel_snapshot_type(), name))) {
+		chan = ast_channel_get_by_name(name);
+		if (!chan) {
 			astman_send_error(s, m, "No such channel");
-			ast_free(str);
+			ast_free(variable_str);
 			return 0;
 		}
 	}
 
 	astman_send_ack(s, m, "Channel status will follow");
 
-	if (!ast_strlen_zero(cvariables)) {
+	if (!ast_strlen_zero(id)) {
+		snprintf(id_text, sizeof(id_text), "ActionID: %s\r\n", id);
+	} else {
+		id_text[0] = '\0';
+	}
+
+	if (!ast_strlen_zero(chan_variables)) {
 		AST_STANDARD_APP_ARGS(vars, variables);
 	}
 
 	/* if we look by name, we break after the first iteration */
-	for (; msg; ao2_ref(msg, -1), msg = all ? ao2_iterator_next(&it_chans) : NULL) {
-		struct ast_channel_snapshot *snapshot = stasis_message_data(msg);
-		struct ast_channel *c;
-		struct ast_str *built = ast_manager_build_channel_state_string_prefix(snapshot, "");
-		long elapsed_seconds = 0;
+	for (; chan; all ? chan = ast_channel_iterator_next(it_chans) : 0) {
+		struct timeval now;
+		long elapsed_seconds;
+		struct ast_bridge *bridge;
 
-		if (!built) {
-			continue;
-		}
+		ast_channel_lock(chan);
+
+		now = ast_tvnow();
+		elapsed_seconds = ast_tvdiff_sec(now, ast_channel_creationtime(chan));
 
-		if (!ast_strlen_zero(cvariables) && (c = ast_channel_get_by_name(snapshot->name))) {
+		if (!ast_strlen_zero(chan_variables)) {
 			int i;
-			ast_str_reset(str);
+			ast_str_reset(variable_str);
 			for (i = 0; i < vars.argc; i++) {
 				char valbuf[512], *ret = NULL;
 
 				if (vars.name[i][strlen(vars.name[i]) - 1] == ')') {
-					if (ast_func_read(c, vars.name[i], valbuf, sizeof(valbuf)) < 0) {
+					if (ast_func_read(chan, vars.name[i], valbuf, sizeof(valbuf)) < 0) {
 						valbuf[0] = '\0';
 					}
 					ret = valbuf;
 				} else {
-					pbx_retrieve_variable(c, vars.name[i], &ret, valbuf, sizeof(valbuf), NULL);
+					pbx_retrieve_variable(chan, vars.name[i], &ret, valbuf, sizeof(valbuf), NULL);
 				}
 
-				ast_str_append(&str, 0, "Variable: %s=%s\r\n", vars.name[i], ret);
+				ast_str_append(&variable_str, 0, "Variable: %s=%s\r\n", vars.name[i], ret);
 			}
-			ast_channel_unref(c);
 		}
 
 		channels++;
 
-
-		if (!ast_tvzero(snapshot->creationtime)) {
-			elapsed_seconds = now.tv_sec - snapshot->creationtime.tv_sec;
-		}
+		bridge = ast_channel_get_bridge(chan);
 
 		astman_append(s,
 			"Event: Status\r\n"
 			"Privilege: Call\r\n"
+			"Channel: %s\r\n"
+			"ChannelState: %u\r\n"
+			"ChannelStateDesc: %s\r\n"
+			"CallerIDNum: %s\r\n"
+			"CallerIDName: %s\r\n"
+			"ConnectedLineNum: %s\r\n"
+			"ConnectedLineName: %s\r\n"
+			"Accountcode: %s\r\n"
+			"Context: %s\r\n"
+			"Exten: %s\r\n"
+			"Priority: %d\r\n"
+			"Uniqueid: %s\r\n"
 			"Type: %s\r\n"
 			"DNID: %s\r\n"
 			"EffectiveConnectedLineNum: %s\r\n"
@@ -3954,43 +3970,56 @@ static int action_status(struct mansession *s, const struct message *m)
 			"Seconds: %ld\r\n"
 			"%s"
 			"%s"
-			"%s"
 			"\r\n",
-			snapshot->type,
-			snapshot->caller_dnid,
-			S_OR(snapshot->effective_number, "<unknown>"),
-			S_OR(snapshot->effective_name, "<unknown>"),
-			snapshot->hanguptime.tv_sec,
-			snapshot->bridgeid,
-			snapshot->linkedid,
-			snapshot->appl,
-			snapshot->data,
-			snapshot->nativeformats,
-			snapshot->readformat,
-			snapshot->readtrans,
-			snapshot->writeformat,
-			snapshot->writetrans,
-			snapshot->callgroup,
-			snapshot->pickupgroup,
-			(long) elapsed_seconds,
-			ast_str_buffer(built),
-			ast_str_buffer(str),
-			idText);
+			ast_channel_name(chan),
+			ast_channel_state(chan),
+			ast_state2str(ast_channel_state(chan)),
+			S_COR(ast_channel_caller(chan)->id.number.valid, ast_channel_caller(chan)->id.number.str, "<unknown>"),
+			S_COR(ast_channel_caller(chan)->id.name.valid, ast_channel_caller(chan)->id.name.str, "<unknown>"),
+			S_COR(ast_channel_connected(chan)->id.number.valid, ast_channel_connected(chan)->id.number.str, "<unknown>"),
+			S_COR(ast_channel_connected(chan)->id.name.valid, ast_channel_connected(chan)->id.name.str, "<unknown>"),
+			ast_channel_accountcode(chan),
+			ast_channel_context(chan),
+			ast_channel_exten(chan),
+			ast_channel_priority(chan),
+			ast_channel_uniqueid(chan),
+			ast_channel_tech(chan)->type,
+			S_OR(ast_channel_dialed(chan)->number.str, ""),
+			S_COR(ast_channel_connected_effective_id(chan).number.valid, ast_channel_connected_effective_id(chan).number.str, "<unknown>"),
+			S_COR(ast_channel_connected_effective_id(chan).name.valid, ast_channel_connected_effective_id(chan).name.str, "<unknown>"),
+			ast_channel_whentohangup(chan)->tv_sec,
+			bridge ? bridge->uniqueid : "",
+			ast_channel_linkedid(chan),
+			ast_channel_appl(chan),
+			ast_channel_data(chan),
+			ast_getformatname_multiple(nativeformats, sizeof(nativeformats), ast_channel_nativeformats(chan)),
+			ast_getformatname(ast_channel_readformat(chan)),
+			ast_translate_path_to_str(ast_channel_readtrans(chan), &read_transpath),
+			ast_getformatname(ast_channel_writeformat(chan)),
+			ast_translate_path_to_str(ast_channel_writetrans(chan), &write_transpath),
+			ast_channel_callgroup(chan),
+			ast_channel_pickupgroup(chan),
+			(long)elapsed_seconds,
+			ast_str_buffer(variable_str),
+			id_text);
+
+		ao2_cleanup(bridge);
 
-		ast_free(built);
+		ast_channel_unlock(chan);
+		chan = ast_channel_unref(chan);
 	}
 
-	if (all) {
-		ao2_iterator_destroy(&it_chans);
+	if (it_chans) {
+		ast_channel_iterator_destroy(it_chans);
 	}
 
 	astman_append(s,
 		"Event: StatusComplete\r\n"
 		"%s"
 		"Items: %d\r\n"
-		"\r\n", idText, channels);
+		"\r\n", id_text, channels);
 
-	ast_free(str);
+	ast_free(variable_str);
 
 	return 0;
 }
diff --git a/main/pbx.c b/main/pbx.c
index b1c50e5ab..3c7b127e6 100644
--- a/main/pbx.c
+++ b/main/pbx.c
@@ -8369,8 +8369,7 @@ static char *handle_show_device2extenstate(struct ast_cli_entry *e, int cmd, str
 /*! \brief CLI support for listing chanvar's variables in a parseable way */
 static char *handle_show_chanvar(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
 {
-	RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
-	struct ast_channel_snapshot *snapshot;
+	struct ast_channel *chan;
 	struct ast_var_t *var;
 
 	switch (cmd) {
@@ -8384,19 +8383,23 @@ static char *handle_show_chanvar(struct ast_cli_entry *e, int cmd, struct ast_cl
 		return ast_complete_channels(a->line, a->word, a->pos, a->n, 3);
 	}
 
-	if (a->argc != e->args + 1)
+	if (a->argc != e->args + 1) {
 		return CLI_SHOWUSAGE;
+	}
 
-	if (!(msg = stasis_cache_get(ast_channel_cache_by_name(), ast_channel_snapshot_type(), a->argv[3]))) {
+	chan = ast_channel_get_by_name(a->argv[e->args]);
+	if (!chan) {
 		ast_cli(a->fd, "Channel '%s' not found\n", a->argv[e->args]);
 		return CLI_FAILURE;
 	}
-	snapshot = stasis_message_data(msg);
 
-	AST_LIST_TRAVERSE(snapshot->channel_vars, var, entries) {
+	ast_channel_lock(chan);
+	AST_LIST_TRAVERSE(ast_channel_varshead(chan), var, entries) {
 		ast_cli(a->fd, "%s=%s\n", ast_var_name(var), ast_var_value(var));
 	}
+	ast_channel_unlock(chan);
 
+	ast_channel_unref(chan);
 	return CLI_SUCCESS;
 }
 
@@ -10187,7 +10190,7 @@ static void *pbx_outgoing_exec(void *data)
 		struct ast_app *app = pbx_findapp(outgoing->app);
 
 		if (app) {
-			ast_verb(4, "Launching %s(%s) on %s\n", outgoing->app, outgoing->appdata,
+			ast_verb(4, "Launching %s(%s) on %s\n", outgoing->app, S_OR(outgoing->appdata, ""),
 				ast_channel_name(ast_dial_answered(outgoing->dial)));
 			pbx_exec(ast_dial_answered(outgoing->dial), app, outgoing->appdata);
 		} else {
@@ -11444,14 +11447,11 @@ int pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 	AST_LIST_TRAVERSE_SAFE_END;
 
 	if (value && (newvariable = ast_var_assign(name, value))) {
-		if (headp == &globals)
+		if (headp == &globals) {
 			ast_verb(2, "Setting global variable '%s' to '%s'\n", name, value);
+		}
 		AST_LIST_INSERT_HEAD(headp, newvariable, entries);
 		ast_channel_publish_varset(chan, name, value);
-
-		if (headp != &globals) {
-			ast_channel_publish_snapshot(chan);
-		}
 	}
 
 	if (chan)
diff --git a/main/pickup.c b/main/pickup.c
index a415f1672..5be0c03ab 100644
--- a/main/pickup.c
+++ b/main/pickup.c
@@ -361,9 +361,7 @@ int ast_do_pickup(struct ast_channel *chan, struct ast_channel *target)
 		goto pickup_failed;
 	}
 
-	ast_channel_lock(target);
-	target_snapshot = ast_channel_snapshot_create(target);
-	ast_channel_unlock(target);
+	target_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(target));
 	if (!target_snapshot) {
 		goto pickup_failed;
 	}
diff --git a/main/stasis_bridges.c b/main/stasis_bridges.c
index 1e0b36edf..c5df5f4f9 100644
--- a/main/stasis_bridges.c
+++ b/main/stasis_bridges.c
@@ -407,9 +407,7 @@ struct stasis_message *ast_bridge_blob_create(
 	}
 
 	if (chan) {
-		ast_channel_lock(chan);
-		obj->channel = ast_channel_snapshot_create(chan);
-		ast_channel_unlock(chan);
+		obj->channel = ast_channel_snapshot_get_latest(ast_channel_uniqueid(chan));
 		if (obj->channel == NULL) {
 			return NULL;
 		}
@@ -593,9 +591,7 @@ static int bridge_channel_snapshot_pair_init(struct ast_bridge_channel_pair *pai
 		}
 	}
 
-	ast_channel_lock(pair->channel);
-	snapshot_pair->channel_snapshot = ast_channel_snapshot_create(pair->channel);
-	ast_channel_unlock(pair->channel);
+	snapshot_pair->channel_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(pair->channel));
 	if (!snapshot_pair->channel_snapshot) {
 		return -1;
 	}
@@ -1072,9 +1068,7 @@ void ast_bridge_publish_attended_transfer_link(int is_external, enum ast_transfe
 
 	transfer_msg->dest_type = AST_ATTENDED_TRANSFER_DEST_LINK;
 	for (i = 0; i < 2; ++i) {
-		ast_channel_lock(locals[i]);
-		transfer_msg->dest.links[i] = ast_channel_snapshot_create(locals[i]);
-		ast_channel_unlock(locals[i]);
+		transfer_msg->dest.links[i] = ast_channel_snapshot_get_latest(ast_channel_uniqueid(locals[i]));
 		if (!transfer_msg->dest.links[i]) {
 			return;
 		}
diff --git a/main/stasis_cache.c b/main/stasis_cache.c
index c1dab8539..8b4304e5f 100644
--- a/main/stasis_cache.c
+++ b/main/stasis_cache.c
@@ -127,9 +127,17 @@ struct stasis_caching_topic *stasis_caching_unsubscribe_and_join(struct stasis_c
 	return NULL;
 }
 
+/*!
+ * \brief The key for an entry in the cache
+ * \note The items in this struct must be immutable for the item in the cache
+ */
 struct cache_entry_key {
+	/*! The message type of the item stored in the cache */
 	struct stasis_message_type *type;
+	/*! The unique ID of the item stored in the cache */
 	const char *id;
+	/*! The hash, computed from \c type and \c id */
+	unsigned int hash;
 };
 
 struct stasis_cache_entry {
@@ -166,6 +174,12 @@ static void cache_entry_dtor(void *obj)
 	AST_VECTOR_FREE(&entry->remote);
 }
 
+static void cache_entry_compute_hash(struct cache_entry_key *key)
+{
+	key->hash = ast_hashtab_hash_string(stasis_message_type_name(key->type));
+	key->hash += ast_hashtab_hash_string(key->id);
+}
+
 static struct stasis_cache_entry *cache_entry_create(struct stasis_message_type *type, const char *id, struct stasis_message *snapshot)
 {
 	struct stasis_cache_entry *entry;
@@ -187,6 +201,7 @@ static struct stasis_cache_entry *cache_entry_create(struct stasis_message_type
 		return NULL;
 	}
 	entry->key.type = ao2_bump(type);
+	cache_entry_compute_hash(&entry->key);
 
 	is_remote = ast_eid_cmp(&ast_eid_default, stasis_message_eid(snapshot)) ? 1 : 0;
 	if (AST_VECTOR_INIT(&entry->remote, is_remote)) {
@@ -211,7 +226,6 @@ static int cache_entry_hash(const void *obj, int flags)
 {
 	const struct stasis_cache_entry *object;
 	const struct cache_entry_key *key;
-	int hash = 0;
 
 	switch (flags & OBJ_SEARCH_MASK) {
 	case OBJ_SEARCH_KEY:
@@ -227,9 +241,7 @@ static int cache_entry_hash(const void *obj, int flags)
 		return 0;
 	}
 
-	hash += ast_hashtab_hash_string(stasis_message_type_name(key->type));
-	hash += ast_hashtab_hash_string(key->id);
-	return hash;
+	return (int)key->hash;
 }
 
 static int cache_entry_cmp(void *obj, void *arg, int flags)
@@ -347,6 +359,7 @@ static struct stasis_cache_entry *cache_find(struct ao2_container *entries, stru
 
 	search_key.type = type;
 	search_key.id = id;
+	cache_entry_compute_hash(&search_key);
 	entry = ao2_find(entries, &search_key, OBJ_SEARCH_KEY | OBJ_NOLOCK);
 
 	/* Ensure that what we looked for is what we found. */
diff --git a/main/stasis_channels.c b/main/stasis_channels.c
index f38edb0e1..ad9da50cf 100644
--- a/main/stasis_channels.c
+++ b/main/stasis_channels.c
@@ -195,18 +195,12 @@ static void channel_snapshot_dtor(void *obj)
 
 	ast_string_field_free_memory(snapshot);
 	ao2_cleanup(snapshot->manager_vars);
-	ao2_cleanup(snapshot->channel_vars);
 }
 
 struct ast_channel_snapshot *ast_channel_snapshot_create(struct ast_channel *chan)
 {
 	struct ast_channel_snapshot *snapshot;
 	struct ast_bridge *bridge;
-	char nativeformats[256];
-	struct ast_str *write_transpath = ast_str_alloca(256);
-	struct ast_str *read_transpath = ast_str_alloca(256);
-	struct ast_party_id effective_connected_id;
-	struct ast_callid *callid;
 
 	/* no snapshots for dummy channels */
 	if (!ast_channel_tech(chan)) {
@@ -263,38 +257,16 @@ struct ast_channel_snapshot *ast_channel_snapshot_create(struct ast_channel *cha
 		ao2_cleanup(bridge);
 	}
 
-	ast_string_field_set(snapshot, nativeformats, ast_getformatname_multiple(nativeformats, sizeof(nativeformats),
-		ast_channel_nativeformats(chan)));
-	ast_string_field_set(snapshot, readformat, ast_getformatname(ast_channel_readformat(chan)));
-	ast_string_field_set(snapshot, writeformat, ast_getformatname(ast_channel_writeformat(chan)));
-	ast_string_field_set(snapshot, writetrans, ast_translate_path_to_str(ast_channel_writetrans(chan), &write_transpath));
-	ast_string_field_set(snapshot, readtrans, ast_translate_path_to_str(ast_channel_readtrans(chan), &read_transpath));
-
-	effective_connected_id = ast_channel_connected_effective_id(chan);
-	ast_string_field_set(snapshot, effective_name,
-		S_COR(effective_connected_id.name.valid, effective_connected_id.name.str, ""));
-	ast_string_field_set(snapshot, effective_number,
-		S_COR(effective_connected_id.number.valid, effective_connected_id.number.str, ""));
-
-	if ((callid = ast_channel_callid(chan))) {
-		ast_callid_strnprint(snapshot->callid, sizeof(snapshot->callid), callid);
-		ast_callid_unref(callid);
-	}
-
 	snapshot->creationtime = ast_channel_creationtime(chan);
-	snapshot->hanguptime = *(ast_channel_whentohangup(chan));
 	snapshot->state = ast_channel_state(chan);
 	snapshot->priority = ast_channel_priority(chan);
 	snapshot->amaflags = ast_channel_amaflags(chan);
 	snapshot->hangupcause = ast_channel_hangupcause(chan);
 	ast_copy_flags(&snapshot->flags, ast_channel_flags(chan), 0xFFFFFFFF);
 	snapshot->caller_pres = ast_party_id_presentation(&ast_channel_caller(chan)->id);
-	snapshot->callgroup = ast_channel_callgroup(chan);
-	snapshot->pickupgroup = ast_channel_pickupgroup(chan);
 	ast_set_flag(&snapshot->softhangup_flags, ast_channel_softhangup_internal_flag(chan));
 
 	snapshot->manager_vars = ast_channel_get_manager_vars(chan);
-	snapshot->channel_vars = ast_channel_get_vars(chan);
 	snapshot->tech_properties = ast_channel_tech(chan)->properties;
 
 	return snapshot;
@@ -347,7 +319,11 @@ void ast_channel_publish_dial_forward(struct ast_channel *caller, struct ast_cha
 
 	if (caller) {
 		ast_channel_lock(caller);
-		caller_snapshot = ast_channel_snapshot_create(caller);
+		if (ast_strlen_zero(dialstatus)) {
+			caller_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(caller));
+		} else {
+			caller_snapshot = ast_channel_snapshot_create(caller);
+		}
 		ast_channel_unlock(caller);
 		if (!caller_snapshot) {
 			return;
@@ -356,7 +332,11 @@ void ast_channel_publish_dial_forward(struct ast_channel *caller, struct ast_cha
 	}
 
 	ast_channel_lock(peer);
-	peer_snapshot = ast_channel_snapshot_create(peer);
+	if (ast_strlen_zero(dialstatus)) {
+		peer_snapshot = ast_channel_snapshot_get_latest(ast_channel_uniqueid(peer));
+	} else {
+		peer_snapshot = ast_channel_snapshot_create(peer);
+	}
 	ast_channel_unlock(peer);
 	if (!peer_snapshot) {
 		return;
@@ -682,9 +662,24 @@ void ast_channel_publish_snapshot(struct ast_channel *chan)
 	stasis_publish(ast_channel_topic(chan), message);
 }
 
+void ast_channel_publish_cached_blob(struct ast_channel *chan, struct stasis_message_type *type, struct ast_json *blob)
+{
+	struct stasis_message *message;
+
+	if (!blob) {
+		blob = ast_json_null();
+	}
+
+	message = ast_channel_blob_create_from_cache(ast_channel_uniqueid(chan), type, blob);
+	if (message) {
+		stasis_publish(ast_channel_topic(chan), message);
+	}
+	ao2_cleanup(message);
+}
+
 void ast_channel_publish_blob(struct ast_channel *chan, struct stasis_message_type *type, struct ast_json *blob)
 {
-	RAII_VAR(struct stasis_message *, message, NULL, ao2_cleanup);
+	struct stasis_message *message;
 
 	if (!blob) {
 		blob = ast_json_null();
@@ -694,11 +689,12 @@ void ast_channel_publish_blob(struct ast_channel *chan, struct stasis_message_ty
 	if (message) {
 		stasis_publish(ast_channel_topic(chan), message);
 	}
+	ao2_cleanup(message);
 }
 
 void ast_channel_publish_varset(struct ast_channel *chan, const char *name, const char *value)
 {
-	RAII_VAR(struct ast_json *, blob, NULL, ast_json_unref);
+	struct ast_json *blob;
 
 	ast_assert(name != NULL);
 	ast_assert(value != NULL);
@@ -711,7 +707,15 @@ void ast_channel_publish_varset(struct ast_channel *chan, const char *name, cons
 		return;
 	}
 
-	ast_channel_publish_blob(chan, ast_channel_varset_type(), blob);
+	if (chan && !ast_channel_has_manager_vars()) {
+		ast_channel_publish_cached_blob(chan, ast_channel_varset_type(), blob);
+	} else {
+		/* This function is NULL safe. If there are manager variables,
+		 * we have to produce the full snapshot.
+		 */
+		ast_channel_publish_blob(chan, ast_channel_varset_type(), blob);
+	}
+	ast_json_unref(blob);
 }
 
 static struct ast_manager_event_blob *varset_to_ami(struct stasis_message *msg)
@@ -1179,3 +1183,4 @@ int ast_stasis_channels_init(void)
 
 	return res;
 }
+