core.statsmanager: Allow special "manual" value for statistics_interval

When set, no periodic statistics collection is done by
core.statsmanager, instead some module is expected to call collect()
when it suits. Obviously only one such module should be enabled.

Quoth jonas’
> correct way is to scrape the internal sources on each call to /metrics
> in the context of Prometheus

"manual" as opposed to "automatic", from the point of view of
statsmanager.

1 files changed, 18 insertions, 6 deletions

diff --git a/core/statsmanager.lua b/core/statsmanager.lua
index 1f958194..bca7510f 100644
--- a/core/statsmanager.lua
+++ b/core/statsmanager.lua
@@ -6,7 +6,7 @@ local fire_event = prosody.events.fire_event;
 
 local stats_interval_config = config.get("*", "statistics_interval");
 local stats_interval = tonumber(stats_interval_config);
-if stats_interval_config and not stats_interval then
+if stats_interval_config and not stats_interval and stats_interval_config ~= "manual" then
 	log("error", "Invalid 'statistics_interval' setting, statistics will be disabled");
 end
 
@@ -19,6 +19,9 @@ if not stats_provider and stats_interval then
 elseif stats_provider and not stats_interval then
 	stats_interval = 60;
 end
+if stats_interval_config == "manual" then
+	stats_interval = nil;
+end
 
 local builtin_providers = {
 	internal = "util.statistics";
@@ -65,8 +68,7 @@ if stats then
 		return f(name, conf);
 	end
 
-	if stats_interval then
-		log("debug", "Statistics enabled using %s provider, collecting every %d seconds", stats_provider_name, stats_interval);
+	if stats_interval or stats_interval_config == "manual" then
 
 		local mark_collection_start = measure("times", "stats.collection");
 		local mark_processing_start = measure("times", "stats.processing");
@@ -96,9 +98,14 @@ if stats then
 			end
 			return stats_interval;
 		end
-		timer.add_task(stats_interval, collect);
-		prosody.events.add_handler("server-started", function () collect() end, -1);
-		prosody.events.add_handler("server-stopped", function () collect() end, -1);
+		if stats_interval then
+			log("debug", "Statistics enabled using %s provider, collecting every %d seconds", stats_provider_name, stats_interval);
+			timer.add_task(stats_interval, collect);
+			prosody.events.add_handler("server-started", function () collect() end, -1);
+			prosody.events.add_handler("server-stopped", function () collect() end, -1);
+		else
+			log("debug", "Statistics enabled using %s provider, no scheduled collection", stats_provider_name);
+		end
 	else
 		log("debug", "Statistics enabled using %s provider, collection is disabled", stats_provider_name);
 	end
@@ -107,8 +114,13 @@ else
 	function measure() return measure; end
 end
 
+local exported_collect = nil;
+if stats_interval_config == "manual" then
+	exported_collect = collect;
+end
 
 return {
+	collect = exported_collect;
 	measure = measure;
 	get_stats = function ()
 		return latest_stats, changed_stats, stats_extra;