Statistics: Rewrite statistics backends to use OpenMetrics The metric subsystem of Prosody has had some shortcomings from the perspective of the current state-of-the-art in metric observability. The OpenMetrics standard [0] is a formalization of the data model (and serialization format) of the well-known and widely-used Prometheus [1] software stack. The previous stats subsystem of Prosody did not map well to that format (see e.g. [2] and [3]); the key reason is that it was trying to do too much math on its own ([2]) while lacking first-class support for "families" of metrics ([3]) and structured metric metadata (despite the `extra` argument to metrics, there was no standard way of representing common things like "tags" or "labels"). Even though OpenMetrics has grown from the Prometheus world of monitoring, it maps well to other popular monitoring stacks such as: - InfluxDB (labels can be mapped to tags and fields as necessary) - Carbon/Graphite (labels can be attached to the metric name with dot-separation) - StatsD (see graphite when assuming that graphite is used as backend, which is the default) The util.statsd module has been ported to use the OpenMetrics model as a proof of concept. An implementation which exposes the util.statistics backend data as Prometheus metrics is ready for publishing in prosody-modules (most likely as mod_openmetrics_prometheus to avoid breaking existing 0.11 deployments). At the same time, the previous measure()-based API had one major advantage: It is really simple and easy to use without requiring lots of knowledge about OpenMetrics or similar concepts. For that reason as well as compatibility with existing code, it is preserved and may even be extended in the future. However, code relying on the `stats-updated` event as well as `get_stats` from `statsmanager` will break because the data model has changed completely; in case of `stats-updated`, the code will simply not run (as the event was renamed in order to avoid conflicts); the `get_stats` function has been removed completely (so it will cause a traceback when it is attempted to be used). Note that the measure_*_event methods have been removed from the module API. I was unable to find any uses or documentation and thus deemed they should not be ported. Re-implementation is possible when necessary. [0]: https://openmetrics.io/ [1]: https://prometheus.io/ [2]: #959 [3]: #960

-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--


local full_sessions = prosody.full_sessions;
local bare_sessions = prosody.bare_sessions;

local st = require "util.stanza";
local jid_bare = require "util.jid".bare;
local jid_split = require "util.jid".split;
local user_exists = require "core.usermanager".user_exists;

local function process_to_bare(bare, origin, stanza)
	local user = bare_sessions[bare];

	local t = stanza.attr.type;
	if t == "error" then
		return true; -- discard
	elseif t == "groupchat" then
		origin.send(st.error_reply(stanza, "cancel", "service-unavailable"));
	elseif t == "headline" then
		if user and stanza.attr.to == bare then
			for _, session in pairs(user.sessions) do
				if session.presence and session.priority >= 0 then
					session.send(stanza);
				end
			end
		end  -- current policy is to discard headlines if no recipient is available
	else -- chat or normal message
		if user then -- some resources are connected
			local recipients = user.top_resources;
			if recipients then
				local sent;
				for i=1,#recipients do
					sent = recipients[i].send(stanza) or sent;
				end
				if sent then
					return true;
				end
			end
		end
		-- no resources are online
		local node, host = jid_split(bare);
		local ok
		if user_exists(node, host) then
			ok = module:fire_event('message/offline/handle', {
				username = node;
				origin = origin,
				stanza = stanza,
			});
		end

		if not ok then
			origin.send(st.error_reply(stanza, "cancel", "service-unavailable"));
		end
	end
	return true;
end

module:hook("message/full", function(data)
	-- message to full JID received
	local origin, stanza = data.origin, data.stanza;

	local session = full_sessions[stanza.attr.to];
	if session and session.send(stanza) then
		return true;
	else -- resource not online
		return process_to_bare(jid_bare(stanza.attr.to), origin, stanza);
	end
end, -1);

module:hook("message/bare", function(data)
	-- message to bare JID received
	local origin, stanza = data.origin, data.stanza;

	return process_to_bare(stanza.attr.to or (origin.username..'@'..origin.host), origin, stanza);
end, -1);