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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

local t_concat = table.concat;

local path_sep = package.config:sub(1,1);

local path_util = {}

-- Helper function to resolve relative paths (needed by config)
function path_util.resolve_relative_path(parent_path, path)
	if path then
		-- Some normalization
		parent_path = parent_path:gsub("%"..path_sep.."+$", "");
		path = path:gsub("^%.%"..path_sep.."+", "");

		local is_relative;
		if path_sep == "/" and path:sub(1,1) ~= "/" then
			is_relative = true;
		elseif path_sep == "\\" and (path:sub(1,1) ~= "/" and (path:sub(2,3) ~= ":\\" and path:sub(2,3) ~= ":/")) then
			is_relative = true;
		end
		if is_relative then
			return parent_path..path_sep..path;
		end
	end
	return path;
end

-- Helper function to convert a glob to a Lua pattern
function path_util.glob_to_pattern(glob)
	return "^"..glob:gsub("[%p*?]", function (c)
		if c == "*" then
			return ".*";
		elseif c == "?" then
			return ".";
		else
			return "%"..c;
		end
	end).."$";
end

function path_util.join(a, b, c, ...) -- (... : string) --> string
	-- Optimization: Avoid creating table for most uses
	if b then
		if c then
			if ... then
				return t_concat({a,b,c,...}, path_sep);
			end
			return a..path_sep..b..path_sep..c;
		end
		return a..path_sep..b;
	end
	return a;
end

function path_util.complement_lua_path(installer_plugin_path)
	-- Checking for duplicates
	-- The commands using luarocks need the path to the directory that has the /share and /lib folders.
	local lua_version = _VERSION:match(" (.+)$");
	local lua_path_sep = package.config:sub(3,3);
	local dir_sep = package.config:sub(1,1);
	local sub_path = dir_sep.."lua"..dir_sep..lua_version..dir_sep;
	if not string.find(package.path, installer_plugin_path, 1, true) then
		package.path = package.path..lua_path_sep..installer_plugin_path..dir_sep.."share"..sub_path.."?.lua";
		package.path = package.path..lua_path_sep..installer_plugin_path..dir_sep.."share"..sub_path.."?"..dir_sep.."init.lua";
	end
	if not string.find(package.path, installer_plugin_path, 1, true) then
		package.cpath = package.cpath..lua_path_sep..installer_plugin_path..dir_sep.."lib"..sub_path.."?.so";
	end
end

return path_util;