File

util/error.lua @ 11523:5f15ab7c6ae5

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
author Jonas Schäfer <jonas@wielicki.name>
date Sun, 18 Apr 2021 11:47:41 +0200 (2021-04-18)
parent 11224:8143fd2f138b
child 12975:d10957394a3c
child 13078:6da83deb8d7f
line wrap: on
line source
local id = require "util.id";

local util_debug; -- only imported on-demand

-- Library configuration (see configure())
local auto_inject_traceback = false;

local error_mt = { __name = "error" };

function error_mt:__tostring()
	return ("error<%s:%s:%s>"):format(self.type, self.condition, self.text or "");
end

local function is_error(e)
	return getmetatable(e) == error_mt;
end

local function configure(opt)
	if opt.auto_inject_traceback ~= nil then
		auto_inject_traceback = opt.auto_inject_traceback;
		if auto_inject_traceback then
			util_debug = require "util.debug";
		end
	end
end

-- Do we want any more well-known fields?
-- Or could we just copy all fields from `e`?
-- Sometimes you want variable details in the `text`, how to handle that?
-- Translations?
-- Should the `type` be restricted to the stanza error types or free-form?
-- What to set `type` to for stream errors or SASL errors? Those don't have a 'type' attr.

local function new(e, context, registry, source)
	if is_error(e) then return e; end
	local template = registry and registry[e];
	if not template then
		if type(e) == "table" then
			template = {
				code = e.code;
				type = e.type;
				condition = e.condition;
				text = e.text;
				extra = e.extra;
			};
		else
			template = {};
		end
	end
	context = context or {};

	if auto_inject_traceback then
		context.traceback = util_debug.get_traceback_table(nil, 2);
	end

	local error_instance = setmetatable({
		instance_id = id.short();

		type = template.type or "cancel";
		condition = template.condition or "undefined-condition";
		text = template.text;
		code = template.code;
		extra = template.extra;

		context = context;
		source = source;
	}, error_mt);

	return error_instance;
end

-- compact --> normal form
local function expand_registry(namespace, registry)
	local mapped = {}
	for err,template in pairs(registry) do
		local e = {
			type = template[1];
			condition = template[2];
			text = template[3];
		};
		if namespace and template[4] then
			e.extra = { namespace = namespace, condition = template[4] };
		end
		mapped[err] = e;
	end
	return mapped;
end

local function init(source, namespace, registry)
	if type(namespace) == "table" then
		-- registry can be given as second argument if namespace is not used
		registry, namespace = namespace, nil;
	end
	local _, protoerr = next(registry, nil);
	if protoerr and type(next(protoerr)) == "number" then
		registry = expand_registry(namespace, registry);
	end

	local function wrap(e, context)
		if is_error(e) then
			return e;
		end
		local err = new(registry[e] or {
			type = "cancel", condition = "undefined-condition"
		}, context, registry, source);
		err.context.wrapped_error = e;
		return err;
	end

	return {
		source = source;
		registry = registry;
		new = function (e, context)
			return new(e, context, registry, source);
		end;
		coerce = function (ok, err, ...)
			if ok then
				return ok, err, ...;
			end
			return nil, wrap(err);
		end;
		wrap = wrap;
		is_error = is_error;
	};
end

local function coerce(ok, err, ...)
	if ok or is_error(err) then
		return ok, err, ...;
	end

	local new_err = new({
		type = "cancel", condition = "undefined-condition"
	}, { wrapped_error = err });

	return ok, new_err, ...;
end

local function from_stanza(stanza, context, source)
	local error_type, condition, text, extra_tag = stanza:get_error();
	local error_tag = stanza:get_child("error");
	context = context or {};
	context.stanza = stanza;
	context.by = error_tag.attr.by or stanza.attr.from;

	local uri;
	if condition == "gone" or condition == "redirect" then
		uri = error_tag:get_child_text(condition, "urn:ietf:params:xml:ns:xmpp-stanzas");
	end

	return new({
		type = error_type or "cancel";
		condition = condition or "undefined-condition";
		text = text;
		extra = (extra_tag or uri) and {
			uri = uri;
			tag = extra_tag;
		} or nil;
	}, context, nil, source);
end

return {
	new = new;
	init = init;
	coerce = coerce;
	is_error = is_error;
	is_err = is_error; -- COMPAT w/ older 0.12 trunk
	from_stanza = from_stanza;
	configure = configure;
}