File

plugins/mod_http_errors.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
parent 11404:f7704f987439
child 11662:a8798e04b5c8
line wrap: on
line source

module:set_global();

local server = require "net.http.server";
local codes = require "net.http.codes";
local xml_escape = require "util.stanza".xml_escape;
local render = require "util.interpolation".new("%b{}", xml_escape);

local show_private = module:get_option_boolean("http_errors_detailed", false);
local always_serve = module:get_option_boolean("http_errors_always_show", true);
local default_message = { module:get_option_string("http_errors_default_message", "That's all I know.") };
local default_messages = {
	[400] = { "What kind of request do you call that??" };
	[403] = { "You're not allowed to do that." };
	[404] = { "Whatever you were looking for is not here. %";
		"Where did you put it?", "It's behind you.", "Keep looking." };
	[500] = { "% Check your error log for more info.";
		"Gremlins.", "It broke.", "Don't look at me." };
	["/"] = {
		"A study in simplicity.";
		"Better catch it!";
		"Don't just stand there, go after it!";
		"Well, say something, before it runs too far!";
		"Welcome to the world of XMPP!";
		"You can do anything in XMPP!"; -- "The only limit is XML.";
		"You can do anything with Prosody!"; -- the only limit is memory?
	};
};

local messages = setmetatable(module:get_option("http_errors_messages", {}), { __index = default_messages });

local html = [[
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>{title}</title>
<style>
body{margin-top:14%;text-align:center;background-color:#f8f8f8;font-family:sans-serif}
h1{font-size:xx-large}
p{font-size:x-large}
p.warning>span{font-size:large;background-color:yellow}
p.extra{font-size:large;font-family:courier}
@media(prefers-color-scheme:dark){
body{background-color:#161616;color:#eee}
p.warning>span{background-color:inherit;color:yellow}
}
</style>
</head>
<body>
<h1>{title}</h1>
<p>{message}</p>
{warning&<p class="warning"><span>&#9888; {warning?} &#9888;</span></p>}
{extra&<p class="extra">{extra?}</p>}
</body>
</html>
]];

local function get_page(code, extra)
	local message = messages[code];
	if always_serve or message then
		message = message or default_message;
		return render(html, {
			title = rawget(codes, code) or ("Code "..tostring(code));
			message = message[1]:gsub("%%", function ()
				return message[math.random(2, math.max(#message,2))];
			end);
			extra = extra;
		});
	end
end

-- Main error page handler
module:hook_object_event(server, "http-error", function (event)
	if event.response then
		event.response.headers.content_type = "text/html; charset=utf-8";
	end
	return get_page(event.code, (show_private and event.private_message) or event.message or (event.error and event.error.text));
end);

-- Way to use the template for other things so to give a consistent appearance
module:hook("http-message", function (event)
	if event.response then
		event.response.headers.content_type = "text/html; charset=utf-8";
	end
	return render(html, event);
end);

-- Something nicer shown instead of 404 at the root path, if nothing else handles this path
module:hook_object_event(server, "http-error", function (event)
	local request, response = event.request, event.response;
	if request and response and request.path == "/" and response.status_code == 404 then
		response.headers.content_type = "text/html; charset=utf-8";
		local message = messages["/"];
		return render(html, {
				title = "Prosody is running!";
				message = message[math.random(#message)];
			});
	end
end, 1);