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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 |
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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>⚠ {warning?} ⚠</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);