util.dbuffer: Add efficient shortcuts for discard() in certain cases
If the buffer is already empty, nothing to do. If we're throwing away the
whole buffer, we can just empty it and avoid read_chunk() (which in turn
may collapse()). These shortcuts are much more efficient.
-- Export statistics in OpenMetrics format
--
-- Copyright (C) 2014 Daurnimator
-- Copyright (C) 2018 Emmanuel Gil Peyrot <linkmauve@linkmauve.fr>
-- Copyright (C) 2021 Jonas Schäfer <jonas@zombofant.net>
--
-- This module is MIT/X11 licensed.
module:set_global();
local statsman = require "core.statsmanager";
local ip = require "util.ip";
local get_metric_registry = statsman.get_metric_registry;
local collect = statsman.collect;
local get_metrics;
local permitted_ips = module:get_option_set("openmetrics_allow_ips", { "::1", "127.0.0.1" });
local permitted_cidr = module:get_option_string("openmetrics_allow_cidr");
local function is_permitted(request)
local ip_raw = request.ip;
if permitted_ips:contains(ip_raw) or
(permitted_cidr and ip.match(ip.new_ip(ip_raw), ip.parse_cidr(permitted_cidr))) then
return true;
end
return false;
end
function get_metrics(event)
if not is_permitted(event.request) then
return 403; -- Forbidden
end
local response = event.response;
response.headers.content_type = "application/openmetrics-text; version=0.0.4";
if collect then
-- Ensure to get up-to-date samples when running in manual mode
collect()
end
local registry = get_metric_registry()
if registry == nil then
response.headers.content_type = "text/plain; charset=utf-8"
response.status_code = 404
return "No statistics provider configured\n"
end
return registry:render();
end
module:depends "http";
module:provides("http", {
default_path = "metrics";
route = {
GET = get_metrics;
};
});