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Statistics: Rewrite statistics backends to use OpenMetrics

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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
This commit is contained in:
Jonas Schäfer 2021-04-18 11:47:41 +02:00
parent 75ca81a26e
commit 5d597837f5
7 changed files with 1119 additions and 503 deletions
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204
core/statsmanager.lua
View file

@ -3,6 +3,8 @@ local config = require "core.configmanager";
local log = require "util.logger".init("stats");
local timer = require "util.timer";
local fire_event = prosody.events.fire_event;
local array = require "util.array";
local timed = require "util.openmetrics".timed;
local stats_interval_config = config.get("*", "statistics_interval");
local stats_interval = tonumber(stats_interval_config);
@ -57,15 +59,149 @@ if stats == nil then
log("error", "Error loading statistics provider '%s': %s", stats_provider, stats_err);
end
local measure, collect;
local latest_stats = {};
local changed_stats = {};
local stats_extra = {};
local measure, collect, metric, cork, uncork;
if stats then
function measure(type, name, conf)
local f = assert(stats[type], "unknown stat type: "..type);
return f(name, conf);
function metric(type_, name, unit, description, labels, extra)
local registry = stats.metric_registry
local f = assert(registry[type_], "unknown metric family type: "..type_);
return f(registry, name, unit or "", description or "", labels, extra);
end
local function new_legacy_metric(stat_type, name, unit, description, fixed_label_key, fixed_label_value, extra)
local label_keys = array()
local conf = extra or {}
if fixed_label_key then
label_keys:push(fixed_label_key)
end
unit = unit or ""
local mf = metric(stat_type, "prosody_" .. name, unit, description, label_keys, conf);
if fixed_label_key then
mf = mf:with_partial_label(fixed_label_value)
end
return mf:with_labels()
end
local function unwrap_legacy_extra(extra, type_, name, unit)
local description = extra and extra.description or "Legacy "..type_.." metric "..name
unit = extra and extra.unit or unit
return description, unit
end
-- These wrappers provide the pre-OpenMetrics interface of statsmanager
-- and moduleapi (module:measure).
local legacy_metric_wrappers = {
amount = function(name, fixed_label_key, fixed_label_value, extra)
local initial = 0
if type(extra) == "number" then
initial = extra
else
initial = extra and extra.initial or initial
end
local description, unit = unwrap_legacy_extra(extra, "amount", name)
local m = new_legacy_metric("gauge", name, unit, description, fixed_label_key, fixed_label_value)
m:set(initial or 0)
return function(v)
m:set(v)
end
end;
counter = function(name, fixed_label_key, fixed_label_value, extra)
if type(extra) == "number" then
-- previous versions of the API allowed passing an initial
-- value here; we do not allow that anymore, it is not a thing
-- which makes sense with counters
extra = nil
end
local description, unit = unwrap_legacy_extra(extra, "counter", name)
local m = new_legacy_metric("counter", name, unit, description, fixed_label_key, fixed_label_value)
m:set(0)
return function(v)
m:add(v)
end
end;
rate = function(name, fixed_label_key, fixed_label_value, extra)
if type(extra) == "number" then
-- previous versions of the API allowed passing an initial
-- value here; we do not allow that anymore, it is not a thing
-- which makes sense with counters
extra = nil
end
local description, unit = unwrap_legacy_extra(extra, "counter", name)
local m = new_legacy_metric("counter", name, unit, description, fixed_label_key, fixed_label_value)
m:set(0)
return function()
m:add(1)
end
end;
times = function(name, fixed_label_key, fixed_label_value, extra)
local conf = {}
if extra and extra.buckets then
conf.buckets = extra.buckets
else
conf.buckets = { 0.001, 0.01, 0.1, 1.0, 10.0, 100.0 }
end
local description, _ = unwrap_legacy_extra(extra, "times", name)
local m = new_legacy_metric("histogram", name, "seconds", description, fixed_label_key, fixed_label_value, conf)
return function()
return timed(m)
end
end;
sizes = function(name, fixed_label_key, fixed_label_value, extra)
local conf = {}
if extra and extra.buckets then
conf.buckets = extra.buckets
else
conf.buckets = { 1024, 4096, 32768, 131072, 1048576, 4194304, 33554432, 134217728, 1073741824 }
end
local description, _ = unwrap_legacy_extra(extra, "sizes", name)
local m = new_legacy_metric("histogram", name, "bytes", description, fixed_label_key, fixed_label_value, conf)
return function(v)
m:sample(v)
end
end;
distribution = function(name, fixed_label_key, fixed_label_value, extra)
if type(extra) == "string" then
-- compat with previous API
extra = { unit = extra }
end
local description, unit = unwrap_legacy_extra(extra, "distribution", name, "")
local m = new_legacy_metric("summary", name, unit, description, fixed_label_key, fixed_label_value)
return function(v)
m:sample(v)
end
end;
};
-- Argument order switched here to support the legacy statsmanager.measure
-- interface.
function measure(stat_type, name, extra, fixed_label_key, fixed_label_value)
local wrapper = assert(legacy_metric_wrappers[stat_type], "unknown legacy metric type "..stat_type)
return wrapper(name, fixed_label_key, fixed_label_value, extra)
end
if stats.cork then
function cork()
return stats:cork()
end
function uncork()
return stats:uncork()
end
else
function cork() end
function uncork() end
end
if stats_interval or stats_interval_config == "manual" then
@ -76,27 +212,23 @@ if stats then
function collect()
local mark_collection_done = mark_collection_start();
fire_event("stats-update");
-- ensure that the backend is uncorked, in case it got stuck at
-- some point, to avoid infinite resource use
uncork()
mark_collection_done();
local manual_result = nil
if stats.get_stats then
if stats.metric_registry then
-- only if supported by the backend, we fire the event which
-- provides the current metric values
local mark_processing_done = mark_processing_start();
changed_stats, stats_extra = {}, {};
for stat_name, getter in pairs(stats.get_stats()) do
-- luacheck: ignore 211/type
local type, value, extra = getter();
local old_value = latest_stats[stat_name];
latest_stats[stat_name] = value;
if value ~= old_value then
changed_stats[stat_name] = value;
end
if extra then
stats_extra[stat_name] = extra;
end
end
fire_event("stats-updated", { stats = latest_stats, changed_stats = changed_stats, stats_extra = stats_extra });
local metric_registry = stats.metric_registry;
fire_event("openmetrics-updated", { metric_registry = metric_registry })
mark_processing_done();
manual_result = metric_registry;
end
return stats_interval;
return stats_interval, manual_result;
end
if stats_interval then
log("debug", "Statistics enabled using %s provider, collecting every %d seconds", stats_provider_name, stats_interval);
@ -112,6 +244,22 @@ if stats then
else
log("debug", "Statistics disabled");
function measure() return measure; end
local dummy_mt = {}
function dummy_mt.__newindex()
end
function dummy_mt:__index()
return self
end
function dummy_mt:__call()
return self
end
local dummy = {}
setmetatable(dummy, dummy_mt)
function metric() return dummy; end
function cork() end
function uncork() end
end
local exported_collect = nil;
@ -122,10 +270,10 @@ end
return {
collect = exported_collect;
measure = measure;
get_stats = function ()
return latest_stats, changed_stats, stats_extra;
end;
get = function (name)
return latest_stats[name], stats_extra[name];
cork = cork;
uncork = uncork;
metric = metric;
get_metric_registry = function ()
return stats and stats.metric_registry or nil
end;
};