restify-prom-bundle

Restify middleware to export standard http prometheus metrics.

Usage

const promBundle = require('restify-prom-bundle');
const restify = require('restify');

const server = restify.createServer({ /* options */ });

server.pre(promBundle.preMiddleware(server, { /* options */ }));

server.get('/api', (req, res) => {
  // Custom metrics can be added by using the client.
  const counter = new promBundle.client.Gauge(
    'my_custom_counter',
    'My custom counter'
  );

  counter.inc();
  res.end('OK');
});

server.listen(8000);

// The /metrics route is now available with metrics.

Since prom-client is a singleton, it can be accessed from everywhere by just require'ing / import the module, aggregated metrics will be exposed on the route.

API

preMiddleware(server[, options]) => Restify.Handler

Creates the restify pre-middleware to

• Creates the expose route used by prometheus server to index metrics
• Setup default metrics you want to measure

Options :

Name	Type	Default	Description
route	string	'/metrics'	Exposed route (as GET) for metrics. If false no route will be exposed.
defaults	string[]	All metrics	Name of default metrics (see table below) to add for each routes.
exclude	string string[] RegExp Function	undefined	URI(s), uri that match regular expression or uri that passed to function returns true that will be excluded from default metrics.
promDefaultDelay	number	10000	How often (ms) should prom-client fire default probes
maxPathsToCount	number	100	How many paths at max should we measure calls on (restify_path_count), use 0 for unlimited (See below.

Default metrics :

Name	Metric Name	Type	Description
status	restify_status_codes	Counter	Number of response for each HTTP status code with status_code as label.
pathDuration	restify_path_duration	Histogram	Duration (seconds) by percentiles taken by each restify-defined path to generate the response with the path, status_code and the method as labels.
pathCount	restify_path_count	Counter	Number of calls to each path with the path, status_code and the method as labels.

duration metrics precision will depends on the pre-middleware registering order, the sooner you register (first server.pre() call), the better it will be.

prom-client: client

Singleton instance of prom-client to set custom metrics.

Paths limitation

If a huge number of different non-routed requests (404) are sent to the server, the process will have to keep a restify_path_count label for each one and the process memory will increase undefinitively. In addition, the prometheus (and grafana) service that uses this probes will be flooded. To prevent this situation, number of measured paths are limited to maxPathsToCount.

This does not affect restify_path_duration as it only measures the restify-defined paths, nor restify_status_codes as it's limited to HTTP status codes.

Once maxPathsToMeasure paths are measured, every new paths will be ignored for restify_path_duration and restify_path_count.

Grafana dashboard

A sample grafana dashboard can be found here .