Prometheus metrics for socket.io

Usage no npm install needed!

<script type="module">
  import balenaSocketPrometheusMetrics from 'https://cdn.skypack.dev/@balena/socket-prometheus-metrics';



Exposes a metrics endpoint for prometheus to collect data about socket.io.


npm install socket.io-prometheus-metrics
# or
yarn add socket.io-prometheus-metrics


Basic usage

import * as http from 'http';
import * as io from 'socket.io';
import * as prometheus from 'socket.io-prometheus-metrics';

const server = http.createServer();
const io = io(server);



Metrics is then available at localhost:9090/metrics.

Prometheus default metrics can also be enabled by setting the collectDefaultMetrics option to true

prometheus.metrics(io, {
    collectDefaultMetrics: true

If you wish to serve the metrics yourself the createServer options can be set to false and metrics can be collected from the register

const ioMetrics = prometheus.metrics(io, {
    createServer: false

const metrics = ioMetrics.register.metrics();


Option Default Description
path "/metrics" Metrics path
port 9090 Metrics port
createServer true Auto create http server
collectDefaultMetrics false Collect prometheus default metrics
checkForNewNamespaces true Collect metrics for namespaces that will be added at runtime

Socket.io metrics

all metrics have socket_io_ prefix in their names.

Name Help Labels
socket_io_connected Number of currently connected sockets
socket_io_connect_total Total count of socket.io connection requests namespace
socket_io_disconnect_total Total count of socket.io disconnections namespace
socket_io_errors_total Total count of socket.io errors namespace
socket_io_events_received_total Total count of socket.io received events event, namespace
socket_io_events_sent_total Total count of socket.io sent events event, namespace
socket_io_receive_bytes Total socket.io bytes received event, namespace
socket_io_transmit_bytes Total socket.io bytes transmitted event, namespace

Prometheus default metrics

available if collectDefaultMetrics is set to true

More information here and here.

Namespaces support

Default namespace has label value of '/'.

By default library checks io.nsps variable for new namespaces to collect metrics from. This check occurs every 2 seconds.

You can disable this functionality by providing checkForNewNamespaces option with false value. For example:

prometheus.metrics(io, {
    checkForNewNamespaces: false

With this functionality disabled, library will only collect metrics from namespaces that were available at the moment of call to prometheus.metrics(io, ...), default namespace is included.

More information about socket.io namespaces here.


Licensed under the Apache 2.0 License. See the LICENSE file for details.