socket.io-prom-metrics

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

Installation

npm install socket.io-prom-metrics

Usage

Basic usage

// server.ts

import { createServer } from "http";
import { Server, Socket } from "socket.io";
import * as prometheus from "socket.io-prom-metrics";


const server = createServer();
const io = new Server(server);


io.on("connection", (socket: Socket) => {
    console.log(`${socket.id} is connected.`)
    // Add event here
});


io.of("/custom-namespace").on("connection", (socket: Socket) => {
    console.log(`${socket.id} is connected.`)
    // Add event here
});


// init prometheus
prometheus.metrics(io); // running on port 9090 (default port) | http://localhost:9090/metrics


// start server
server.listen(3000, () => {
    console.log("prometheus running on port 9090 : http://localhost:9090/metrics");
    console.log("server running on port 3000")
});

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();

Options

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.

License

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