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.