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| 1 | +# Socket.IO cluster adapter |
| 2 | + |
| 3 | +The `@socket.io/cluster-adapter` package allows broadcasting packets between multiple Socket.IO servers. |
| 4 | + |
| 5 | + |
| 6 | + |
| 7 | +It can be used in conjunction with [`@socket.io/sticky`](https://github.com/socketio/socket.io-sticky) to broadcast packets between the workers of the same Node.js [cluster](https://nodejs.org/api/cluster.html). |
| 8 | + |
| 9 | +Supported features: |
| 10 | + |
| 11 | +- [broadcasting](https://socket.io/docs/v4/broadcasting-events/) |
| 12 | +- [utility methods](https://socket.io/docs/v4/server-instance/#Utility-methods) |
| 13 | + - [`socketsJoin`](https://socket.io/docs/v4/server-instance/#socketsJoin) |
| 14 | + - [`socketsLeave`](https://socket.io/docs/v4/server-instance/#socketsLeave) |
| 15 | + - [`disconnectSockets`](https://socket.io/docs/v4/server-instance/#disconnectSockets) |
| 16 | + - [`fetchSockets`](https://socket.io/docs/v4/server-instance/#fetchSockets) |
| 17 | + - [`serverSideEmit`](https://socket.io/docs/v4/server-instance/#serverSideEmit) |
| 18 | + |
| 19 | +Related packages: |
| 20 | + |
| 21 | +- Postgres adapter: https://github.com/socketio/socket.io-postgres-adapter/ |
| 22 | +- Redis adapter: https://github.com/socketio/socket.io-redis-adapter/ |
| 23 | +- MongoDB adapter: https://github.com/socketio/socket.io-mongo-adapter/ |
| 24 | + |
| 25 | +**Table of contents** |
| 26 | + |
| 27 | +- [Installation](#installation) |
| 28 | +- [Usage](#usage) |
| 29 | +- [License](#license) |
| 30 | + |
| 31 | +## Installation |
| 32 | + |
| 33 | +``` |
| 34 | +npm install @socket.io/cluster-adapter |
| 35 | +``` |
| 36 | + |
| 37 | +## Usage |
| 38 | + |
| 39 | +```js |
| 40 | +const cluster = require("cluster"); |
| 41 | +const http = require("http"); |
| 42 | +const { Server } = require("socket.io"); |
| 43 | +const numCPUs = require("os").cpus().length; |
| 44 | +const { setupMaster, setupWorker } = require("@socket.io/sticky"); |
| 45 | +const { createAdapter, setupPrimary } = require("@socket.io/cluster-adapter"); |
| 46 | + |
| 47 | +if (cluster.isMaster) { |
| 48 | + console.log(`Master ${process.pid} is running`); |
| 49 | + |
| 50 | + const httpServer = http.createServer(); |
| 51 | + |
| 52 | + // setup sticky sessions |
| 53 | + setupMaster(httpServer, { |
| 54 | + loadBalancingMethod: "least-connection", |
| 55 | + }); |
| 56 | + |
| 57 | + // setup connections between the workers |
| 58 | + setupPrimary(); |
| 59 | + |
| 60 | + // needed for packets containing buffers (you can ignore it if you only send plaintext objects) |
| 61 | + // Node.js < 16.0.0 |
| 62 | + cluster.setupMaster({ |
| 63 | + serialization: "advanced", |
| 64 | + }); |
| 65 | + // Node.js > 16.0.0 |
| 66 | + // cluster.setupPrimary({ |
| 67 | + // serialization: "advanced", |
| 68 | + // }); |
| 69 | + |
| 70 | + httpServer.listen(3000); |
| 71 | + |
| 72 | + for (let i = 0; i < numCPUs; i++) { |
| 73 | + cluster.fork(); |
| 74 | + } |
| 75 | + |
| 76 | + cluster.on("exit", (worker) => { |
| 77 | + console.log(`Worker ${worker.process.pid} died`); |
| 78 | + cluster.fork(); |
| 79 | + }); |
| 80 | +} else { |
| 81 | + console.log(`Worker ${process.pid} started`); |
| 82 | + |
| 83 | + const httpServer = http.createServer(); |
| 84 | + const io = new Server(httpServer); |
| 85 | + |
| 86 | + // use the cluster adapter |
| 87 | + io.adapter(createAdapter()); |
| 88 | + |
| 89 | + // setup connection with the primary process |
| 90 | + setupWorker(io); |
| 91 | + |
| 92 | + io.on("connection", (socket) => { |
| 93 | + /* ... */ |
| 94 | + }); |
| 95 | +} |
| 96 | +``` |
| 97 | + |
| 98 | +## License |
| 99 | + |
| 100 | +[MIT](LICENSE) |
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