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fastify-sse-v2

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Provide Server-Sent Events to Fastify

// repository documentation

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# Fastify SSE Plugin

![CI check](https://github.com/NodeFactoryIo/fastify-sse-v2/workflows/CI%20check/badge.svg?branch=master)
[![npm version](https://badge.fury.io/js/fastify-sse-v2.svg)](https://badge.fury.io/js/fastify-sse-v2)

Fastify plugin for sending [Server-sent events](https://en.wikipedia.org/wiki/Server-sent_events).

For `fastify@2.x` use [fastify-sse-v2@1.x](https://github.com/NodeFactoryIo/fastify-sse-v2/tree/1.x)!

### How to use?

```terminal
yarn add fastify-sse-v2
```

```javascript
import { FastifySSEPlugin } from "fastify-sse-v2";

const server = fastify();
server.register(FastifySSEPlugin);
```

#### Sending events from AsyncIterable source

```javascript
import { FastifySSEPlugin } from "fastify-sse-v2";

const server = fastify();
server.register(FastifySSEPlugin);

server.get("/", function (req, res) {
  res.sse(
    (async function* source() {
      for (let i = 0; i < 10; i++) {
        sleep(2000);
        yield { id: String(i), data: "Some message" };
      }
    })()
  );
});
```

#### Sending individual events

```javascript
import { FastifySSEPlugin } from "fastify-sse-v2";

const server = fastify();
server.register(FastifySSEPlugin);

server.get("/", async function (req, res) {
  for (let i = 0; i < 10; i++) {
    await sleep(2000);
    res.sse({ id: String(i), data: "Some message" });
  }
});

fastify.get("/listenForChanges", {}, (request, reply) => {
  const listenStream = fastify.db
    .watch("doc-uuid")
    .on("data", (data) => reply.sse({ data: JSON.stringify(data) }))
    .on("delete", () => reply.sse({ event: "close" }));
  request.socket.on("close", () => listenStream.end());
});
```

##### Note

- When sending individual events, the connection is kept open until you call `reply.sseContext.source.end()` to terminate the stream.

##### Sending events from EventEmmiters

- [not supported in all nodejs versions](https://nodejs.org/api/events.html#events_events_on_emitter_eventname_options)

```javascript
import { FastifySSEPlugin } from "fastify-sse-v2";
import { on } from "events";

const server = fastify();
server.register(FastifySSEPlugin);

server.get("/", function (req, res) {
  res.sse(
    (async function* () {
      for await (const [event] of on(eventEmmitter, "update")) {
        yield {
          event: event.name,
          data: JSON.stringify(event),
        };
      }
    })()
  );
});
```

##### Note

- to remove event listeners (or some other cleanup) when client closes connection,
  you can listen on connection closing event: `request.socket.on('close', () => abortController.abort());
`

##### Change server send retry behavior

```javascript
import { FastifySSEPlugin } from "fastify-sse-v2";

const server = fastify();

server.register(FastifySSEPlugin) // retryDelay default 3000

server.register(FastifySSEPlugin, {
  retryDelay: false // disable retryDelay
  retryDelay: 5000 // override 5000
})
```

##### Change default highWaterMark

```javascript
import { FastifySSEPlugin } from "fastify-sse-v2";

const server = fastify();

server.register(FastifySSEPlugin) // highWaterMark defaults to 16384 bytes (16kb)

server.register(FastifySSEPlugin, {
  highWaterMark: 1024 // override default setting of 16384 (16kb) with 1024 (1kb)
})
```

##### Note

- You can set parameter `retryDelay` to `false` to disable the default behavior of sending retry, or set parameter `retryDelay` to `milliseconds` override the default 3000 retry interval .
- You can set parameter `highWaterMark` to define the buffer size (in bytes) that determines when the buffer is full and a 'flush' should be performed. Default is 16kb. (![Learn more](https://nodejs.org/en/learn/modules/backpressuring-in-streams#how-does-backpressure-resolve-these-issues))

fastify-sse-v2

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