Fastify SSE Plugin

!CI check

Fastify plugin for sending Server-sent events.

For fastify@2.x use fastify-sse-v2@1.x!

$3

``terminal
yarn add fastify-sse-v2
`

Register fastify-sse-v2 plugin into your fastify instance:

`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

`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)