@fastify/early-hints
Draft proposal of plugin handling the HTTP 103 code. Based on : https://github.com/fastify/fastify/issues/2683
Install
npm i @fastify/early-hints
Options
You can pass the following options during the plugin registration:
await fastify.register(import('@fastify/early-hints'), {
warn: true // default: false
})
warn: indicates if the plugin should log warnings if invalid values are supplied as early hints
Usage
Reply.writeEarlyHints
This method is used to write early hints with any header you need. It accepts
either object or Array of headers and return Promise.
const Fastify = require("fastify");
const eh = require("@fastify/early-hints");
const fastify = Fastify({ logger: true });
fastify.register(eh);
fastify.get("/", async (request, reply) => {
// object
await reply.writeEarlyHints({
'Content-Security-Policy': 'style-src: self;',
Link: ['</style.css>; rel=preload; as=style', '</script.js>; rel=preload; as=script']
})
// array
await reply.writeEarlyHints([
{ name: 'Content-Security-Policy', value: 'style-src: self;' },
{ name: 'Link', value: '</style.css>; rel=preload; as=style' },
{ name: 'Link', value: '</script.js>; rel=preload; as=script' },
])
return { hello: "world" };
});
const start = async () => {
try {
await fastify.listen({ port: 3000 });
fastify.log.info(`server listening on ${fastify.server.address().port}`);
} catch (err) {
fastify.log.error(err);
process.exit(1);
}
};
start();
Result
$ curl -D - http://localhost:3000
HTTP/1.1 103 Early Hints
Content-Security-Policy: style-src: self;
Link: </style.css>; rel=preload; as=style
Link: </script.js>; rel=preload; as=script
HTTP/1.1 103 Early Hints
Content-Security-Policy: style-src: self;
Link: </style.css>; rel=preload; as=style
Link: </script.js>; rel=preload; as=script
HTTP/1.1 200 OK
content-type: application/json; charset=utf-8
content-length: 17
Date: Thu, 12 Nov 2020 22:45:54 GMT
Connection: keep-alive
{"hello":"world"}
Reply.writeEarlyHintsLinks
This method used to write only the Link header. It accepts an Array and
return Promise.
const Fastify = require("fastify");
const eh = require("@fastify/early-hints");
const fastify = Fastify({ logger: true });
fastify.register(eh);
fastify.get("/", async (request, reply) => {
await reply.writeEarlyHintsLinks([
"Link: </style.css>; rel=preload; as=style",
"Link: </script.js>; rel=preload; as=script",
])
await reply.writeEarlyHintsLinks([
{ href: "//example.com", rel: "preload", as: "style" },
{ href: "//example.com", rel: "preload", as: "style", cors: true },
{ href: "//example.com", rel: "preconnect" },
{ href: "//example2.com", rel: "preconnect", cors: true },
{ href: "//example3.com", rel: "preconnect", cors: "use-credentials" },
])
return { hello: "world" };
});
const start = async () => {
try {
await fastify.listen({ port: 3000 });
fastify.log.info(`server listening on ${fastify.server.address().port}`);
} catch (err) {
fastify.log.error(err);
process.exit(1);
}
};
start();
Result
$ curl -D - http://localhost:3000
HTTP/1.1 103 Early Hints
Link: </style.css>; rel=preload; as=style
Link: </script.js>; rel=preload; as=script
HTTP/1.1 103 Early Hints
Link: </style.css>; rel=preload; as=style
Link: </script.js>; rel=preload; as=script
Link: <//example.com>; rel=preload; as=style
Link: <//example.com>; rel=preload; as=style; crossorigin
Link: <//example.com>; rel=preconnect
Link: <//example2.com>; rel=preconnect; crossorigin
Link: <//example3.com>; rel=preconnect; crossorigin=use-credentials
HTTP/1.1 200 OK
content-type: application/json; charset=utf-8
content-length: 17
Date: Thu, 12 Nov 2020 22:45:54 GMT
Connection: keep-alive
{"hello":"world"}
Browser Limitation
Currently (2022-09-29), only Chrome 103 is supporting 103 Early Hints and
Chrome will ignore 103 Early Hints in the following situations.
- Early Hints sent on subresource requests
- Early Hints sent on iframe navigation
- Early Hints sent on HTTP/1.1 or earlier
- Second and following Early Hints
Read more on https://chromium.googlesource.com/chromium/src/+/master/docs/early-hints.md#103-early-hints
References
License
Licensed under MIT.