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Mastering Server-Side Development with Fastify: Response Techniques

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Chapter 1: Introduction to Fastify

Fastify is a lightweight framework designed for creating backend web applications in Node.js. In this article, we'll explore how to manage responses effectively when developing with Fastify.

Section 1.1: Sending String Responses

To send a simple string response, you can utilize the reply.send method. Here’s an example:

const fastify = require('fastify')({});

fastify.get('/', function(req, reply) {

reply.send('plain string');

});

const start = async () => {

try {

await fastify.listen(3000, '0.0.0.0');

} catch (err) {

fastify.log.error(err);

process.exit(1);

}

};

start();

Section 1.2: Stream Responses

Fastify also allows you to send stream responses. For example:

const fastify = require('fastify')({});

fastify.get('/', function(req, reply) {

const fs = require('fs');

const stream = fs.createReadStream('some-file', 'utf8');

reply.send(stream);

});

const start = async () => {

try {

await fastify.listen(3000, '0.0.0.0');

} catch (err) {

fastify.log.error(err);

process.exit(1);

}

};

start();

If the file some-file contains the text foo, that will be the output when accessing the root route.

Section 1.3: Buffer Responses

You can also send buffer responses using the fs.readFile method:

const fastify = require('fastify')({});

fastify.get('/', function(req, reply) {

fs.readFile('some-file', (err, fileBuffer) => {

reply.send(err || fileBuffer);

});

});

const start = async () => {

try {

await fastify.listen(3000, '0.0.0.0');

} catch (err) {

fastify.log.error(err);

process.exit(1);

}

};

start();

This code reads a file and responds with its content.

Section 1.4: Handling Errors

To manage errors, you can use the http-errors library. Here’s an example of how to send a 410 Gone status code:

const fastify = require('fastify')({});

const httpErrors = require('http-errors');

fastify.get('/', function(req, reply) {

reply.send(httpErrors.Gone());

});

const start = async () => {

try {

await fastify.listen(3000, '0.0.0.0');

} catch (err) {

fastify.log.error(err);

process.exit(1);

}

};

start();

Additionally, you can set up a custom error handler to respond based on the error type:

fastify.setErrorHandler(function (error, request, reply) {

request.log.warn(error);

const statusCode = error.statusCode >= 400 ? error.statusCode : 500;

reply

.code(statusCode)

.type('text/plain')

.send(statusCode >= 500 ? 'Internal server error' : error.message);

});

Section 1.5: Custom Not Found Responses

To manage not found errors, you can create a custom handler:

fastify.setNotFoundHandler(function (request, reply) {

reply

.code(404)

.type('text/plain')

.send('a custom not found');

});

fastify.get('/', function(req, reply) {

reply.callNotFound();

});

This way, when a route isn’t found, the application responds with a custom message.

Chapter 2: Practical Application

In this section, we will delve deeper into using Fastify for building a RESTful API.

This video demonstrates how to build a RESTful API using Fastify, Prisma, and TypeScript.

In this video, we explore whether a Node.js server can handle one million concurrent requests, showcasing real-world app benchmarking on a dedicated VPS.

Conclusion

Fastify provides a robust framework for sending various types of HTTP responses. By understanding how to implement string, stream, buffer responses, and error handling, you can create more effective backend applications.

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