Load plugin after another fastify

Question

I'm currently working on an api where I autoload my plugins but I would like to add global hooks on all routes. What I'm currently doing is I load all my plugins and after I load my middlewares but I have a problem I'm trying to use mongoClient created by fastify-mongo but I always end up with the error mongo is not defined.

When I'm using it on my controller everything works i thinks I get this error because the plugin is not fully loaded, I did find .ready but it doesn't work

plugin/mongo.js

import fp from 'fastify-plugin';
import mongoPl from '@fastify/mongodb';

async function mongo(fastify, opts) {
  fastify.register(mongoPl, {
    forceClose: true,
    url: 'mongodb://mongo:27017'
  });

}
export default fp(mongo, {
  name: 'mongo'
});

libs/middleware

import fp from "fastify-plugin";

async function hooks(fastify, opts) {
  fastify.addHook('onRequest', (req, res, done) => {

    // Inject mongo client
    mongoClient(req);

    done();
  });

}

async function mongoClient(req){
  try {
    req.db = this.mongo.client.db('db-name');
  }catch (e) {
    console.error(e);
  }
}

export default fp(hooks, {
  name: 'hooksMiddleware'
});

app.js

app.register(AutoLoad, {
  dir: join(import.meta.url, 'plugins'),
  options: Object.assign({})
}).after(() => {
  app.register(hooksMiddleware, {});
});

Answer 1

Your setup looks good, but the this context in mongoClient function is undefined.

Here some fixes:

async function hooks(fastify, opts) {
  fastify.addHook('onRequest', (req, res, done) => {

    // Inject mongo client
    mongoClient.call(fastify, req);

    done();
  });

}

Or:

async function hooks(fastify, opts) {

  // NOTE: I changed from arrow to an anonymous function
  fastify.addHook('onRequest', function (req, res, done) {

    // Inject mongo client
    mongoClient.call(this, req);

    done();
  });

}

You need to know:

• the this context is set only on those named function that you provide to Fastify. The mongoClient function is just a function outside the Fastify's control
• the this context cannot be set for arrow function. (opinion) I will never stop to say: use arrow function only for 1-line function, otherwise named function are always the best choice (better stack tracing, more readable)