Fastify plugin dependency - Registering MySQL before routes - node.js

Question

I'm new to NodeJS and Fastify and I'm fairly sure I'm making a basic mistake here but I can't see what it is.
I have separated out my MySQL connection and routes into separate plugins. It appears that the MySQL plugin is not registering in time, leading to the routes not working.
I was under the impression that registering plugins was done asynchronously (loading one plugin at a time), but it can't seem to find "fastify.mysql.query".
Error:
"Cannot read properties of undefined (reading 'query')","stack":"TypeError: Cannot read properties of undefined (reading 'query')\n at Object.<anonymous> (/Users/dally/Projects/NodeJS/boodil-payments-api/routes/payments.js:4:23)\n at preHandlerCallback (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/fastify/lib/handleRequest.js:126:28)\n at preValidationCallback (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/fastify/lib/handleRequest.js:110:5)\n at handler (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/fastify/lib/handleRequest.js:74:7)\n at handleRequest (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/fastify/lib/handleRequest.js:22:5)\n at runPreParsing (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/fastify/lib/route.js:487:5)\n at Object.routeHandler [as handler] (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/fastify/lib/route.js:434:7)\n at Router.lookup (/Users/dally/Projects/NodeJS/boodil-payments-api/node_modules/find-my-way/index.js:368:14)\n at Server.emit (node:events:527:28)\n at parserOnIncoming (node:_http_server:956:12)"},"msg":"Cannot read properties of undefined (reading 'query')"}
Server.js
const fastify = require('fastify')({ logger: true })
fastify.register(require('./config/db'))
fastify.register(require('./routes/payments'))
const PORT = 2000
const start = async () => {
try {
await fastify.listen({ port: PORT })
}
catch (e) {
fastify.log.error(e)
process.exit(1)
}
}
start()
DB.js
module.exports = function (fastify, options, done) {
fastify.register(require('#fastify/mysql'), {
connectionString: 'mysql://root:password#localhost/boodil'
})
done()
}
payment.js
function paymentRoutes(fastify, opts, done) {
fastify.get('/get-transactions', (req, reply) => {
fastify.mysql.query(
'SELECT * FROM transactions',
function onResult(err, result) {
reply.send(err || result)
}
)
})
fastify.get('/get-transaction:id', (req, reply) => {
fastify.mysql.query(
'SELECT * FROM transactions where id = ?', [req.params.id],
function onResult(err, result) {
reply.send(err || result)
}
)
})
done()
}
module.exports = paymentRoutes

Answer 1

As said in comments, you need to use the fastify-plugin wrapper in your DB.js file.
To understand this error, you must get confident with fastify's encapsulation context.
It is worth reading these answers:
https://stackoverflow.com/a/61054534/3309466
https://stackoverflow.com/a/73586266/3309466
In practice: your database connection was isolated into a context that was unreachable by the paymentRoutes.
I'm coming from a PHP/Laravel background where this is quite standard
What fastify refuses is creating a global context where all you need is shared. Of course, you can do it, by it is not the default behaviour. You need to declare that the exported plugin has something that can be used by other contexts.