Samples on error handling in Fastify handlers

fastifyHandlersErrorHandling.js

'use strict'

const fastify = require('fastify')({
  logger: {
    serializers: {
      req: function (req) {
        return { path: req.url, headers: req.headers, payload: req.body }
      }
    }
  }
})

fastify.addHook('onError', async (request, reply, error) => {

  console.log('ERROR HOOK FIRED')
  console.error(error)

  return
})
/*
  fastify.setErrorHandler((error, request, reply)=>{
        
    // Note that Fastify doesn't catch uncaught errors within callback 
    // based routes for you, so any uncaught errors will result in a crash. 
    // If routes are declared as async though - the error will safely 
    // be caught by the promise and routed to the default error handler 
    // of Fastify for a generic Internal Server Error response. 
    // For customizing this behavior, you should use setErrorHandler.
    
    console.log('SHIT HAPPENS')
    // report to STDOUT
    fastify.log.error(error)

    reply.send(error)
})
*/

const myMod = async (shouldICrash) => {

  if (shouldICrash) throw new Error('BOOM')

  return 0
}

const myOthMod = (shouldICrash) => {
  return new Promise((resolve, reject) => {
    if (shouldICrash) return reject(new Error('BOOM'))

    resolve(0)
  })
}

// HAPPY CASE PROMISE/CALLBACK
fastify.get('/', function (request, reply) {
  reply.send({ hello: 'world' })
})

// HAPPY CASE ASYNC
fastify.get('/asyncok', async (request, reply) => {
  const res = await myMod(false)
  reply.send(res)
})

// ERROR CASES
// ERROR CASES
// ERROR CASES

// OK
fastify.get('/asyncerr', async (request, reply) => {
  const res = await myMod(true)
  reply.send(res)
})

// OK (but results in a process crash)
fastify.get('/err', (request, reply) => {
  // uncaught error
  throw new Error('boom')
  reply.send(res)
})

// OK
fastify.get('/caughterr', (request, reply) => {
  // result is 500
  reply.send(Error('BOOM'))
})

// NO (results in a leaked descriptor)
fastify.get('/promiseerr', (request, reply) => {
  myOthMod(true).then(res => {
    reply.send(res)
  }) // uncaught promise on sync handler
})

// YES
fastify.get('/asyncpromiseerr', async (request, reply) => {
  const res = await myOthMod(true) // uncaught promise on sync handler
  reply.send(res)
})


fastify.listen(3000, function (err, address) {
  if (err) {
    fastify.log.error(err)
    process.exit(1)
  }
  fastify.log.info(`server listening on ${address}`)
})