Lifecycle

Following the schema of the internal lifecycle of Fastify.
On the right branch of every section there is the next phase of the lifecycle, on the left branch there is the corresponding error code that will be generated if the parent throws an error (note that all the errors are automatically handled by Fastify).

Incoming Request
  │
  └─▶ Routing
        │
        └─▶ Instance Logger
             │
   4**/5** ◀─┴─▶ onRequest Hook
                  │
        4**/5** ◀─┴─▶ preParsing Hook
                        │
              4**/5** ◀─┴─▶ Parsing
                             │
                   4**/5** ◀─┴─▶ preValidation Hook
                                  │
                            415 ◀─┴─▶ Validation
                                        │
                              4**/5** ◀─┴─▶ preHandler Hook
                                              │
                                    4**/5** ◀─┴─▶ User Handler
                                                    │
                                                    └─▶ Reply
                                                          │
                                                4**/5** ◀─┴─▶ preSerialization Hook
                                                                │
                                                                └─▶ onSend Hook
                                                                      │
                                                            4**/5** ◀─┴─▶ Outgoing Response
                                                                            │
                                                                            └─▶ onResponse Hook

Reply Lifecycle

Whenever the user handles the request the result may be:

• in async handler: it returns a payload
• in async handler: it throws an Error
• in sync handler: it sends a payload
• in sync handler: it sends an Error instance

So, when the reply is being submitted, the data flow performed is the following:

                        ★ schema validation Error
                                    │
                                    └─▶ schemaErrorFormatter
                                               │
                          reply sent ◀── JSON ─┴─ Error instance
                                                      │
                                                      │         ★ throw an Error
                     ★ send or return                 │                 │
                            │                         ▼                 │
       reply sent ◀── JSON ─┴─ Error instance ──▶ setErrorHandler ◀─────┘
                                                      │
                                 reply sent ◀── JSON ─┴─ Error instance ──▶ onError Hook
                                                                                │
                                                                                └─▶ reply sent

Note: reply sent means that the JSON payload will be serialized by:

• the reply serialized if set
• or by the serializer compiler when a JSON schema has been set for the returning HTTP status code
• or by the default JSON.stringify function