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| <h1 align="center">Fastify</h1> | |
| ## Lifecycle | |
| <a id="lifecycle"></a> | |
| 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 | |
| │ | |
| 400 ◀─┴─▶ Validation | |
| │ | |
| 4**/5** ◀─┴─▶ preHandler Hook | |
| │ | |
| 4**/5** ◀─┴─▶ User Handler | |
| │ | |
| └─▶ Reply | |
| │ | |
| 4**/5** ◀─┴─▶ preSerialization Hook | |
| │ | |
| └─▶ onSend Hook | |
| │ | |
| 4**/5** ◀─┴─▶ Outgoing Response | |
| │ | |
| └─▶ onResponse Hook | |
| ``` | |
| At any point before or during the `User Handler`, `reply.hijack()` can be called | |
| to prevent Fastify from: | |
| - Running all the following hooks and user handler | |
| - Sending the response automatically | |
| NB (*): If `reply.raw` is used to send a response back to the user, `onResponse` | |
| hooks will still be executed | |
| ## Reply Lifecycle | |
| <a id="reply-lifecycle"></a> | |
| 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 | |
| If the reply was hijacked, we skip all the below steps. Otherwise, when it 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](./Server.md#setreplyserializer) if set | |
| - or by the [serializer compiler](./Server.md#setserializercompiler) when a JSON | |
| schema has been set for the returning HTTP status code | |
| - or by the default `JSON.stringify` function | |