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backend/node_modules/fastify/docs/Reference/Lifecycle.md

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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