Uncaught Errors

    Given that it is not possible to process all uncaught errors sensibly, the best way to deal with them is to crash.

    Catching Errors In Promises

    In Node.js, unhandled promise rejections (that is, without a handler) can also cause memory and file descriptor leaks. While unhandledRejection is deprecated in Node.js, unhandled rejections will not throw, and still potentially leak. You should use a module like make-promises-safe to ensure unhandled rejections always throw.

    If you are using promises, you should attach a .catch() handler synchronously.

    Fastify follows an all-or-nothing approach and aims to be lean and optimal as much as possible. The developer is responsible for making sure that the errors are handled properly.

    Errors In Input Data

    Most errors are a result of unexpected input data, so we recommend validating your input data against a JSON schema.

    Catching Uncaught Errors In Fastify

    Fastify tries to catch as many uncaught errors as it can without hindering performance. This includes:

    1. synchronous routes, e.g. app.get('/', () => { throw new Error('kaboom') })
    2. async routes, e.g. app.get('/', async () => { throw new Error('kaboom') })

    The error in both cases will be caught safely and routed to Fastify’s default error handler for a generic 500 Internal Server Error response.

    To customize this behavior you should use setErrorHandler.

    From the :

    If you have defined a custom error handler for using setErrorHandler the error will be routed there. otherwise, it will be routed to Fastify’s generic error handler.

    Some things to consider in your custom error handler:

      • objects are serialized, triggering the preSerialization lifecycle hook if you have one defined
      • strings, buffers, and streams are sent to the client, with appropriate headers (no serialization)

    • You can throw a new error in your custom error handler

      • errors (new error or the received error parameter re-thrown) - will trigger the onError lifecycle hook and send the error to the user

    FST_ERR_BAD_URL

    The router received an invalid url.

    FST_ERR_CTP_ALREADY_PRESENT

    The parser for this content type was already registered.

    FST_ERR_CTP_BODY_TOO_LARGE

    The request body is larger than the provided limit.

    This setting can be defined in the Fastify server instance:

    FST_ERR_CTP_EMPTY_TYPE

    The content type cannot be an empty string.

    FST_ERR_CTP_INVALID_CONTENT_LENGTH

    Request body size did not match Content-Length.

    FST_ERR_CTP_INVALID_HANDLER

    An invalid handler was passed for the content type.

    FST_ERR_CTP_INVALID_MEDIA_TYPE

    The received media type is not supported (i.e. there is no suitable Content-Type parser for it).

    FST_ERR_CTP_INVALID_PARSE_TYPE

    The provided parse type is not supported. Accepted values are string or buffer.

    FST_ERR_CTP_INVALID_TYPE

    The should be a string.

    FST_ERR_DEC_ALREADY_PRESENT

    A decorator with the same name is already registered.

    FST_ERR_DEC_MISSING_DEPENDENCY

    FST_ERR_HOOK_INVALID_HANDLER

    The hook callback must be a function.

    FST_ERR_HOOK_INVALID_TYPE

    The hook name must be a string.

    FST_ERR_LOG_INVALID_DESTINATION

    The logger accepts either a 'stream' or a 'file' as the destination.

    FST_ERR_PROMISE_NOT_FULFILLED

    A promise may not be fulfilled with ‘undefined’ when statusCode is not 204.

    FST_ERR_REP_ALREADY_SENT

    A response was already sent.

    FST_ERR_REP_INVALID_PAYLOAD_TYPE

    Reply payload can be either a string or a Buffer.

    FST_ERR_SCH_ALREADY_PRESENT

    A schema with the same $id already exists.

    FST_ERR_SCH_MISSING_ID

    The schema provided does not have $id property.

    FST_ERR_SCH_SERIALIZATION_BUILD

    The JSON schema provided for serialization of a route response is not valid.

    FST_ERR_SCH_VALIDATION_BUILD

    The JSON schema provided for validation to a route is not valid.

    FST_ERR_SEND_INSIDE_ONERR

    You cannot use send inside the onError hook.

    FST_ERR_SEND_UNDEFINED_ERR

    Undefined error has occurred.