Class MessageHandler<TContent>`Abstract`

Base class for message handlers to handle incoming messages from the subscribed queue. *

Type Parameters

TContent

Index

Constructors

Properties

messageType middleware overrides?

Methods

mapError? onMessage onMessageFailure?

Constructors

constructor

new MessageHandler<TContent>(
    messageType: string,
    overrides?: SubscriptionConfig,
    middleware?: OnMessageMiddleware<unknown>[],
): MessageHandler<TContent>
The MessageHandler constructor
Type Parameters
- TContent
Parameters
- messageType: string
  The type of the message which this MessageHandler handles.
- Optionaloverrides: SubscriptionConfig
  Custom adjustments to overwrite Rascal subscription configuration settings.
- middleware: OnMessageMiddleware<unknown>[] = []
  Middleware functions that should be executed for this specific message handler in addition to the global ones.
Returns MessageHandler<TContent>

Properties

`Readonly`messageType

messageType: string

The type of the message which this MessageHandler handles.

`Readonly`middleware

middleware: OnMessageMiddleware<unknown>[] = []

Middleware functions that should be executed for this specific message handler in addition to the global ones.

`Optional` `Readonly`overrides

overrides?: SubscriptionConfig

Custom adjustments to overwrite Rascal subscription configuration settings.

Methods

`Optional`mapError

mapError?(error: unknown): Error
Function to map thrown error of unspecified type to a more human-readable error. Defining this mapping function eliminates the need to wrap onMessage contents into an explicit try-catch block.
Parameters
- error: unknown
Returns Error

`Abstract`onMessage

onMessage(
    payload: TContent,
    message: MessageInfo<TContent>,
    ackOrNack: AckOrNack,
): Promise<void>
Main message handling function.
Parameters
- payload: TContent
  non-binary message payload (usually a json)
- message: MessageInfo<TContent>
  message with all related message metadata, including message envelope
- ackOrNack: AckOrNack
  acknowledgment or rejection callback that can be called to forcefully complete the message processing.
Returns Promise<void>

`Optional`onMessageFailure

onMessageFailure?(
    payload: TContent,
    message: MessageInfo<TContent>,
    error: Error,
): Promise<void>
Function that will be called after the last retry attempt has failed. Useful for handling errors in an explicit way.
Parameters
- payload: TContent
  non-binary message payload (usually a json)
- message: MessageInfo<TContent>
  message with all related message metadata, including message envelope
- error: Error
  error object that caused message processing to repeatedly fail
Returns Promise<void>