Async timeout and SCA expiration qualifiers

Answer

When the Service component architecture (SCA) binding is set to asynchronous, the server will create a queue on the application bus. The request and response messages will be put into this queue. When the request message is put into the queue, the message time to live value will be set according to the request expiration qualifier. If the message will not be picked up, a timeout exception will be thrown.

The response qualifier works as follows: when the response reaches the queue, the message time to live value will be set according to the response expiration value. If this value is reached and the requester component has not picked up the message, a timeout exception will be thrown.

The Async timeout property of a Callout primitive specifies the time to wait for a response when performing an asynchronous deferred response invocation. If timeout occurs, the failed terminal is fired.

The Async timeout starts counting when the callout is invoked, while the response expiration only starts when the response is received from the backend.

Both asynchronous reliability qualifiers and the async timeout property can be used to control the timeout. If a callout primitive is implemented, it is recommended to set the request and response expiration values to 0, and use the async timeout feature of the callout primitive to control the timeout.