FailoverException is used to indicate that a synchronous request has failed to receive the reply that it is waiting for because the fail-over process has been started whilst it was waiting for its reply. Synchronous methods generally raise this exception to indicate that they must be re-tried once the fail-over process has completed.
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| Used to indicate failure of a synchronous request due to fail-over. |
@todo This exception is created and passed as an argument to a method, rather than thrown. The exception is beingused to represent an event, passed out to other threads. Use of exceptions as arguments rather than as exceptions is extremly confusing. Ideally use a condition or set a flag and check it instead. This exceptions-as-events pattern seems to be in a similar style to Mina code, which is not pretty, but potentially acceptable for that reason. We have the option of extending the mina model to add more events to it, that is, anything that is interested in handling failover as an event occurs below the main amq event handler, which knows the specific interface of the qpid handlers, which can pass this down as an explicit event, without it being an exception. Add failover method to BlockingMethodFrameListener, have it set a flag or interrupt the waiting thread, which then creates and raises this exception.