Exceptions
A summary of the exceptions that can be thrown in a program using the CAMEO API:
List of exceptions
| Exception | Where | Description |
|---|---|---|
| ConnectionTimeout | Server.init(), Requester.init(), Subscriber.init(), all functions or methods accessing a remote Server | A timeout occurs in a connection. |
| InitException | Server.init(), Responder.init(), ResponderRouter.init(), Requester.init(), Publisher.init(), Subscriber.init() | Cannot initialize the object. |
| SynchronizationTimeout | Requester.init(), Subscriber.init() | Timeout occurs during the synchronization of objects. |
| InvalidArgumentException | Server.init() | Bad endpoint value. |
| StartException | Server.start() | The application cannot be started. |
| UnregisteredApplicationException | This.init() | Maximum number of running apps reached. |
| KeyAlreadyExistsException | This.Com.storeKeyValue() | Key is already stored for the application. |
| UndefinedKeyException | This.Com.getKeyValue(), App.Com.getKeyValue() | Key does not exist. |
More details on the exceptions
The most common exception is ConnectionTimeout that can occur in any call to a remote Server object. As the process of the requests to a remote Server object should be quick, a ConnectionTimeout should mean that the network was not fast enough or the remote computer is not accessible any more.
However a call to a local Server object may not throw such a ConnectionTimeout exception. That is why a good practice is:
- Set a timeout to remote Server objects.
- Do not set a timeout to local Server objects.
A SynchronizationTimeout exception has a different meaning. It concerns blocking init() calls for the Requester and Subscriber objects. Indeed, a Requester may block indefinitely if the Responder is never ready. In that case, setting a timeout makes the init() call exit.
An InitException exception should be thrown if the underlying communication object cannot be initialized i.e. ZeroMQ sockets.
An InvalidArgumentException happens when the provided endpoint is invalid e.g. "tc://serv:10000" or "tcp://serv:".
The StartException exception occurs when the CAMEO server is unable to start the requested application. It can happen if the program is not accessible or the maximum number of running apps is reached.
The UnregisteredApplicationException exception occurs for an application that is not registered in the CAMEO server and tries to attach to it. If the maximum number of running apps is reached, it cannot attach.
The exceptions KeyAlreadyExistsException and UndefinedKeyException are thrown in the communication objects. These exceptions concern the implementation of a communication object e.g. Requester, Responder, etc.
Notice that a Requester.receive() call does not throw an exception if a timeout occurs. However the object returned is null and Requester.hasTimedout() returns true.