17.2. Exceptions¶

Fast DDS provides a RpcException base class for all the exceptions that can be thrown by the RPC API. It also provides some builtin exceptions, described in the following table:

RPC Builtin Exceptions¶
Exception	Description
`RpcBrokenPipeException`	Exception thrown by the RPC API when the communication with the remote endpoint breaks.
`RpcFeedCancelledException`	Exception thrown by the RPC API when the feed is cancelled.
`RpcTimeoutException`	Exception thrown by the RPC API when an operation times out.

According to the RPC over DDS specification 7.5.2, server-side error conditions are communicated back to the client using error codes, represented by the RemoteExceptionCode_t enumeration. Fast DDS provides a RpcRemoteException subclass that serves as a base class for a set of exceptions that can be thrown by the RPC API when a server-side error condition occurs.

The following table describes the equivalence between error codes and exceptions:

Equivalence between error codes and exceptions¶
Error code	Description	Exception
`REMOTE_EX_UNSUPPORTED`	Operation is valid but it is unsupported (a.k.a. not implemented).	`RemoteUnsupportedError`
`REMOTE_EX_INVALID_ARGUMENT`	The value of a parameter passed has an illegal value.	`RemoteInvalidArgumentError`
`REMOTE_EX_OUT_OF_RESOURCES`	The remote service ran out of resources while processing the request.	`RemoteOutOfResourcesError`
`REMOTE_EX_UNKNOWN_OPERATION`	The operation called is unknown.	`RemoteUnknownOperationError`
`REMOTE_EX_UNKNOWN_EXCEPTION`	A generic, unspecified exception was raised by the service implementation.	`RemoteUnknownExceptionError`

Finally, user can also define custom exceptions in the IDL interface file (see Exceptions), that can be raised by calling an operation method. Fast DDS provides a RpcOperationError subclass that serves as a base class for all these kind of exceptions, which are generated by Fast DDS-Gen tool from the IDL file.