c++ early client side termination of SERVER_STREAMING RPC

[osscon...@gmail.com]

Hi,

I am writing a C++ future/promised based interface around the grpc c++ API. Some important details around termination of the streams are not clear to me, even after reading through discussions here and many open/closed issues in the GitHub repository.

Suppose a client calls a SERVER_STREAMING RPC using ClientAsyncReader, ClientContext etc. 

Finish()

Can only be called after cq.Next() returns ok = false for a Read() operation. So the normal sequence could look like:

• Read(), ok =true
• Read(), ok =true
• Read(), ok =true
• Read(), ok = true
• Read(), ok = false // nothing more to read
• Finish(), ok = true // gets RPC status
• Delete ClientAsyncReader and ClientContext

Now suppose the client throws an exception while processing the response returned by the second Read(). From what I understand I have to call ClientContext::TryCancel() and then keep calling Read() until ok = false, then call Finish():

• Read(), ok =true
• Read(), ok =true, exception while applying business logic
• ClientContext::TryCancel()
• Read(), ok =true // could happen from what I understand
• Read(),  false = true
• Finish(), ok = true
• Delete ClientAsyncReader and ClientContext

I have a strong feeling it's required to *always* call Finish() before releasing resources, but I have not found any doc/issue/discussion, which confirms it 100%. Is there any other alternative way to terminate the stream in an orderly fashion?

Patrick

[osscon...@gmail.com]

Assuming I have no uncompleted async operation (like Read()), is it then valid to skip the Read()-Finish() sequence and immediately release the resources?

• Read(), ok =true
• Read(), ok =true, exception while applying business logic
• ClientContext::TryCancel()

• Delete ClientAsyncReader and ClientContext

Patrick