[jira] Resolved: (QPID-750) MessageFlow needs sensible defaults, defined constants

["Gordon Sim (JIRA)" <qp...@incubator.apache.org>]

     [ https://issues.apache.org/jira/browse/QPID-750?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gordon Sim resolved QPID-750.
-----------------------------

       Resolution: Fixed
    Fix Version/s: M3

By using the SubscriptionManager explicit allocation of credit etc can be delegated to a utility class. There are also now constants for the magic numbers.

> MessageFlow needs sensible defaults, defined constants
> ------------------------------------------------------
>
>                 Key: QPID-750
>                 URL: https://issues.apache.org/jira/browse/QPID-750
>             Project: Qpid
>          Issue Type: Improvement
>          Components: C++ Client
>            Reporter: Jonathan Robie
>             Fix For: M3
>
>
> Currently, the C++ client must explicitly allocate credit with messageFlow to receive messages, e.g. 
>      session.messageSubscribe(arg::queue="message_queue", arg::destination="listener_destination");
>      session.messageFlow(arg::destination="listener_destination", arg::unit=0, arg::value=1);//messages ### Define a constant?
>      session.messageFlow(arg::destination="listener_destination", arg::unit=1, arg::value=0xFFFFFFFF);//bytes ###### Define a constant?
> This complicates introductory examples and simple programs. It would be helpful to have a sensible default message flow that is used if the user does not explicitly allocate credit. (I am guessing that it's unlikely that someone would want to subscribe to a queue and not receive messages, so we don't have to worry about this case.)
> Even when explicit control over the number and size of messages received is important, there are no defined constants to make it clear what the above calls mean. How is the programmer supposed to know that arg::unit=0 in the second parameter means setting the number of messages to receive? Defined constants would make this code much more readable.
> What guidelines should we give users for the settings of message flow parameters in real programs?
> Jonathan

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