Re: Asynchonrous and synchronous messages on same channel

Bela Ban wrote:

> Yes:
> - MessageDispatcher has to be prepared to match responses to requests, 
> that's some overhead
> - You want to install a Marshaller if you expect return values, 
> otherwise we use simple&slow Java serialization
> - Since you pass org.jgroups.Messages around, you want to 
> marshal/unmarshal the buffer inside of those messages yourself, 
> otherwise we again use Java serialization
> 
>> The use case I'm thinking of here is casting of unreliable messages to
>> distributed topic peers in JBM, so we can expect a lot of traffic.
> 
> I would not use the MessageDispatcher here,  because you don't need 
> correlation, simple Channel.send() will do I think
> 

Hmmm.. The more I think about, I can see that we certainly don't need to 
wait for responses (i.e. we don't need message dispatcher) when sending 
unreliable messages, but I'm not 100% sure for reliable messages.

When sending a reliable message to a topic, which has multiple 
subscriptions on different nodes, we persist the message if there are 
any durable subscriptions on the sending node, and then the message is 
cast across the group. So we already have the reliability guarantee 
before we cast the message.

If the stack configuration we use can give us a strong enough 
reliability guarantee then i don't think we need to wait for any return 
values to "be sure" the messsage reached the nodes.

There are some use cases where we do need return values - these are when 
sending "control messages" e.g. "a new subscription has been added to a 
topic" and each group member needs to know this.

Thoughts?


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