Re: [Sandesha2] Acknowledging policy

[Aleksander Slominski]

hi, my comments below. Chamikara Jayalath wrote: ----- Original Message ----- From: Chamikara Jayalath To: sandesha-dev@ws.apache.org Sent: Friday, January 06, 2006 3:06 AM Subject: [Sandesha2] Acknowledging policy Hi All, It seems like we need to do some adjustments to our acknowledging policy. Currently acknowledging incoming application messages is done by the SandeshaInHandler. So acknowledging happens before the message is actually delivered to the service.   >>But the message is received by the RMEndpoint and that means we should acknowledge. But it seems like we can provide a better quality reliability by not acknowledging till we actually invoke the service. This way we can guarantee the delivering of the message to the service even in the in-memory case. (I.e. if the client receive an ack he can be sure that the service got actually invoked).   >>Yes, but the problem is once the message is received by the RMEndpoint it is RMEndpoints responsibility to invoke the web service. So what we want >>is to improve the reliability of the RMEndpoint. >>IMHO we should not expect the initial sender to wait till the web service gets invoked for an acknowledgment. >>Consider a scenario where we have 3 messages and the RMEndpoint manager in the destination receive 2 and 3 but not 1. We use INORDER >>invocation. Now we will not acknowledge for any of the messages since we did not receive message 1. This is not correct, because then the >>RMEndpoint manager in the client side will keep on sending all the 3 messages again and again. yes, But if the server sends the messages and fail before he actually invoke the service, the client will proceed believing that the service got actually invoked. It is not important weather the message got lost in the wire, or it got lost within the server, the result is the same (the service did not get invoked). So the result is equal to acknowledging a message the server did not receive. But performance wise what you say is very correct. If the server consume a long time to invoke the service, the client will also have to wait a long time for an acknowledgement. i am not sure but it looks to me that those are two different levels of reliability: reliable *message* delivery and reliable *service invocation*. the former is what i though WS-RM is for and the latter is not supported in WS-RM unless some special QoS (Policy?) is used? i think that in case of in-memory storage not much can be done for reliability but ask user to buy UPS :) IMHO the in-memory storage should be not a default in Sandesha2 as it does not meet requirements of WS-RM instead some persistent storage should be a default one - maybe just using text files to store message (as even embedded RDBMS may be overkill for simple installations)? thanks, alek -- The best way to predict the future is to invent it - Alan Kay