[xmlblaster-devel] Reconnected xml-rpc callbacks result in duplicate messages

["Brad Clements" <bkc at murkworks.com>]

I've been googling for an answer to this problem, and I'm wondering what's the best 
way to handle this.

I'm using Python and pyBlaster.py to subscribe an xml-rpc server for callbacks.

My xml-rpc server keeps track of pings from the server, and if it doesn't get any for a 
while it will re-login and re-subscribe to one key.

Also, I'm running my server under DaemonTools, so if it dies, daemontools will restart 
it.

It seems that if my server gets restarted, xml-blaster sees it as a new login (but with the 
same callback information).  It then sends two messages where I expect only one.

And, if I restart my server again, then I'll get 3 messages and so on.

I know this is a hard problem for xmlblaster to deal with, especially since I can 
subscribe on behalf of another callback listener, so how's xmlblaster supposed to know 
what to do? 

xmlblaster thinks my server is still logged in (because the client doesn't get the chance 
to logout in this particular case), and the client subscribes to the same key every time.

So, there's two things I need to do:

1. stop multiple duplicate messages 

I've been going through the reference guide, and finding a complete list of QoS 
parameters is hard.

I know I whined about this last year (sorry), but it sure would be nice to have a 
complete QoS list on one page in the docs.

And, having Docs not in a frame would make it easier to bookmark.

Anyway, I found

qos.subscribe.multiSubscribe

and

qos.subscribe.duplicateUpdates

Which of these is better to use in my situation? I only ever want one copy of any single 
message. I think multiSubscribe=false is the better choice, but neither option mentions 
the other one and under what conditions I'd pick one over the other.


2. Cleanup the old logins to avoid resource exhaustion 

my server logs in, subscribes and makes no further requests on the client connection. 
So, it's sessionTimeout = 0

I login with the same userid every time. Is there any way I can say "hey, only one login 
allowed at a time and each new login will logout the previous instance and clear it's 
callback". ?

Ah, looks like <session timeout="0" clearSessions="true" />  is what I want here.

Yes?









-- 
Brad Clements,                bkc at murkworks.com   (315)268-1000
http://www.murkworks.com                          (315)268-9812 Fax
http://www.wecanstopspam.org/                   AOL-IM: BKClements