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Re: [xmlblaster] server sometimes stops matching XPath subscription properly


Thank you for your response. We found the problem and I had meant to write back sooner but then got bogged down.

Yes, we put our own domain specific information in the key. When I was publishing the first message on a topic I was not carful to include all the information we later use in making XPATH subscriptions. Once I realized what was going I was able to resolve it. But I would think that it would be more intuitive for the XPATH to match against what is in the key of the *latest* publication not the first. Does that make sense?

Thanks again for your consistently prompt and helpful responses.


At 11:54 PM 10/28/2004 +0200, you wrote:
Hi Marshall,
what your describe here is really strange and we would certainly need more information. Could you reproduce this behaviour with a simple client ?

Maybe just check one thing first:
Are you changing the key of a topic when publishing a message ? The key should be kept invariant and xpath queries on it always refere to the key passed on the initial publish (when the topic was created).


Marshall Shapiro wrote:
I'm having some really odd xmlBlaster server behavior, and I'm hoping you might have some ideas even though I don't have that much information to give you.
I put my projects own metadata into the xmlBlaster key before publishing. Clients in our system subscribe either to a topic or using XPath (matching our metadata in the key). What we started seeing is that some times XPath subscriptions and queries stop working. Clients subscribed to the corresponding topic still get the messages, but those subscribed to the XPath don't. Stranger still is that I can change the XPath string and get it to match. I give you an example below. These issues happen intermittently, but now we have gotten into this state more often than not. I am using 0.91. It happens on servers running on both WinXP and linux.
Here's an example. The xmlBlaster key that gets published looks something like the following:

 <key oid='ComponentControl' contentMime='text/xml'>

If I set the XPath string to "//product/System/Component/Control", the server says it doesn't match, and client doesn't receive the message. On the other hand if I were to set the XPath string to "//product" it does match and deliver the message.
Please let me know if you have any ideas of what can be going on. If you need any more information let me know.
Thank you.

Michele Laghi
mailto:laghi at swissinfo.org
tel. +46 8 7492952 / mob. +46 70 4103964