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Re: [xmlblaster] server sometimes stops matching XPath subscription properly
Michele Laghi wrote:
I know it sounds a little confusing but the key is a per-topic invariant
(or constant) and XPATH is used to group such topics together, it is not
not intended to group message instances together.
If you want to search on specific message instances, i.e. on information
which is dynamically changing (as the 'classical' JMS approach), then
you have the MIME Filter Plugins which can query client properties
(SQL92) or even the content of the message (regex)
... and the XPath full text search plugin ...
or you can write your
own very specific plugin.
Having these two search alternatives allows us to cover a wide range of
Marshall Shapiro wrote:
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
Thanks again for your consistently prompt and helpful responses.
At 11:54 PM 10/28/2004 +0200, you wrote:
what your describe here is really strange and we would certainly need
more information. Could you reproduce this behaviour with a simple
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.
mailto:laghi at swissinfo.org
tel. +46 8 7492952 / mob. +46 70 4103964