This post is part of a series exploring the unique aspects and capabilities of WebSphere Liberty when running on z/OS.
We'll also explore considerations when moving from WebSphere traditional on z/OS to Liberty on z/OS.
To start at the beginning, follow this link to the first post.
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If I had thought of it sooner I would have started accumulating some general best practices or maybe “Dave’s Rules of Liberty” or something like that. If I’d done that, one of them definitely would have been “When making configuration changes, verify you got what you wanted.”
While you can change this behavior (look for OnError in the doc) by default Liberty will tend to detect a configuration error, log it, and muddle on. So if you make some change in server.xml (or something included directly or indirectly) and restart the server, don’t just assume because the server started that it was all fine. You can have random text goo or just an almost-spelled-correctly keyword in a config element and Liberty will just shrug and carry on.
To know that you got what you wanted, there might be messages related to the config thing you changed that will tell you it is now doing the thing you want. For example, if you added a new feature into feature manager you should see it listed in the list of enabled feature message (that we’ll get to one of these weeks).
But you should also be looking for error/warning messages that Liberty was confused by what you asked and decided to just ignore it and….yup…carry on.
The message you’re looking for (mostly) is CWWKG0014E. It will read something like this:
CWWKG0014E: The configuration parser detected an XML syntax error while parsing the root of the configuration and the referenced configuration documents. Error: <text> File: <path> Line: <number> Column: <number>
The <text> will tell you what it didn’t like and the rest of the message should point you to the server.xml or included file and the line/column where it got upset.
So..while you might want to consider changing the OnError setting for your servers, just not having any errors doesn’t necessarily mean you got what you wanted.
I’ll say it again, any time you make a change to your server’s configuration you should verify by looking at the logs that you actually got the change you wanted. Then you can carry on.