Agon S. Buchholz wrote:
[ Strange phenomena like: Creating new articles and searching for existing ones causes "deadlocks" without browser timouts or error messages, new articles can only created, if even, by entering the article's name directly in the browser's location bar etc. ]
To close this thread finally, just one closing remark. I'm pretty sure that I've found out what was causing this strange behaviour: It seemed to be caused by an overflowed Job queue. When I checked [[Special:Statistics]], it showed numbers in the range of several hundred thousand jobs, at one site even close to 1,5 mio. jobs.
Even if I don't fully understand what these jobs are, they are related to templates; I'm making heavy use of templates, every article uses at least one, and thus even changing just a couple of templates, embedded in a few hundred pages, seems to multiply this job queue considerably. At least that's what [1] suggestes: "Why the job queue exists: Updating links tables when a template changes".
Thus I ran ./maintenance/runJobs.php for a few days (getting rid of this Jobs definitely takes a lot of time), and now the Job queue is down to 1, and the problems have disappeared completely.
Just for the record: If your MediaWiki doesn't answer as quickly as you are used to, or creating new articles seems to "deadlock", you might want to have a look at the size of your Job queue, especially if you're using lot's of templates.
Regards, -asb