Nepomuk Tasks: KActivityManager Crash

  • user warning: Table './drupal_wetnet/wetnet_comments' is marked as crashed and should be repaired query: SELECT COUNT(*) FROM wetnet_comments c WHERE c.nid = 5552 AND c.status = 0 in /srv/www/domains/ on line 991.
  • user warning: Table './drupal_wetnet/wetnet_comments' is marked as crashed and should be repaired query: SELECT c.cid as cid,, c.nid, c.subject, c.comment, c.format, c.timestamp,, c.mail, c.homepage, u.uid, AS registered_name, u.signature, u.signature_format, u.picture,, c.thread, c.status FROM wetnet_comments c INNER JOIN wetnet_users u ON c.uid = u.uid WHERE c.nid = 5552 AND c.status = 0 ORDER BY c.thread DESC LIMIT 0, 50 in /srv/www/domains/ on line 991.
n7ipb's picture

After a little silence during which I was occupied with Eastern and OpenLink related work I bring you news about the second Nepomuk task: the KActivityManager crash.

Ivan Cukic already “fixed” the bug by simply not using Nepomuk but an SQLite backend (at least that is how I understood it, correct me if I am wrong). However, I wanted to fix the root of the original problem.

Soprano provides the communication channel between Nepomuk and its clients. It is based on a very simple custom protocol going through a local socket. So far QLocalSocket, ie. Qt’s implementation was used. The problem with QLocalSocket is that it is a QObject. Thus, it cannot live in two threads at the same time. The hacky solution was to maintain one socket per thread. Sadly that resulted in complicated maintenance code which was impossible to get right. Hence crashes like #269573 or #283451 (basically any crash involving The Soprano::ClientConnection) were never fixed.

A few days ago I finally gave up and decided to get rid of QLocalSocket and replace it with my own implementation. The only problem is that in order to keep Windows compatibility I had to keep the old implementation around by adding quite a lot of #ifdefs.

And now I could use some testers for a Soprano client library that does only create a single connection to the server instead of one per thread. I already pushed the new code into Soprano’s git master. So all you need to do is run KDE on top of that.

Oh, and while at it I finally fixed the problem with re-connecting of clients. So now a restart of Nepomuk will no longer leave the clients with dangling connections, unable to perform queries. That fix, however, is in kdelibs.

Well, the day was long, I am tired, and this blog post feels a little boring. So before in addition to that it gets too long I will stop.

See original: Planet KDE Nepomuk Tasks: KActivityManager Crash