Handling Deadlock

This post is all about handling deadlock and what I did to avoid deadlock. This is the first time I have worked on handling deadlock. I have chosen an issue from fedora-bodhi which was about handling deadlock. The error was ”Deadlock found when trying to get lock; try restarting transaction” which is usually common when it comes to database.

Deadlock is an unwanted situation that arises when a process waits for indefinite time for a resource that is held by another process. So there is some way to avoid deadlock or handle deadlock. The transaction involved with the deadlock can either be rolled back or restarted.

try:
    Perform table transaction
    break
except:
    Catch the error
    Try again to perform table transaction

Lmacken guided me with some hints to handle Bugzilla deadlock. Since it was bugzilla server side issue it was not simple for me to reproduce the bug. But it was quite easy to handle bugzilla server-side deadlock. The deadlock was arising when an user was going to add comment to a bug in Bugzilla. So it was definitely a server side issue but could be handled with some little trick in bodhiLmacken told me to catch the fault triggered by the call of adding comment and try again. It was an xmlrpclib.Fault exception. Thus the technique to handle deadlock is the same as declared above. And I was finally done with my patch. Thanks to Lmacken for helping me to solve the bug and understand the technique :).

Hence I learnt how to handle deadlock and my pull request was merged 🙂

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