[ovirt-devel] Debug vdsm 4.0.0 report error: libvirt: XML-RPC error : Failed to connect socket to '/var/run/libvirt/libvirt-sock': Permission denied

[Milan Zamazal]

"lifuqiong" <lifuqiong at cncloudsec.com> writes:

>          I know it’s a multithreaded application , and debug vdsm is a very
>           difficult job, but without debug, I don’t know which code I should
>           replace or logging, Is there any remote debug solution like ovirt
>           engine?  I found that
>
> I can do remote debug in simple python application , but I didn’t success yet remote debugging vdsm. 

As Michal mentioned, making a breakpoint in Vdsm may break things due to
the stopped execution of the given thread.  Inserting logging messages
to proper places of the code, where you need to get some information
about the runtime state, is typically much simpler and good enough
solution.

If you still want to try more interactive approach and need to access
`vdsm' user, you can change the login shell of `vdsm' account to /bin/sh
and then use `su - vdsm' from root account.  But I don't recommend doing
that on any production system.

>          Now one of our case I want to consider using ovirt as our solution ,
>           we may do little change over ovirt. but as described above, without
>           debug , we can hardly understand vdsm clearly and cannot do correctly
>           code change.
>
> Is there some good advice ?

If you want to study Vdsm runtime execution, read the logs, there's
plenty of information there.  When you are interested in a particular
place in the source code, where you intend to perform the changes, and
some information is missing, simply add your own debugging calls there,
restart Vdsm and watch the log.  I do it all the time and it works. :-)