[Engine-devel] vdsm checkConnectivity pitfals

[Ayal Baron]

----- Original Message -----
> 
> Hi all,
> 
> VDSM network provisioning api exposes a validity check to know the
> newly
> applied changes works. The actual
> check is comparing the /var/run/vdsm/client.log modified time to the
> time when the check began and repeats
> that check after sleeping 1 seconds for X time (where X is
> connectivityTimeOut)
> 
> def clientSeen(timeout):
>      start = time.time()
>      while timeout >= 0:
>          if os.stat(constants.P_VDSM_CLIENT_LOG).st_mtime > start:
>              return True
>          time.sleep(1)
>          timeout -= 1
>      return False
> 
> Main issues I spot are:
> 1. In case the host is in maintenance, the caller of the API must
> generate traffic, concurrently to running api call,
> and then must join and sync threads to realize when all is done. see
> http://gerrit.ovirt.org/#change,584
> 2. locally calling vdsClient also modifies the client.log  - we can't
> rely on that no one will do that during the call.
> 3. Failure writing to the client log will fail network provisioning!
> 
> All of the above makes it not very reliable as a check and harder to
> call, without posing races, as client.
> 
> Possible alternate solution:
> 1.  We can try to reach the api caller socket in return, maybe use
> http
> code 100 ?
> 2. pass in the API a URL which the VDSM will call. could be a
> health-check servlet or something similar.
> 
> Any toughs?

introduce bi-directional communications over qmf.

> 
> 
> 
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