[OpenAFS-devel] "Lost contact with file server" problems

Jeffrey Altman jaltman@secure-endpoints.com
Thu, 08 Sep 2005 12:41:52 -0400


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Harald Barth wrote:

>>Examine the capture you took yesterday when things were not working. 
>>Look for the AFS kvno in one of the messages from the client to the server.
>>Since you are using some varient of the Kerberos 5 based tokens, the kvno
>>should always be reported as 213 or 256.   If it is anything else, then the
>>client is confused. 
> 
> 
> Either my snapshot is not good enough or my ethereal driving license is not
> adequate.
> 
> But I see more symptoms that indicate that we may have hunted but not
> completely killed that bug:
> 
> Sep  8 17:05:30 d10n03 kxd[1204]: from fjell.pdc.kth.se(130.237.221.161): lama@NADA.KTH.SE -> lama
> 
> Sep  8 17:05:32 d10n03 kernel: afs: Lost contact with file server 130.237.232.195 in cell pdc.kth.se (all multi-homed ip addresses down for the server)
> Sep  8 17:05:32 d10n03 kernel: afs: Lost contact with file server 130.237.232.195 in cell pdc.kth.se (all multi-homed ip addresses down for the server)
> 
> Sep  8 17:05:35 d10n03 kernel: afs: Tokens for user of AFS id 12020 for cell pdc.kth.se have expired
> 
> Sep  8 17:12:50 d10n03 kernel: afs: file server 130.237.232.195 in cell pdc.kth.se is back up (multi-homed address; other same-host interfaces may still be down
> )
> 
> 1. User logs in which in this case probably means than an expired
>    ticket is used as a token.
> 
> 2. Client complains that the server which has the user's $HOME
>    is all down
> 
> 3. Client discovers that the token has expired
> 
> 4. Some minutes later the client recovers. Problem is: Would a batch
> job try to start between 17:06 and 17:11 it would crash because AFS is
> not available that very moment. 
> 
> So how can I prevent that the server is flagged down because of a
> expired token? Seems to me still like a timing issue - sometimes the
> server is flagged down first (which gives great grief) and sometimes
> the client discovers that this one connection was no big deal and
> nukes the connection first.
> 
> AFS version is 1.3.87 which has patch
> checkservers-set-back-deadtime-correctly-20050804 and I added patch
> rx-propagate-error-20050902 to.
> 
> Roland: And you don't see this any more? In this case: Lucky you.
> 
> Harald.

So the question I then ask is whether or not the determination that the
server is down is being performed using an authenticated or
unauthenticated connection?  Testing for "DOWN" should be performed
using an unauthenticated connection specifically to avoid the problem of
a "bad" token being installed into the client.

Jeffrey Altman


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