[OpenAFS] Cache Consistency problem

[Kağan Coşkun]

I have inspected the afs logs. Our problems seem to be broken callbacks.
Possibly this is due to a network problem but do you have any idea that AFS 
may somehow cause it.

Kaan

Fri Dec 20 17:19:21 2002 CB: new identity for host 194.27.149.175:2424, 
deleting
Fri Dec 20 17:31:25 2002 VAttachVolume: Error reading diskDataHandle vol 
header /vicepb//V0536871635.vol; error=101
Fri Dec 20 17:31:25 2002 VAttachVolume: Error attaching volume 
/vicepb//V0536871635.vol; volume needs salvage; error=101
Fri Dec 20 17:41:15 2002 CB: RCallBackConnectBack (host.c) failed for host 
194.27.149.175:36064
Fri Dec 20 17:47:12 2002 CB: RCallBackConnectBack (host.c) failed for host 
194.27.149.159:12960
Fri Dec 20 17:53:08 2002 CB: RCallBackConnectBack (host.c) failed for host 
194.27.149.175:36175
Fri Dec 20 17:54:04 2002 CB: RCallBackConnectBack (host.c) failed for host 
194.27.149.38:51062
Fri Dec 20 18:00:00 2002 CB: RCallBackConnectBack (host.c) failed for host 
194.27.149.175:33612
Fri Dec 20 18:01:28 2002 Host 194.27.149.175:2424 used to support WhoAreYou, 
deleting.
Fri Dec 20 18:03:34 2002 CB: new identity for host 194.27.149.175:2424, 
deleting



>Kağan Coşkun wrote:
>
> > Hi All,
> >
> > We are having some cache consistency problems. Sometimes the afs
> > client on our web server does not represent the actual files on the
> > some volumes. That is when someone uploads a new file to his directory
> > the file is not noticed on the client side. The volume is a read/write
> > volume. And the problem can be overcomed by creating a file on the
> > volume using the client and also flush commands work too.
>
>
>AFS (and OpenAFS) provides open/close consistency, not read/write 
>consistency.  After a file is written and closed, a new open() on any 
>client will see the fresh data.  The mechanism in use here is the callback 
>that Paul Blackburn mentioned.  The problem is likely that the web server 
>is caching the opens on the files that it is serving, so it is not seeing 
>(serving) the fresh data.  If the web server shares a client cache with the 
>updater, they both will see the same data, as you noticed.  So basically 
>the web server is keeping a cache of open files that is overriding the 
>usual AFS mechanism for automatically noticing the fresh data.  By 
>contrast, DCE/DFS provides read/write consistency, so after a write() 
>completes, a read() on any client retrieves fresh data.
>
>		Craig


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