why do attempts to access a nfs v3 filesystem (ro,soft) block the process for minutes at a time? (when the nfs server is down)

[Tom H <tom@limepepper.co.uk>]

(apologies for the cross post from the deprecated list)

Hi all,

I have a web server which serves some content from an nfs filesystem
mounted like so;
nfsserver1:/somemount /var/www/html/somefiles  nfs     rw,soft
             0 0

# mount | grep nfs
nfsserver1:/somemount on /var/www/html/somefiles type nfs
(ro,soft,addr=xx.xx.xx.xx)

According to the documentation, an NFS operation on a soft mount should
wait for a "major timeout" and then report "server not responding" to
syslog and return an error. where a major timeout is after default
retrans=3 retransmissions.

I understand the process to be like this;
call --->0.7 secs --->retransmission--->1.4
secs--->retransmission--->2.8 secs--->server not responding(major timeout)

However it is pretty clear that this is retrying indefinitely (or at 
least many more times that I would like), as the
log files show loads of;
Jul 16 07:56:09 server1 kernel: nfs: server server2 not responding,
timed out
Jul 16 07:57:09 server1 last message repeated 4 times
Jul 16 07:57:09 server1 last message repeated 6 times

and eventually this kills the apache server as all the available
processes are blocked during "retrying indefinitely", until the apache
server is restarted. (restarting the nfs server at this point does not
seem to recover the apache child processes)

So what should my strategy be to stop the failed mount killing apache. I
care more about the apache staying up, as I don't have that much control
over the nfs server..

(also I noticed that it seems to timeout quicker with the mount options
set like (soft, timeo=7, retrans=3) which is unexpected, because they
are supposed to be the default)

Regards and thanks in advance,
T