[Bug 1089941] Re: rpc.statd causes NFS clients to hang while doing hostname lookups

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: nfs-utils (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1089941

Title:
  rpc.statd causes NFS clients to hang while doing hostname lookups

Status in nfs-utils package in Ubuntu:
  Confirmed

Bug description:
  It appears that rpc.statd from nfs-utils 1.2.5-3ubuntu3.1  will cause
  clients to hang if the resolution of the IP address of a client takes
  several seconds.

  We've recently deployed Ubuntu 12.04 NFS servers and shortly after installation clients were hanging.   At the time, the server was logging messages like:
  Dec 11 20:06:19 nfs-server kernel: [18392.347264] statd: server rpc.statd not responding, timed out
  Dec 11 20:06:19 nfs-server kernel: [18392.347298] lockd: cannot monitor client1
  Dec 11 20:06:54 nfs-server kernel: [18427.364941] statd: server rpc.statd not responding, timed out
  Dec 11 20:06:54 nfs-server kernel: [18427.364972] lockd: cannot monitor client2
  Dec 11 20:07:29 nfs-server kernel: [18462.382624] statd: server rpc.statd not responding, timed out
  Dec 11 20:07:29 nfs-server kernel: [18462.382654] lockd: cannot monitor client3

  I did some stracing of rpc.statd and noticed that it was talking to
  avahi and then hanging for several seconds.  Apparently mdns lookups
  through avahai have a timeout of 5 seconds.   It turns out that a few
  client systems didn't have working reverse DNS and was causing mdns4
  to kick in to attempt to resolve them.  The host without the reverse
  DNS was on a different subnet so it's not surprising that avahi
  couldn't find it.

  At the time our nsswitch.conf had:
  hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4

  After disabling mdns4 and restarting statd the problem did not reoccur.  mdns4_minimal does not exhibit the problem as it filters out most IP addresses:
  hosts:          files mdns4_minimal [NOTFOUND=return] dns

  I suspect that if other directory services (DNS, LDAP, whatever) are
  slow to return results for the hosts table that it will behave in the
  same way.

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