+++ This bug was initially created as a clone of Bug #495890 +++ autofs5 produce massive number of DNS queries when one nfs server name is associated with many IP adresses. For example when one host has 40 IP adresses associated mounting one autofs directory produce ~160 DNS queries. steps to reproduce : 1) Configure roundrobin DNS so that the autofs client resolve host1.example.com as below . host host1.example.com host1.example.com has address 10.65.6.193 host1.example.com has address 10.65.7.143 host1.example.com has address 10.65.7.225 host1.example.com has address 10.65.6.128 2) nfs server exports /tmp *(ro) on autofs5 client , configure the map such as , /etc/auto.master : /misc /etc/auto.misc /etc/auto.misc : test host1.example.com:/tmp Capture the network packets using tcpdump. On the client cd into /misc/test. Check the number of DNS queries in the captured dump. The table below lists the number of host lookups for varying number of ip addresses. 1 ip : 2 DNS lookup . 2 ip : 14 DNS lookups 3 ip : 20 DNS lookups 4 ip : 26 DNS lookups The problem is also seen with autofs on RHEL 5. Using the following patch fixes the problem. http://ftp.kernel.org/pub/linux/daemons/autofs/v5/autofs-5.0.3-remove-redundant-dns-name-lookups.patch --- Additional comment from ikent on 2009-04-15 09:48:02 EDT --- (In reply to comment #0) > The problem is also seen with autofs on RHEL 5. That's true. > > Using the following patch fixes the problem. > http://ftp.kernel.org/pub/linux/daemons/autofs/v5/autofs-5.0.3-remove-redundant-dns-name-lookups.patch Right, this is one of the few (I think there are probably only two things actually) that haven't been back ported to 5.0.1 in RHEL. Sorry about this, I'll get onto it.
This issue has been fixed in the latest autofs package autofs-5.0.1-0.rc2.125. The autofs RHTS test bugzillas/bz495895 can be used to verify this correction.
I'm afraid I must frop the manual umount recovery patch. Internal regression testing has shown that it causes problems with the autofs submount handling and after trying to fix it for some time without success I have to concede defeat on this, at least for now, as time has run out for RHEL-5.4. At least this doesn't affect the fix for the root cause we identified so, if you would like this further investigated, please log a new bug and I'll revisit it for RHEL-5.5. Sorry, for the inconvenience.
~~ Attention - RHEL 5.4 Beta Released! ~~ RHEL 5.4 Beta has been released! There should be a fix present in the Beta release that addresses this particular request. Please test and report back results here, at your earliest convenience. RHEL 5.4 General Availability release is just around the corner! If you encounter any issues while testing Beta, please describe the issues you have encountered and set the bug into NEED_INFO. If you encounter new issues, please clone this bug to open a new issue and request it be reviewed for inclusion in RHEL 5.4 or a later update, if it is not of urgent severity. Please do not flip the bug status to VERIFIED. Only post your verification results, and if available, update Verified field with the appropriate value. Questions can be posted to this bug or your customer or partner representative.
Release note added. If any revisions are required, please set the "requires_release_notes" flag to "?" and edit the "Release Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Previously, when autofs looked up a host name where when one NFS server name was associated with multiple IP adresses, autofs would repeat the query many times. As a consequence of these multiple queries, the mount would take a long time. Now, redundant queries have been removed, so that autofs performs the mount more quickly.
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2009-1397.html