[Dovecot] dovecot-auth: Too many open files

All,

[version: dovecot-0.99.11-4.EL4.src.rpm]

We recently experienced an issue that prevented all new IMAP logins from occurring. Although it appears that it was due to running out of available system file descriptors, I'm still not sure what the true root cause was as I can't replicate the same error in our test environment. The system file descriptor max was set at (per cat /proc/sys/fs/file-nr) 380081 , and we're averaging around 7,000 in use. It appears that the main issue was dovecot-auth, so does this appear to fall in line with the known PAM bug in this version?

Auth config: auth_userdb = passwd auth_passdb = pam

Checked maillogs (cleansed):

Oct 16 11:48:05 host dovecot-auth: PAM: pipe() failed: Too many open files Oct 16 04:48:06 host imap-login: Disconnected [::ffff:] Oct 16 11:48:11 host dovecot-auth: PAM: pipe() failed: Too many open files Oct 16 04:48:11 host imap-login: Aborted login [::ffff:] Oct 16 04:48:11 host dovecot-auth: PAM unable to dlopen(/lib/security/pam_nologin.so) Oct 16 04:48:11 host dovecot-auth: PAM [dlerror: /lib/security/pam_nologin.so: cannot open shared object file: Too many open files] Oct 16 04:48:11 host dovecot-auth: PAM adding faulty module: /lib/security/pam_nologin.so Oct 16 04:48:11 host dovecot-auth: PAM unable to dlopen(/lib/security/pam_stack.so) Oct 16 04:48:11 host dovecot-auth: PAM [dlerror: /lib/security/pam_stack.so: cannot open shared object file: Too many open files]

So, during the event I performed an strace against the dovecot-auth process and noticed the following error as well:

accept(3, 0xbfe05a50, [2]) = -1 EMFILE (Too many open files) gettimeofday({1192538310, 41972}, NULL) = 0 poll([{fd=3, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL, revents=POLLIN}, {fd=0, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=18, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=10, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=7, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=23, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=8, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=11, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=12, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=13, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=14, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=19, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=16, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=17, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=6, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=15, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=20, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=21, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=9, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=22, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=24, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=25, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=26, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=27, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=28, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=34, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=33, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=29, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=37, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=30, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=31, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, {fd=41, events=POLLIN|POLLPRI|POLLERR|POLLHUP|POLLNVAL}, ...], 1020, 1585) = 1 gettimeofday({1192538310, 99354}, {480, 0}) = 0

Then I checked for the current network connections:

netstat | grep imap | wc -l 42

Then used lsof to check for open files:

while true ; do lsof | awk '{ print $3 }' | wc -l ; sleep 4 ; done 21728 21668 (restarted dovecot) 1838 1953 1864 2066 2018 2020 2036 2189 2661 2558 2490 (cont @2,000)

Thanks!

Joe Allesi