Number of imap process increasing over time

[Shaheen Bakhtiar]

Good morning,

Rebuilt our IMAP server from scratch using Cyrus 2.4.17 on FC22 x86_64. The server is a single process 2.3GH 8 core AMD 64bit with 4G of memory.

Ever since the rebuild we are experience an ever growing number of imapd processes, when we first boot the server we have ~200 using 2.4G of memory. In about 3 to 4 days we have ~1500 imapd processes taking up all available physical memory and all all available swap memory (an additional 4G).

and our logs are filled with messages like:
Aug 14 06:26:01 postoffice kernel: Out of memory: Kill process 15427 (imapd) score 1 or sacrifice child
Aug 14 06:26:01 postoffice kernel: Killed process 15427 (imapd) total-vm:179648kB, anon-rss:7756kB, file-rss:672kB

SNMP Graphs of what’s happening:
https://www.dropbox.com/s/7bnu82h54alrzkz/postoffice%20OOM.png?dl=0

I’m not ruling out a DoS, but the logs from the tcpdump (currently) don’t support that, neither do the SNMP from the router. Checking the IDS, but I find it more than coincidental that this started happening after we upgraded. We had no such issues prior to the upgrade.

Any ideas would be greatly appreciated, 
Shawn