BUG? File descriptor use in cmd_append (for MULTIAPPEND) results in many open files

Nik Conwell nik at bu.edu
Mon Dec 11 14:38:55 EST 2006

On Dec 11, 2006, at 1:27 PM, Andrew Morgan wrote:

> On Mon, 11 Dec 2006, Nik Conwell wrote:
>> On Dec 11, 2006, at 12:29 PM, Andrew Morgan wrote:
>>> On Mon, 11 Dec 2006, Nik Conwell wrote:
>>>> I'm using the UW mailutil to transfer mailboxes from UW to Cyrus  
>>>> (2.3.7). It uses APPEND, specifically multiappend (single APPEND  
>>>> with multiple messages being appended).  Cyrus-imapd handles  
>>>> this multiappend by creating stage files for each appended  
>>>> message and leaving the file descriptor open.  The problem is  
>>>> that after 240 messages, we run out of file descriptors and so  
>>>> an open() of the next stage file fails with EMFILE.  I updated / 
>>>> etc/cyrus.conf to make the max fds be 1024 (AFAICT kernel MAX)  
>>>> which helped somewhat but not for larger mailboxes with > 1008  
>>>> messages.
>>>> Shouldn't the multiappend/append be closing the FD for each  
>>>> stage file and then reopening it later as it needs it?
>>>> Do people just tweak their kernels to have some insane number of  
>>>> FDs available in order to compensate for this?
>>>> Or, do people not use mailutil and instead use something that  
>>>> issues multiple append commands rather than a single append with  
>>>> multiple e-mails?
>>> We run with a much, much larger number of file descriptors here.   
>>> I've increased the system limit to around 200k (/proc/sys/fs/file- 
>>> max on linux). This is for the day-to-day running of Cyrus, so I  
>>> don't know if you would need a higher limit for running mailutil  
>>> (but I doubt it).
>>> In practice, each of my backends has only used a maximum of  
>>> around 12k file descriptors, but I'd hate to run out!  :)
>> That's for the entire system though, right?  I'm running into a  
>> 1024 limit per process, namely the cyrus imap server process has  
>> all the appended stage files open.  Am I missing something  
>> fundamental here?  (I probably am because I would have figured  
>> people would have run into this issue already...)
>> BTW - my /proc/sys/fs/file-max has 406572.
> Ah, then you just need to up the ulimits in your cyrus init script.  
> Something like:
> # Crank up the limits
> ulimit -n 209702
> ulimit -u 2048
> ulimit -c 102400

That did the trick.  Thanks a lot.

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