On 08/26/2013 04:05 AM, 刘莹莹 wrote:

hello: I have a question on imap process: if a client connect to dovecot like foxmail(version 10) , dovecot will start at least 3 imap processes , and these imap processes will online until client logout , if the client not logout ,the imap process will always online. this is similar to the long connection and imap's auto logout timer is not effect in this case. Try to set: verbose_proctitle = yes in your config. This will let you see why each process is open. Also read this http://wiki2.dovecot.org/LoginProcess and make sure you're using "High-performance mode", or basically service_count = 0 for imap-login.

now I have two questions:

1: if there are a large number of users online at the same time ( eg about 30 000 users): so dovecot should shart at least 30 000 * 3 imap processes, if user not logout ,so many processes are online all the time .this is terrible. I dot'n know if there is a solution ?? now I have changed the timeout = 2min and test ,dovecot active disconnected imap process ,but I don't think this is a appropriate option.

A process is kept open on the server only if the client keeps a connection open. This is the client's choice. A non-malicious client does not keep a connection open without a reason. The most common reason is that they are using the IDLE command. In simpler words, every process exists because it's serving an active client, these are not wasted processes that dovecot forgot to kill because the client forgot to log out.

2: I want to know why auto logout timer duration of IMAP protocol must be not less than 30 minuters ??

That was actually discussed here before.. maybe someone wants to comment on that again. But either way. If you actually have 30,000 users, you will not likely have 90,000 processes. Every mail client behaves completely differently. Many do just connect on a fixed interval and disconnect immediately if there is no new mail. Others will keep a certain number of open connections, one for each folder being monitored. Actual memory utilization for each process can be around 500-800 KB, or tens of megabytes for large mailboxes.

My English is not vary good ,I'm sorry but I really want to know the answer . thanks