Ken Perl writes:
On Fri, Dec 2, 2011 at 8:03 PM, Sam Varshavchik wrote:> Changes to esmtpd require the restart of the esmtp listener, which will kill> existing smtp sessions. But so what. The senders will simply try again. For > any authdaemon change, only authdaemond needs to be restarted, "authdaemond> stop" and "authdaemond start". This won't affect any existing smtp sessions.When a session is terminated by courier, what code and error will return to client to handle such situation, then a client will have chance to retry?
When the daemons are forcibly restarted, there is no explicit error code that gets sent. The processes get killed and the network connection gets closed. The peer gets an indication that the network connection has been terminated, and it'll do what it does, for that situation.
I noticed that courier daemons reboot at regularly time in a day, I guess this will break existing smtp session too, will this has big
No. There's more than one daemon, and the ones that restart themselves are the ones that handle outgoing messages only, and they do it only when there are no deliveries in progress. If it's been too long, no new message deliveries get started, and when all the existing ones are done, the server restarts itself, then resumes all message deliveries.
The processes that handle incoming connections and messages are not persistent, and they do not restart. For incoming messages, SMTP and client IMAP or POP3 connections, a new process gets started for each individual network connection, and the process terminates when the connection is closed.
If you manually stop and restart the entire server, those existing processes will naturally get killed, forcibly, and their connections get dropped. But the regular daemon restarts that you see do not include these processes.
impact in a very busy mail system and there often are lots of smtp sessions, then all kinds of the MUA have to reopen the sessions and transfer the data again? will it possible to implement a gracefully restart?
That's what already happens.
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