Re: closing all inactive server connections

[Simon Josefsson <simon@josefsson.org>]

Katsumi Yamaoka <yamaoka@jpl.org> writes:

> Well, I tried looking into the IMAP code although I've never
> used nnimap.  And I found the functions that communicate with
> the server all have the following form:
>
>   (while (and (memq (process-status PROCESS) '(open run))
> 	      (wait-for-a-string-that-the-PROCESS-returns))
>     (accept-process-output PROCESS 1)
>     (sit-for 1))
>
> This can be an infinite loop if the process-status keeps `open'
> or `run' even though the connection has actually died.

Can that happen?  Wouldn't that be an emacs bug?  Shouldn't
process-status return exit or closed if a connect/process has gone away?

> In particular, the `imap-wait-for-tag' function can be the cause of
> the hanging since it sends the LOGOUT command to the dead server and
> waits for the response.  So, I tried modifying it so as to quit in a
> certain time.  The patch to imap.el is below.  Anyway, it needs to be
> reviewed by someone who is skilled in IMAP.  The default value of
> `imap-timeout-seconds' might be too small for slow connections.
>
> --- imap.el~	2007-01-24 07:15:37 +0000
> +++ imap.el	2007-07-31 08:50:30 +0000
> @@ -1182,14 +1182,25 @@
>  			 imap-server auth)))))
>  	imap-state))))
>  
> +(defvar imap-timeout-seconds 1
> +  "*Number of seconds in which `imap-close' gives up working.")

This is a bad idea even for fast servers -- some operations (such as
deleting or renaming a mailabox) can take several minutes.  Gnus
shouldn't assume the server isn't responding in this (and other) cases.

Ted Zlatanov <tzz@lifelogs.com> writes:

> Maybe it should be generalized, however, to an IMAP timeout per (server,
> group name, command) combination (as a regex or a function), so you can
> assign "LOGOUT" a longer timeout with a slower server.  This could also
> be a server tuning parameter for nnimap instead of an imap.el parameter.

Having the timeout be restricted to just LOGOUT seems to make more sense
to me.  If the server doesn't respond to a LOGOUT within a short period
of time, one might as well disconnect.

/Simon