Wietse Venema:
> Juliana Rodrigueiro:
> > Excerpt of maillog version > 2.11.1:
> > Mar 27 14:46:50 localdomain postfix/lmtp[24750]: 6CEFF61:
> > to=<d...@localdomain.com>, orig_to=<dst@localhost>,
> > relay=localdomain.com[/var/
> > imap/socket/lmtp], delay=0.02, delays=0.01/0/0.01/0, dsn=2.1.5, status=sent
> > (250 2.1.5 Ok SESSIONID=<localdomain.com-24421-1553694410-1>)
> > Mar 27 14:46:50 localdomain postfix/lmtp[24752]: 6E8CE63:
> > to=<d...@localdomain.com>, orig_to=<dst@localhost>,
> > relay=localdomain.com[/var/
> > imap/socket/lmtp], delay=0.02, delays=0/0/0.01/0.01, dsn=2.1.5, status=sent
> > (250 2.1.5 Ok SESSIONID=<localdomain.com-24753-1553694410-1>)
> > Mar 27 14:46:50 localdomain postfix/qmgr[24339]: 6E8CE63: removed
>
> The a/b/c/d delays logging shows:
> a = time from message arrival to last active queue entry
> b = time from last active queue entry to connection setup
> c = time in connection setup, including DNS, EHLO and STARTTLS
> d = time in message transmission
>
> Here the delays are 0.01s or less.
>
> > Mar 27 14:46:52 localdomain postfix/lmtp[24752]: 764A06A:
> > to=<d...@localdomain.com>, orig_to=<dst@localhost>,
> > relay=localdomain.com[/var/
> > imap/socket/lmtp], delay=2, delays=0/2/0/0, dsn=2.1.5, status=sent (250
> > 2.1.5
> > Ok SESSIONID=<localdomain.com-24757-1553694412-1>)
>
> The message had to wait 2s until a delivery agent became available, for
> reasons that will become clear later.
>
> > Mar 27 14:46:54 localdomain postfix/lmtp[24750]: 778DC61:
> > to=<d...@localdomain.com>, orig_to=<dst@localhost>,
> > relay=localdomain.com[/var/
> > imap/socket/lmtp], delay=4, delays=0.01/2/2/0.02, dsn=2.1.5, status=sent
> > (250
> > 2.1.5 Ok SESSIONID=<localdomain.com-24421-1553694414-1>)
>
> The message had to wait 2s until a delivery agent became available,
> and then it spent 2s in connection setup (including DNS lookup).
>
> > Mar 27 14:46:58 localdomain postfix/lmtp[24750]: 7CFDE72:
> > to=<d...@localdomain.com>, orig_to=<dst@localhost>,
> > relay=localdomain.com[/var/
> > imap/socket/lmtp], delay=8.1, delays=0/6/2/0.02, dsn=2.1.5, status=sent
> > (250
> > 2.1.5 Ok SESSIONID=<localdomain.com-24421-1553694418-1>)
>
> This message had to wait 6s until a delivery agent became available,
> and then it spent 2s in connection setup (including DNS lookup).
>
> There is a clear pattern in here: under load, the LMTP client spends
> 2s in connection setup (including DNS lookup).
>
To get rid of the 2s delays:
/etc/postfix/main.cf:
lmtp_connection_cache_on_demand = no
Please let us know if that helps. Meanwhile we can develop a proper fix.
Wietse
