On 20/07/2026 16:53, MK via dovecot wrote:
[snip]
Hi
it appears to be a bug in dovecot 2.4.x when iterating thousands of users.
See
https://dovecot.org/mailman3/archives/list/[email protected]/message/P5QBZAYXNAMNYHYA3BRLN4J3GUKX26WP/
The fix I posted there did bypass the issue during a test I did. I am
not sure it could be treated as a definitive fix. Another workaround is
to iterate outside dovecot.
John
Hi,
did you get a feedback from someone of the dovecot developer? Since your
request is 4 month ago.
So this sounds like my used workarround seem to be the best we can do at the
moment, as Philip did the same.
Do you have experiences if this works with about 40k users or more too?
(doveadm user '*', cache this and then execute doveadm -u for each user)
Oliver
__________
Hi Oliver
so far I haven't seen any follow up from the development team.
It's bad that no one is taking care of it.
I guess it is not one of the high priority issues at the moment.
In my experience doveadm user '*' also runs into the same trouble for
large numbers of users. I got issues with even 20K users on 2.4.x.
At the moment I'm using it for ~ 4400 user and have no problems. I'm curious to
see how it works with 40k users.
Where the users are in a mysql database, you could query the db directly
to get the usernames and then execute doveadm -u for each user.
Sure, that's an option if the doveadm iterate did not work for that mutch user.
Thanks
Oliver
Hi all
this is a revised fix. This looks like the minimal fix. The alternative
is to refactor the auth-master-connection code to make it compatible
with the 2.4 throttling logic. Setting output_throttle_size to zero will
then just use the same throttling mechanism as there was in 2.3.21,
which is still present in 2.4 for this code path. The problem arises
when both mechanisms are active.
John
diff -u dovecot-2.4.4/src/auth/auth-master-connection.c.orig
dovecot-2.4.4/src/auth/auth-master-connection.c
--- dovecot-2.4.4/src/auth/auth-master-connection.c.orig 2026-07-20
22:55:09.153747336 +0200
+++ dovecot-2.4.4/src/auth/auth-master-connection.c 2026-07-20
22:55:32.423163048 +0200
@@ -740,7 +740,7 @@
.dont_send_version = TRUE,
.input_max_size = MAX_INBUF_SIZE,
.output_max_size = SIZE_MAX,
- .output_throttle_size = MAX_OUTBUF_SIZE,
+ .output_throttle_size = 0,
};
static int
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