Hi all!

I've bumped into an issue which Dovecot which has me a bit stumped; All of a sudden (ie. no obvious changes made to the config as far as I know) Dovecot seems to never stop 'imap-login' processes. This continues to the point where it will hit the 'process_limit'. For a 50-ish user install the limit was set to 100 but I increased it to 512. The only thing this changes it that Dovecot takes a little longer to hit the limit.

I started having this problem with Dovecot version 2.3.2.1. After which I updated to the latest version of Dovecot (2.3.9.2) to see if that would fix my problem. However I'm still experiencing the same issue.

For a bit of context; We use Dovecot with Open-Xchange where users login via OIDC, get a token and then use that token with Dovecot with the 'oauthbearer' auth method. However users can also login via a username / password combo stored in LDAP for clients that don't support 'oauthbearer' (ie. about all the mail clients ;-). We run Dovecot on SmartOS (ie. Illumos, a Solaris derivative).

Oddly enough 'doveadm' is under the impression there are only 3 users loggedin (when there are 512 imap-login processes). I think 'doveadm who' doesn't show users who are authenticated via an token (oauthbearer) because I only see 3 users and I don't see my own user which is logged in via Open-Xchange by using oauthbearer as auth method. I've anonimized the output but you get the idea:

----8<-------------------- # doveadm who username # proto (pids) (ips) foo1@foo.nl 2 imap (78393 78391) (52.XXX.XXX.XXX) foo2@foo.nl 2 imap (72548 72547) (52.XXX.XXX.XXX) foo3@foo.nl 2 imap (480893 481231) (54.XXX.XXX.XXX 54.XXX.XXX.XXX) ----8<--------------------

I don't know if the above issue is related to my problem but the oauthbearer sessions not showing up seems like a bug? Meanwhile there are 512 Dovecot imap-login processes:

----8<-------------------- # ptree | grep imap-login | wc -l 513 ----8<--------------------

I realise that the 'imap-login' process also works as a IMAP proxy and that it stays alive during the entire session of the client since it handles the TLS part of the connection. However there are nowhere near 512 connections active. As far as I know IMAP doesn't support multiplexing (ie. multiple IMAP sessions in a single TCP connection) so with 512 imap-login proccess I would expect to see a lot more connections then I'm seeing:

----8<-------------------- # netstat -a TCP: IPv4 Local Address Remote Address Swind Send-Q Rwind Recv-Q State

  *.ssh                *.*                 0      0 1048576      0 LISTEN

dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 52.XXX.XXX.XXX.53136 178176 0 1049580 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 52.XXX.XXX.XXX.53188 126848 0 1049580 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 83.XXX.XXX.XXX.64845 132352 0 1048960 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.2.7937 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.3.4983 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.2.34369 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.3.15041 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.2.49044 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.3.6340 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 10.100.2.2.11331 16384 0 1049800 0 CLOSE_WAIT dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 52.XXX.XXX.XXX.49920 94976 0 1049580 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.58569 10.100.3.84.ldap 1049792 0 1049800 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.33749 10.100.3.84.ldap 1049792 0 1049800 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps 52.XXX.XXX.XXX.49966 46464 0 1049580 0 ESTABLISHED *.4190 *.* 0 0 1048576 0 LISTEN *.24 *.* 0 0 1048576 0 LISTEN *.imap2 *.* 0 0 1048576 0 LISTEN *.imaps *.* 0 0 1048576 0 LISTEN dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps ec2-54-210-254-232.compute-1.amazonaws.com.32892 107904 0 1049800 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.ssh 10.101.2.14.59256 64128 35 1049880 0 ESTABLISHED dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl.imaps ec2-54-167-34-137.compute-1.amazonaws.com.3890 549632 0 1049800 0 ESTABLISHED

TCP: IPv6 Local Address Remote Address Swind Send-Q Rwind Recv-Q State If

  *.ssh                             *.*                              0      0 1048576      0 LISTEN

Active UNIX domain sockets Address Type Vnode Conn Local Address Remote Address ----8<--------------------

This is the running Dovecot config:

----8<-------------------- # doveconf -n -c /etc/dovecot/dovecot.conf # 2.3.9.2 (cf2918cac): /etc/dovecot/dovecot.conf # Pigeonhole version 0.5.9 (db4e9a2f) # OS: SunOS 5.11 i86pc # Hostname: dovecot-1.inst.sp-prod.nl1.cns.supersecretcorp.nl auth_failure_delay = 3 secs auth_mechanisms = plain oauthbearer xoauth2 base_dir = /var/run/dovecot/ disable_plaintext_auth = no first_valid_uid = 1000 hostname = imap.supersecretcorp.nl instance_name = dovecot-1 listen = * lmtp_rcpt_check_quota = yes log_path = /dev/stderr mail_attachment_dir = /var/lib/dovecot/attachments mail_attachment_fs = sis-queue /var/lib/dovecot/attachments/queue:posix mail_attachment_hash = %{sha256} mail_attribute_dict = file:~/mdbox/dovecot-attributes mail_gid = vmail mail_home = /var/lib/dovecot/vmail/%d/%n mail_location = mdbox:~/mdbox mail_plugins = " quota notify" mail_server_admin = mailto:it@ask.supersecretcorp.nl mail_temp_dir = /var/lib/dovecot/tmp mail_uid = vmail managesieve_notify_capability = mailto managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date index ihave duplicate mime foreverypart extracttext metric imap_command_fetch_ok { event_name = imap_command_finished filter { name = FETCH tagged_reply_stat = OK } } metric imap_command_list { event_name = imap_command_finished filter { name = LIST tagged_reply_state = OK } } metric imap_command_search { event_name = imap_command_finished filter { name = SEARCH tagged_reply_stat = OK } } metric imap_command_select { event_name = imap_command_finished filter { name = SELECT tagged_reply_state = OK } } metric imap_select_no { event_name = imap_command_finished filter { name = SELECT tagged_reply_state = NO } } metric imap_select_no_notfound { event_name = imap_command_finished filter { name = SELECT tagged_reply = NO*Mailbox doesn't exist:* } } metric storage_http_gets { categories = storage event_name = http_request_finished filter { method = get } } namespace inbox { hidden = no inbox = yes list = yes location = mailbox Drafts { special_use = \Drafts } mailbox Junk { special_use = \Junk } mailbox Sent { special_use = \Sent } mailbox "Sent Messages" { special_use = \Sent } mailbox "Sent objects" { special_use = \Sent } mailbox Spam { special_use = \Junk } mailbox Trash { special_use = \Trash } prefix = separator = / subscriptions = yes type = private } passdb { args = /etc/dovecot/dovecot-oauth2.conf.ext driver = oauth2 mechanisms = oauthbearer xoauth2 } passdb { args = /etc/dovecot/dovecot-ldap-passdb.conf.ext driver = ldap } plugin { push_notification_driver = ox:url=http://#hidden_use-P_to_show#@open-xchange.svc.sp-prod.nl1.cns.supersecretco... user_from_metadata quota = count:User quota quota_rule2 = Trash:storage=+25M quota_vsizes = yes sieve = file:~/sieve;active=~/.dovecot.sieve sieve_max_actions = 32 sieve_max_redirects = 4 sieve_max_script_size = 1M sieve_quota_max_scripts = 500 sieve_quota_max_storage = 10M sieve_vacation_send_from_recipient = yes } postmaster_address = postmaster@supersecretcorp.nl protocols = imap lmtp sieve service auth-worker { user = $default_internal_user } service auth { unix_listener auth-userdb { group = vmail mode = 0770 user = dovecot } user = $default_internal_user } service imap-login { process_limit = 512 process_min_avail = 1 service_count = 1 } service imap { process_limit = 512 } service lmtp { inet_listener lmtp { address = * port = 24 } user = vmail } service managesieve-login { inet_listener sieve { port = 4190 } process_min_avail = 0 service_count = 1 } service managesieve { process_limit = 256 } service stats { unix_listener stats-reader { group = vmail mode = 0660 user = vmail } unix_listener stats-writer { group = vmail mode = 0660 user = vmail } } ssl_client_ca_dir = /opt/local/etc/openssl/certs ssl_dh = # hidden, use -P to show it ssl_min_protocol = TLSv1.2 submission_host = postfix.svc.sp-prod.nl1.cns.supersecretcorp.nl:25 userdb { args = /etc/dovecot/dovecot-ldap-userdb.conf.ext driver = ldap } protocol imap { mail_plugins = " quota notify imap_quota" ssl_cert = </etc/dovecot/pki/imap.supersecretcorp.nl.crt ssl_key = # hidden, use -P to show it } protocol submission { ssl_cert = </etc/dovecot/pki/smtp.supersecretcorp.nl.crt ssl_key = # hidden, use -P to show it } protocol lmtp { mail_plugins = quota sieve notify push_notification postmaster_address = postmaster@supersecretcorp.nl } remote 10.100.2.0/23 { protocol imap { imap_metadata = yes } } ----8<--------------------

Hoping anyone can offer any insights!

Kind regards,

Jasper