Dug a bit more because we are still seeing this issue after upgrading.
Apparently this error has to do with a high rate of log messages:
Oct 4 16:54:39 f.imapd.sonic.net dovecot: log(30450): Warning: Log connection
fd 34 listen_fd 34 prefix 'imap-postlogin: ' is sending input faster than we
can write
But how do I determine what is doing so much logging? The mail logs on
the system seem fine. This server in particular has had that same
warning for 4 days, with the corresponding log process consuming 100%
cpu. There is no stuck postlogin script spewing to the logs that I can
see.
Quoting Grant Keller (2021-09-30 19:04:02)
> Hello,
>
> As stated in the subject we have been doing a pretty big version
> upgrade. Both new and old are on CentOS 7. For the second time, one of
> our upgraded servers have had the dovecot log process start consuming
> 100% cpu, and the strace output shows it trying to access
> /etc/localtime:
> stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2819, ...}) = 0
> stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2819, ...}) = 0
> stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2819, ...}) = 0
> stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2819, ...}) = 0
> stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2819, ...}) = 0
> stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2819, ...}) = 0
>
> With no other output then that multiple times a second. The process
> itself shows this from ps:
> root 76106 8.3 0.0 15384 6532 ? R Sep29 140:21 dovecot/log
> [service too fast: 34/34/imap-postlogin: ]
> As a part of this upgrade we also modified our postlogin script to
> include an index location for each user, so I am not sure if this is
> related to that change or a change in the logging service. Any help
> tracking this down is appreciated.
>
> # OS: Linux 3.10.0-1160.42.2.el7.x86_64 x86_64 CentOS Linux release 7.9.2009
> (Core)
> # Hostname: d.lab.imapd.sonic.net
> auth_failure_delay = 0
> auth_master_user_separator = *
> auth_username_format = %Ln
> auth_verbose = yes
> auth_verbose_passwords = sha1
> auth_worker_max_count = 64
> default_client_limit = 10000
> listen = *
> login_log_format_elements = user=<%u> session=%{session} method=%m rip=%r
> lip=%l mpid=%e %c
> login_trusted_networks = 64.142.18.0/24 64.142.111.71/32 64.142.111.37/32
> 76.191.254.238/32 64.142.111.79/32 64.142.111.34/32 157.131.224.152/32
> 157.131.224.153/32 184.23.168.75/32 184.23.168.76/32
> mail_fsync = always
> mail_log_prefix = "%s(%u): session=%{session} "
> mail_plugins = zlib
> maildir_very_dirty_syncs = yes
> mmap_disable = yes
> passdb {
> args = /etc/dovecot/master-users
> driver = passwd-file
> master = yes
> }
> passdb {
> args = imap
> driver = pam
> }
> plugin {
> lazy_expunge = DELETED_MESSAGES.
> mail_log_events = delete expunge flag_change
> mail_log_fields = uid box msgid from flags size
> mwi_update_debug = no
> mwi_update_events = flag_change delete undelete expunge copy save
> mwi_update_hosts = 76.191.249.68 76.191.255.180
> mwi_update_master_user = _mwi-master
> mwi_update_port = 6472
> mwi_update_watch_folder = INBOX.Voicemail
> quota = fs:User quota
> stats_refresh = 30 secs
> stats_track_cmds = yes
> }
> protocols = imap pop3
> service anvil {
> client_limit = 10000
> }
> service auth {
> client_limit = 10000
> vsz_limit = 1 G
> }
> service doveadm {
> inet_listener {
> port = 1842
> }
> unix_listener doveadm-server {
> mode = 0666
> }
> }
> service imap-login {
> inet_listener imap {
> port = 143
> }
> inet_listener imaps {
> port = 993
> ssl = yes
> }
> process_limit = 7000
> process_min_avail = 32
> vsz_limit = 256 M
> }
> service imap-postlogin {
> executable = script-login -d /etc/dovecot/bin/sonic-imap-postlogin
> user = $default_internal_user
> }
> service imap {
> executable = imap imap-postlogin
> process_limit = 7000
> vsz_limit = 2516 M
> }
> service pop3-login {
> inet_listener pop3 {
> port = 110
> }
> inet_listener pop3s {
> port = 995
> ssl = yes
> }
> process_limit = 2000
> process_min_avail = 32
> vsz_limit = 512 M
> }
> service pop3-postlogin {
> executable = script-login -d /etc/dovecot/bin/sonic-pop3-postlogin
> user = $default_internal_user
> }
> service pop3 {
> executable = pop3 pop3-postlogin
> process_limit = 2000
> vsz_limit = 512 M
> }
> shutdown_clients = no
> ssl = no
> ssl_cipher_list = ALL:!LOW:!SSLv2:!EXP:!aNULL
> syslog_facility = local0
> userdb {
> driver = passwd
> }
> verbose_proctitle = yes
> protocol imap {
> imap_id_send = support-url support-email
> imap_max_line_length = 128 k
> mail_max_userip_connections = 20
> mail_plugins = zlib mwi_update mail_log notify imap_zlib
> }
> protocol pop3 {
> mail_plugins = zlib lazy_expunge
> pop3_fast_size_lookups = yes
> pop3_uidl_format = %f
> }
>
>
>
> Grant Keller
> System Operations
> grant.kel...@sonic.com
Grant Keller
System Operations
grant.kel...@sonic.com
