[Dovecot] dovecot-imapd eating 100% cpu every once in a while

Sat Dec 7 05:11:56 EET 2013

Hello,

About once or twice a week, dovecot's imap-login process on my system
seems gets out of control, eating 100% CPU for about 2 hours. Afterwards
everything seems to go back to normal.

I am using Dovecot 2.1.7 on a 64 bit Debian wheezy system.

When running gdb on the process in this stage, I get the following
traceback:

#0  0x00007fcba50c5a90 in read () from /lib/x86_64-linux-gnu/libc.so.6
#1  0x00007fcba4aa01aa in ?? () from /usr/lib/x86_64-linux-gnu/libcrypto.so.1.0.0
#2  0x00007fcba4a9df09 in BIO_read () from /usr/lib/x86_64-linux-gnu/libcrypto.so.1.0.0
#3  0x00007fcba4dbac8c in ?? () from /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0
#4  0x00007fcba4dbbe75 in ?? () from /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0
#5  0x00007fcba4dbd8d0 in ?? () from /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0
#6  0x00007fcba4dad07a in ?? () from /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0
#7  0x00007fcba4db143b in ?? () from /usr/lib/x86_64-linux-gnu/libssl.so.1.0.0
#8  0x00007fcba5622b61 in ssl_handshake (proxy=0x7fcba7870bb0) at ssl-proxy-openssl.c:465
#9  ssl_step (proxy=0x7fcba7870bb0) at ssl-proxy-openssl.c:528
#10 0x00007fcba53d2016 in io_loop_call_io (io=0x7fcba786fc80) at ioloop.c:379
#11 0x00007fcba53d2cc7 in io_loop_handler_run (ioloop=ioloop at entry=0x7fcba778c6e0)
    at ioloop-epoll.c:213
#12 0x00007fcba53d1a28 in io_loop_run (ioloop=0x7fcba778c6e0) at ioloop.c:398
#13 0x00007fcba53be483 in master_service_run (service=0x7fcba778c590, 
    callback=callback at entry=0x7fcba5620100 <client_connected>) at master-service.c:544
#14 0x00007fcba562079e in login_binary_run (binary=<optimized out>, argc=1, argv=0x7fcba778c370)
    at main.c:406
#15 0x00007fcba5015ead in __libc_start_main () from /lib/x86_64-linux-gnu/libc.so.6
#16 0x00007fcba5a52b2d in _start ()

strace -tt says:

16:14:19.693378 gettimeofday({1381421659, 693415}, NULL) = 0
16:14:19.693490 time(NULL)              = 1381421659
16:14:19.693588 read(18, 0x7fcba7876a43, 5) = -1 EAGAIN (Resource temporarily unavailable)
16:14:19.693688 epoll_wait(14, {{EPOLLOUT, {u32=2810463600, u64=140512665552240}}}, 10, 4294967295) = 1
16:14:19.693796 gettimeofday({1381421659, 693823}, NULL) = 0
16:14:19.693890 time(NULL)              = 1381421659
16:14:19.693984 read(18, 0x7fcba7876a43, 5) = -1 EAGAIN (Resource temporarily unavailable)
16:14:19.694084 epoll_wait(14, {{EPOLLOUT, {u32=2810463600, u64=140512665552240}}}, 10, 4294967295) = 1
16:14:19.694177 gettimeofday({1381421659, 694203}, NULL) = 0
16:14:19.694269 time(NULL)              = 1381421659
16:14:19.694399 read(18, 0x7fcba7876a43, 5) = -1 EAGAIN (Resource temporarily unavailable)
16:14:19.694563 epoll_wait(14, {{EPOLLOUT, {u32=2810463600, u64=140512665552240}}}, 10, 4294967295) = 1
16:14:19.694706 gettimeofday({1381421659, 694757}, NULL) = 0
16:14:19.694849 time(NULL)              = 1381421659
16:14:19.694976 read(18, 0x7fcba7876a43, 5) = -1 EAGAIN (Resource temporarily unavailable)
16:14:19.695091 epoll_wait(14, {{EPOLLOUT, {u32=2810463600, u64=140512665552240}}}, 10, 4294967295) = 1
16:14:19.695201 gettimeofday({1381421659, 695230}, NULL) = 0
16:14:19.695300 time(NULL)              = 1381421659
16:14:19.695420 read(18, 0x7fcba7876a43, 5) = -1 EAGAIN (Resource temporarily unavailable)
16:14:19.695555 epoll_wait(14,  <unfinished ...>

dovecot -n output is:

# 2.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 3.2.0-4-amd64 x86_64 Debian 7.2 ext3
first_valid_uid = 8
last_valid_uid = 8
mail_access_groups = spamd-clients
mail_gid = mail
mail_location = mdbox:/var/spool/mail/%n/mdbox
mail_plugins = fts quota fts_lucene
mail_uid = mail
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 ihave
namespace inbox {
  inbox = yes
  location = 
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Spam {
    special_use = \Junk
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix = 
}
passdb {
  args = scheme=SHA512-CRYPT username_format=%n /etc/dovecot/users
  driver = passwd-file
}
plugin {
  antispam_backend = pipe
  antispam_pipe_program = /usr/local/bin/spamc_wrapper
  antispam_pipe_program_notspam_args = -L;ham
  antispam_pipe_program_spam_args = -L;spam
  antispam_spam = Spam
  antispam_trash = Trash;Papierkorb
  fts = lucene
  fts_lucene = whitespace_chars=@.
  quota = dict:User quota::file:%h/quota
  quota_rule = *:storage=1G
  quota_rule2 = Trash:storage=+100M
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
}
protocols = " imap lmtp sieve"
service auth {
  unix_listener auth-client {
    mode = 0600
    user = Debian-exim
  }
}
service lmtp {
  inet_listener lmtp {
    address = 127.0.0.1
    port = 2003
  }
}
service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
  process_min_avail = 0
  service_count = 1
}
ssl_cert = </etc/dovecot/dovecot.pem
ssl_key = </etc/dovecot/private/dovecot.pem
userdb {
  args = username_format=%n /etc/dovecot/users
  driver = passwd-file
  override_fields = home=/var/spool/mail/%n
}
protocol lmtp {
  mail_plugins = fts quota fts_lucene sieve
}
protocol lda {
  mail_plugins = fts quota fts_lucene sieve
}
protocol imap {
  mail_max_userip_connections = 50
  mail_plugins = fts quota fts_lucene imap_quota antispam
}

Is this a bug in dovecot, or am I doing something wrong? Is there
something I can do to debug this further?

Best,
Nikolaus

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