dovecot auth using 100% CPU

[Edward Betts]

Every few days I find that dovecot auth is using all my CPU.

This is from dovecot 2.2.13, I've just upgraded to 2.2.18

strace -r -p 17956 output:

Process 17956 attached
     0.000000 lseek(19, 0, SEEK_CUR)    = -1 ESPIPE (Illegal seek)
     0.000057 getsockname(19, {sa_family=AF_LOCAL, NULL}, [2]) = 0
     0.000043 epoll_ctl(15, EPOLL_CTL_ADD, 19, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP, {u32=850618928, u64=140128453618224}}) = 0
     0.000040 write(19, "VERSION\tauth-worker\t1\t0\nDBHASH\t5"..., 97) = -1 EPIPE (Broken pipe)
     0.000035 --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=17956, si_uid=108} ---
     0.000020 epoll_wait(15, {{EPOLLIN|EPOLLHUP, {u32=850618928, u64=140128453618224}}}, 14, 12614) = 1
     0.000031 read(19, "", 8192)        = 0
     0.000026 epoll_ctl(15, EPOLL_CTL_DEL, 19, 7fff77616870) = 0
     0.000027 close(19)                 = 0
     0.000029 socket(PF_LOCAL, SOCK_STREAM, 0) = 19
     0.000027 fcntl(19, F_GETFL)        = 0x2 (flags O_RDWR)
     0.000028 fcntl(19, F_SETFL, O_RDWR|O_NONBLOCK) = 0
     0.000029 connect(19, {sa_family=AF_LOCAL, sun_path="auth-worker"}, 110) = 0
     0.000033 fstat(19, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
     0.000033 lseek(19, 0, SEEK_CUR)    = -1 ESPIPE (Illegal seek)
     0.000026 getsockname(19, {sa_family=AF_LOCAL, NULL}, [2]) = 0
     0.000030 epoll_ctl(15, EPOLL_CTL_ADD, 19, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP, {u32=850618928, u64=140128453618224}}) = 0
     0.000035 write(19, "VERSION\tauth-worker\t1\t0\nDBHASH\t5"..., 97) = -1 EPIPE (Broken pipe)
     0.000029 --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=17956, si_uid=108} ---
     0.000015 epoll_wait(15, {{EPOLLIN|EPOLLHUP, {u32=850618928, u64=140128453618224}}}, 14, 12614) = 1
     0.000031 read(19, "", 8192)        = 0
     0.000026 epoll_ctl(15, EPOLL_CTL_DEL, 19, 7fff77616870) = 0
     0.000027 close(19)                 = 0
     0.000028 socket(PF_LOCAL, SOCK_STREAM, 0) = 19
     0.000036 fcntl(19, F_GETFL)        = 0x2 (flags O_RDWR)
     0.000026 fcntl(19, F_SETFL, O_RDWR|O_NONBLOCK) = 0
     0.000024 connect(19, {sa_family=AF_LOCAL, sun_path="auth-worker"}, 110) = 0
     0.000034 fstat(19, {st_mode=S_IFSOCK|0777, st_size=0, ...}) = 0
     0.000030 lseek(19, 0, SEEK_CUR)    = -1 ESPIPE (Illegal seek)
     0.000025 getsockname(19, {sa_family=AF_LOCAL, NULL}, [2]) = 0
     0.000031 epoll_ctl(15, EPOLL_CTL_ADD, 19, {EPOLLIN|EPOLLPRI|EPOLLERR|EPOLLHUP, {u32=850618928, u64=140128453618224}}) = 0
     0.000036 write(19, "VERSION\tauth-worker\t1\t0\nDBHASH\t5"..., 97) = -1 EPIPE (Broken pipe)
     0.000030 --- SIGPIPE {si_signo=SIGPIPE, si_code=SI_USER, si_pid=17956, si_uid=108} ---
     0.000016 epoll_wait(15, {{EPOLLIN|EPOLLHUP, {u32=850618928, u64=140128453618224}}}, 14, 12614) = 1
     0.000031 read(19, "", 8192)        = 0
     0.000027 epoll_ctl(15, EPOLL_CTL_DEL, 19, 7fff77616870) = 0
     0.000028 close(19)                 = 0

Any ideas what's wrong? The machine is running Debian.
-- 
Edward.