We had an issue today with IMAP clients (Thunderbird, Outlook) having to redownload headers for folders. This issue was eerily close to a MySQL database structure change that shouldn't have affected any related queries, however we did notice an event of user CPU % not being reported via SNMP around the same time for the server. There are no entries in our dovecot error log around the outage.
We're running Dovecot 1.1.13 with MySQL being used for user and password queries, and Maildir for storage on a fibre channel SAN. However, it is possible for some stores to be on an NFS mount (supporting legacy during migration), which is why there is the nfs options in the below config.
I'm wondering if someone could shed light on what could cause this to occur. I imagine it's related to the index cache's, but the lack of any mention in the error logs has me puzzled.
Output of dovecot -n:
# 1.1.13: /usr/local/etc/dovecot.conf # OS: FreeBSD 7.0-RELEASE i386 base_dir: /var/run/dovecot log_path: /var/log/dovecot-error.log info_log_path: /var/log/dovecot-info.log protocols: imap pop3 ssl_disable: yes disable_plaintext_auth: no login_dir: /var/run/dovecot/login login_executable(default): /usr/local/libexec/dovecot/imap-login login_executable(imap): /usr/local/libexec/dovecot/imap-login login_executable(pop3): /usr/local/libexec/dovecot/pop3-login mail_max_userip_connections: 100 first_valid_uid: 89 mail_privileged_group: 89 mail_uid: 89 mail_gid: 89 mail_location: maildir:~/Maildir mail_debug: yes mmap_disable: yes mail_nfs_storage: yes mail_nfs_index: yes lock_method: dotlock mail_executable(default): /usr/local/libexec/dovecot/rawlog /usr/local/libexec/dovecot/imap mail_executable(imap): /usr/local/libexec/dovecot/rawlog /usr/local/libexec/dovecot/imap mail_executable(pop3): /usr/local/libexec/dovecot/pop3 mail_plugin_dir(default): /usr/local/lib/dovecot/imap mail_plugin_dir(imap): /usr/local/lib/dovecot/imap mail_plugin_dir(pop3): /usr/local/lib/dovecot/pop3 pop3_uidl_format(default): %08Xu%08Xv pop3_uidl_format(imap): %08Xu%08Xv pop3_uidl_format(pop3): %f namespace: type: private separator: . prefix: INBOX. inbox: yes list: yes subscriptions: yes auth default: mechanisms: plain apop cache_size: 10240 cache_negative_ttl: 30 username_format: %Lu passdb: driver: sql args: /usr/local/etc/dovecot-sql.conf userdb: driver: sql args: /usr/local/etc/dovecot-sql.conf