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.. _imap-developer-guidance-replication-examples:
.. Note: This document was converted from the original by Nic Bernstein
(Onlight). Any formatting mistakes are my fault and not the
original author's.
Cyrus IMAP Server: Replication Examples
=======================================
Introduction
------------
The replication system creates a link between two Cyrus mailstores: a
master and a replica system. Both systems can be live mailstores with
active users: here in Cambridge we install systems in pairs.
Typically half of the users will be using each system, and each system
replicates to its partner. In the event of a failover everyone uses the
remaining system in a pair. This is typically safe as the IMAP/POP/SMTP
servers define which of the two systems is the live server for any given
account, and the replica just plays a game of follow my leader.
Occasionally I think about introducing some form of sanity check so that
we have to explicitly issue a command to the remaining backend system as
well as the proxies in the event of a failover.
A short example of replication in action
----------------------------------------
::
Index:
#: Annotation
C: Command issued by client
S: Command issued by server
# Authentication between systems is done using SSH key based authentication:
C: $ ssh -x cyrus-2 /usr/local/cyrus/bin/sync_server
S: * Sync Server v0.0 [EXPERIMENTAL]
# Create new auth_state and ask for all information about given list of
# folders (namely user.dpc22). Returns:
#
# "**" unsolicited response for each mailbox. Returns:
# Folder UniqueID, Name, ACL, UIDlast, timestamp for last seen update.
#
# "*" response for each mail message in folder:
# UID, GUID, flags (other than \Seen state)
C: user_some dpc22 user.dpc22
S: ** 6b98205c796c6c61 user.dpc22 \
S: "dpc22 lrswipcda anonymous 0 " 4151 1062945305
S: * 1 000000000000000000000000 ()
S: * 3697 0101003f4c56b00545000000 ()
S: * 3919 0101003f4c56b04b2900000d ()
S: * 3937 0101003f4c56b0514900001f ()
S: * 4066 0101003f4c56b07422000002 ()
S: * 4089 0101003f4c56b07e56000023 (\answered)
S: * 4118 0101003f4c56b08328000016 ()
S: * 4131 0101003f4c56b084d7000002 ()
S: * 4136 0101003f4c56b087f3000001 ()
S: * 4140 0101003f4c56b08c9d000026 ()
S: OK User_Some finished
# Select a folder to work with
C: select user.dpc22
S: OK 6b98205c796c6c61 4151 1062945305
# Remove message with UID "1" from folder list (message which has been
# sitting in my inbox since January, has no GUID defined)
C: expunge 1
S: OK Expunge Complete
# Set some user flags on message UID "4140"
C: setflags 4140 (hello world)
S: OK Updated flags on 1 messages okay
# Demonstrate that something has changed:
C: status
S: * 3697 0101003f4c56b00545000000 ()
S: * 3919 0101003f4c56b04b2900000d ()
S: * 3937 0101003f4c56b0514900001f ()
S: * 4066 0101003f4c56b07422000002 ()
S: * 4089 0101003f4c56b07e56000023 (\answered)
S: * 4118 0101003f4c56b08328000016 ()
S: * 4131 0101003f4c56b084d7000002 ()
S: * 4136 0101003f4c56b087f3000001 ()
S: * 4140 0101003f4c56b08c9d000026 (hello world)
S: OK 4151
# Now lets correct the damage that we just inflicted:
C: $ replicate -s cyrus-2 -v -v -m user.dpc22
S: MAILBOXES user.dpc22
S: USER_SOME dpc22 user.dpc22
S: SELECT user.dpc22
S: SETFLAGS [1 msgs]
S: UPLOAD [1 msgs]
S: SETSEEN dpc22 ...
S: ENDUSER
C: $ ssh -x cyrus-2 /usr/local/cyrus/bin/sync_server
S: * Sync Server v0.0 [EXPERIMENTAL]
S: user_some dpc22 user.dpc22
S: ** 6b98205c796c6c61 user.dpc22 \
S: "dpc22 lrswipcda anonymous 0 " 4156 1062968731
S: * 1 000000000000000000000000 ()
S: * 3697 0101003f4c56b00545000000 ()
S: * 3919 0101003f4c56b04b2900000d ()
S: * 3937 0101003f4c56b0514900001f ()
S: * 4066 0101003f4c56b07422000002 ()
S: * 4089 0101003f4c56b07e56000023 (\answered)
S: * 4118 0101003f4c56b08328000016 ()
S: * 4131 0101003f4c56b084d7000002 ()
S: * 4136 0101003f4c56b087f3000001 ()
S: * 4140 0101003f4c56b08c9d000026 ()
S: OK User_Some finished
# Back where we started: the replication engine reinserted message UID 0
# which was missing, and removed "hello world" from message UID 4140
Tracking messages between folders
---------------------------------
::
# I've just saved a message from my inbox into a folder named "zzz",
# creating the folder the process.
C: $ replicate -s cyrus-2 -v -v -m user.dpc22 user.dpc22.zzz
Replication action on two MAILBOX objects:
S: MAILBOXES user.dpc22 user.dpc22.zzz
Ask server for contents of the two folders:
S: USER_SOME dpc22 ...
Reserve message with given GUID in user.dpc22 so that it can be moved
S: RESERVE user.dpc22 ...
Remove message from source folder (reserved copy left behind)
S: SELECT user.dpc22
S: EXPUNGE [1 msgs]
S: SETSEEN dpc22 ...
Create target folder and copy in message that we reserved (doesn't have to
be uploaded again)
S: CREATE user.dpc22.zzz 7f6f384c3f5ba99a
S: "dpc22 lrswipcda anonymous 0 " 0 1062971802
S: SELECT user.dpc22.zzz
S: UPLOAD [1 msgs]
S: SETSEEN dpc22 ...
S: ENDUSER
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