Message ordering in a messaging system

Abstract

A method and system (200) for message handling in a messaging system by: receiving messages from applications associated with transactions and placing the received messages in a queue (230) for subsequent retrieval; receiving requests of prepare, commit and abort for the transactions; deferring retrieval of messages from the queue so as to occur in the same sequence as the prepare requests of the transactions with which the respective messages are associated; and retrieving from the queue messages associated with a transaction in the order in which the messages were put by the application. Preferably deferral is achieved by deferring completion of transaction commits as required to occur in the same order as the prepare message requests. Deferral may be implemented by (i) using a three phase commit protocol having Prepare, Commit, and Release phases and by implementing the Release phase within the Commit phase of the same or a different transaction so that a standard two-phase coordinator may be used, or (ii) by completing a first part of a commit phase as requested and deferring a second part of the commit phase as required. This permits appropriate message ordering in a transactional system, and in particular permits the correct implementation of a database replication system (220) using coordinated message transport that is fed the changes during database transactions.

Dependencies are inferred from the claim text.