Browse Prior Art Database

Ordering a Stream of Publications in a Publish/Subscribe System

IP.com Disclosure Number: IPCOM000123512D
Original Publication Date: 1998-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 33K

Publishing Venue

IBM

Related People

Johnson, PW: AUTHOR [+2]

Abstract

Typical message processing systems using the publish/subscribe concept require publishers to send messages to a master broker or an ordering service to ensure that subscribers receive messages in the same order regardless of their postion in the hierarchy.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 94% of the total text.

Ordering a Stream of Publications in a Publish/Subscribe System

   Typical message processing systems using the
publish/subscribe concept require publishers to send messages to a
master broker or an ordering service to ensure that subscribers
receive messages in the same order regardless of their postion in the
hierarchy.

   In the system described here a totally ordered stream is
divided into two streams: pre-ordered and post-ordered.  The master
broker subscribes to the pre-ordered stream.

   A local stream is totally ordered.  If a local stream is
published to a distributed stream, the sequence of messages in it
will be preserved unless unusual situations occur, such as queue
filling up.  In the same way, a stream (local or distributed)
containing messages from several publishers will preserve each
publisher's sequence in normal circumstances.  Receivers can verify
this by means of a publisher's sequence number in a message.  However
subject to these constraints, messages may arrive at different parts
of the network in different sequences in a distributed stream.

   To achieve total ordering of a distributed stream, all
messages should pass through a local stream.

   Subscribers may receive the unordered or the ordered
stream.  Publishers may only publish to the unordered stream.  A
sequence number will be added by the local stream's broker, known as
the master broker for the ordered stream.  Technically, this is a
join and an update operation performed...