Publish and subscribe data processing with ability to...

Details Publish and subscribe data processing with ability to... Publish and subscribe data processing with ability to...

1999-04-09

2001-03-13

Maung, Zarni (Department: 2756)

Electrical computers and digital processing systems: multicomput

Computer network managing

Computer network access regulating

C709S224000, C706S062000, C707S793000, C707S793000

Reexamination Certificate

active

06202093

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of data processing and more specifically to data processing which distributes messages from suppliers (called, hereinafter, “publishers”) of data messages to consumers (called, hereinafter “subscribers”) of such messages.
BACKGROUND OF THE INVENTION
Publish/subscribe data processing systems have become very popular in recent years as a way of distributing data messages from publishing computers to subscribing computers. The increasing popularity of the Internet, which has connected a wide variety of computers all over the world, has helped to make such publish/subscribe systems even more popular. Using the Internet, a World Wide Web browser application (the term “application” or “process” refers to a software program, or portion thereof, running on a computer) can be used in conjunction with the publisher or subscriber in order to graphically display messages. Such systems are especially useful where data supplied by a publisher is constantly changing and a large number of subscribers needs to be quickly updated with the latest data. Perhaps the best example of where this is useful is in the distribution of stock market data.
In such systems, publisher applications of data messages do not need to know the identity or location of the subscriber applications which will receive the messages. The publishers need only connect to a publish/subscribe distribution agent process, which is included in a group of such processes making up a broker network, and send messages to the distribution agent process, specifying the subject of the message to the distribution agent process. The distribution agent process then distributes the published messages to subscriber applications which have previously indicated to the broker network that they would like to receive data messages on particular subjects. Thus, the subscribers also do not need to know the identity or location of the publishers. The subscribers need only connect to a distribution agent process.
One such publish/subscribe broker network which is currently in use, and which has been developed by the Transarc Corp. (a wholly owned subsidiary of the assignee of the present patent application, IBM Corp.) is shown in FIG.
1
. Publishers
11
and
12
connect to the publish/subscribe broker network
2
and send published messages to broker network
2
which distributes the messages to subscribers
31
,
32
,
33
,
34
. Publishers
11
and
12
, which are data processing applications which output data messages, connect to broker network
2
using the well known inter-application data connection protocol known as remote procedure call (or RPC). Each publisher application could be running on a separate machine, alternatively, a single machine could be running a plurality of publisher applications. The broker network
2
is made up of a plurality of distribution agents (
21
through
27
, which will also be referred to herein as “brokers”) which are connected in a hierarchial fashion which will be described below as a “tree structure”. These distribution agents, each of which could be running on a separate machine, are data processing applications which distribute data messages through the broker network
2
from publishers to subscribers. Subscriber applications
31
,
32
,
33
and
34
connect to the broker network
2
via RPC in order to receive published messages.
Publishers
11
and
12
first connect via RPC directly to a root distribution agent
21
which in turn connects via RPC to second level distribution agents
22
and
23
which in turn connect via RPC to third level distribution agents
24
,
25
,
26
and
27
(also known as “leaf distribution agents” since they are the final distribution agents in the tree structure). Each distribution agent could be running on its own machine, or alternatively, groups of distribution agents could be running on the same machine. The leaf distribution agents connect via RPC to subscriber applications
31
through
34
, each of which could be running on its own machine.
In order to allow the broker network
2
to determine which published messages should be sent to which subscribers, publishers provide the root distribution agent
21
with the name of a distribution stream for each published message. A distribution stream (called hereinafter a “stream”) is an ordered sequence of messages having a name (e.g., “stock” for a stream of stock market quotes) to distinguish the stream from other streams. Likewise, subscribers provide the leaf distribution agents
31
through
34
with the name of the streams to which they would like to subscribe. In this way, the broker network
2
keeps track of which subscribers are interested in which streams so that when publishers publish messages to such streams, the messages can be distributed to the corresponding subscribers. Subscribers are also allowed to provide filter expressions to the broker in order to limit the messages which will be received on a particular stream (e.g., a subscriber
31
interested in only IBM stock quotes could subscribe to the stream “stock” by making an RPC call to leaf distribution agent
24
and include a filter expression stating that only messages on the “stock” stream relating to IBM stock should be sent to subscriber
31
).
The above-described publish/subscribe broker network architecture provides the advantage of central coordination of all published messages, since all publishers must connect to the same distribution agent (the root) in order to publish a message to the broker network hierarchy. For example, total ordering of published messages throughout the broker hierarchy is greatly facilitated, since the root can easily assign sequence numbers to each published message on a stream. However, this architecture also has the disadvantage of publisher inflexibility, since each publisher is constrained to publishing from the single root distribution agent, even when it would be much easier for a publisher to connect to a closer distribution agent.
Accordingly, publish/subscribe software designers are beginning to consider architectures where publishers are allowed to publish messages directly to any distribution agent in the broker network. This clearly has the advantage of removing the above-mentioned constraint on publishers. However, as with any tradeoff, it presents other problems. One of the major problems is that since a publisher can publish from any distribution agent, subscription data (data indicating which subscribers have subscribed to which streams/topics) must be propagated throughout the broker network, as it cannot be determined from where a publisher on a particular topic/stream will publish from. Propagating subscription data throughout the broker network is the only way (besides sending published messages to each distribution agent) to guarantee that published messages, from wherever they may be published, will make their way to the subscribers who have requested the messages. This requirement imposes a great strain on the broker network, as it not only presents a high data traffic level throughout the network but also the subscription data must be locally stored and maintained with respect to each distribution agent in the broker network.
Another problem with this latter publish/subscribe architecture is that since publishers are allowed to publish from any distribution agent in the network, it is very likely that a high rate of data traffic will exist on the network, since publications and subscriptions will flow between publishers and subscribers wherever they may be located in the network.
SUMMARY OF THE INVENTION
According to one aspect, the present invention provides a publishing data processing apparatus for use in a publish/subscribe data processing broker network having a plurality of broker data processing apparatuses each of which has an input for receiving published messages directly from a publisher application and/or receiving subscription data directly from a subscriber application, comprising: means for publishing a mess

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