[47] EVENT SERVICE UPDATED!
(Part of the CORBA FAQ, Copyright © 1996-99)


[47.1] WHAT IS THE EVENT SERVICE? NEW!

[Recently created (3/1999). Click here to go to the next FAQ in the “chain” of recent changes]

The CORBA event service provides support for the producer/consumer pattern. It support a channel which provides the producer with the ability to create “events” and the consumers with the ability to receive these “events”. Events are any valid IDL defined interface or data type. Both consumer and producer applications must be a CORBA server. There may be multiple channels in use. A single channel may have multiple producers and multiple consumers. A consumer receives all the events on the channel.

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[47.2] ARE THERE MORE THAN ONE TYPE OF EVENT SERVICE? NEW!

[Recently created (3/1999). Click here to go to the next FAQ in the “chain” of recent changes]

The Event Service specification supports two types of event reception. One is push and one is pull. The push model allows consumers to receive ongoing events by just connecting. The pull model requires that the consumer poll for all events sent to the channel since the last pull. The Event service also allow the events to be either typed or in typed. In the typed model, the Event service ensures that the channel support a specific IDL datatypes. In the untyped model the Chnnel distributes events as an ANY. In this case, it is up to the consumer to enforce type safety.

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[47.3] WHAT IS THE QUALITY OF SERVICE PROVIDED BY THE EVENT SERVICE? NEW!

[Recently created (3/1999). Click here to go to the next FAQ in the “chain” of recent changes]

The Event Service specification does not require a specific quality of service. It is up to the implementor of the event service to determine what the provided level is. For example, an event service implentation may ensure that events are deliver even if some piece to the event service fails. An event service could also support transactional events using OTS. An event service could also provide deliver via a non IIOP transport such as UDP broadcast or multicast. This could, of course, limit interoperability. An event service could also ensure that connections to a channel are persistent. This would mean that consumers would not have to re-connect if the server failed and then came back online.

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Revised Oct 27, 1999