Publish/subscribe messaging and topic spaces

You can use publish/subscribe messaging to publish one message to many subscribers. A producing application publishes a message on a given subject area or topic. 特定訊息(發佈)的主題是訊息的一項內容。 Consumer applications that have subscribed to the topic each receive a copy of the message. A topic space is a hierarchy of publish/subscribe topics. These topics have publication points automatically defined on each messaging engine in their associated service integration bus.

服務整合主題空間目的地不會在特定匯流排成員中本地化。服務整合會維護主題空間中的訂閱清單,且會對照清單來比對每一項發佈。當新的發佈符合主題空間中的一或多項訂閱時,服務整合會向每位訂閱者遞送一份發佈資訊。必要的話,服務整合可以將發佈訊息放在佇列中,直到訂閱者準備好接收它。如果新的發佈不符合任何訂閱,服務整合會捨棄發佈資訊。

A topic space has a set of default publish/subscribe permissions for all topics in the hierarchy. An administrator can configure individual publish/subscribe topics with specific permissions and mediations. Publish/subscribe topics inherit such configurations from higher publish/subscribe topics in the topic space hierarchy and the topic space itself.

Publish/subscribe topics with the same name can exist in multiple topic spaces, but there can be only one topic space with a given name in the bus. For example, consider a publish/subscribe topic hierarchy split into the following topic spaces:
library
Topics for document management.
sales
Topics for marketing and sales tracking.
The publish/subscribe topic "volumes" can appear in the topic hierarchy in both topic spaces, and can have different meanings in each.

A producing application can attach to any messaging engine on the bus. Messages are stored in the message store for the messaging engine to which the producer is attached. As a result, a topic space can have messages stored in a number of message stores at various (producing) messaging engines in the bus. Messages for a publish/subscribe topic are published to a publication point and automatically forwarded to all other publication points for which there are subscribers on that topic.

Figure 1. Publish/subscribe messaging
This figure is described in the surrounding text.

The default messaging provider supports durable subscriptions to publish/subscribe topics. These enable a subscriber to receive a copy of all messages published to a topic, even messages published during periods of time when the subscriber is not connected to the server. For a given JMS connection factory or activation specification, all publish/subscribe messages to be delivered to durable subscriptions are stored on the publication point of the messaging engine named by the durable subscription home property. Therefore if that messaging engine is unavailable, subscribers cannot retrieve messages. These undelivered messages are preserved and sent to the durable subscriptions after the messaging engine restarts.


指出主題類型的圖示 概念主題



時間戳記圖示 前次更新: July 9, 2016 11:10
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