The consequences of changing durable subscriptions

When an application connects to an existing durable subscription, but specifies parameters that differ from those that were used to create the existing subscription, the subscription is deleted then recreated with the new parameters. A durable subscription can be changed in this way only when it has no active consumers.

In the basic case, there is only one active consumer at any time, so the application can change the durable subscription without affecting other subscribers. However, the situation is more complicated for cloned subscriptions.

A cloned durable subscription has multiple active subscribers, which are usually clones of a particular application.
  • For cloned message-driven bean (MDB) applications, the subscribers are always active on the subscription, and so the administrator must stop all instances of the MDB application before the subscription can be altered. (If the MDB application instances are recycled one at a time then each individual instance is thrown out when it tries to connect using the changed properties, because there are existing consumers.)
  • For cloned EJB applications, administrators should ensure that all instances of the EJB application are stopped before the subscription can be changed, to avoid the following problem. Enterprise beans have active subscribers for a durable subscription for relatively short spaces of time. If the EJB application instances are recycled individually then there is a period in which different instances of the application have different views of the subscription configuration. This causes the subscription to be deleted and recreated which can lead to the loss of messages. Subscriptions can be deleted and recreated multiple times until the new definition is constant across all instances.
Note: 傳訊服務利用 WAS_HOME/temp 目錄中的 server_name-durableSubscriptions.ser 檔來追蹤訊息驅動 Bean 的可延續訂閱。 如果您解除安裝包含訊息驅動 Bean 的應用程式,則使用這個檔案來取消訂閱可延續的訂閱。如果您必須刪除 WAS_HOME/temp 目錄或其中的其他檔案,請務必保留這個檔案。

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時間戳記圖示 前次更新: July 9, 2016 11:10
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