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invoked before a Subscription is activated by an Event Processor |
Usage
Pre-Subscription plugins are invoked before a Subscription is activated by an Event Processor. This is an opportunity to take any action on the Subscription, including but not limited to:
- validation
- logging
- auditing
- optimization
- security filtering
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Invocation
Pre-Subscription plugins are invoked serially, prioritized by descending OSGi service ranking. That is, the plugin with the highest service ranking will be executed first.
The output of a Pre-Subscription plugin is sent to the next Pre-Subscription plugin, until all have executed and the create Subscription operation is sent to the Event Processor.
Examples
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includes a Pre-Subscription Plugin example in the SDK that illustrates how to modify a subscription's filter. This example is located in the
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trunk at
sdk/sample-plugins/ddf/sdk/plugin/presubscription.