When an acquisition stops, it may take time for an extension
within an acquisition to stop. Therefore, Oracle recommends that you provide a
mechanism to stop an extension's runtime object in a more timely way (recall
that a runtime object is either a
DataSourceRuntime or a
ManipulatorRuntime).
There are several requests or conditions that may cause IAS Server to
stop an acquisition:
- An IAS data developer
requests a stop by running the
stopCrawl task of the IAS Server Command-line Utility
(ias-cmd).
- An IAS data developer
requests a stop by calling the
stopCrawl() method of the IAS Server API.
- An acquisition may abort
because it encountered a fatal error during the acquisition processing or
record manipulation processing.
When an acquisition stops, it has the following effects in the IAS
Extension API:
- Calls to
PipelineComponentRuntimeContext.isStopped() return
true.
- Calls to
OutputChannel.output() throw a
PipelineStoppedException exception.
- Calls to
ErrorChannel.discard() throw a
PipelineStoppedException exception.
- IAS Server calls
PipelineComponentRuntime.stop() on all data source and
manipulator extensions in the acquisition.
There are several mechanisms to stop an extension's runtime in a more
timely way:
- You can poll the
PipelineComponentRuntimeContext.isStopped() method,
and if it returns
true, you throw a
PipelineStoppedException and let the exception
propagate through the system. There is example code that implements
isStopped() in the CSV data source extension provided
with the integrator Acquisition System.
- In addition to polling, you
can override
PipelineComponentRuntime.stop() on an extension. Your
implementation of
stop() should perform any tasks that help the
extension stop more quickly, for example, terminating any pending network
requests or closing or cancelling any output requests. This approach is
particularly useful in situations where the extension is doing time-consuming
work between calls to
OutputChannel.output().
