com.diffusiondata.gateway.framework

Interface PollingSourceHandler

All Superinterfaces:

ServiceHandler, SourceHandler

public interface PollingSourceHandler
extends SourceHandler

The interface that a polling source handler must implement.

The handler is polled at the frequency defined by the configured polling interval. The next poll is called after the interval time has expired starting from when the previous poll completed.

A polling source handler will not be polled until the start method has been called. It will also not be polled if the pause method has been called and polling will not resume until the resume method is called.

An object that implements this interface must be returned when the GatewayApplication.addPollingSource method is called. A different object must be returned for each different service. The object must implement the poll() method to publish any update(s) to Diffusion using the supplied Publisher.

Author:

DiffusionData Limited

Nested Class Summary

Nested classes/interfaces inherited from interface com.diffusiondata.gateway.framework.SourceHandler

SourceHandler.SourceServiceProperties

Nested classes/interfaces inherited from interface com.diffusiondata.gateway.framework.ServiceHandler

ServiceHandler.PauseReason, ServiceHandler.ResumeReason

Method Summary

Modifier and Type	Method and Description
CompletableFuture<?>	poll() Polls the handler for a new value or values.

Methods inherited from interface com.diffusiondata.gateway.framework.SourceHandler

getSourceServiceProperties

Methods inherited from interface com.diffusiondata.gateway.framework.ServiceHandler

pause, resume, start, stop

Method Detail

poll

CompletableFuture<?> poll()

Polls the handler for a new value or values.

The handler should use its Publisher to publish all available updates to Diffusion and then complete.

If when called, the handler is no longer able to operate then it should use its StateHandler to report this to the framework and complete successfully.

This method must return CompletableFuture that completes successfully when the poll processing is complete. The method can choose to initiate the processing in a separate thread and return immediately or block until all processing is done.

Returns:

a completable future that completes successfully when all updates have been published to Diffusion or alternatively, a change of status has been reported to the framework.

If the task completes successfully, the CompletableFuture result should be null. The result type is any rather than Void to provide forward compatibility with future iterations of this API that may provide a non-null result with a more specific result type.

If the future completes exceptionally the framework will stop polling the handler and the service will go to a PAUSED state.

If an unchecked exception is thrown, instead of returning a failed completable future, the exception will be caught and logged, but this will not have any effect on further poll calls.