io.spine.server.delivery

Class DeliveryMonitor

java.lang.Object

io.spine.server.delivery.DeliveryMonitor

@SPI
public class DeliveryMonitor
extends java.lang.Object

A controlling monitor of a Inbox Delivery process.

In some cases when a funnel-like Entity (e.g. some projection of a business report subscribed to half of the domain events) has a lot of messages in its Inbox, the delivery process may be slowed down for other targets in the same shard, while all the messages are being dispatched the "busy" Entity. Depending on the number of messages to deliver, it may take a lot of time.

Environments such as Google AppEngine Standard imply restrictions on the duration of the request processing. Therefore, it may be necessary to stop the message delivery for this shard at some point, and re-schedule the shard processing again by sending another request and thus resetting the processing clock.

Constructor Summary

Constructors

Constructor and Description
DeliveryMonitor()

Method Summary

Modifier and Type	Method and Description
void	onDeliveryCompleted(DeliveryStats stats) Called once some delivery process has completed and the corresponding shard has been released.
void	onDeliveryStarted(io.spine.server.delivery.ShardIndex index)
boolean	shouldContinueAfter(io.spine.server.delivery.DeliveryStage stage) Determines if the delivery execution should be continued after the given stage is completed.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DeliveryMonitor

public DeliveryMonitor()

Method Detail

shouldContinueAfter

public boolean shouldContinueAfter(io.spine.server.delivery.DeliveryStage stage)

Determines if the delivery execution should be continued after the given stage is completed.

If false is returned, the ongoing delivery run for the served shard will be stopped at this application node. The node will release the previously picked up shard.

To trigger the new delivery processing for this shard, use Delivery.deliverMessagesFrom(ShardIndex).

This method is called synchronously, meaning that the delivery process will not resume until a value is returned from this method call.

Parameters:

stage - the stage of delivery which has ended

Returns:

true to continue the delivery, false to stop

Implementation Note:

The default implementation stops the execution once there were zero messages delivered in the given stage.

onDeliveryCompleted

public void onDeliveryCompleted(DeliveryStats stats)

Called once some delivery process has completed and the corresponding shard has been released.

The descendants may override this method to understand when it is safe to pick up the corresponding shard again. Another usage scenario is calculation of the message delivery throughput.

Parameters:

stats - the statistics of the performed delivery

onDeliveryStarted

public void onDeliveryStarted(io.spine.server.delivery.ShardIndex index)