org.springframework.cloud.gcp.pubsub.reactive

Class PubSubReactiveFactory

java.lang.Object

org.springframework.cloud.gcp.pubsub.reactive.PubSubReactiveFactory

public final class PubSubReactiveFactory
extends Object

A factory for procuring Flux instances backed by GCP Pub/Sub Subscriptions. The Scheduler, that is given to the constructor, is used for regularly polling the subscription, when the demand is unlimited. The scheduler is not used when there is a specific demand (a.k.a backpressure).

Since:

1.2

Author:

Elena Felder, Maurice Zeijen

Constructor Summary

Constructors

Constructor and Description
PubSubReactiveFactory(PubSubSubscriberOperations subscriberOperations, reactor.core.scheduler.Scheduler scheduler) Instantiate `PubSubReactiveFactory` capable of generating subscription-based streams.
PubSubReactiveFactory(PubSubSubscriberOperations subscriberOperations, reactor.core.scheduler.Scheduler scheduler, int maxMessages) Instantiate `PubSubReactiveFactory` capable of generating subscription-based streams.

Method Summary

Modifier and Type	Method and Description
reactor.core.publisher.Flux<AcknowledgeablePubsubMessage>	poll(String subscriptionName, long pollingPeriodMs) Create an infinite stream Flux of AcknowledgeablePubsubMessage objects.

Methods inherited from class java.lang.Object

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

Constructor Detail

PubSubReactiveFactory

public PubSubReactiveFactory(PubSubSubscriberOperations subscriberOperations,
                             reactor.core.scheduler.Scheduler scheduler)

Instantiate `PubSubReactiveFactory` capable of generating subscription-based streams.

maxMessages is set to Integer.MAX_VALUE.

Parameters:

subscriberOperations - template for interacting with GCP Pub/Sub subscriber operations.

scheduler - scheduler to use for asynchronously retrieving Pub/Sub messages.

PubSubReactiveFactory

public PubSubReactiveFactory(PubSubSubscriberOperations subscriberOperations,
                             reactor.core.scheduler.Scheduler scheduler,
                             int maxMessages)

Instantiate `PubSubReactiveFactory` capable of generating subscription-based streams.

Parameters:

subscriberOperations - template for interacting with GCP Pub/Sub subscriber operations.

scheduler - scheduler to use for asynchronously retrieving Pub/Sub messages.

maxMessages - max number of messages that may be pulled from the source subscription in case of unlimited demand.

Method Detail

poll

public reactor.core.publisher.Flux<AcknowledgeablePubsubMessage> poll(String subscriptionName,
                                                                      long pollingPeriodMs)

Create an infinite stream Flux of AcknowledgeablePubsubMessage objects.

The Flux respects backpressure by using of Pub/Sub Synchronous Pull to retrieve batches of up to the requested number of messages until the full demand is fulfilled or subscription terminated.

For unlimited demand, the underlying subscription will be polled at a regular interval, requesting up to maxMessages messages at each poll.

For specific demand, as many messages as are available will be returned immediately, with remaining demand being fulfilled in the future. Pub/Sub timeout will cause a retry with the same demand.

Any exceptions that are thrown by the Pub/Sub client will be passed as an error to the stream. The error handling operators, like Flux.retry(), can be used to recover and continue streaming messages.

Parameters:

subscriptionName - subscription from which to retrieve messages.

pollingPeriodMs - how frequently to poll the source subscription in case of unlimited demand, in milliseconds.

Returns:

infinite stream of AcknowledgeablePubsubMessage objects.