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gerrit / modules / events-broker / 6a7af2d433f05414e14bb9736d66f186eb67921a
commit6a7af2d433f05414e14bb9736d66f186eb67921a[log] [tgz]
authorMarcin Czech <maczech@gmail.com>Fri Aug 20 14:03:49 2021 +0200
committerMarcin Czech <maczech@gmail.com>Fri Aug 27 18:43:41 2021 +0200
treea89476d17ad6b547029cdcbf8889575e7ea77c5a
parent6ad7192d1ee2ef17cf1d27370605d8a2f48e61d3 [diff]
Make publishing stream events wait for the message to be published

To allow message publishing in a ordered way wait for the message
publishing to be ACK by the broker before publishing next one. This
ensure producing messages in an ordered way even if the underlying
broker implementation does not supports message delivery ordering. The
messages are ordered up until the events-broker, but not necessarily in
the broker implementation.
Waiting for ACK may introduce latency, because of the broker
availability. To avoid blocking the main thread(UI or replication)
wait for the ACK in a separate thread.

NOTE: This change does not guarantee message *delivery* ordering but
message producing ordering. Message delivery ordering depends on the
broker implementation and should be addressed in a separate change.

Bug: Issue 14909
Change-Id: I99628f78fd9fe60bfadf3ab913d47bb9280727ae
5 files changed
tree: a89476d17ad6b547029cdcbf8889575e7ea77c5a
  1. src/
  2. .gitignore
  3. BUILD
  4. Jenkinsfile
  5. LICENSE
  6. pom.xml
  7. README.md
README.md

Events Broker API for Gerrit Code Review

API of a generic events broker for use with Gerrit Code Review.

Enables the de-coupling between Gerrit, plugins and the different implementations of a generic events broker.

Stream Events Publisher

It is a quite common use case for consumers of this library to listen for Gerrit events and to stream them on a specific topic.

Since the implementation of such logic is always the same, this library provides a generic stream events publisher which will perform the relevant operations.

In order to listen and stream gerrit events, consumers of this API need to provide a named annotation with the name of the stream events topic and java.util.concurrent.Executor binding annotated with StreamEventPublisherExecutor annotation. A default single threaded implementation (StreamEventPublisherExecutor) is provided by the library. The last step is to explicitly bind the Stream Events Publisher, as such:

import com.gerritforge.gerrit.eventbroker.StreamEventPublisher;
import com.google.gerrit.extensions.registration.DynamicSet;
import com.google.gerrit.server.events.EventListener;
import com.google.inject.AbstractModule;
import com.google.inject.TypeLiteral;
import com.google.inject.name.Names;

public class SomeModule extends AbstractModule {
    @Override
    protected void configure() {
        bind(new TypeLiteral<String>() {
        })
                .annotatedWith(Names.named(StreamEventPublisher.STREAM_EVENTS_TOPIC))
                .toInstance("name_of_the_stream_events_topic");
        
        bind(Executor.class).annotatedWith(StreamEventPublisherExecutor.class).toProvider(StreamEventPublisherExecutorProvider.class);
        DynamicSet.bind(binder(), EventListener.class).to(StreamEventPublisher.class);
    }
}

Note: To avoid message duplication Stream Events Publisher uses gerrit.instanceId and Event.instanceId to filter out forwarded events.