Events Broker API for sending Gerrit Code Review events

Clone this repo:
  1. 32c83ad Move message logging to events broker by Christoforos Miliotis · 4 months ago master
  2. fec27ce Merge branch 'stable-3.8' by Alvaro Vilaplana Garcia · 5 months ago stable-3.9
  3. 79881fc Merge branch 'stable-3.7' into stable-3.8 by Luca Milanesio · 5 months ago stable-3.8
  4. dbf6638 Merge branch 'stable-3.6' into stable-3.7 by Alvaro Vilaplana Garcia · 5 months ago stable-3.7
  5. 2633fe1 Merge branch 'stable-3.5' into stable-3.6 by Alvaro Vilaplana Garcia · 5 months ago stable-3.6

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 binding for the StreamEventPublisherConfig configuration 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 java.util.concurrent.Executor;

import com.gerritforge.gerrit.eventbroker.publisher.StreamEventPublisher;
import com.gerritforge.gerrit.eventbroker.publisher.StreamEventPublisherConfig;
import com.gerritforge.gerrit.eventbroker.publisher.executor.StreamEventPublisherExecutor;
import com.gerritforge.gerrit.eventbroker.publisher.executor.StreamEventPublisherExecutorProvider;
import com.google.gerrit.extensions.registration.DynamicSet;
import com.google.gerrit.server.events.EventListener;
import com.google.inject.AbstractModule;

public class SomeModule extends AbstractModule {
    @Override
    protected void configure() {
        long messagePublishingTimeout = 1000L;

        bind(StreamEventPublisherConfig.class)
                .toInstance(new StreamEventPublisherConfig(
                    "name_of_the_stream_events_topic",
                    messagePublishingTimeout));

        bind(Executor.class).annotatedWith(StreamEventPublisherExecutor.class).toProvider(StreamEventPublisherExecutorProvider.class);
        DynamicSet.bind(binder(), EventListener.class).to(StreamEventPublisher.class);
    }
}

Alternative way to setup Stream Event Publisher is to use default Guice module StreamEventPublisherModule:

import com.gerritforge.gerrit.eventbroker.publisher.StreamEventPublisherConfig;
import com.gerritforge.gerrit.eventbroker.publisher.StreamEventPublisherModule;
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() {
        long messagePublishingTimeout = 1000L;
        bind(StreamEventPublisherConfig.class)
                .toInstance(new StreamEventPublisherConfig(
                    "name_of_the_stream_events_topic",
                    messagePublishingTimeout));
        install(new StreamEventPublisherModule());
    }
}

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

Broker Metrics

When StreamEventPublisher is used user can optionally bind an implementation of the BrokerMetrics` interface. This will allow to collect metrics about successful/failure stream events publishing. If no binding is provided default implementation will skip collecting metrics:

import com.google.gerrit.extensions.registration.DynamicItem;
import com.google.inject.AbstractModule;

public class SomeModule extends AbstractModule {
    @Override
    protected void configure() {
        DynamicItem.bind(binder(), BrokerMetrics.class)
            .to(BrokerMetricsImpl.class)
            .in(Scopes.SINGLETON);
    }
}

Note: BrokerMetrics implementation must be bound in a plugin module.