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gerrit / modules / events-broker / 32c83ad1aedaa2f389893de70561f74f683afe57
commit32c83ad1aedaa2f389893de70561f74f683afe57[log] [tgz]
authorChristoforos Miliotis <christoforos.miliotis.dev@gmail.com>Thu Nov 02 11:53:28 2023 +0000
committerChristoforos Miliotis <christoforos.miliotis.dev@gmail.com>Mon Nov 20 19:15:27 2023 +0000
tree427cc8828f6420cea2da364135dc55745c29bd8d
parentfec27cee2d281e6b22974fe75e73a988b749fdb0 [diff]
Move message logging to events broker

The message log file is currently populated in an inconsistent way when
it comes to publishing messages. Publishing of some messages, like index
events, are still logged, however anything related to the stream events
topic is not, since this functionality was moved from multi-site to
events-broker. But it looks like the logging aspect was left out at the
time.

It makes sense to move all the message logging classes to the `events-
broker`, so they are together with the logic that publishes the stream
events, and used directly. This way, the clients of the library will not
even need to worry (or care) about updating the message log, this will
happen transparently.

The logic in `StreamEventPublisher` was already dealing with updating
the metrics. Incrementing the metrics is another feature that should be
tightly coupled with the publishing of the messages, however it looks
like some changes are required to allow each client of the library to
inject their own broker metrics. This will be done in a separate change.

Bug: Issue 294904654
Change-Id: I4e27619a0dde52c29626a33d2bcfb93d5945d509
5 files changed
tree: 427cc8828f6420cea2da364135dc55745c29bd8d
  1. src/
  2. .gitignore
  3. BUILD
  4. Jenkinsfile
  5. LICENSE
  6. 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 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.