src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/ForwardedEventHandler.java

// Copyright (C) 2018 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.googlesource.gerrit.plugins.multisite.forwarder;

import com.google.gerrit.extensions.registration.DynamicItem;
import com.google.gerrit.server.events.Event;
import com.google.gerrit.server.events.EventDispatcher;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.util.ManualRequestContext;
import com.google.gerrit.server.util.OneOffRequestContext;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Dispatch event to the {@link EventDispatcher}. This class is meant to be used on the receiving
 * side of the {@link StreamEventForwarder} since it will prevent dispatched event to be forwarded
 * again causing an infinite forwarding loop between the 2 nodes.
 */
@Singleton
public class ForwardedEventHandler {
  private static final Logger log = LoggerFactory.getLogger(ForwardedEventHandler.class);

  private final DynamicItem<EventDispatcher> dispatcher;
  private final OneOffRequestContext oneOffCtx;

  @Inject
  public ForwardedEventHandler(
      DynamicItem<EventDispatcher> dispatcher, OneOffRequestContext oneOffCtx) {
    this.dispatcher = dispatcher;
    this.oneOffCtx = oneOffCtx;
  }

  /**
   * Dispatch an event in the local node, event will not be forwarded to the other node.
   *
   * @param event The event to dispatch
   */
  public void dispatch(Event event) throws PermissionBackendException {
    try (ManualRequestContext ctx = oneOffCtx.open()) {
      Context.setForwardedEvent(true);
      log.debug("dispatching event {}", event.getType());
      dispatcher.get().postEvent(event);
    } finally {
      Context.unsetForwardedEvent();
    }
  }
}