src/main/java/com/googlesource/gerrit/plugins/replication/pull/event/StreamEventListener.java

// Copyright (C) 2022 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.replication.pull.event;

import static com.googlesource.gerrit.plugins.replication.pull.ApplyObjectCacheModule.APPLY_OBJECTS_CACHE;
import static java.util.Objects.requireNonNull;

import com.google.common.base.Strings;
import com.google.common.cache.Cache;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.entities.Project.NameKey;
import com.google.gerrit.entities.RefNames;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.extensions.restapi.RestApiException;
import com.google.gerrit.server.config.GerritInstanceId;
import com.google.gerrit.server.data.RefUpdateAttribute;
import com.google.gerrit.server.events.Event;
import com.google.gerrit.server.events.EventListener;
import com.google.gerrit.server.events.ProjectCreatedEvent;
import com.google.gerrit.server.events.ProjectEvent;
import com.google.gerrit.server.events.RefUpdatedEvent;
import com.google.gerrit.server.git.WorkQueue;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.name.Named;
import com.googlesource.gerrit.plugins.replication.pull.ApplyObjectsCacheKey;
import com.googlesource.gerrit.plugins.replication.pull.FetchOne;
import com.googlesource.gerrit.plugins.replication.pull.Source;
import com.googlesource.gerrit.plugins.replication.pull.SourcesCollection;
import com.googlesource.gerrit.plugins.replication.pull.api.DeleteRefCommand;
import com.googlesource.gerrit.plugins.replication.pull.api.FetchAction;
import com.googlesource.gerrit.plugins.replication.pull.api.FetchJob;
import com.googlesource.gerrit.plugins.replication.pull.api.FetchJob.Factory;
import com.googlesource.gerrit.plugins.replication.pull.api.ProjectInitializationAction;
import com.googlesource.gerrit.plugins.replication.pull.api.PullReplicationApiRequestMetrics;
import com.googlesource.gerrit.plugins.replication.pull.filter.ExcludedRefsFilter;
import java.io.IOException;
import java.util.Optional;
import org.eclipse.jgit.lib.ObjectId;

public class StreamEventListener implements EventListener {
  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
  private static final String ZERO_ID_NAME = ObjectId.zeroId().name();

  private final DeleteRefCommand deleteCommand;
  private final ExcludedRefsFilter refsFilter;
  private final Factory fetchJobFactory;
  private final ProjectInitializationAction projectInitializationAction;
  private final Provider<PullReplicationApiRequestMetrics> metricsProvider;
  private final SourcesCollection sources;
  private final String instanceId;
  private final WorkQueue workQueue;
  private final Cache<ApplyObjectsCacheKey, Long> refUpdatesSucceededCache;

  @Inject
  public StreamEventListener(
      @Nullable @GerritInstanceId String instanceId,
      DeleteRefCommand deleteCommand,
      ProjectInitializationAction projectInitializationAction,
      WorkQueue workQueue,
      FetchJob.Factory fetchJobFactory,
      Provider<PullReplicationApiRequestMetrics> metricsProvider,
      SourcesCollection sources,
      ExcludedRefsFilter excludedRefsFilter,
      @Named(APPLY_OBJECTS_CACHE) Cache<ApplyObjectsCacheKey, Long> refUpdatesSucceededCache) {
    this.instanceId = instanceId;
    this.deleteCommand = deleteCommand;
    this.projectInitializationAction = projectInitializationAction;
    this.workQueue = workQueue;
    this.fetchJobFactory = fetchJobFactory;
    this.metricsProvider = metricsProvider;
    this.sources = sources;
    this.refsFilter = excludedRefsFilter;
    this.refUpdatesSucceededCache = refUpdatesSucceededCache;

    requireNonNull(
        Strings.emptyToNull(this.instanceId), "gerrit.instanceId cannot be null or empty");
  }

  @Override
  public void onEvent(Event event) {
    try {
      fetchRefsForEvent(event);
    } catch (AuthException | PermissionBackendException | IOException e) {
      logger.atSevere().withCause(e).log(
          "This is the event handler of Gerrit's event-bus. It isn't"
              + "supposed to throw any exception, otherwise the other handlers "
              + "won't be executed");
    }
  }

  public void fetchRefsForEvent(Event event)
      throws AuthException, PermissionBackendException, IOException {
    if (instanceId.equals(event.instanceId) || !shouldReplicateProject(event)) {
      return;
    }

    PullReplicationApiRequestMetrics metrics = metricsProvider.get();
    metrics.start(event);
    if (event instanceof RefUpdatedEvent) {
      RefUpdatedEvent refUpdatedEvent = (RefUpdatedEvent) event;
      if (!isRefToBeReplicated(refUpdatedEvent.getRefName())) {
        logger.atFine().log(
            "Skipping excluded ref '%s' for project '%s'",
            refUpdatedEvent.getRefName(), refUpdatedEvent.getProjectNameKey());
        return;
      }

      if (isProjectDelete(refUpdatedEvent)) {
        return;
      }

      if (isRefDelete(refUpdatedEvent)) {
        deleteRef(refUpdatedEvent);
        return;
      }

      if (isApplyObjectsCacheHit(refUpdatedEvent)) {
        logger.atFine().log(
            "Skipping refupdate '%s'  '%s'=>'%s' (eventCreatedOn=%d) for project '%s' because has been already replicated via apply-object",
            refUpdatedEvent.getRefName(),
            refUpdatedEvent.refUpdate.get().oldRev,
            refUpdatedEvent.refUpdate.get().newRev,
            refUpdatedEvent.eventCreatedOn,
            refUpdatedEvent.getProjectNameKey());
        return;
      }

      fetchRefsAsync(
          refUpdatedEvent.getRefName(),
          refUpdatedEvent.instanceId,
          refUpdatedEvent.getProjectNameKey(),
          metrics);
    } else if (event instanceof ProjectCreatedEvent) {
      ProjectCreatedEvent projectCreatedEvent = (ProjectCreatedEvent) event;
      try {
        projectInitializationAction.initProject(getProjectRepositoryName(projectCreatedEvent));
        fetchRefsAsync(
            FetchOne.ALL_REFS,
            projectCreatedEvent.instanceId,
            projectCreatedEvent.getProjectNameKey(),
            metrics);
      } catch (AuthException | PermissionBackendException | IOException e) {
        logger.atSevere().withCause(e).log(
            "Cannot initialise project:%s", projectCreatedEvent.projectName);
        throw e;
      }
    }
  }

  private void deleteRef(RefUpdatedEvent refUpdatedEvent) {
    try {
      deleteCommand.deleteRef(
          refUpdatedEvent.getProjectNameKey(),
          refUpdatedEvent.getRefName(),
          refUpdatedEvent.instanceId);
    } catch (IOException | RestApiException e) {
      logger.atSevere().withCause(e).log(
          "Cannot delete ref %s project:%s",
          refUpdatedEvent.getRefName(), refUpdatedEvent.getProjectNameKey());
    }
  }

  private boolean isRefToBeReplicated(String refName) {
    return !refsFilter.match(refName);
  }

  private boolean shouldReplicateProject(Event event) {
    if (!(event instanceof ProjectEvent)) {
      return false;
    }

    Optional<Source> maybeSource =
        sources.getAll().stream()
            .filter(s -> s.getRemoteConfigName().equals(event.instanceId))
            .findFirst();

    if (!maybeSource.isPresent()) {
      return false;
    }

    Source source = maybeSource.get();
    if (event instanceof ProjectCreatedEvent) {
      ProjectCreatedEvent projectCreatedEvent = (ProjectCreatedEvent) event;

      return source.isCreateMissingRepositories()
          && source.wouldCreateProject(projectCreatedEvent.getProjectNameKey());
    }

    ProjectEvent projectEvent = (ProjectEvent) event;
    return source.wouldFetchProject(projectEvent.getProjectNameKey());
  }

  private boolean isRefDelete(RefUpdatedEvent event) {
    return ZERO_ID_NAME.equals(event.refUpdate.get().newRev);
  }

  private boolean isProjectDelete(RefUpdatedEvent event) {
    return RefNames.isConfigRef(event.getRefName()) && isRefDelete(event);
  }

  protected void fetchRefsAsync(
      String refName,
      String sourceInstanceId,
      NameKey projectNameKey,
      PullReplicationApiRequestMetrics metrics) {
    FetchAction.Input input = new FetchAction.Input();
    input.refName = refName;
    input.label = sourceInstanceId;
    workQueue.getDefaultQueue().submit(fetchJobFactory.create(projectNameKey, input, metrics));
  }

  private String getProjectRepositoryName(ProjectCreatedEvent projectCreatedEvent) {
    return String.format("%s.git", projectCreatedEvent.projectName);
  }

  private boolean isApplyObjectsCacheHit(RefUpdatedEvent refUpdateEvent) {
    RefUpdateAttribute refUpdateAttribute = refUpdateEvent.refUpdate.get();
    Long refUpdateSuccededTimestamp =
        refUpdatesSucceededCache.getIfPresent(
            ApplyObjectsCacheKey.create(
                refUpdateAttribute.newRev, refUpdateAttribute.refName, refUpdateAttribute.project));

    return refUpdateSuccededTimestamp != null
        && refUpdateEvent.eventCreatedOn <= refUpdateSuccededTimestamp;
  }
}