server/src/main/java/org/apache/druid/server/coordinator/helper/DruidCoordinatorRuleRunner.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.druid.server.coordinator.helper;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Lists;
import org.apache.druid.client.DataSourcesSnapshot;
import org.apache.druid.java.util.common.DateTimes;
import org.apache.druid.java.util.emitter.EmittingLogger;
import org.apache.druid.metadata.MetadataRuleManager;
import org.apache.druid.server.coordinator.CoordinatorStats;
import org.apache.druid.server.coordinator.DruidCluster;
import org.apache.druid.server.coordinator.DruidCoordinator;
import org.apache.druid.server.coordinator.DruidCoordinatorRuntimeParams;
import org.apache.druid.server.coordinator.ReplicationThrottler;
import org.apache.druid.server.coordinator.rules.Rule;
import org.apache.druid.timeline.DataSegment;
import org.apache.druid.timeline.SegmentId;
import org.joda.time.DateTime;

import java.util.List;
import java.util.Optional;
import java.util.Set;

/**
 */
public class DruidCoordinatorRuleRunner implements DruidCoordinatorHelper
{
  private static final EmittingLogger log = new EmittingLogger(DruidCoordinatorRuleRunner.class);
  private static int MAX_MISSING_RULES = 10;

  private final ReplicationThrottler replicatorThrottler;

  private final DruidCoordinator coordinator;

  public DruidCoordinatorRuleRunner(DruidCoordinator coordinator)
  {
    this(
        new ReplicationThrottler(
            coordinator.getDynamicConfigs().getReplicationThrottleLimit(),
            coordinator.getDynamicConfigs().getReplicantLifetime()
        ),
        coordinator
    );
  }

  public DruidCoordinatorRuleRunner(ReplicationThrottler replicatorThrottler, DruidCoordinator coordinator)
  {
    this.replicatorThrottler = replicatorThrottler;
    this.coordinator = coordinator;
  }

  @Override
  public DruidCoordinatorRuntimeParams run(DruidCoordinatorRuntimeParams params)
  {
    replicatorThrottler.updateParams(
        coordinator.getDynamicConfigs().getReplicationThrottleLimit(),
        coordinator.getDynamicConfigs().getReplicantLifetime()
    );

    CoordinatorStats stats = new CoordinatorStats();
    DruidCluster cluster = params.getDruidCluster();

    if (cluster.isEmpty()) {
      log.warn("Uh... I have no servers. Not assigning anything...");
      return params;
    }

    // find available segments which are not overshadowed by other segments in DB
    // only those would need to be loaded/dropped
    // anything overshadowed by served segments is dropped automatically by DruidCoordinatorCleanupOvershadowed
    // If metadata store hasn't been polled yet, use empty overshadowed list
    final DataSourcesSnapshot dataSourcesSnapshot = params.getDataSourcesSnapshot();
    Set<SegmentId> overshadowed = ImmutableSet.of();
    if (dataSourcesSnapshot != null) {
      overshadowed = Optional
          .ofNullable(dataSourcesSnapshot.getOvershadowedSegments())
          .orElse(ImmutableSet.of());
    }

    for (String tier : cluster.getTierNames()) {
      replicatorThrottler.updateReplicationState(tier);
    }

    DruidCoordinatorRuntimeParams paramsWithReplicationManager = params
        .buildFromExistingWithoutAvailableSegments()
        .withReplicationManager(replicatorThrottler)
        .build();

    // Run through all matched rules for available segments
    DateTime now = DateTimes.nowUtc();
    MetadataRuleManager databaseRuleManager = paramsWithReplicationManager.getDatabaseRuleManager();

    final List<SegmentId> segmentsWithMissingRules = Lists.newArrayListWithCapacity(MAX_MISSING_RULES);
    int missingRules = 0;
    for (DataSegment segment : params.getAvailableSegments()) {
      if (overshadowed.contains(segment.getId())) {
        // Skipping overshadowed segments
        continue;
      }
      List<Rule> rules = databaseRuleManager.getRulesWithDefault(segment.getDataSource());
      boolean foundMatchingRule = false;
      for (Rule rule : rules) {
        if (rule.appliesTo(segment, now)) {
          stats.accumulate(rule.run(coordinator, paramsWithReplicationManager, segment));
          foundMatchingRule = true;
          break;
        }
      }

      if (!foundMatchingRule) {
        if (segmentsWithMissingRules.size() < MAX_MISSING_RULES) {
          segmentsWithMissingRules.add(segment.getId());
        }
        missingRules++;
      }
    }

    if (!segmentsWithMissingRules.isEmpty()) {
      log.makeAlert("Unable to find matching rules!")
         .addData("segmentsWithMissingRulesCount", missingRules)
         .addData("segmentsWithMissingRules", segmentsWithMissingRules)
         .emit();
    }

    return params.buildFromExisting().withCoordinatorStats(stats).build();
  }
}