solr/solrj/src/java/org/apache/solr/client/solrj/cloud/autoscaling/AddReplicaSuggester.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.solr.client.solrj.cloud.autoscaling;

import java.lang.invoke.MethodHandles;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import org.apache.solr.client.solrj.SolrRequest;
import org.apache.solr.client.solrj.request.CollectionAdminRequest;
import org.apache.solr.common.cloud.Replica;
import org.apache.solr.common.params.CollectionParams;
import org.apache.solr.common.util.Pair;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import static org.apache.solr.common.params.CollectionParams.CollectionAction.ADDREPLICA;

class AddReplicaSuggester extends Suggester {
  private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

  SolrRequest init() {
    SolrRequest operation = tryEachNode(true);
    if (operation == null) operation = tryEachNode(false);
    return operation;
  }

  SolrRequest tryEachNode(boolean strict) {
    Set<Pair<String, String>> shards = (Set<Pair<String, String>>) hints.getOrDefault(Hint.COLL_SHARD, Collections.emptySet());
    if (shards.isEmpty()) {
      throw new RuntimeException("add-replica requires 'collection' and 'shard'");
    }
    for (Pair<String, String> shard : shards) {
      Replica.Type type = Replica.Type.get((String) hints.get(Hint.REPLICATYPE));
      //iterate through  nodes and identify the least loaded
      List<Violation> leastSeriousViolation = null;
      Row bestNode = null;
      // nocommit
      // possible optimization? for large clusters compare only up to
      // that many eligible rows from the top
      int limitTopRows = getMatrix().size() > 100 ? 3 : getMatrix().size();

      for (int i = getMatrix().size() - 1; i >= 0; i--) {
        Row row = getMatrix().get(i);
        if (!isNodeSuitableForReplicaAddition(row, null)) continue;
        Row tmpRow = row.addReplica(shard.first(), shard.second(), type, strict);
        List<Violation> errs = testChangedMatrix(strict, tmpRow, tmpRow.session);
        if (!containsNewErrors(errs)) {
          if ((errs.isEmpty() && isLessDeviant()) ||//there are no violations but this is deviating less
              isLessSerious(errs, leastSeriousViolation)) {//there are errors , but this has less serious violation
            leastSeriousViolation = errs;
            bestNode = tmpRow;
          }
          if (bestNode != null && limitTopRows-- < 0) {
            break;
          }
        }
      }

      if (bestNode != null) {// there are no rule violations
        this.session = bestNode.session;
        //log.info("--- Row cache stats: " + Utils.toJSONString(Row.cacheStats));
        return CollectionAdminRequest
            .addReplicaToShard(shard.first(), shard.second())
            .setType(type)
            .setNode(bestNode.node);
      }
    }

    return null;
  }


  @Override
  public CollectionParams.CollectionAction getAction() {
    return ADDREPLICA;
  }
}