aratno commented on code in PR #1922: URL: https://github.com/apache/cassandra-java-driver/pull/1922#discussion_r1538174008
########## core/src/main/java/com/datastax/oss/driver/internal/core/loadbalancing/RackAwareWeightedLoadBalancingPolicy.java: ########## @@ -0,0 +1,264 @@ +/* + * 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 com.datastax.oss.driver.internal.core.loadbalancing; + +import static java.util.concurrent.TimeUnit.SECONDS; + +import com.datastax.oss.driver.api.core.config.DefaultDriverOption; +import com.datastax.oss.driver.api.core.context.DriverContext; +import com.datastax.oss.driver.api.core.metadata.Node; +import com.datastax.oss.driver.api.core.session.Request; +import com.datastax.oss.driver.api.core.session.Session; +import com.datastax.oss.driver.internal.core.util.ArrayUtils; +import com.datastax.oss.driver.internal.core.util.collection.QueryPlan; +import com.datastax.oss.driver.internal.core.util.collection.SimpleQueryPlan; +import edu.umd.cs.findbugs.annotations.NonNull; +import java.util.ArrayList; +import java.util.Comparator; +import java.util.Objects; +import java.util.Queue; +import java.util.Random; +import java.util.Set; +import java.util.concurrent.ThreadLocalRandom; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A load balancing policy that optimally balances between sending load to local token holder, + * rack replicas, and local datacenter replicas (in that order). + * + * The default weights are good for the vast majority of use cases, but you can tweak them to get different behavior. + */ +public class RackAwareWeightedLoadBalancingPolicy extends DefaultLoadBalancingPolicy { + private static final Logger LOG = + LoggerFactory.getLogger(RackAwareWeightedLoadBalancingPolicy.class); + // Each client will randomly skew so traffic is introduced gradually to a newly up replica + // Each client will start sending at a period between 15s and 30, and they will gradually + // increase load over the next 15 seconds. + private static final long DELAY_TRAFFIC_SKEW_MILLIS = SECONDS.toMillis(15); + private static final long DELAY_TRAFFIC_MILLIS = + DELAY_TRAFFIC_SKEW_MILLIS + ThreadLocalRandom.current().nextLong(DELAY_TRAFFIC_SKEW_MILLIS); + + // By default we will only score this many nodes, the rest will get added on without scoring. + // We don't usually need to score every single node if there are more than a few. + static final int DEFAULT_SCORED_PLAN_SIZE = 8; Review Comment: It's a reasonable default - just thinking through what we should document for tuning. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
