[GitHub] [pulsar] hangc0276 commented on a diff in pull request #14971: [feature][broker] Add new load manager strategy for load manager to select broker having load below average.

[GitBox <gi...@apache.org>]

hangc0276 commented on code in PR #14971:
URL: https://github.com/apache/pulsar/pull/14971#discussion_r880188103


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pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/impl/ThresholdLoadManagerStrategy.java:
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@@ -0,0 +1,131 @@
+/**
+ * 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.pulsar.broker.loadbalance.impl;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.ThreadLocalRandom;
+import lombok.extern.slf4j.Slf4j;
+import org.apache.pulsar.broker.ServiceConfiguration;
+import org.apache.pulsar.broker.loadbalance.LoadData;
+import org.apache.pulsar.broker.loadbalance.ModularLoadManagerStrategy;
+import org.apache.pulsar.policies.data.loadbalancer.BrokerData;
+import org.apache.pulsar.policies.data.loadbalancer.BundleData;
+import org.apache.pulsar.policies.data.loadbalancer.LocalBrokerData;
+
+/**
+ * Placement strategy which randomly selects a broker from those having resource usage below average load.
+ */
+@Slf4j
+public class ThresholdLoadManagerStrategy implements ModularLoadManagerStrategy {
+    // Maintain this list to reduce object creation.
+    private final ArrayList<String> bestBrokers;
+
+    // candidate broker -> broker usage.
+    private final Map<String, Double> brokerUsages;
+
+    public ThresholdLoadManagerStrategy() {
+        bestBrokers = new ArrayList<>();
+        brokerUsages = new HashMap<>();
+    }
+
+    private static double getScore(final BrokerData brokerData, final ServiceConfiguration conf) {
+        final double overloadThreshold = conf.getLoadBalancerBrokerOverloadedThresholdPercentage() / 100.0;
+        final double maxUsage = brokerData.getLocalData().getMaxResourceUsage();
+        if (maxUsage > overloadThreshold) {
+            log.warn("Broker {} is overloaded: max usage={}", brokerData.getLocalData().getWebServiceUrl(), maxUsage);
+            return Double.POSITIVE_INFINITY;
+        }
+
+        double brokerResourceUsage = brokerData.getLocalData().getMaxResourceUsageWithWeight(
+                conf.getLoadBalancerCPUResourceWeight(), conf.getLoadBalancerMemoryResourceWeight(),
+                conf.getLoadBalancerDirectMemoryResourceWeight(), conf.getLoadBalancerBandwithInResourceWeight(),
+                conf.getLoadBalancerBandwithOutResourceWeight());
+
+        if (log.isDebugEnabled()) {
+            log.debug("Broker {} resource usage {}",
+                    brokerData.getLocalData().getWebServiceUrl(), brokerResourceUsage);
+        }
+        return brokerResourceUsage;
+    }
+
+    /**
+     * Find a suitable broker to assign the given bundle to.
+     *
+     * @param candidates
+     *            The candidates for which the bundle may be assigned.
+     * @param bundleToAssign
+     *            The data for the bundle to assign.
+     * @param loadData
+     *            The load data from the leader broker.
+     * @param conf
+     *            The service configuration.
+     * @return The name of the selected broker as it appears on ZooKeeper.
+     */
+    @Override
+    public Optional<String> selectBroker(final Set<String> candidates, final BundleData bundleToAssign,
+                                         final LoadData loadData,
+                                         final ServiceConfiguration conf) {
+        bestBrokers.clear();
+        brokerUsages.clear();
+
+        // Maintain of list of all the brokers below average load, and then randomly
+        // select one of them at the end.
+        double sumScore = 0.0;
+        for (String broker : candidates) {
+            final BrokerData brokerData = loadData.getBrokerData().get(broker);
+            final double score = getScore(brokerData, conf);

Review Comment:
   Do we need take the throughput into consideration when calculating score?



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