[GitHub] [pulsar] lhotari 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>]

lhotari commented on code in PR #14971:
URL: https://github.com/apache/pulsar/pull/14971#discussion_r874770259


##########
pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/impl/ThresholdLoadManagerStrategy.java:
##########
@@ -0,0 +1,133 @@
+/**
+ * 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 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;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Placement strategy which selects a broker based on which one has resource usage below average load.
+ */
+public class ThresholdLoadManagerStrategy implements ModularLoadManagerStrategy {
+    private static final Logger log = LoggerFactory.getLogger(ThresholdLoadManagerStrategy.class);
+
+    // 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);
+            if (score == Double.POSITIVE_INFINITY) {
+                final LocalBrokerData localData = brokerData.getLocalData();
+                log.warn(
+                        "Broker {} is overloaded: CPU: {}%, MEMORY: {}%, DIRECT MEMORY: {}%, BANDWIDTH IN: {}%, "
+                                + "BANDWIDTH OUT: {}%",
+                        broker, localData.getCpu().percentUsage(), localData.getMemory().percentUsage(),
+                        localData.getDirectMemory().percentUsage(), localData.getBandwidthIn().percentUsage(),
+                        localData.getBandwidthOut().percentUsage());
+                continue;
+            }
+            sumScore += score;
+            brokerUsages.put(broker, score);
+        }
+
+        if (brokerUsages.isEmpty()) {
+            // All brokers are overloaded.
+            // Assign randomly in this case.
+            bestBrokers.addAll(candidates);
+        } else {
+            double avgUsage = sumScore / brokerUsages.size();
+            for (Map.Entry<String, Double> entry : brokerUsages.entrySet()) {
+                if (entry.getValue() <= avgUsage) {

Review Comment:
   @dragonls it makes sense to do random selection. It seems that this is an important detail which is missing from the PR description. Please add this information to the description of the algorithm.



-- 
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: commits-unsubscribe@pulsar.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org