HBASE-23073 Add an optional costFunction to balance regions according to a capacity rule (#677)

Signed-off-by: Wellington Chevreuil <wchevreuil@apache.org>

hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/HeterogeneousRegionCountCostFunction.java

@@ -0,0 +1,282 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hadoop.hbase.master.balancer;
+
+import java.io.BufferedReader;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.ServerName;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This is an optional Cost function designed to allow region count skew across RegionServers. A
+ * rule file is loaded from the local FS or HDFS before balancing. It contains lines of rules. A
+ * rule is composed of a regexp for hostname, and a limit. For example, we could have:
+ * <p>
+ * * rs[0-9] 200 * rs1[0-9] 50
+ * </p>
+ * RegionServers with hostname matching the first rules will have a limit of 200, and the others 50.
+ * If there's no match, a default is set. The costFunction is trying to fill all RegionServers
+ * linearly, meaning that if the global usage is at 50%, then all RegionServers should hold half of
+ * their capacity in terms of regions. In order to use this CostFunction, you need to set the
+ * following options:
+ * <ul>
+ * <li>hbase.master.balancer.stochastic.additionalCostFunctions</li>
+ * <li>hbase.master.balancer.stochastic.heterogeneousRegionCountRulesFile</li>
+ * <li>hbase.master.balancer.stochastic.heterogeneousRegionCountDefault</li>
+ * </ul>
+ * The rule file can be located on local FS or HDFS, depending on the prefix (file//: or hdfs://).
+ */
+@InterfaceAudience.Private
+public class HeterogeneousRegionCountCostFunction extends StochasticLoadBalancer.CostFunction {
+
+  /**
+   * configuration used for the path where the rule file is stored.
+   */
+  static final String HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_FILE =
+      "hbase.master.balancer.heterogeneousRegionCountRulesFile";
+  private static final Logger LOG =
+      LoggerFactory.getLogger(HeterogeneousRegionCountCostFunction.class);
+  /**
+   * Default rule to apply when the rule file is not found. Default to 200.
+   */
+  private static final String HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_DEFAULT =
+      "hbase.master.balancer.heterogeneousRegionCountDefault";
+  /**
+   * Cost for the function. Default to 500, can be changed.
+   */
+  private static final String REGION_COUNT_SKEW_COST_KEY =
+      "hbase.master.balancer.stochastic.heterogeneousRegionCountCost";
+  private static final float DEFAULT_REGION_COUNT_SKEW_COST = 500;
+  private final String rulesPath;
+
+  /**
+   * Contains the rules, key is the regexp for ServerName, value is the limit
+   */
+  private final Map<Pattern, Integer> limitPerRule;
+
+  /**
+   * This is a cache, used to not go through all the limitPerRule map when searching for limit
+   */
+  private final Map<ServerName, Integer> limitPerRS;
+  private final Configuration conf;
+  private int defaultNumberOfRegions;
+
+  /**
+   * Total capacity of regions for the cluster, based on the online RS and their associated rules
+   */
+  private int totalCapacity = 0;
+  double overallUsage;
+
+  HeterogeneousRegionCountCostFunction(final Configuration conf) {
+    super(conf);
+    this.conf = conf;
+    this.limitPerRS = new HashMap<>();
+    this.limitPerRule = new HashMap<>();
+    this.setMultiplier(conf.getFloat(REGION_COUNT_SKEW_COST_KEY, DEFAULT_REGION_COUNT_SKEW_COST));
+    this.rulesPath = conf.get(HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_FILE);
+    this.defaultNumberOfRegions =
+        conf.getInt(HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_DEFAULT, 200);
+
+    if (this.defaultNumberOfRegions < 0) {
+      LOG.warn("invalid configuration '" + HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_DEFAULT
+          + "'. Setting default to 200");
+      this.defaultNumberOfRegions = 200;
+    }
+    if (conf.getFloat(StochasticLoadBalancer.RegionCountSkewCostFunction.REGION_COUNT_SKEW_COST_KEY,
+      StochasticLoadBalancer.RegionCountSkewCostFunction.DEFAULT_REGION_COUNT_SKEW_COST) > 0) {
+      LOG.warn("regionCountCost is not set to 0, "
+          + " this will interfere with the HeterogeneousRegionCountCostFunction!");
+    }
+  }
+
+  /**
+   * Called once per LB invocation to give the cost function to initialize it's state, and perform
+   * any costly calculation.
+   */
+  @Override
+  void init(final BaseLoadBalancer.Cluster cluster) {
+    this.cluster = cluster;
+    this.loadRules();
+  }
+
+  @Override
+  protected double cost() {
+    double cost = 0;
+    final double targetUsage = ((double) this.cluster.numRegions / (double) this.totalCapacity);
+
+    for (int i = 0; i < this.cluster.numServers; i++) {
+      // retrieve capacity for each RS
+      final ServerName sn = this.cluster.servers[i];
+      final double limit = this.limitPerRS.getOrDefault(sn, defaultNumberOfRegions);
+      final double nbrRegions = this.cluster.regionsPerServer[i].length;
+      final double usage = nbrRegions / limit;
+      if (usage > targetUsage) {
+        // cost is the number of regions above the local limit
+        final double localCost = (nbrRegions - Math.round(limit * targetUsage)) / limit;
+        cost += localCost;
+      }
+    }
+
+    return cost / (double) this.cluster.numServers;
+  }
+
+  /**
+   * used to load the rule files.
+   */
+  void loadRules() {
+    final List<String> lines = readFile(this.rulesPath);
+    if (null == lines) {
+      LOG.warn("cannot load rules file, keeping latest rules file which has "
+          + this.limitPerRule.size() + " rules");
+      return;
+    }
+
+    LOG.info("loading rules file '" + this.rulesPath + "'");
+    this.limitPerRule.clear();
+    for (final String line : lines) {
+      try {
+        if (line.length() == 0) {
+          continue;
+        }
+        if (line.startsWith("#")) {
+          continue;
+        }
+        final String[] splits = line.split(" ");
+        if (splits.length != 2) {
+          throw new IOException(
+              "line '" + line + "' is malformated, " + "expected [regexp] [limit]. Skipping line");
+        }
+
+        final Pattern pattern = Pattern.compile(splits[0]);
+        final Integer limit = Integer.parseInt(splits[1]);
+        this.limitPerRule.put(pattern, limit);
+      } catch (final IOException | NumberFormatException | PatternSyntaxException e) {
+        LOG.error("error on line: " + e);
+      }
+    }
+    this.rebuildCache();
+  }
+
+  /**
+   * used to read the rule files from either HDFS or local FS
+   */
+  private List<String> readFile(final String filename) {
+    if (null == filename) {
+      return null;
+    }
+    try {
+      if (filename.startsWith("file:")) {
+        return readFileFromLocalFS(filename);
+      }
+      return readFileFromHDFS(filename);
+    } catch (IOException e) {
+      LOG.error("cannot read rules file located at ' " + filename + " ':" + e.getMessage());
+      return null;
+    }
+  }
+
+  /**
+   * used to read the rule files from HDFS
+   */
+  private List<String> readFileFromHDFS(final String filename) throws IOException {
+    final Path path = new Path(filename);
+    final FileSystem fs = FileSystem.get(this.conf);
+    final BufferedReader reader = new BufferedReader(new InputStreamReader(fs.open(path)));
+    return readLines(reader);
+  }
+
+  /**
+   * used to read the rule files from local FS
+   */
+  private List<String> readFileFromLocalFS(final String filename) throws IOException {
+    BufferedReader reader = new BufferedReader(new FileReader(filename));
+    return readLines(reader);
+  }
+
+  private List<String> readLines(BufferedReader reader) throws IOException {
+    final List<String> records = new ArrayList<>();
+    String line;
+    while ((line = reader.readLine()) != null) {
+      records.add(line);
+    }
+    reader.close();
+    return records;
+  }
+
+  /**
+   * Rebuild cache matching ServerNames and their capacity.
+   */
+  private void rebuildCache() {
+    LOG.debug("Rebuilding cache of capacity for each RS");
+    this.limitPerRS.clear();
+    this.totalCapacity = 0;
+    if (null == this.cluster) {
+      return;
+    }
+    for (int i = 0; i < this.cluster.numServers; i++) {
+      final ServerName sn = this.cluster.servers[i];
+      final int capacity = this.findLimitForRS(sn);
+      LOG.debug(sn.getHostname() + " can hold " + capacity + " regions");
+      this.totalCapacity += capacity;
+    }
+    overallUsage = (double) this.cluster.numRegions / (double) this.totalCapacity;
+    LOG.info("Cluster can hold " + this.cluster.numRegions + "/" + this.totalCapacity + " regions ("
+        + Math.round(overallUsage * 100) + "%)");
+    if (overallUsage >= 1) {
+      LOG.warn("Cluster is overused");
+    }
+  }
+
+  /**
+   * Find the limit for a ServerName. If not found then return the default value
+   * @param serverName the server we are looking for
+   * @return the limit
+   */
+  int findLimitForRS(final ServerName serverName) {
+    boolean matched = false;
+    int limit = -1;
+    for (final Map.Entry<Pattern, Integer> entry : this.limitPerRule.entrySet()) {
+      if (entry.getKey().matcher(serverName.getHostname()).matches()) {
+        matched = true;
+        limit = entry.getValue();
+        break;
+      }
+    }
+    if (!matched) {
+      limit = this.defaultNumberOfRegions;
+    }
+    // Feeding cache
+    this.limitPerRS.put(serverName, limit);
+    return limit;
+  }
+
+  int getNumberOfRulesLoaded() {
+    return this.limitPerRule.size();
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/master/balancer/StochasticLoadBalancer.java

@@ -1192,9 +1192,9 @@ public class StochasticLoadBalancer extends BaseLoadBalancer {
    * regions on a cluster.
    */
   static class RegionCountSkewCostFunction extends CostFunction {
-    private static final String REGION_COUNT_SKEW_COST_KEY =
+    static final String REGION_COUNT_SKEW_COST_KEY =
         "hbase.master.balancer.stochastic.regionCountCost";
-    private static final float DEFAULT_REGION_COUNT_SKEW_COST = 500;
+    static final float DEFAULT_REGION_COUNT_SKEW_COST = 500;
 
     private double[] stats = null;
 

hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancerHeterogeneousCost.java

@@ -0,0 +1,275 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hadoop.hbase.master.balancer;
+
+import static junit.framework.TestCase.assertNotNull;
+import static junit.framework.TestCase.assertTrue;
+import static org.junit.Assert.assertNull;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Random;
+import java.util.TreeMap;
+import java.util.concurrent.ThreadLocalRandom;
+
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseConfiguration;
+import org.apache.hadoop.hbase.ServerName;
+import org.apache.hadoop.hbase.client.RegionInfo;
+import org.apache.hadoop.hbase.client.RegionReplicaUtil;
+import org.apache.hadoop.hbase.master.RackManager;
+import org.apache.hadoop.hbase.master.RegionPlan;
+import org.apache.hadoop.hbase.testclassification.MasterTests;
+import org.apache.hadoop.hbase.testclassification.MediumTests;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+@Category({ MasterTests.class, MediumTests.class })
+public class TestStochasticLoadBalancerHeterogeneousCost extends BalancerTestBase {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+      HBaseClassTestRule.forClass(TestStochasticLoadBalancerHeterogeneousCost.class);
+
+  private static final Logger LOG =
+      LoggerFactory.getLogger(TestStochasticLoadBalancerHeterogeneousCost.class);
+  private static final double allowedWindow = 1.20;
+
+  @BeforeClass
+  public static void beforeAllTests() {
+    BalancerTestBase.conf = HBaseConfiguration.create();
+    BalancerTestBase.conf.setFloat("hbase.master.balancer.stochastic.regionCountCost", 0);
+    BalancerTestBase.conf.setFloat("hbase.master.balancer.stochastic.primaryRegionCountCost", 0);
+    BalancerTestBase.conf.setFloat("hbase.master.balancer.stochastic.tableSkewCost", 0);
+    BalancerTestBase.conf.setBoolean("hbase.master.balancer.stochastic.runMaxSteps", true);
+    BalancerTestBase.conf.set(StochasticLoadBalancer.COST_FUNCTIONS_COST_FUNCTIONS_KEY,
+      HeterogeneousRegionCountCostFunction.class.getName());
+
+    BalancerTestBase.conf.set(
+      HeterogeneousRegionCountCostFunction.HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_FILE,
+      TestStochasticLoadBalancerHeterogeneousCostRules.DEFAULT_RULES_TMP_LOCATION);
+
+    BalancerTestBase.loadBalancer = new StochasticLoadBalancer();
+    BalancerTestBase.loadBalancer.setConf(BalancerTestBase.conf);
+  }
+
+  @Test
+  public void testDefault() throws IOException {
+    final List<String> rules = Collections.emptyList();
+
+    final int numNodes = 2;
+    final int numRegions = 300;
+    final int numRegionsPerServer = 250;
+
+    // Initial state: { rs1:50 , rs0:250 }
+    // Cluster can hold 300/400 regions (75%)
+    // Expected balanced Cluster: { rs0:150 , rs1:150 }
+    this.testHeterogeneousWithCluster(numNodes, numRegions, numRegionsPerServer, rules);
+  }
+
+  @Test
+  public void testOneGroup() throws IOException {
+    final List<String> rules = Collections.singletonList("rs.* 100");
+
+    final int numNodes = 4;
+    final int numRegions = 300;
+    final int numRegionsPerServer = 30;
+
+    // Initial state: { rs0:30 , rs1:30 , rs2:30 , rs3:210 }.
+    // The cluster can hold 300/400 regions (75%)
+    // Expected balanced Cluster: { rs0:75 , rs1:75 , rs2:75 , rs3:75 }
+    this.testHeterogeneousWithCluster(numNodes, numRegions, numRegionsPerServer, rules);
+  }
+
+  @Test
+  public void testTwoGroups() throws IOException {
+    final List<String> rules = Arrays.asList("rs[0-4] 200", "rs[5-9] 50");
+
+    final int numNodes = 10;
+    final int numRegions = 500;
+    final int numRegionsPerServer = 50;
+
+    // Initial state: { rs0:50 , rs1:50 , rs2:50 , rs3:50 , rs4:50 , rs5:50 , rs6:50 , rs7:50 ,
+    // rs8:50 , rs9:50 }
+    // the cluster can hold 500/1250 regions (40%)
+    // Expected balanced Cluster: { rs5:20 , rs6:20 , rs7:20 , rs8:20 , rs9:20 , rs0:80 , rs1:80 ,
+    // rs2:80 , rs3:80 , rs4:80 }
+    this.testHeterogeneousWithCluster(numNodes, numRegions, numRegionsPerServer, rules);
+  }
+
+  @Test
+  public void testFourGroups() throws IOException {
+    final List<String> rules = Arrays.asList("rs[1-3] 200", "rs[4-7] 250", "rs[8-9] 100");
+
+    final int numNodes = 10;
+    final int numRegions = 800;
+    final int numRegionsPerServer = 80;
+
+    // Initial state: { rs0:80 , rs1:80 , rs2:80 , rs3:80 , rs4:80 , rs5:80 , rs6:80 , rs7:80 ,
+    // rs8:80 , rs9:80 }
+    // Cluster can hold 800/2000 regions (40%)
+    // Expected balanced Cluster: { rs8:40 , rs9:40 , rs2:80 , rs3:80 , rs1:82 , rs0:94 , rs4:96 ,
+    // rs5:96 , rs6:96 , rs7:96 }
+    this.testHeterogeneousWithCluster(numNodes, numRegions, numRegionsPerServer, rules);
+  }
+
+  @Test
+  public void testOverloaded() throws IOException {
+    final List<String> rules = Collections.singletonList("rs[0-1] 50");
+
+    final int numNodes = 2;
+    final int numRegions = 120;
+    final int numRegionsPerServer = 60;
+
+    TestStochasticLoadBalancerHeterogeneousCostRules.createSimpleRulesFile(rules);
+    final Map<ServerName, List<RegionInfo>> serverMap =
+        this.createServerMap(numNodes, numRegions, numRegionsPerServer, 1, 1);
+    final List<RegionPlan> plans = BalancerTestBase.loadBalancer.balanceCluster(serverMap);
+    // As we disabled all the other cost functions, balancing only according to
+    // the heterogeneous cost function should return nothing.
+    assertNull(plans);
+  }
+
+  private void testHeterogeneousWithCluster(final int numNodes, final int numRegions,
+      final int numRegionsPerServer, final List<String> rules) throws IOException {
+
+    TestStochasticLoadBalancerHeterogeneousCostRules.createSimpleRulesFile(rules);
+    final Map<ServerName, List<RegionInfo>> serverMap =
+        this.createServerMap(numNodes, numRegions, numRegionsPerServer, 1, 1);
+    this.testWithCluster(serverMap, null, true, false);
+  }
+
+  protected void testWithCluster(final Map<ServerName, List<RegionInfo>> serverMap,
+      final RackManager rackManager, final boolean assertFullyBalanced,
+      final boolean assertFullyBalancedForReplicas) {
+    final List<ServerAndLoad> list = this.convertToList(serverMap);
+    LOG.info("Mock Cluster : " + this.printMock(list) + " " + this.printStats(list));
+
+    BalancerTestBase.loadBalancer.setRackManager(rackManager);
+
+    // Run the balancer.
+    final List<RegionPlan> plans = BalancerTestBase.loadBalancer.balanceCluster(serverMap);
+    assertNotNull(plans);
+
+    // Check to see that this actually got to a stable place.
+    if (assertFullyBalanced || assertFullyBalancedForReplicas) {
+      // Apply the plan to the mock cluster.
+      final List<ServerAndLoad> balancedCluster = this.reconcile(list, plans, serverMap);
+
+      // Print out the cluster loads to make debugging easier.
+      LOG.info("Mock Balanced cluster : " + this.printMock(balancedCluster));
+
+      if (assertFullyBalanced) {
+        final List<RegionPlan> secondPlans =
+            BalancerTestBase.loadBalancer.balanceCluster(serverMap);
+        assertNull(secondPlans);
+
+        // create external cost function to retrieve limit
+        // for each RS
+        final HeterogeneousRegionCountCostFunction cf =
+            new HeterogeneousRegionCountCostFunction(conf);
+        assertNotNull(cf);
+        BaseLoadBalancer.Cluster cluster =
+            new BaseLoadBalancer.Cluster(serverMap, null, null, null);
+        cf.init(cluster);
+
+        // checking that we all hosts have a number of regions below their limit
+        for (final ServerAndLoad serverAndLoad : balancedCluster) {
+          final ServerName sn = serverAndLoad.getServerName();
+          final int numberRegions = serverAndLoad.getLoad();
+          final int limit = cf.findLimitForRS(sn);
+
+          double usage = (double) numberRegions / (double) limit;
+          LOG.debug(
+            sn.getHostname() + ":" + numberRegions + "/" + limit + "(" + (usage * 100) + "%)");
+
+          // as the balancer is stochastic, we cannot check exactly the result of the balancing,
+          // hence the allowedWindow parameter
+          assertTrue("Host " + sn.getHostname() + " should be below "
+              + cf.overallUsage * allowedWindow * 100 + "%",
+            usage <= cf.overallUsage * allowedWindow);
+        }
+      }
+
+      if (assertFullyBalancedForReplicas) {
+        this.assertRegionReplicaPlacement(serverMap, rackManager);
+      }
+    }
+  }
+
+  @Override
+  protected Map<ServerName, List<RegionInfo>> createServerMap(int numNodes, int numRegions,
+      int numRegionsPerServer, int replication, int numTables) {
+    // construct a cluster of numNodes, having a total of numRegions. Each RS will hold
+    // numRegionsPerServer many regions except for the last one, which will host all the
+    // remaining regions
+    int[] cluster = new int[numNodes];
+    for (int i = 0; i < numNodes; i++) {
+      cluster[i] = numRegionsPerServer;
+    }
+    cluster[cluster.length - 1] = numRegions - ((cluster.length - 1) * numRegionsPerServer);
+    Map<ServerName, List<RegionInfo>> clusterState = mockClusterServers(cluster, numTables);
+    if (replication > 0) {
+      // replicate the regions to the same servers
+      for (List<RegionInfo> regions : clusterState.values()) {
+        int length = regions.size();
+        for (int i = 0; i < length; i++) {
+          for (int r = 1; r < replication; r++) {
+            regions.add(RegionReplicaUtil.getRegionInfoForReplica(regions.get(i), r));
+          }
+        }
+      }
+    }
+
+    return clusterState;
+  }
+
+  @Override
+  protected TreeMap<ServerName, List<RegionInfo>> mockClusterServers(int[] mockCluster,
+      int numTables) {
+    int numServers = mockCluster.length;
+    TreeMap<ServerName, List<RegionInfo>> servers = new TreeMap<>();
+    for (int i = 0; i < numServers; i++) {
+      int numRegions = mockCluster[i];
+      ServerAndLoad sal = createServer("rs" + i);
+      List<RegionInfo> regions = randomRegions(numRegions, numTables);
+      servers.put(sal.getServerName(), regions);
+    }
+    return servers;
+  }
+
+  private Queue<ServerName> serverQueue = new LinkedList<>();
+
+  private ServerAndLoad createServer(final String host) {
+    if (!this.serverQueue.isEmpty()) {
+      ServerName sn = this.serverQueue.poll();
+      return new ServerAndLoad(sn, 0);
+    }
+    Random rand = ThreadLocalRandom.current();
+    int port = rand.nextInt(60000);
+    long startCode = rand.nextLong();
+    ServerName sn = ServerName.valueOf(host, port, startCode);
+    return new ServerAndLoad(sn, 0);
+  }
+}

hbase-server/src/test/java/org/apache/hadoop/hbase/master/balancer/TestStochasticLoadBalancerHeterogeneousCostRules.java

@@ -0,0 +1,161 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hadoop.hbase.master.balancer;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.hbase.HBaseClassTestRule;
+import org.apache.hadoop.hbase.HBaseTestingUtility;
+import org.apache.hadoop.hbase.testclassification.MasterTests;
+import org.apache.hadoop.hbase.testclassification.SmallTests;
+import org.apache.hadoop.hdfs.DistributedFileSystem;
+import org.apache.hadoop.hdfs.MiniDFSCluster;
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+@Category({ MasterTests.class, SmallTests.class })
+public class TestStochasticLoadBalancerHeterogeneousCostRules extends BalancerTestBase {
+
+  @ClassRule
+  public static final HBaseClassTestRule CLASS_RULE =
+      HBaseClassTestRule.forClass(TestStochasticLoadBalancerHeterogeneousCostRules.class);
+
+  static final String DEFAULT_RULES_TMP_LOCATION = "/tmp/hbase-balancer.rules";
+  static Configuration conf;
+  private HeterogeneousRegionCountCostFunction costFunction;
+
+  @BeforeClass
+  public static void beforeAllTests() throws Exception {
+    createSimpleRulesFile(new ArrayList<>());
+    conf = new Configuration();
+    conf.set(HeterogeneousRegionCountCostFunction.HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_FILE,
+      DEFAULT_RULES_TMP_LOCATION);
+  }
+
+  static void createSimpleRulesFile(final List<String> lines) throws IOException {
+    cleanup();
+    final Path file = Paths.get(DEFAULT_RULES_TMP_LOCATION);
+    Files.write(file, lines, Charset.forName("UTF-8"));
+  }
+
+  protected static void cleanup() {
+    final File file = new File(DEFAULT_RULES_TMP_LOCATION);
+    file.delete();
+  }
+
+  @AfterClass
+  public static void afterAllTests() {
+    cleanup();
+  }
+
+  @Test
+  public void testNoRules() {
+    cleanup();
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(0, this.costFunction.getNumberOfRulesLoaded());
+  }
+
+  @Test
+  public void testBadFormatInRules() throws IOException {
+    createSimpleRulesFile(new ArrayList<>());
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(0, this.costFunction.getNumberOfRulesLoaded());
+
+    createSimpleRulesFile(Collections.singletonList("bad rules format"));
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(0, this.costFunction.getNumberOfRulesLoaded());
+
+    createSimpleRulesFile(Arrays.asList("srv[1-2] 10", "bad_rules format", "a"));
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(1, this.costFunction.getNumberOfRulesLoaded());
+  }
+
+  @Test
+  public void testTwoRules() throws IOException {
+    createSimpleRulesFile(Arrays.asList("^server1$ 10", "^server2 21"));
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(2, this.costFunction.getNumberOfRulesLoaded());
+  }
+
+  @Test
+  public void testBadRegexp() throws IOException {
+    createSimpleRulesFile(Collections.singletonList("server[ 1"));
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(0, this.costFunction.getNumberOfRulesLoaded());
+  }
+
+  @Test
+  public void testNoOverride() throws IOException {
+    createSimpleRulesFile(Arrays.asList("^server1$ 10", "^server2 21"));
+    this.costFunction = new HeterogeneousRegionCountCostFunction(conf);
+    this.costFunction.loadRules();
+    Assert.assertEquals(2, this.costFunction.getNumberOfRulesLoaded());
+
+    // loading malformed configuration does not overload current
+    cleanup();
+    this.costFunction.loadRules();
+    Assert.assertEquals(2, this.costFunction.getNumberOfRulesLoaded());
+  }
+
+  @Test
+  public void testLoadingFomHDFS() throws Exception {
+
+    HBaseTestingUtility hBaseTestingUtility = new HBaseTestingUtility();
+    hBaseTestingUtility.startMiniDFSCluster(3);
+
+    MiniDFSCluster cluster = hBaseTestingUtility.getDFSCluster();
+    DistributedFileSystem fs = cluster.getFileSystem();
+
+    String path = cluster.getURI() + DEFAULT_RULES_TMP_LOCATION;
+
+    // writing file
+    FSDataOutputStream stream = fs.create(new org.apache.hadoop.fs.Path(path));
+    stream.write("server1 10".getBytes());
+    stream.flush();
+    stream.close();
+
+    Configuration configuration = hBaseTestingUtility.getConfiguration();
+
+    // start costFunction
+    configuration.set(
+      HeterogeneousRegionCountCostFunction.HBASE_MASTER_BALANCER_HETEROGENEOUS_RULES_FILE, path);
+    this.costFunction = new HeterogeneousRegionCountCostFunction(configuration);
+    this.costFunction.loadRules();
+    Assert.assertEquals(1, this.costFunction.getNumberOfRulesLoaded());
+
+    hBaseTestingUtility.shutdownMiniCluster();
+  }
+}