HBASE-22686 ZkSplitLogWorkerCoordination doesn't allow a regionserver to pick up all of the split work it is capable of

hbase-server/src/main/java/org/apache/hadoop/hbase/coordination/ZkSplitLogWorkerCoordination.java

@@ -328,34 +328,10 @@ public class ZkSplitLogWorkerCoordination extends ZooKeeperListener implements
   }
 
   /**
-   * This function calculates how many splitters this RS should create based on expected average
-   * tasks per RS and the hard limit upper bound(maxConcurrentTasks) set by configuration. <br>
-   * At any given time, a RS allows spawn MIN(Expected Tasks/RS, Hard Upper Bound)
-   * @param numTasks total number of split tasks available
-   * @return number of tasks this RS can grab
-   */
-  private int getNumExpectedTasksPerRS(int numTasks) {
-    // at lease one RS(itself) available
-    int availableRSs = 1;
-    try {
-      List<String> regionServers =
-          ZKUtil.listChildrenNoWatch(watcher, watcher.rsZNode);
-      availableRSs = Math.max(availableRSs, (regionServers == null) ? 0 : regionServers.size());
-    } catch (KeeperException e) {
-      // do nothing
-      LOG.debug("getAvailableRegionServers got ZooKeeper exception", e);
-    }
-    int expectedTasksPerRS = (numTasks / availableRSs) + ((numTasks % availableRSs == 0) ? 0 : 1);
-    return Math.max(1, expectedTasksPerRS); // at least be one
-  }
-
-  /**
-   * @param expectedTasksPerRS Average number of tasks to be handled by each RS
    * @return true if more splitters are available, otherwise false.
    */
-  private boolean areSplittersAvailable(int expectedTasksPerRS) {
-    return (Math.min(expectedTasksPerRS, maxConcurrentTasks)
-        - this.tasksInProgress.get()) > 0;
+  private boolean areSplittersAvailable() {
+    return maxConcurrentTasks - tasksInProgress.get() > 0;
   }
 
   /**
@@ -436,13 +412,14 @@ public class ZkSplitLogWorkerCoordination extends ZooKeeperListener implements
         }
       }
       int numTasks = paths.size();
-      int expectedTasksPerRS = getNumExpectedTasksPerRS(numTasks);
       boolean taskGrabbed = false;
       for (int i = 0; i < numTasks; i++) {
         while (!shouldStop) {
-          if (this.areSplittersAvailable(expectedTasksPerRS)) {
-            LOG.debug("Current region server " + server.getServerName()
+          if (this.areSplittersAvailable()) {
+            if (LOG.isTraceEnabled()) {
+              LOG.trace("Current region server " + server.getServerName()
                 + " is ready to take more tasks, will get task list and try grab tasks again.");
+            }
             int idx = (i + offset) % paths.size();
             // don't call ZKSplitLog.getNodeName() because that will lead to
             // double encoding of the path name
@@ -450,9 +427,11 @@ public class ZkSplitLogWorkerCoordination extends ZooKeeperListener implements
                 paths.get(idx)));
             break;
           } else {
-            LOG.debug("Current region server " + server.getServerName()
+            if (LOG.isTraceEnabled()) {
+              LOG.trace("Current region server " + server.getServerName()
                 + " has " + this.tasksInProgress.get()
                 + " tasks in progress and can't take more.");
+            }
             Thread.sleep(100);
           }
         }

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitLogWorker.java

@@ -455,53 +455,6 @@ public class TestSplitLogWorker {
     }
   }
 
-  /**
-   * The test checks SplitLogWorker should not spawn more splitters than expected num of tasks per
-   * RS
-   * @throws Exception
-   */
-  @Test(timeout=60000)
-  public void testAcquireMultiTasksByAvgTasksPerRS() throws Exception {
-    LOG.info("testAcquireMultiTasks");
-    SplitLogCounters.resetCounters();
-    final String TATAS = "tatas";
-    final ServerName RS = ServerName.valueOf("rs,1,1");
-    final ServerName RS2 = ServerName.valueOf("rs,1,2");
-    final int maxTasks = 3;
-    Configuration testConf = HBaseConfiguration.create(TEST_UTIL.getConfiguration());
-    testConf.setInt("hbase.regionserver.wal.max.splitters", maxTasks);
-    RegionServerServices mockedRS = getRegionServer(RS);
-
-    // create two RS nodes
-    String rsPath = ZKUtil.joinZNode(zkw.rsZNode, RS.getServerName());
-    zkw.getRecoverableZooKeeper().create(rsPath, null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
-    rsPath = ZKUtil.joinZNode(zkw.rsZNode, RS2.getServerName());
-    zkw.getRecoverableZooKeeper().create(rsPath, null, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
-
-    for (int i = 0; i < maxTasks; i++) {
-      zkw.getRecoverableZooKeeper().create(ZKSplitLog.getEncodedNodeName(zkw, TATAS + i),
-        new SplitLogTask.Unassigned(ServerName.valueOf("mgr,1,1"), this.mode).toByteArray(),
-          Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
-    }
-
-    SplitLogWorker slw = new SplitLogWorker(ds, testConf, mockedRS, neverEndingTask);
-    slw.start();
-    try {
-      int acquiredTasks = 0;
-      waitForCounter(SplitLogCounters.tot_wkr_task_acquired, 0, 2, WAIT_TIME);
-      for (int i = 0; i < maxTasks; i++) {
-        byte[] bytes = ZKUtil.getData(zkw, ZKSplitLog.getEncodedNodeName(zkw, TATAS + i));
-        SplitLogTask slt = SplitLogTask.parseFrom(bytes);
-        if (slt.isOwned(RS)) {
-          acquiredTasks++;
-        }
-      }
-      assertEquals(2, acquiredTasks);
-    } finally {
-      stopSplitLogWorker(slw);
-    }
-  }
-
   /**
    * Create a mocked region server service instance
    * @param server