HBASE-20548 Master fails to startup on large clusters, refreshing block distribution

Signed-off-by: Andrew Purtell <apurtell@apache.org>

hbase-rsgroup/src/main/java/org/apache/hadoop/hbase/rsgroup/RSGroupBasedLoadBalancer.java

@@ -466,4 +466,9 @@ public class RSGroupBasedLoadBalancer implements RSGroupableBalancer {
   public void setRsGroupInfoManager(RSGroupInfoManager rsGroupInfoManager) {
     this.rsGroupInfoManager = rsGroupInfoManager;
   }
+
+  @Override
+  public void postMasterStartupInitialize() {
+    this.internalBalancer.postMasterStartupInitialize();
+  }
 }

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

@@ -1003,6 +1003,17 @@ public class HMaster extends HRegionServer implements MasterServices {
     }
 
     zombieDetector.interrupt();
+
+    /*
+     * After master has started up, lets do balancer post startup initialization. Since this runs
+     * in activeMasterManager thread, it should be fine.
+     */
+    long start = System.currentTimeMillis();
+    this.balancer.postMasterStartupInitialize();
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("Balancer post startup initialization complete, took " + (
+          (System.currentTimeMillis() - start) / 1000) + " seconds");
+    }
   }
 
   /**

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

@@ -159,6 +159,11 @@ public interface LoadBalancer extends Configurable, Stoppable, ConfigurationObse
   @Override
   void onConfigurationChange(Configuration conf);
 
+  /**
+   * If balancer needs to do initialization after Master has started up, lets do that here.
+   */
+  void postMasterStartupInitialize();
+
   /**
    * @return true if Master carries regions
    */

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

@@ -1151,6 +1151,19 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
     }
   }
 
+  @Override
+  public void postMasterStartupInitialize() {
+    if (services != null && regionFinder != null) {
+      try {
+        Set<RegionInfo> regions =
+            services.getAssignmentManager().getRegionStates().getRegionAssignments().keySet();
+        regionFinder.refreshAndWait(regions);
+      } catch (Exception e) {
+        LOG.warn("Refreshing region HDFS Block dist failed with exception, ignoring", e);
+      }
+    }
+  }
+
   public void setRackManager(RackManager rackManager) {
     this.rackManager = rackManager;
   }
@@ -1249,7 +1262,7 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
       return assignments;
     }
 
-    Cluster cluster = createCluster(servers, regions, false);
+    Cluster cluster = createCluster(servers, regions);
     List<RegionInfo> unassignedRegions = new ArrayList<>();
 
     roundRobinAssignment(cluster, regions, unassignedRegions,
@@ -1288,11 +1301,7 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
     return assignments;
   }
 
-  protected Cluster createCluster(List<ServerName> servers,
+  protected Cluster createCluster(List<ServerName> servers, Collection<RegionInfo> regions) {
-      Collection<RegionInfo> regions, boolean forceRefresh) {
-    if (forceRefresh && useRegionFinder) {
-      regionFinder.refreshAndWait(regions);
-    }
     // Get the snapshot of the current assignments for the regions in question, and then create
     // a cluster out of it. Note that we might have replicas already assigned to some servers
     // earlier. So we want to get the snapshot to see those assignments, but this will only contain
@@ -1346,7 +1355,7 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
     final List<ServerName> finalServers = idleServers.isEmpty() ?
             servers : idleServers;
     List<RegionInfo> regions = Lists.newArrayList(regionInfo);
-    Cluster cluster = createCluster(finalServers, regions, false);
+    Cluster cluster = createCluster(finalServers, regions);
     return randomAssignment(cluster, regionInfo, finalServers);
   }
 
@@ -1419,8 +1428,6 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
     int numRandomAssignments = 0;
     int numRetainedAssigments = 0;
 
-    Cluster cluster = createCluster(servers, regions.keySet(), true);
-
     for (Map.Entry<RegionInfo, ServerName> entry : regions.entrySet()) {
       RegionInfo region = entry.getKey();
       ServerName oldServerName = entry.getValue();
@@ -1463,6 +1470,7 @@ public abstract class BaseLoadBalancer implements LoadBalancer {
 
     // If servers from prior assignment aren't present, then lets do randomAssignment on regions.
     if (randomAssignRegions.size() > 0) {
+      Cluster cluster = createCluster(servers, regions.keySet());
       for (Map.Entry<ServerName, List<RegionInfo>> entry : assignments.entrySet()) {
         ServerName sn = entry.getKey();
         for (RegionInfo region : entry.getValue()) {