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Posted to commits@hbase.apache.org by zh...@apache.org on 2016/07/15 01:59:08 UTC

hbase git commit: HBASE-16219 addendum move MasterMetaBootstrap to the right place

Repository: hbase
Updated Branches:
  refs/heads/master 6462a615c -> 243fe287b


HBASE-16219 addendum move MasterMetaBootstrap to the right place


Project: http://git-wip-us.apache.org/repos/asf/hbase/repo
Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/243fe287
Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/243fe287
Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/243fe287

Branch: refs/heads/master
Commit: 243fe287b9055f4a16dda0175d5247d2d7a6b81e
Parents: 6462a61
Author: zhangduo <zh...@apache.org>
Authored: Fri Jul 15 09:56:01 2016 +0800
Committer: zhangduo <zh...@apache.org>
Committed: Fri Jul 15 09:58:17 2016 +0800

----------------------------------------------------------------------
 .../hadoop/hbase/MasterMetaBootstrap.java       | 257 -------------------
 .../hbase/master/MasterMetaBootstrap.java       | 257 +++++++++++++++++++
 2 files changed, 257 insertions(+), 257 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/hbase/blob/243fe287/hbase-server/src/main/java/org/apache/hadoop/hbase/MasterMetaBootstrap.java
----------------------------------------------------------------------
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/MasterMetaBootstrap.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/MasterMetaBootstrap.java
deleted file mode 100644
index 0504555..0000000
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/MasterMetaBootstrap.java
+++ /dev/null
@@ -1,257 +0,0 @@
-/**
- *
- * 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.hadoop.hbase.master;
-
-import java.io.IOException;
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.List;
-import java.util.HashSet;
-import java.util.Set;
-
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
-import org.apache.hadoop.hbase.HConstants;
-import org.apache.hadoop.hbase.HRegionInfo;
-import org.apache.hadoop.hbase.ServerName;
-import org.apache.hadoop.hbase.TableName;
-import org.apache.hadoop.hbase.classification.InterfaceAudience;
-import org.apache.hadoop.hbase.client.RegionReplicaUtil;
-import org.apache.hadoop.hbase.client.TableState;
-import org.apache.hadoop.hbase.monitoring.MonitoredTask;
-import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
-import org.apache.hadoop.hbase.zookeeper.MetaTableLocator;
-import org.apache.hadoop.hbase.zookeeper.ZKUtil;
-import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
-import org.apache.zookeeper.KeeperException;
-
-/**
- * Used by the HMaster on startup to split meta logs and assign the meta table.
- */
-@InterfaceAudience.Private
-public class MasterMetaBootstrap {
-  private static final Log LOG = LogFactory.getLog(MasterMetaBootstrap.class);
-
-  private final MonitoredTask status;
-  private final HMaster master;
-
-  private Set<ServerName> previouslyFailedServers;
-  private Set<ServerName> previouslyFailedMetaRSs;
-
-  public MasterMetaBootstrap(final HMaster master, final MonitoredTask status) {
-    this.master = master;
-    this.status = status;
-  }
-
-  public void splitMetaLogsBeforeAssignment() throws IOException, KeeperException {
-    // get a list for previously failed RS which need log splitting work
-    // we recover hbase:meta region servers inside master initialization and
-    // handle other failed servers in SSH in order to start up master node ASAP
-    previouslyFailedServers = master.getMasterWalManager().getFailedServersFromLogFolders();
-
-    // log splitting for hbase:meta server
-    ServerName oldMetaServerLocation = master.getMetaTableLocator()
-        .getMetaRegionLocation(master.getZooKeeper());
-    if (oldMetaServerLocation != null && previouslyFailedServers.contains(oldMetaServerLocation)) {
-      splitMetaLogBeforeAssignment(oldMetaServerLocation);
-      // Note: we can't remove oldMetaServerLocation from previousFailedServers list because it
-      // may also host user regions
-    }
-    previouslyFailedMetaRSs = getPreviouselyFailedMetaServersFromZK();
-    // need to use union of previouslyFailedMetaRSs recorded in ZK and previouslyFailedServers
-    // instead of previouslyFailedMetaRSs alone to address the following two situations:
-    // 1) the chained failure situation(recovery failed multiple times in a row).
-    // 2) master get killed right before it could delete the recovering hbase:meta from ZK while the
-    // same server still has non-meta wals to be replayed so that
-    // removeStaleRecoveringRegionsFromZK can't delete the stale hbase:meta region
-    // Passing more servers into splitMetaLog is all right. If a server doesn't have hbase:meta wal,
-    // there is no op for the server.
-    previouslyFailedMetaRSs.addAll(previouslyFailedServers);
-  }
-
-  public void assignMeta() throws InterruptedException, IOException, KeeperException {
-    assignMeta(previouslyFailedMetaRSs, HRegionInfo.DEFAULT_REPLICA_ID);
-  }
-
-  public void processDeadServers() throws IOException {
-    // Master has recovered hbase:meta region server and we put
-    // other failed region servers in a queue to be handled later by SSH
-    for (ServerName tmpServer : previouslyFailedServers) {
-      master.getServerManager().processDeadServer(tmpServer, true);
-    }
-  }
-
-  public void assignMetaReplicas()
-      throws IOException, InterruptedException, KeeperException {
-    int numReplicas = master.getConfiguration().getInt(HConstants.META_REPLICAS_NUM,
-           HConstants.DEFAULT_META_REPLICA_NUM);
-    final Set<ServerName> EMPTY_SET = new HashSet<ServerName>();
-    for (int i = 1; i < numReplicas; i++) {
-      assignMeta(EMPTY_SET, i);
-    }
-    unassignExcessMetaReplica(numReplicas);
-  }
-
-  private void splitMetaLogBeforeAssignment(ServerName currentMetaServer) throws IOException {
-    if (RecoveryMode.LOG_REPLAY == master.getMasterWalManager().getLogRecoveryMode()) {
-      // In log replay mode, we mark hbase:meta region as recovering in ZK
-      master.getMasterWalManager().prepareLogReplay(currentMetaServer,
-        Collections.<HRegionInfo>singleton(HRegionInfo.FIRST_META_REGIONINFO));
-    } else {
-      // In recovered.edits mode: create recovered edits file for hbase:meta server
-      master.getMasterWalManager().splitMetaLog(currentMetaServer);
-    }
-  }
-
-  private void unassignExcessMetaReplica(int numMetaReplicasConfigured) {
-    final ZooKeeperWatcher zooKeeper = master.getZooKeeper();
-    // unassign the unneeded replicas (for e.g., if the previous master was configured
-    // with a replication of 3 and now it is 2, we need to unassign the 1 unneeded replica)
-    try {
-      List<String> metaReplicaZnodes = zooKeeper.getMetaReplicaNodes();
-      for (String metaReplicaZnode : metaReplicaZnodes) {
-        int replicaId = zooKeeper.getMetaReplicaIdFromZnode(metaReplicaZnode);
-        if (replicaId >= numMetaReplicasConfigured) {
-          RegionState r = MetaTableLocator.getMetaRegionState(zooKeeper, replicaId);
-          LOG.info("Closing excess replica of meta region " + r.getRegion());
-          // send a close and wait for a max of 30 seconds
-          ServerManager.closeRegionSilentlyAndWait(master.getClusterConnection(),
-              r.getServerName(), r.getRegion(), 30000);
-          ZKUtil.deleteNode(zooKeeper, zooKeeper.getZNodeForReplica(replicaId));
-        }
-      }
-    } catch (Exception ex) {
-      // ignore the exception since we don't want the master to be wedged due to potential
-      // issues in the cleanup of the extra regions. We can do that cleanup via hbck or manually
-      LOG.warn("Ignoring exception " + ex);
-    }
-  }
-
-  /**
-   * Check <code>hbase:meta</code> is assigned. If not, assign it.
-   */
-  protected void assignMeta(Set<ServerName> previouslyFailedMetaRSs, int replicaId)
-      throws InterruptedException, IOException, KeeperException {
-    final AssignmentManager assignmentManager = master.getAssignmentManager();
-
-    // Work on meta region
-    int assigned = 0;
-    long timeout = master.getConfiguration().getLong("hbase.catalog.verification.timeout", 1000);
-    if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
-      status.setStatus("Assigning hbase:meta region");
-    } else {
-      status.setStatus("Assigning hbase:meta region, replicaId " + replicaId);
-    }
-
-    // Get current meta state from zk.
-    RegionState metaState = MetaTableLocator.getMetaRegionState(master.getZooKeeper(), replicaId);
-    HRegionInfo hri = RegionReplicaUtil.getRegionInfoForReplica(HRegionInfo.FIRST_META_REGIONINFO,
-        replicaId);
-    RegionStates regionStates = assignmentManager.getRegionStates();
-    regionStates.createRegionState(hri, metaState.getState(),
-        metaState.getServerName(), null);
-
-    if (!metaState.isOpened() || !master.getMetaTableLocator().verifyMetaRegionLocation(
-        master.getClusterConnection(), master.getZooKeeper(), timeout, replicaId)) {
-      ServerName currentMetaServer = metaState.getServerName();
-      if (master.getServerManager().isServerOnline(currentMetaServer)) {
-        if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
-          LOG.info("Meta was in transition on " + currentMetaServer);
-        } else {
-          LOG.info("Meta with replicaId " + replicaId + " was in transition on " +
-                    currentMetaServer);
-        }
-        assignmentManager.processRegionsInTransition(Collections.singletonList(metaState));
-      } else {
-        if (currentMetaServer != null) {
-          if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
-            splitMetaLogBeforeAssignment(currentMetaServer);
-            regionStates.logSplit(HRegionInfo.FIRST_META_REGIONINFO);
-            previouslyFailedMetaRSs.add(currentMetaServer);
-          }
-        }
-        LOG.info("Re-assigning hbase:meta with replicaId, " + replicaId +
-            " it was on " + currentMetaServer);
-        assignmentManager.assignMeta(hri);
-      }
-      assigned++;
-    }
-
-    if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
-      // TODO: should we prevent from using state manager before meta was initialized?
-      // tableStateManager.start();
-      master.getTableStateManager()
-        .setTableState(TableName.META_TABLE_NAME, TableState.State.ENABLED);
-    }
-
-    if ((RecoveryMode.LOG_REPLAY == master.getMasterWalManager().getLogRecoveryMode())
-        && (!previouslyFailedMetaRSs.isEmpty())) {
-      // replay WAL edits mode need new hbase:meta RS is assigned firstly
-      status.setStatus("replaying log for Meta Region");
-      master.getMasterWalManager().splitMetaLog(previouslyFailedMetaRSs);
-    }
-
-    assignmentManager.setEnabledTable(TableName.META_TABLE_NAME);
-    master.getTableStateManager().start();
-
-    // Make sure a hbase:meta location is set. We need to enable SSH here since
-    // if the meta region server is died at this time, we need it to be re-assigned
-    // by SSH so that system tables can be assigned.
-    // No need to wait for meta is assigned = 0 when meta is just verified.
-    if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) enableCrashedServerProcessing(assigned != 0);
-    LOG.info("hbase:meta with replicaId " + replicaId + " assigned=" + assigned + ", location="
-      + master.getMetaTableLocator().getMetaRegionLocation(master.getZooKeeper(), replicaId));
-    status.setStatus("META assigned.");
-  }
-
-  private void enableCrashedServerProcessing(final boolean waitForMeta)
-      throws IOException, InterruptedException {
-    // If crashed server processing is disabled, we enable it and expire those dead but not expired
-    // servers. This is required so that if meta is assigning to a server which dies after
-    // assignMeta starts assignment, ServerCrashProcedure can re-assign it. Otherwise, we will be
-    // stuck here waiting forever if waitForMeta is specified.
-    if (!master.isServerCrashProcessingEnabled()) {
-      master.setServerCrashProcessingEnabled(true);
-      master.getServerManager().processQueuedDeadServers();
-    }
-
-    if (waitForMeta) {
-      master.getMetaTableLocator().waitMetaRegionLocation(master.getZooKeeper());
-    }
-  }
-
-  /**
-   * This function returns a set of region server names under hbase:meta recovering region ZK node
-   * @return Set of meta server names which were recorded in ZK
-   */
-  private Set<ServerName> getPreviouselyFailedMetaServersFromZK() throws KeeperException {
-    final ZooKeeperWatcher zooKeeper = master.getZooKeeper();
-    Set<ServerName> result = new HashSet<ServerName>();
-    String metaRecoveringZNode = ZKUtil.joinZNode(zooKeeper.recoveringRegionsZNode,
-      HRegionInfo.FIRST_META_REGIONINFO.getEncodedName());
-    List<String> regionFailedServers = ZKUtil.listChildrenNoWatch(zooKeeper, metaRecoveringZNode);
-    if (regionFailedServers == null) return result;
-
-    for (String failedServer : regionFailedServers) {
-      ServerName server = ServerName.parseServerName(failedServer);
-      result.add(server);
-    }
-    return result;
-  }
-}

http://git-wip-us.apache.org/repos/asf/hbase/blob/243fe287/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterMetaBootstrap.java
----------------------------------------------------------------------
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterMetaBootstrap.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterMetaBootstrap.java
new file mode 100644
index 0000000..0504555
--- /dev/null
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterMetaBootstrap.java
@@ -0,0 +1,257 @@
+/**
+ *
+ * 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.hadoop.hbase.master;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.HashSet;
+import java.util.Set;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.HRegionInfo;
+import org.apache.hadoop.hbase.ServerName;
+import org.apache.hadoop.hbase.TableName;
+import org.apache.hadoop.hbase.classification.InterfaceAudience;
+import org.apache.hadoop.hbase.client.RegionReplicaUtil;
+import org.apache.hadoop.hbase.client.TableState;
+import org.apache.hadoop.hbase.monitoring.MonitoredTask;
+import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos.SplitLogTask.RecoveryMode;
+import org.apache.hadoop.hbase.zookeeper.MetaTableLocator;
+import org.apache.hadoop.hbase.zookeeper.ZKUtil;
+import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
+import org.apache.zookeeper.KeeperException;
+
+/**
+ * Used by the HMaster on startup to split meta logs and assign the meta table.
+ */
+@InterfaceAudience.Private
+public class MasterMetaBootstrap {
+  private static final Log LOG = LogFactory.getLog(MasterMetaBootstrap.class);
+
+  private final MonitoredTask status;
+  private final HMaster master;
+
+  private Set<ServerName> previouslyFailedServers;
+  private Set<ServerName> previouslyFailedMetaRSs;
+
+  public MasterMetaBootstrap(final HMaster master, final MonitoredTask status) {
+    this.master = master;
+    this.status = status;
+  }
+
+  public void splitMetaLogsBeforeAssignment() throws IOException, KeeperException {
+    // get a list for previously failed RS which need log splitting work
+    // we recover hbase:meta region servers inside master initialization and
+    // handle other failed servers in SSH in order to start up master node ASAP
+    previouslyFailedServers = master.getMasterWalManager().getFailedServersFromLogFolders();
+
+    // log splitting for hbase:meta server
+    ServerName oldMetaServerLocation = master.getMetaTableLocator()
+        .getMetaRegionLocation(master.getZooKeeper());
+    if (oldMetaServerLocation != null && previouslyFailedServers.contains(oldMetaServerLocation)) {
+      splitMetaLogBeforeAssignment(oldMetaServerLocation);
+      // Note: we can't remove oldMetaServerLocation from previousFailedServers list because it
+      // may also host user regions
+    }
+    previouslyFailedMetaRSs = getPreviouselyFailedMetaServersFromZK();
+    // need to use union of previouslyFailedMetaRSs recorded in ZK and previouslyFailedServers
+    // instead of previouslyFailedMetaRSs alone to address the following two situations:
+    // 1) the chained failure situation(recovery failed multiple times in a row).
+    // 2) master get killed right before it could delete the recovering hbase:meta from ZK while the
+    // same server still has non-meta wals to be replayed so that
+    // removeStaleRecoveringRegionsFromZK can't delete the stale hbase:meta region
+    // Passing more servers into splitMetaLog is all right. If a server doesn't have hbase:meta wal,
+    // there is no op for the server.
+    previouslyFailedMetaRSs.addAll(previouslyFailedServers);
+  }
+
+  public void assignMeta() throws InterruptedException, IOException, KeeperException {
+    assignMeta(previouslyFailedMetaRSs, HRegionInfo.DEFAULT_REPLICA_ID);
+  }
+
+  public void processDeadServers() throws IOException {
+    // Master has recovered hbase:meta region server and we put
+    // other failed region servers in a queue to be handled later by SSH
+    for (ServerName tmpServer : previouslyFailedServers) {
+      master.getServerManager().processDeadServer(tmpServer, true);
+    }
+  }
+
+  public void assignMetaReplicas()
+      throws IOException, InterruptedException, KeeperException {
+    int numReplicas = master.getConfiguration().getInt(HConstants.META_REPLICAS_NUM,
+           HConstants.DEFAULT_META_REPLICA_NUM);
+    final Set<ServerName> EMPTY_SET = new HashSet<ServerName>();
+    for (int i = 1; i < numReplicas; i++) {
+      assignMeta(EMPTY_SET, i);
+    }
+    unassignExcessMetaReplica(numReplicas);
+  }
+
+  private void splitMetaLogBeforeAssignment(ServerName currentMetaServer) throws IOException {
+    if (RecoveryMode.LOG_REPLAY == master.getMasterWalManager().getLogRecoveryMode()) {
+      // In log replay mode, we mark hbase:meta region as recovering in ZK
+      master.getMasterWalManager().prepareLogReplay(currentMetaServer,
+        Collections.<HRegionInfo>singleton(HRegionInfo.FIRST_META_REGIONINFO));
+    } else {
+      // In recovered.edits mode: create recovered edits file for hbase:meta server
+      master.getMasterWalManager().splitMetaLog(currentMetaServer);
+    }
+  }
+
+  private void unassignExcessMetaReplica(int numMetaReplicasConfigured) {
+    final ZooKeeperWatcher zooKeeper = master.getZooKeeper();
+    // unassign the unneeded replicas (for e.g., if the previous master was configured
+    // with a replication of 3 and now it is 2, we need to unassign the 1 unneeded replica)
+    try {
+      List<String> metaReplicaZnodes = zooKeeper.getMetaReplicaNodes();
+      for (String metaReplicaZnode : metaReplicaZnodes) {
+        int replicaId = zooKeeper.getMetaReplicaIdFromZnode(metaReplicaZnode);
+        if (replicaId >= numMetaReplicasConfigured) {
+          RegionState r = MetaTableLocator.getMetaRegionState(zooKeeper, replicaId);
+          LOG.info("Closing excess replica of meta region " + r.getRegion());
+          // send a close and wait for a max of 30 seconds
+          ServerManager.closeRegionSilentlyAndWait(master.getClusterConnection(),
+              r.getServerName(), r.getRegion(), 30000);
+          ZKUtil.deleteNode(zooKeeper, zooKeeper.getZNodeForReplica(replicaId));
+        }
+      }
+    } catch (Exception ex) {
+      // ignore the exception since we don't want the master to be wedged due to potential
+      // issues in the cleanup of the extra regions. We can do that cleanup via hbck or manually
+      LOG.warn("Ignoring exception " + ex);
+    }
+  }
+
+  /**
+   * Check <code>hbase:meta</code> is assigned. If not, assign it.
+   */
+  protected void assignMeta(Set<ServerName> previouslyFailedMetaRSs, int replicaId)
+      throws InterruptedException, IOException, KeeperException {
+    final AssignmentManager assignmentManager = master.getAssignmentManager();
+
+    // Work on meta region
+    int assigned = 0;
+    long timeout = master.getConfiguration().getLong("hbase.catalog.verification.timeout", 1000);
+    if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
+      status.setStatus("Assigning hbase:meta region");
+    } else {
+      status.setStatus("Assigning hbase:meta region, replicaId " + replicaId);
+    }
+
+    // Get current meta state from zk.
+    RegionState metaState = MetaTableLocator.getMetaRegionState(master.getZooKeeper(), replicaId);
+    HRegionInfo hri = RegionReplicaUtil.getRegionInfoForReplica(HRegionInfo.FIRST_META_REGIONINFO,
+        replicaId);
+    RegionStates regionStates = assignmentManager.getRegionStates();
+    regionStates.createRegionState(hri, metaState.getState(),
+        metaState.getServerName(), null);
+
+    if (!metaState.isOpened() || !master.getMetaTableLocator().verifyMetaRegionLocation(
+        master.getClusterConnection(), master.getZooKeeper(), timeout, replicaId)) {
+      ServerName currentMetaServer = metaState.getServerName();
+      if (master.getServerManager().isServerOnline(currentMetaServer)) {
+        if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
+          LOG.info("Meta was in transition on " + currentMetaServer);
+        } else {
+          LOG.info("Meta with replicaId " + replicaId + " was in transition on " +
+                    currentMetaServer);
+        }
+        assignmentManager.processRegionsInTransition(Collections.singletonList(metaState));
+      } else {
+        if (currentMetaServer != null) {
+          if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
+            splitMetaLogBeforeAssignment(currentMetaServer);
+            regionStates.logSplit(HRegionInfo.FIRST_META_REGIONINFO);
+            previouslyFailedMetaRSs.add(currentMetaServer);
+          }
+        }
+        LOG.info("Re-assigning hbase:meta with replicaId, " + replicaId +
+            " it was on " + currentMetaServer);
+        assignmentManager.assignMeta(hri);
+      }
+      assigned++;
+    }
+
+    if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) {
+      // TODO: should we prevent from using state manager before meta was initialized?
+      // tableStateManager.start();
+      master.getTableStateManager()
+        .setTableState(TableName.META_TABLE_NAME, TableState.State.ENABLED);
+    }
+
+    if ((RecoveryMode.LOG_REPLAY == master.getMasterWalManager().getLogRecoveryMode())
+        && (!previouslyFailedMetaRSs.isEmpty())) {
+      // replay WAL edits mode need new hbase:meta RS is assigned firstly
+      status.setStatus("replaying log for Meta Region");
+      master.getMasterWalManager().splitMetaLog(previouslyFailedMetaRSs);
+    }
+
+    assignmentManager.setEnabledTable(TableName.META_TABLE_NAME);
+    master.getTableStateManager().start();
+
+    // Make sure a hbase:meta location is set. We need to enable SSH here since
+    // if the meta region server is died at this time, we need it to be re-assigned
+    // by SSH so that system tables can be assigned.
+    // No need to wait for meta is assigned = 0 when meta is just verified.
+    if (replicaId == HRegionInfo.DEFAULT_REPLICA_ID) enableCrashedServerProcessing(assigned != 0);
+    LOG.info("hbase:meta with replicaId " + replicaId + " assigned=" + assigned + ", location="
+      + master.getMetaTableLocator().getMetaRegionLocation(master.getZooKeeper(), replicaId));
+    status.setStatus("META assigned.");
+  }
+
+  private void enableCrashedServerProcessing(final boolean waitForMeta)
+      throws IOException, InterruptedException {
+    // If crashed server processing is disabled, we enable it and expire those dead but not expired
+    // servers. This is required so that if meta is assigning to a server which dies after
+    // assignMeta starts assignment, ServerCrashProcedure can re-assign it. Otherwise, we will be
+    // stuck here waiting forever if waitForMeta is specified.
+    if (!master.isServerCrashProcessingEnabled()) {
+      master.setServerCrashProcessingEnabled(true);
+      master.getServerManager().processQueuedDeadServers();
+    }
+
+    if (waitForMeta) {
+      master.getMetaTableLocator().waitMetaRegionLocation(master.getZooKeeper());
+    }
+  }
+
+  /**
+   * This function returns a set of region server names under hbase:meta recovering region ZK node
+   * @return Set of meta server names which were recorded in ZK
+   */
+  private Set<ServerName> getPreviouselyFailedMetaServersFromZK() throws KeeperException {
+    final ZooKeeperWatcher zooKeeper = master.getZooKeeper();
+    Set<ServerName> result = new HashSet<ServerName>();
+    String metaRecoveringZNode = ZKUtil.joinZNode(zooKeeper.recoveringRegionsZNode,
+      HRegionInfo.FIRST_META_REGIONINFO.getEncodedName());
+    List<String> regionFailedServers = ZKUtil.listChildrenNoWatch(zooKeeper, metaRecoveringZNode);
+    if (regionFailedServers == null) return result;
+
+    for (String failedServer : regionFailedServers) {
+      ServerName server = ServerName.parseServerName(failedServer);
+      result.add(server);
+    }
+    return result;
+  }
+}