HBASE-6487 assign region doesn't check if the region is already assigned

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1374423 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -2085,8 +2085,13 @@ Server {
         LOG.warn("assignRegion specifier type: expected: " + RegionSpecifierType.REGION_NAME
           + " actual: " + type);
       }
-      HRegionInfo regionInfo = assignmentManager.getRegionStates().getRegionInfo(regionName);
+      RegionStates regionStates = assignmentManager.getRegionStates();
+      HRegionInfo regionInfo = regionStates.getRegionInfo(regionName);
       if (regionInfo == null) throw new UnknownRegionException(Bytes.toString(regionName));
+      RegionState regionState = regionStates.getRegionState(regionInfo);
+      if (regionState != null && !regionState.isOffline()) {
+        throw new IOException("Region " + regionInfo + " is not offline");
+      }
       if (cpHost != null) {
         if (cpHost.preAssign(regionInfo)) {
           return arr;

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

@@ -132,6 +132,13 @@ public class RegionStates {
     return regionAssignments.containsKey(hri);
   }
 
+  /**
+   * @return the server the specified region assigned to; null if not assigned.
+   */
+  public synchronized ServerName getAssignedServer(final HRegionInfo hri) {
+    return regionAssignments.get(hri);
+  }
+
   /**
    * Wait for the state map to be updated by assignment manager.
    */
@@ -519,7 +526,11 @@ public class RegionStates {
     try {
       Pair<HRegionInfo, ServerName> p =
         MetaReader.getRegion(server.getCatalogTracker(), regionName);
-      return p == null ? null : p.getFirst();
+      HRegionInfo hri = p == null ? null : p.getFirst();
+      if (hri != null) {
+        createRegionState(hri);
+      }
+      return hri;
     } catch (IOException e) {
       server.abort("Aborting because error occoured while reading " +
         Bytes.toStringBinary(regionName) + " from .META.", e);

hbase-server/src/main/ruby/shell/commands/assign.rb

@@ -24,8 +24,7 @@ module Shell
       def help
         return <<-EOF
 Assign a region.Use with caution.If region already assigned,
-this command will just go ahead and reassign
+this command will throw an exception. For experts only.
-the region anyways. For experts only.
 EOF
       end