diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/master/RegionState.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/master/RegionState.java
index 04f62d48551..a930732595b 100644
--- a/hbase-client/src/main/java/org/apache/hadoop/hbase/master/RegionState.java
+++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/master/RegionState.java
@@ -176,6 +176,8 @@ public class RegionState {
   private final HRegionInfo hri;
   private final ServerName serverName;
   private final State state;
+  // The duration of region in transition
+  private long ritDuration;
 
   public RegionState(HRegionInfo region, State state) {
     this(region, state, System.currentTimeMillis(), null);
@@ -188,10 +190,16 @@ public class RegionState {
 
   public RegionState(HRegionInfo region,
       State state, long stamp, ServerName serverName) {
+    this(region, state, stamp, serverName, 0);
+  }
+
+  public RegionState(HRegionInfo region, State state, long stamp, ServerName serverName,
+      long ritDuration) {
     this.hri = region;
     this.state = state;
     this.stamp = stamp;
     this.serverName = serverName;
+    this.ritDuration = ritDuration;
   }
 
   public State getState() {
@@ -210,6 +218,19 @@ public class RegionState {
     return serverName;
   }
 
+  public long getRitDuration() {
+    return ritDuration;
+  }
+
+  /**
+   * Update the duration of region in transition
+   * @param previousStamp previous RegionState's timestamp
+   */
+  @InterfaceAudience.Private
+  void updateRitDuration(long previousStamp) {
+    this.ritDuration += (this.stamp - previousStamp);
+  }
+
   /**
    * PENDING_CLOSE (to be removed) is the same as CLOSING
    */
diff --git a/hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSource.java b/hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSource.java
index 6c8a2802462..f6c9cb8ae82 100644
--- a/hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSource.java
+++ b/hbase-hadoop-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSource.java
@@ -45,6 +45,7 @@ public interface MetricsAssignmentManagerSource extends BaseSource {
   String RIT_COUNT_NAME = "ritCount";
   String RIT_COUNT_OVER_THRESHOLD_NAME = "ritCountOverThreshold";
   String RIT_OLDEST_AGE_NAME = "ritOldestAge";
+  String RIT_DURATION_NAME = "ritDuration";
   String ASSIGN_TIME_NAME = "assign";
   String BULK_ASSIGN_TIME_NAME = "bulkAssign";
 
@@ -72,4 +73,6 @@ public interface MetricsAssignmentManagerSource extends BaseSource {
    * @param age age of the oldest RIT.
    */
   void setRITOldestAge(long age);
+
+  void updateRitDuration(long duration);
 }
diff --git a/hbase-hadoop2-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSourceImpl.java b/hbase-hadoop2-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSourceImpl.java
index a2192d2a9f8..ab504f56054 100644
--- a/hbase-hadoop2-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSourceImpl.java
+++ b/hbase-hadoop2-compat/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManagerSourceImpl.java
@@ -31,6 +31,7 @@ public class MetricsAssignmentManagerSourceImpl
   private MutableGaugeLong ritGauge;
   private MutableGaugeLong ritCountOverThresholdGauge;
   private MutableGaugeLong ritOldestAgeGauge;
+  private MetricHistogram ritDurationHisto;
   private MetricHistogram assignTimeHisto;
   private MetricHistogram bulkAssignTimeHisto;
 
@@ -50,6 +51,7 @@ public class MetricsAssignmentManagerSourceImpl
     ritOldestAgeGauge = metricsRegistry.newGauge(RIT_OLDEST_AGE_NAME, "", 0l);
     assignTimeHisto = metricsRegistry.newTimeHistogram(ASSIGN_TIME_NAME);
     bulkAssignTimeHisto = metricsRegistry.newTimeHistogram(BULK_ASSIGN_TIME_NAME);
+    ritDurationHisto = metricsRegistry.newTimeHistogram(RIT_DURATION_NAME);
   }
 
   @Override
@@ -73,4 +75,9 @@ public class MetricsAssignmentManagerSourceImpl
   public void setRITOldestAge(long ritCount) {
     ritOldestAgeGauge.set(ritCount);
   }
+
+  @Override
+  public void updateRitDuration(long duration) {
+    ritDurationHisto.add(duration);
+  }
 }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManager.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManager.java
index b89d2da7d77..40e79aeff49 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManager.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/MetricsAssignmentManager.java
@@ -64,4 +64,12 @@ public class MetricsAssignmentManager {
   public void updateRITOldestAge(long timestamp) {
     assignmentManagerSource.setRITOldestAge(timestamp);
   }
+
+  /**
+   * update the duration metrics of region is transition
+   * @param duration
+   */
+  public void updateRitDuration(long duration) {
+    assignmentManagerSource.updateRitDuration(duration);
+  }
 }
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/RegionStates.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/RegionStates.java
index 6079ed69d6c..b199374b8a8 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/RegionStates.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/RegionStates.java
@@ -451,7 +451,15 @@ public class RegionStates {
     updateRegionState(hri, State.OPEN, serverName, openSeqNum);
 
     synchronized (this) {
-      regionsInTransition.remove(encodedName);
+      RegionState regionState = regionsInTransition.remove(encodedName);
+      // When region is online and remove from regionsInTransition,
+      // update the RIT duration to assignment manager metrics
+      if (regionState != null && this.server.getAssignmentManager() != null) {
+        long ritDuration = System.currentTimeMillis() - regionState.getStamp()
+            + regionState.getRitDuration();
+        this.server.getAssignmentManager().getAssignmentManagerMetrics()
+            .updateRitDuration(ritDuration);
+      }
       ServerName oldServerName = regionAssignments.put(hri, serverName);
       if (!serverName.equals(oldServerName)) {
         if (LOG.isDebugEnabled()) {
@@ -1126,7 +1134,12 @@ public class RegionStates {
     }
 
     synchronized (this) {
-      regionsInTransition.put(encodedName, regionState);
+      RegionState oldRegionState = regionsInTransition.put(encodedName, regionState);
+      // When region transform old region state to new region state,
+      // accumulate the RIT duration to new region state.
+      if (oldRegionState != null) {
+        regionState.updateRitDuration(oldRegionState.getStamp());
+      }
       putRegionState(regionState);
 
       // For these states, region should be properly closed.