diff --git a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
index 2badbb14b9..85ada8d758 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/DFSClient.java
@@ -3181,4 +3181,18 @@ public RemoteIterator<OpenFileEntry> listOpenFiles(
     checkOpen();
     return new OpenFilesIterator(namenode, tracer, openFilesTypes, path);
   }
+
+  /**
+   * A blocking call to wait for Observer NameNode state ID to reach to the
+   * current client state ID. Current client state ID is given by the client
+   * alignment context.
+   * An assumption is that client alignment context has the state ID set at this
+   * point. This is become ObserverReadProxyProvider sets up the initial state
+   * ID when it is being created.
+   *
+   * @throws IOException
+   */
+  public void msync() throws IOException {
+    namenode.msync();
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
index 5b4c897e4f..20e4259985 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java
@@ -1788,6 +1788,17 @@ AddErasureCodingPolicyResponse[] addErasureCodingPolicies(
   BatchedEntries<OpenFileEntry> listOpenFiles(long prevId,
       EnumSet<OpenFilesType> openFilesTypes, String path) throws IOException;
 
+  /**
+   * Called by client to wait until the server has reached the state id of the
+   * client. The client and server state id are given by client side and server
+   * side alignment context respectively. This can be a blocking call.
+   *
+   * @throws IOException
+   */
+  @Idempotent
+  @ReadOnly
+  void msync() throws IOException;
+
   /**
    * Satisfy the storage policy for a file/directory.
    * @param path Path of an existing file/directory.
diff --git a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java
index e4bca51259..f5aa1749b1 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java
@@ -158,6 +158,8 @@
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MkdirsRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCacheDirectiveRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCachePoolRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MsyncRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MsyncResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.OpenFilesBatchResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RecoverLeaseRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RefreshNodesRequestProto;
@@ -1947,6 +1949,16 @@ public BatchedEntries<OpenFileEntry> listOpenFiles(long prevId,
     }
   }
 
+  @Override
+  public void msync() throws IOException {
+    MsyncRequestProto.Builder req = MsyncRequestProto.newBuilder();
+    try {
+      rpcProxy.msync(null, req.build());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
   @Override
   public void satisfyStoragePolicy(String src) throws IOException {
     SatisfyStoragePolicyRequestProto req =
diff --git a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/ClientNamenodeProtocol.proto b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/ClientNamenodeProtocol.proto
index 49ea3f3687..55113a19ca 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/ClientNamenodeProtocol.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/ClientNamenodeProtocol.proto
@@ -830,6 +830,12 @@ message ListOpenFilesResponseProto {
   repeated OpenFilesTypeProto types = 3;
 }
 
+message MsyncRequestProto {
+}
+
+message MsyncResponseProto {
+}
+
 message SatisfyStoragePolicyRequestProto {
   required string src = 1;
 }
@@ -1024,6 +1030,8 @@ service ClientNamenodeProtocol {
       returns(GetQuotaUsageResponseProto);
   rpc listOpenFiles(ListOpenFilesRequestProto)
       returns(ListOpenFilesResponseProto);
+  rpc msync(MsyncRequestProto)
+      returns(MsyncResponseProto);
   rpc satisfyStoragePolicy(SatisfyStoragePolicyRequestProto)
       returns(SatisfyStoragePolicyResponseProto);
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs-client/src/test/java/org/apache/hadoop/hdfs/protocol/TestReadOnly.java b/hadoop-hdfs-project/hadoop-hdfs-client/src/test/java/org/apache/hadoop/hdfs/protocol/TestReadOnly.java
index 34e84fa489..57db8acfc3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-client/src/test/java/org/apache/hadoop/hdfs/protocol/TestReadOnly.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-client/src/test/java/org/apache/hadoop/hdfs/protocol/TestReadOnly.java
@@ -71,7 +71,8 @@ public class TestReadOnly {
           "getDataEncryptionKey",
           "getCurrentEditLogTxid",
           "getEditsFromTxid",
-          "getQuotaUsage"
+          "getQuotaUsage",
+          "msync"
       )
   );
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java
index ddbc01483f..7ac8471007 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java
@@ -1532,6 +1532,11 @@ public BatchedRemoteIterator.BatchedEntries<OpenFileEntry> listOpenFiles(long pr
     return null;
   }
 
+  @Override
+  public void msync() throws IOException {
+    rpcServer.checkOperation(NameNode.OperationCategory.READ, false);
+  }
+
   @Override
   public void satisfyStoragePolicy(String path) throws IOException {
     rpcServer.checkOperation(NameNode.OperationCategory.WRITE, false);
diff --git a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcServer.java b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcServer.java
index 525d6d563b..ddea4c388e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcServer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcServer.java
@@ -1193,6 +1193,11 @@ public BatchedEntries<OpenFileEntry> listOpenFiles(long prevId,
     return clientProto.listOpenFiles(prevId, openFilesTypes, path);
   }
 
+  @Override // ClientProtocol
+  public void msync() throws IOException {
+    clientProto.msync();
+  }
+
   @Override // ClientProtocol
   public void satisfyStoragePolicy(String path) throws IOException {
     clientProto.satisfyStoragePolicy(path);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java
index e51529e2b1..8a4d4a11ad 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java
@@ -175,6 +175,8 @@
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCacheDirectiveResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCachePoolRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ModifyCachePoolResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MsyncRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.MsyncResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RecoverLeaseRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RecoverLeaseResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.RefreshNodesRequestProto;
@@ -1893,6 +1895,17 @@ public ListOpenFilesResponseProto listOpenFiles(RpcController controller,
     }
   }
 
+  @Override
+  public MsyncResponseProto msync(RpcController controller,
+      MsyncRequestProto req) throws ServiceException {
+    try {
+      server.msync();
+      return MsyncResponseProto.newBuilder().build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
   @Override
   public SatisfyStoragePolicyResponseProto satisfyStoragePolicy(
       RpcController controller,
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
index ebca095817..3f05e13bc0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/NameNodeRpcServer.java
@@ -1380,6 +1380,11 @@ public BatchedEntries<OpenFileEntry> listOpenFiles(long prevId,
     return namesystem.listOpenFiles(prevId, openFilesTypes, path);
   }
 
+  @Override // ClientProtocol
+  public void msync() throws IOException {
+    // TODO : need to be filled up if needed. May be a no-op here.
+  }
+
   @Override // ClientProtocol
   public CorruptFileBlocks listCorruptFileBlocks(String path, String cookie)
       throws IOException {