From 2bd72b9a18ea6630f64bc9dfffc268bb5171a4f4 Mon Sep 17 00:00:00 2001
From: liuwenjing3 <liuwenjing3@360.cn>
Date: Wed, 5 Mar 2025 16:41:06 +0800
Subject: [PATCH] HDFS-17752. Host2DatanodeMap will not update when re-register
 a node with a different hostname

---
 .../server/blockmanagement/DatanodeManager.java   |  9 +++++++++
 .../blockmanagement/TestDatanodeManager.java      | 15 +++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
index bcc77f56db6ae..9299678d68850 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/DatanodeManager.java
@@ -703,6 +703,11 @@ public DatanodeDescriptor getDatanodeByHost(final String host) {
     return host2DatanodeMap.getDatanodeByHost(host);
   }
 
+  /** @return the datanode descriptor for the host. */
+  public DatanodeDescriptor getDatanodeByHostName(final String hostname) {
+    return host2DatanodeMap.getDataNodeByHostName(hostname);
+  }
+
   /** @return the datanode descriptor for the host. */
   public DatanodeDescriptor getDatanodeByXferAddr(String host, int xferPort) {
     return host2DatanodeMap.getDatanodeByXferAddr(host, xferPort);
@@ -1236,6 +1241,10 @@ nodes with its data cleared (or user can just remove the StorageID
               + " is replaced by " + nodeReg + " with the same storageID "
               + nodeReg.getDatanodeUuid());
         }
+
+        if (!updateHost2DatanodeMap) {
+          updateHost2DatanodeMap = !nodeS.getHostName().equals(nodeReg.getHostName());
+        }
         
         boolean success = false;
         try {
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestDatanodeManager.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestDatanodeManager.java
index d881f533adbdf..0714e6b03e421 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestDatanodeManager.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestDatanodeManager.java
@@ -174,6 +174,21 @@ public void testHost2NodeMapCorrectAfterReregister()
 
     assertNull("should be no node with old ip", dm.getDatanodeByHost(ipOld));
     assertNotNull("should be a node with new ip", dm.getDatanodeByHost(ipNew));
+
+    storageID = "someStorageID2";
+    String hostnameOld = "someHostNameOld" + storageID;
+    String hostnameNew = "someHostNameNew" + storageID;
+
+    dm.registerDatanode(new DatanodeRegistration(
+            new DatanodeID("ip", hostnameOld, storageID, 9000, 0, 0, 0),
+            null, null, "version"));
+
+    dm.registerDatanode(new DatanodeRegistration(
+            new DatanodeID("ip", hostnameNew, storageID, 9000, 0, 0, 0),
+            null, null, "version"));
+
+    assertNull("should be no node with old hostname", dm.getDatanodeByHostName(hostnameOld));
+    assertNotNull("should be a node with new hostname", dm.getDatanodeByHostName(hostnameNew));
   }
 
   /**