[GitHub] [hadoop] liuml07 commented on a change in pull request #2245: HADOOP-17159 Ability for forceful relogin in UserGroupInformation class

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liuml07 commented on a change in pull request #2245:
URL: https://github.com/apache/hadoop/pull/2245#discussion_r478602120



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File path: hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/security/UserGroupInformation.java
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@@ -1215,23 +1215,43 @@ private void fixKerberosTicketOrder() {
    * Re-Login a user in from a keytab file. Loads a user identity from a keytab
    * file and logs them in. They become the currently logged-in user. This
    * method assumes that {@link #loginUserFromKeytab(String, String)} had
-   * happened already.
-   * The Subject field of this UserGroupInformation object is updated to have
-   * the new credentials.
+   * happened already. The Subject field of this UserGroupInformation object is
+   * updated to have the new credentials.
+   *
    * @throws IOException
    * @throws KerberosAuthException on a failure
    */
   @InterfaceAudience.Public
   @InterfaceStability.Evolving
   public synchronized void reloginFromKeytab() throws IOException {
+    reloginFromKeytab(false);
+  }
+
+  /**
+   * Force re-Login a user in from a keytab file. Loads a user identity from a
+   * keytab file and logs them in. They become the currently logged-in user.
+   * This method assumes that {@link #loginUserFromKeytab(String, String)} had
+   * happened already. The Subject field of this UserGroupInformation object is
+   * updated to have the new credentials.
+   *
+   * @param ignoreTimeElapsed Force re-login irrespective of the time of last
+   *                          login
+   * @throws IOException
+   * @throws KerberosAuthException on a failure
+   */
+  @InterfaceAudience.Public
+  @InterfaceStability.Evolving
+  public synchronized void reloginFromKeytab(boolean ignoreTimeElapsed)

Review comment:
       I'm thinking of the same problem of the same method signature when potential Hadoop 2 code calling `reloginFromKeytab(false)` upgrades to Hadoop 3. Because of the same method name and a bool parameter, users most likely will not notice the parameter value is for different meanings: in Hadoop 2 here, the bool parameter is for `ignoreTimeElapsed` where in Hadoop 3 it is actually for `checkTGT`.
   
   So is it better to:
   1. Make this new API `public synchronized void reloginFromKeytab(boolean ignoreTimeElapsed)` private
   2. AND we also add the new API as in Hadoop 3: `public void forceReloginFromKeytab()`.
   
   That way, the application code which forces login will have the same code between Hadoop 2 and 3. And the other new API `reloginFromKeytab(boolean)` is private in UGI both in Hadoop 2 and 3.




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