[HDFS-6536] FileSystem.Cache.closeAll() throws authentication exception at the end of a webhdfs client

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: 2.4.0
• Component/s: hdfs-client, webhdfs
• Assignee: Yongjun Zhang
• Reporter: Yongjun Zhang
• Created: 15/Jun/14 10:54
• Updated: 18/Jun/14 10:35
• Resolved: 18/Jun/14 10:35

Description

With a small client program below, when running as user "root" which doesn't have kerberos credential, exception is thrown at the end of the client run. The config is HA security enabled, with client config setting

  <property>
    <name>fs.defaultFS</name>
    <value>webhdfs://ns1</value>
  </property>

The client program:

public class kclient1 {
	public static void main(String[] args) throws IOException {
	  final Configuration conf = new Configuration();
          //a non-root user
          final UserGroupInformation ugi = UserGroupInformation.getUGIFromTicketCache("/tmp/krb5cc_496", "[e-mail]");  

          System.out.println("Starting");
          ugi.doAs(new PrivilegedAction<Object>() {
	  @Override
	      public Object run() {
		  try {
		  	FileSystem fs = FileSystem.get(conf);			
		  	String renewer = "abcdefg";
		  	fs.addDelegationTokens(
		  			renewer, ugi.getCredentials());
		  	// Just to prove that we connected with right credentials.
		  	fs.getFileStatus(new Path("/"));
		  	return fs.getDelegationToken(renewer);
		  } catch (Exception e) {
		  	e.printStackTrace();
		  	return null;
                  }
           }
    });
    System.out.println("THE END");
  }
}		

Output:

[root@yjzc5w-1 tmp2]# hadoop --config /tmp2/conf jar kclient1.jar kclient1.kclient1
Starting
14/06/14 20:38:51 WARN ssl.FileBasedKeyStoresFactory: The property 'ssl.client.truststore.location' has not been set, no TrustStore will be loaded
14/06/14 20:38:52 INFO web.WebHdfsFileSystem: Retrying connect to namenode: yjzc5w-2.xyz.com/172.26.3.87:20101. Already tried 0 time(s); retry policy is org.apache.hadoop.io.retry.RetryPolicies$FailoverOnNetworkExceptionRetry@1a92210, delay 0ms.
To prove that connection with right credentials
to get file status updated updated 7
THE END
14/06/14 20:38:53 WARN ssl.FileBasedKeyStoresFactory: The property 'ssl.client.truststore.location' has not been set, no TrustStore will be loaded
14/06/14 20:38:53 WARN security.UserGroupInformation: PriviledgedActionException as:root (auth:KERBEROS) cause:java.io.IOException: org.apache.hadoop.security.authentication.client.AuthenticationException: GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt)
14/06/14 20:38:53 INFO fs.FileSystem: FileSystem.Cache.closeAll() threw an exception:
java.io.IOException: Authentication failed, url=http://yjzc5w-2.xyz.com:20101/webhdfs/v1/?op=CANCELDELEGATIONTOKEN&user.name=root&token=HAAEaGRmcwRoZGZzAIoBRp2bNByKAUbBp7gcbBQUD6vWmRYJRv03XZj7Jajf8PU8CB8SV0VCSERGUyBkZWxlZ2F0aW9uC2hhLWhkZnM6bnMx
[root@yjzc5w-1 tmp2]# 

We can see the the exception is thrown in the end of the client run.

I found that the problem is that at the end of client run, the FileSystem$Cache$ClientFinalizer is run, in which process the tokens stored in the filesystem cache is get cancelled with the following all:

final class TokenAspect<T extends FileSystem & Renewable> {
  @InterfaceAudience.Private
  public static class TokenManager extends TokenRenewer {
    @Override
    public void cancel(Token<?> token, Configuration conf) throws IOException {
      getInstance(token, conf).cancelDelegationToken(token); <==
    }

where getInstance(token, conf) create a FileSystem as user "root", then call cancelDelegationToken to server side. However, server doesn't have "root" kerberos credential, so throw this exceptoin.

When I run the same program as user "hdfs" which has the kerberos credential, then it's fine.

In this case, the client program doesn't own the delegation token, it should not try to cancel the token. However, the token does not get cancelled because of the exception I described is thrown, which is good.

The remaining question is, do we need to check token ownership before trying to cancel the token. This is a minor issue here, and I'm dropping the severity.

Hi Daryn Sharp, I wonder if you could give a quick comment, really appreciate it!

Issue Links

• duplicates: HDFS-6222 Remove background token renewer from webhdfs