Kerberos in E-MapReduce supports cross-region access, meaning that different Kerberos clusters can access each other. This section describes cross-region access using cluster A and cluster B as an example.

  • Hostname of emr-header-1 in clusterA → emr-header-1.cluster-1234. Region → EMR.1234.COM
  • Hostname of emr-header-1 in clusterB → emr-header-1.cluster-6789. Region → EMR.6789.COM
    Note
    • The hostname can be obtained by executing the hostname command on emr-header-1.
    • The region can be obtained in /etc/krb5.conf on emr-header-1.

Add principal

The emr-header-1 nodes in clusterA and clusterB both run the following command:

# root account
       sh /usr/lib/has-current/bin/hadmin-local.sh /etc/ecm/has-conf -k /etc/ecm/has-conf/admin.keytab
       HadminLocalTool.local: addprinc -pw 123456 krbtgt/EMR.6789.COM@EMR.1234.COM 6789. COM@EMR. 1234. Com
Note
  • The password is 123456. This can be modified.
  • The region of cluster B is EMR.6789.COM. This is the region of the cluster being accessed.
  • The region of cluster A is EMR.1234.COM. This is the region of the cluster that initiates access.

Configure /etc/krb5.conf for clusterA

Configure [regions]/[domain_region]/[capaths] on clusterA as follows:

[libdefaults]
    kdc_realm = EMR. 1234. COM
    default_realm = EMR. 1234. COM
    udp_preference_limit = 4096
    kdc_tcp_port = 88
    kdc_udp_port = 88
    dns_lookup_kdc = false
[realms]
    EMR. 1234. COM = {
                kdc = 10.81.49.3:88
    }
    EMR. 6789. COM = {
                kdc = 10.81.49.7:88
    }
[domain_realm]
    .cluster-1234 = EMR. 1234. COM
    .cluster-6789 = EMR. 6789. COM
[capaths]
    EMR. 1234. COM = {
       EMR. 6789. COM = .
    }
    EMR. 6789. COM = {
       EMR. 1234. COM = .
    }
Synchronize /etc/krb5.conf to all clusterA nodes.

Copy the binding information (only the long domain name emr-xxx-x.cluster-xxx is required) from cluster B's /etc/hosts file to /etc/hosts for all clusterA nodes. 

10.81.45.89  emr-worker-1.cluster-xxx
 10.81.46.222  emr-worker-2.cluster-xx
 10.81.44.177  emr-header-1.cluster-xxx
Note
  • If you want to run a job on clusterA to access clusterB, you must first restart YARN.
  • Configure cluster B's host binding information for all clusterA nodes.

Access services in clusterB

You can use cluster A's Kerberos keytab file /ticket as a cache on cluster A to access services in clusterB.

For example, access the HDFS service in clusterB as follows:

su has;
hadoop fs -ls hdfs://emr-header-1.cluster-6789:9000/
Found 4 items
-rw-r-----   2 has    hadoop         34 2017-12-05 18:15 hdfs://emr-header-1.cluster-6789:9000/abc
drwxrwxrwt   - hadoop hadoop          0 2017-12-05 18:32 hdfs://emr-header-1.cluster-6789:9000/spark-history
drwxrwxrwt   - hadoop hadoop          0 2017-12-05 17:53 hdfs://emr-header-1.cluster-6789:9000/tmp
drwxrwxrwt   - hadoop hadoop          0 2017-12-05 18:24 hdfs://emr-header-1.cluster-6789:9000/user