HBASE-29947 Improve CopyTable command usage to execute in secure clusters

[srinireddy2020]

Improve CopyTable command usage to execute in secure clusters

[vaijosh]

LGTM

[Copilot]

Pull request overview

Improves CopyTable’s CLI help/usage output by adding additional examples aimed at running CopyTable across secure/insecure clusters (including different Kerberos realms).

Changes:

• Add new CopyTable usage examples showing how to set authentication/principal-related settings when copying across clusters with different security modes.
• Include example commands for secure→insecure, cross-realm secure→secure, and insecure→secure scenarios.

Comments suppressed due to low confidence (4)

hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/CopyTable.java:260

• These new examples rely on --peer.adr and -Dhbase.mapred.output.* overrides. Both are marked deprecated in the codebase (see CopyTable usage text for peer.adr, and TableOutputFormat.OUTPUT_CONF_PREFIX which is deprecated since 3.0.0 and slated for removal in 4.0.0). To keep the usage future-proof, please update the examples to use --peer.uri and pass any per-cluster overrides via the connection URI query parameters instead of hbase.mapred.output.*.

    System.err.println(
      " To copy the data of 'TestTable' between the secured cluster and insecure cluster-b");
    System.err.println(" $ hbase org.apache.hadoop.hbase.mapreduce.CopyTable "
      + "-Dhbase.mapred.output.hbase.security.authentication=simple "
      + "--peer.adr=cluster-b-1.example.com,cluster-b-2.example.com,cluster-b-3.example.com:"
      + "2181:/cluster-b" + " TestTable");

hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/CopyTable.java:257

• The example description is ambiguous about direction (“between the secured cluster and insecure cluster-b”), but CopyTable reads from the local cluster and writes to the configured peer. Consider rewording to explicitly state source vs destination (and use consistent terminology like “secure/secured” and “insecure”).

    System.err.println(
      " To copy the data of 'TestTable' between the secured cluster and insecure cluster-b");
    System.err.println(" $ hbase org.apache.hadoop.hbase.mapreduce.CopyTable "

hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/CopyTable.java:265

• Wording/grammar in this example header is a bit hard to parse (“between different realm secured cluster”) and “kerberos” should be capitalized as “Kerberos” in user-facing help text. Please rephrase for clarity (e.g., “between secured clusters in different Kerberos realms”).

    System.err.println(" To copy the data of 'TestTable' between different realm secured cluster.");
    System.err.println(" Assume cluster-b uses different kerberos principal, "
      + "cluster-b/_HOST@EXAMPLE.COM, for master and regionserver kerberos principal from another "
      + "cluster");

hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/CopyTable.java:275

• Similarly here, “between the insecure cluster and secured cluster-b” doesn’t clarify which side is the local cluster vs the configured peer. Since the command always writes to the peer cluster, consider rewording to make the direction explicit.

    System.err.println(
      " To copy the data of 'TestTable' between the insecure cluster and secured cluster-b");
    System.err.println(" $ hbase org.apache.hadoop.hbase.mapreduce.CopyTable "

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