[HDFS-4451] hdfs balancer command returns exit code 1 on success instead of 0

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.0.2-alpha
• Fix Version/s: 2.0.3-alpha
• Component/s: balancer & mover

Environment

Centos 6.3, JDK 1.6.0_25

• Hadoop Flags: Incompatible change, Reviewed
• Release Note: This is an incompatible change from release 2.0.2-alpha and prior releases. Balancer tool exited with exit code 1 on success. It is changed to exit with exit code 0 on success. Non 0 exit code indicates failure.
• Assignee: Unassigned
• Reporter: Joshua Blatt
• Created: 29/Jan/13 17:33
• Updated: 15/Feb/13 13:12
• Resolved: 31/Jan/13 19:03

Description

Though the org.apache.hadoop.util.Tool interface javadocs indicate implementations should return 0 on success, the org.apache.hadoop.hdfs.server.balance.Balancer.Cli implementation returns the int values of this enum instead:

// Exit status
enum ReturnStatus {
SUCCESS(1),
IN_PROGRESS(0),
ALREADY_RUNNING(-1),
NO_MOVE_BLOCK(-2),
NO_MOVE_PROGRESS(-3),
IO_EXCEPTION(-4),
ILLEGAL_ARGS(-5),
INTERRUPTED(-6);

This created an issue for us when we tried to run the hdfs balancer as a cron job. Cron sends emails whenever a executable it runs exits non-zero. We'd either have to disable all emails and miss real issues or fix this bug.

I think both SUCCESS and IN_PROGRESS ReturnStatuses should lead to exit 0.

Marking this change as incompatible because existing scripts which interpret exit 1 as success will be broken (unless they defensively/liberally interpret both exit 1 and exit 0 as success).