hbase-shell/src/main/ruby/shell/commands/balancer.rb

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module Shell
  module Commands
    class Balancer < Command
      def help
        <<-EOF
Trigger the cluster balancer. Returns true if balancer ran, otherwise false (Will not run if regions in transition).

Parameter can be "force" or "dry_run":
 - "dry_run" will run the balancer to generate a plan, but will not actually execute that plan.
   This is useful for testing out new balance configurations. See the active HMaster logs for the results of the dry_run.
 - "ignore_rit" tells master whether we should force the balancer to run even if there is region in transition.
   WARNING: For experts only. Forcing a balance may do more damage than repair when assignment is confused

Examples:

  hbase> balancer
  hbase> balancer "ignore_rit"
  hbase> balancer "dry_run"
  hbase> balancer "dry_run", "ignore_rit"
EOF
      end

      def command(*args)
        resp = admin.balancer(args)
        if resp.isBalancerRan
          formatter.row(["Balancer ran"])
          formatter.row(["Moves calculated: #{resp.getMovesCalculated}, moves executed: #{resp.getMovesExecuted}"])
        else
          formatter.row(["Balancer did not run. See logs for details."])
        end
        resp.isBalancerRan
      end
    end
  end
end