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 and was able to
tell the region servers to unassign all the regions to balance  (the re-assignment itself is async).
Otherwise false (Will not run if regions in transition).
Parameter tells master whether we should force balance 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 "force"
EOF
      end

      def command(force = nil)
        force_balancer = 'false'
        if force == 'force'
          force_balancer = 'true'
        elsif !force.nil?
          raise ArgumentError, "Invalid argument #{force}."
        end
        did_balancer_run = !!admin.balancer(force_balancer)
        formatter.row([did_balancer_run.to_s])
        did_balancer_run
      end
    end
  end
end