Class GroupBalancer

All Implemented Interfaces:
Direct Known Subclasses:

public abstract class GroupBalancer extends Object implements TabletBalancer
A balancer that evenly spreads groups of tablets across all tablet server. This balancer accomplishes the following two goals :
  • Evenly spreads each group across all tservers.
  • Minimizes the total number of groups on each tserver.

To use this balancer you must extend it and implement getPartitioner(). See RegexGroupBalancer as an example.

  • Field Details

  • Constructor Details

    • GroupBalancer

      public GroupBalancer(TableId tableId)
  • Method Details

    • init

      public void init(BalancerEnvironment balancerEnvironment)
      Description copied from interface: TabletBalancer
      Initialize the TabletBalancer. This gives the balancer the opportunity to read the configuration.
      Specified by:
      init in interface TabletBalancer
    • getPartitioner

      protected abstract Function<TabletId,String> getPartitioner()
      A function that groups tablets into named groups.
    • getLocationProvider

      protected Map<TabletId,TabletServerId> getLocationProvider()
    • getWaitTime

      protected long getWaitTime()
      The amount of time to wait between balancing.
    • getMaxMigrations

      protected int getMaxMigrations()
      The maximum number of migrations to perform in a single pass.
    • shouldBalance

      protected boolean shouldBalance(SortedMap<TabletServerId,TServerStatus> current, Set<TabletId> migrations)
      Examine current tserver and migrations and return true if balancing should occur.
    • getAssignments

      public void getAssignments(TabletBalancer.AssignmentParameters params)
      Description copied from interface: TabletBalancer
      Assign tablets to tablet servers. This method is called whenever the manager finds tablets that are unassigned.
      Specified by:
      getAssignments in interface TabletBalancer
    • balance

      public long balance(TabletBalancer.BalanceParameters params)
      Description copied from interface: TabletBalancer
      Ask the balancer if any migrations are necessary. If the balancer is going to self-abort due to some environmental constraint (e.g. it requires some minimum number of tservers, or a maximum number of outstanding migrations), it should issue a log message to alert operators. The message should be at WARN normally and at ERROR if the balancer knows that the problem can not self correct. It should not issue these messages more than once a minute. This method will not be called when there are unassigned tablets.
      Specified by:
      balance in interface TabletBalancer
      the time, in milliseconds, to wait before re-balancing.