Package org.apache.accumulo.core.spi.balancer

Class GroupBalancer

  • All Implemented Interfaces:
    TabletBalancer
    Direct Known Subclasses:
    RegexGroupBalancer
    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.

    Since:
    2.1.0

    • Constructor Detail

      • GroupBalancer

        public GroupBalancer​(TableId tableId)

    • Method Detail

      • 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()
        Returns:
        A function that groups tablets into named groups.

      • 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.

      • 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
        Returns:
        the time, in milliseconds, to wait before re-balancing.