Package org.apache.storm.grouping

# Interface CustomStreamGrouping

All Superinterfaces:
  `Serializable`

All Known Subinterfaces:
  `LoadAwareCustomStreamGrouping`

All Known Implementing Classes:
  `GlobalGrouping`, `GrouperFactory.AllGrouper`, `GrouperFactory.BasicLoadAwareCustomStreamGrouping`, `GrouperFactory.FieldsGrouper`, `GrouperFactory.GlobalGrouper`, `GrouperFactory.NoneGrouper`, `IdentityGrouping`, `IndexHashGrouping`, `LoadAwareShuffleGrouping`, `NGrouping`, `PartialKeyGrouping`, `ShuffleGrouping`

public interface CustomStreamGrouping extends Serializable

- ## Method Summary

  Modifier and Type
  Method
  Description
  `List<Integer>`
  `chooseTasks(int taskId, List<Object> values)`
  This function implements a custom stream grouping.
  `void`
  `prepare(WorkerTopologyContext context, GlobalStreamId stream, List<Integer> targetTasks)`
  Tells the stream grouping at runtime the tasks in the target bolt.

- ## Method Details

  - ### prepare

    void prepare(WorkerTopologyContext context, GlobalStreamId stream, List<Integer> targetTasks)
    Tells the stream grouping at runtime the tasks in the target bolt. This information should be used in chooseTasks to determine the target tasks.

    It also tells the grouping the metadata on the stream this grouping will be used on.

  - ### chooseTasks

    List<Integer> chooseTasks(int taskId, List<Object> values)
    This function implements a custom stream grouping. It takes in as input the number of tasks in the target bolt in prepare and returns the tasks to send the tuples to.
    Parameters:
      `values` - the values to group on