CoLocationGroup (Flink : Runtime 2.0-preview1 API)

All Known Implementing Classes:

CoLocationGroupImpl
```
public interface CoLocationGroup
```
CoLocationGroup refers to a list of JobVertex instances, where the i-th subtask of one vertex has to be executed on the same TaskManager as the i-th subtask of all other JobVertex instances in the same group.
The co-location group is used to make sure that the i-th subtasks for iteration head and iteration tail are scheduled on the same TaskManager.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`org.apache.flink.util.AbstractID`	`getId()`	Returns the unique identifier describing this co-location constraint as a group.
`CoLocationConstraint`	`getLocationConstraint(int subTaskIndex)`	Returns the `CoLocationConstraint` for a specific `subTaskIndex`.
`List<JobVertexID>`	`getVertexIds()`	Returns the IDs of the `JobVertex` instances participating in this group.

- Method Detail
  - getId
```
org.apache.flink.util.AbstractID getId()
```
    Returns the unique identifier describing this co-location constraint as a group.
    
    Returns:
    
    The group's identifier.
  - getVertexIds
```
List<JobVertexID> getVertexIds()
```
    Returns the IDs of the JobVertex instances participating in this group.
    
    Returns:
    
    The group's members represented by their JobVertexIDs.
  - getLocationConstraint
```
CoLocationConstraint getLocationConstraint(int subTaskIndex)
```
    Returns the CoLocationConstraint for a specific subTaskIndex.
    
    Parameters:
    
    subTaskIndex - The index of the subtasks for which a CoLocationConstraint shall be returned.
    
    Returns:
    
    The corresponding CoLocationConstraint instance.