MessageGroupingFunction (pulsar-client-reactive-api 0.3.0 API)

```
public interface MessageGroupingFunction
```
Function to group messages that will be processed by the same instance of concurrent message handler.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`int`	`resolveProcessingGroup(org.apache.pulsar.client.api.Message<?> message, int numberOfGroups)`	Resolves a processing group for a message.

- Method Detail
  - resolveProcessingGroup
```
int resolveProcessingGroup(org.apache.pulsar.client.api.Message<?> message,
                           int numberOfGroups)
```
    Resolves a processing group for a message. This is used for implementing key-ordered message processing with ReactiveMessagePipelineBuilder.ConcurrentOneByOneMessagePipelineBuilder
    
    Parameters:
    
    message - the Pulsar message
    
    numberOfGroups - maximum number of groups
    
    Returns:
    
    processing group for the message, in the range of 0 to numberOfGroups, exclusive