IndexWriterEventListener (Lucene 9.11.1 core API)

```
public interface IndexWriterEventListener
```
A callback event listener for recording key events happened inside IndexWriter

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields
Modifier and Type Field Description

static IndexWriterEventListener NO_OP_LISTENER
A no-op listener that helps to save null checks

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`void`	`beginMergeOnFullFlush(MergePolicy.MergeSpecification merge)`	Invoked at the start of merge on commit
`void`	`endMergeOnFullFlush(MergePolicy.MergeSpecification merge)`	Invoked at the end of merge on commit, due to either merge completed, or merge timed out according to `IndexWriterConfig.setMaxFullFlushMergeWaitMillis(long)`

- Field Detail
  - NO_OP_LISTENER
```
static final IndexWriterEventListener NO_OP_LISTENER
```
    A no-op listener that helps to save null checks
- Method Detail
  - beginMergeOnFullFlush
```
void beginMergeOnFullFlush(MergePolicy.MergeSpecification merge)
```
    Invoked at the start of merge on commit
    
    Parameters:
    
    merge - specification to be tracked
  - endMergeOnFullFlush
```
void endMergeOnFullFlush(MergePolicy.MergeSpecification merge)
```
    Invoked at the end of merge on commit, due to either merge completed, or merge timed out according to IndexWriterConfig.setMaxFullFlushMergeWaitMillis(long)
    
    Parameters:
    
    merge - specification to be tracked