ChangeRequestHistory (druid-server 29.0.1 API)

java.lang.Object
- org.apache.druid.server.coordination.ChangeRequestHistory<T>

```
public class ChangeRequestHistory<T>
extends Object
```
This class keeps a bounded list of segment updates made on the server such as adding/dropping segments. Clients call addChangeRequest(T) or addChangeRequests(java.util.List<T>) to add updates (e. g. of segments). Clients call getRequestsSince(org.apache.druid.server.coordination.ChangeRequestHistory.Counter) to get updates since given counter.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class ChangeRequestHistory.Counter

Constructor Summary

Constructors
Constructor Description

ChangeRequestHistory()

ChangeRequestHistory(int maxSize)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`addChangeRequest(T request)`	Add single segment change update.
`void`	`addChangeRequests(List<T> requests)`	Add batch of segment changes update.
`ChangeRequestHistory.Counter`	`getLastCounter()`
`com.google.common.util.concurrent.ListenableFuture<ChangeRequestsSnapshot<T>>`	`getRequestsSince(ChangeRequestHistory.Counter counter)`	Returns a Future that, on completion, returns list of segment updates and associated counter.
`void`	`stop()`

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - ChangeRequestHistory
```
public ChangeRequestHistory()
```
  - ChangeRequestHistory
```
public ChangeRequestHistory(int maxSize)
```
- Method Detail
  - stop
```
public void stop()
```
  - addChangeRequests
```
public void addChangeRequests(List<T> requests)
```
    Add batch of segment changes update.
  - addChangeRequest
```
public void addChangeRequest(T request)
```
    Add single segment change update.
  - getRequestsSince
```
public com.google.common.util.concurrent.ListenableFuture<ChangeRequestsSnapshot<T>> getRequestsSince(ChangeRequestHistory.Counter counter)
```
    Returns a Future that, on completion, returns list of segment updates and associated counter. If there are no update since given counter then Future completion waits till an updates is provided. If counter is older than max number of changes maintained then ChangeRequestsSnapshot is returned with ChangeRequestsSnapshot.resetCounter set to True. If there were no updates to provide immediately then a future is created and returned to caller. This future is added to the "waitingFutures" list and all the futures in the list get resolved as soon as a segment update is provided.
  - getLastCounter
```
public ChangeRequestHistory.Counter getLastCounter()
```