LearnerSyncThrottler (Apache ZooKeeper - Server 3.9.1 API)

java.lang.Object
- org.apache.zookeeper.server.quorum.LearnerSyncThrottler

```
public class LearnerSyncThrottler
extends Object
```
Utility class to limit the number of concurrent syncs from a leader to observers and followers or from a follower to observers. LearnerHandler objects should call beginSync(boolean) before sending a sync and endSync() after finishing, successfully or not.

Nested Class Summary

Nested Classes
Modifier and Type Class Description

static class LearnerSyncThrottler.SyncType

Constructor Summary

Constructors
Constructor	Description
`LearnerSyncThrottler(int maxConcurrentSyncs, LearnerSyncThrottler.SyncType syncType)`	Constructs a new instance limiting the concurrent number of syncs to `maxConcurrentSyncs`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`beginSync(boolean essential)`	Indicates that a new sync is about to be sent.
`void`	`endSync()`	Indicates that a sync has been completed.
`int`	`getSyncInProgress()`
`void`	`setMaxConcurrentSyncs(int maxConcurrentSyncs)`

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

- Constructor Detail
  - LearnerSyncThrottler
```
public LearnerSyncThrottler(int maxConcurrentSyncs,
                            LearnerSyncThrottler.SyncType syncType)
                     throws IllegalArgumentException
```
    Constructs a new instance limiting the concurrent number of syncs to maxConcurrentSyncs.
    
    Parameters:
    
    maxConcurrentSyncs - maximum concurrent number of syncs
    
    syncType - either a snapshot sync or a txn-based diff sync
    
    Throws:
    
    IllegalArgumentException - when maxConcurrentSyncs is less than 1
- Method Detail
  - beginSync
```
protected void beginSync(boolean essential)
                  throws SyncThrottleException,
                         InterruptedException
```
    Indicates that a new sync is about to be sent.
    
    Parameters:
    
    essential - if true, do not throw an exception even if throttling limit is reached
    
    Throws:
    
    SyncThrottleException - if throttling limit has been exceeded and essential == false, even after waiting for the timeout period, if any
    
    InterruptedException - if thread is interrupted while trying to start a sync; cannot happen if timeout is zero
  - endSync
```
public void endSync()
```
    Indicates that a sync has been completed.
  - setMaxConcurrentSyncs
```
public void setMaxConcurrentSyncs(int maxConcurrentSyncs)
```
  - getSyncInProgress
```
public int getSyncInProgress()
```