CheckpointContext (IBM InfoSphere Streams Java Operator API)

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All Superinterfaces:

OptionalContext
```
public interface CheckpointContext
extends OptionalContext
```
Context information that allows operators to create or restore checkpoint data of their state information.
Operator data can be checkpointed or restored in 2 ways:
1. Periodic: An application specifies a checkpoint: periodic config option for an operator with a corresponding time interval in SPL.
2. Operator-driven: Operator can request a synchronous, operator-driven checkpoint. The checkpoint: operatorDriven option is specified in SPL.
In each of the above scenarios, a valid StateHandler must be registered with the OperatorContext.registerStateHandler() method. In the case of periodic checkpointing, the StateHandler.checkpoint() method will be automatically called by the SPL Runtime at configured interval.
In case of operatorDriven checkpointing, the operator can request a checkpoint by calling the createCheckpoint() method within this interface.
When an operator is restarted, the StateHandler.reset() is automatically called by the SPL Runtime to restore operator's state from checkpoint.
Note that a checkpoint context is only available if checkpointing is enabled for an operator otherwise the OperatorContext.getOptionalContext(CheckpointContext.class) call will return null.
Since:

InfoSphere® Streams Version 4.0

See Also:
OperatorContext.getOptionalContext(Class)

Nested Class Summary

Nested Classes
Modifier and Type Interface and Description

static class CheckpointContext.Kind
TODO

Method Summary

Methods
Modifier and Type	Method and Description
`boolean`	`createCheckpoint()` Create a checkpoint.
`double`	`getCheckpointingInterval()` Returns the checkpointing interval if periodic checkpointing is configured.
`CheckpointContext.Kind`	`getKind()` Return the kind of the configured checkpointing.
`boolean`	`isEnabled()` Return whether checkpointing/restore is enabled.

- Method Detail
  - getKind
```
CheckpointContext.Kind getKind()
```
    Return the kind of the configured checkpointing.
    
    Returns:
    kind of the configured checkpointing.
  - getCheckpointingInterval
```
double getCheckpointingInterval()
```
    Returns the checkpointing interval if periodic checkpointing is configured. This method returns <0 if operatorDriven checkpointing is configured.
    
    Returns:
    the checkpointing interval for periodic checkpointing or <0 otherwise
  - createCheckpoint
```
boolean createCheckpoint()
                         throws java.io.IOException
```
    Create a checkpoint. This will trigger a call to the registered StateHandler.checkpoint() method.
    
    Returns:
    True if checkpointing is successful, false if checkpointing is not enabled.
    
    Throws:
    
    java.io.IOException - if there is any error during creating a checkpoint.
  - isEnabled
```
boolean isEnabled()
```
    Return whether checkpointing/restore is enabled.
    
    Returns:
    True if checkpointing/restore is enabled, false otherwise.