org.gridgain.grid.spi.checkpoint

Interface GridCheckpointSpi

All Superinterfaces:

GridSpi

All Known Implementing Classes:

GridCacheCheckpointSpi, GridJdbcCheckpointSpi, GridNoopCheckpointSpi, GridSharedFsCheckpointSpi

public interface GridCheckpointSpi
extends GridSpi

Checkpoint SPI provides an ability to save an intermediate job state. It can be useful when long running jobs need to store some intermediate state to protect from system or application failures. Grid job can save intermediate state in certain points of the execution (e.g., periodically) and upon start check if previously saved state exists. This allows job to restart from the last save checkpoint in case of preemption or other types of failover.

Note, that since a job can execute on different nodes, checkpoints need to be accessible by all nodes.

To manipulate checkpoints from grid job the following public methods are available on task session (that can be injected into grid job):

• GridComputeTaskSession.loadCheckpoint(String)
• GridComputeTaskSession.removeCheckpoint(String)
• GridComputeTaskSession.saveCheckpoint(String, Object)
• GridComputeTaskSession.saveCheckpoint(String, Object, GridComputeTaskSessionScope, long)
• GridComputeTaskSession.saveCheckpoint(String, Object, GridComputeTaskSessionScope, long, boolean)

GridGain provides the following GridCheckpointSpi implementations:

• GridNoopCheckpointSpi - default
• GridSharedFsCheckpointSpi
• GridS3CheckpointSpi
• GridJdbcCheckpointSpi
• GridCacheCheckpointSpi

NOTE: this SPI (i.e. methods in this interface) should never be used directly. SPIs provide internal view on the subsystem and is used internally by GridGain kernal. In rare use cases when access to a specific implementation of this SPI is required - an instance of this SPI can be obtained via Grid.configuration() method to check its configuration properties or call other non-SPI methods. Note again that calling methods from this interface on the obtained instance can lead to undefined behavior and explicitly not supported.

Method Summary

Methods

Modifier and Type	Method and Description
byte[]	loadCheckpoint(String key) Loads checkpoint from storage by its unique key.
boolean	removeCheckpoint(String key) This method instructs the checkpoint provider to clean saved data for a given key.
boolean	saveCheckpoint(String key, byte[] state, long timeout, boolean overwrite) Saves checkpoint to the storage.
void	setCheckpointListener(GridCheckpointListener lsnr) Sets the checkpoint listener.

Methods inherited from interface org.gridgain.grid.spi.GridSpi

getName, getNodeAttributes, onContextDestroyed, onContextInitialized, spiStart, spiStop

Method Detail

loadCheckpoint

@Nullable
byte[] loadCheckpoint(String key)
                      throws GridSpiException

Loads checkpoint from storage by its unique key.

Parameters:

key - Checkpoint key.

Returns:

Loaded data or null if there is no data for a given key.

Throws:

GridSpiException - Thrown in case of any error while loading checkpoint data. Note that in case when given key is not found this method will return null.

saveCheckpoint

boolean saveCheckpoint(String key,
                     byte[] state,
                     long timeout,
                     boolean overwrite)
                       throws GridSpiException

Saves checkpoint to the storage.

Parameters:

key - Checkpoint unique key.

state - Saved data.

timeout - Every intermediate data stored by checkpoint provider should have a timeout. Timeout allows for effective resource management by checkpoint provider by cleaning saved data that are not needed anymore. Generally, the user should choose the minimum possible timeout to avoid long-term resource acquisition by checkpoint provider. Value 0 means that timeout will never expire.

overwrite - Whether or not overwrite checkpoint if it already exists.

Returns:

true if checkpoint has been actually saved, false otherwise.

Throws:

GridSpiException - Thrown in case of any error while saving checkpoint data.

removeCheckpoint

boolean removeCheckpoint(String key)

This method instructs the checkpoint provider to clean saved data for a given key.

Parameters:

key - Key for the checkpoint to remove.

Returns:

true if data has been actually removed, false otherwise.

setCheckpointListener

void setCheckpointListener(GridCheckpointListener lsnr)

Sets the checkpoint listener.

Parameters:

lsnr - The listener to set or null.