com.hazelcast.spi.impl.merge

Class AbstractContainerCollector<C>

java.lang.Object

com.hazelcast.spi.impl.merge.AbstractContainerCollector<C>

Type Parameters:

C - container of the data structure

Direct Known Subclasses:

AbstractNamedContainerCollector

public abstract class AbstractContainerCollector<C>
extends Object

Collects non-threadsafe containers for SplitBrainHandlerService capable data structures.

The ClusterMergeTask collects all mergeable data from all Hazelcast services. The problem is that it runs on an arbitrary thread, but the data is only modified by specific partition threads. This can cause visibility issues due to a missing happens-before relation.

The collector fetches the data via PartitionSpecificRunnable (which run on the partition threads) and stores them in a ConcurrentHashMap. This guarantees the visibility for the ClusterMergeTask.

The collector can be implemented for data structures which reference their containers by

• partition IDs using AbstractContainerCollector
• container name using AbstractNamedContainerCollector

Note: The collector will retain the collected containers for the merge runnable. So ManagedService.reset() is not allowed to clear or destroy those containers. To ensure this the collector removes the link between the data structure and a container via Iterator.remove() in CollectContainerRunnable#run().

The cleanup of the containers itself is done in destroy() via destroy(Object) after the merge is done, or directly if the container is not collected. Containers from backup partitions are directly cleaned via destroyBackup(Object).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	AbstractContainerCollector.EmptyIterator Empty iterator for containerIterator(int) calls, if the requested partition is empty.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractContainerCollector(NodeEngine nodeEngine)

Method Summary

Modifier and Type	Method and Description
protected abstract Iterator<C>	containerIterator(int partitionId) Returns all containers of the data structure for the given partition ID.
void	destroy() Destroys all collected containers.
protected abstract void	destroy(C container) Destroys the owned data in the container.
protected abstract void	destroyBackup(C container) Destroys the backup data in the container.
ConcurrentMap<Integer,Collection<C>>	getCollectedContainers() Returns the collected containers by partition ID.
protected abstract MergePolicyConfig	getMergePolicyConfig(C container) Returns the MergePolicyConfig of the container.
protected abstract int	getMergingValueCount() Returns the number of collected merging values in this collector.
protected boolean	isMergeable(C container) Determines if the container should be merged.
protected void	onDestroy() Will be called by destroy().
void	run() Collects the containers from the data structure in a thread-safe way.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

AbstractContainerCollector

protected AbstractContainerCollector(NodeEngine nodeEngine)

Method Detail

run

public final void run()

Collects the containers from the data structure in a thread-safe way.

getCollectedContainers

public final ConcurrentMap<Integer,Collection<C>> getCollectedContainers()

Returns the collected containers by partition ID.

Returns:

the collected containers

destroy

public final void destroy()

Destroys all collected containers.

onDestroy

protected void onDestroy()

Will be called by destroy().

Can be overridden by implementations to cleanup local resources.

containerIterator

protected abstract Iterator<C> containerIterator(int partitionId)

Returns all containers of the data structure for the given partition ID.

Returns:

Iterator over the containers of the given partition

getMergePolicyConfig

protected abstract MergePolicyConfig getMergePolicyConfig(C container)

Returns the MergePolicyConfig of the container.

Returns:

the MergePolicyConfig of the container

destroy

protected abstract void destroy(C container)

Destroys the owned data in the container.

Is called if a container is not collected or after the merge has been done.

destroyBackup

protected abstract void destroyBackup(C container)

Destroys the backup data in the container.

Is called if the container is not collected, since it's in a backup partition.

getMergingValueCount

protected abstract int getMergingValueCount()

Returns the number of collected merging values in this collector.

The count is used to calculate the timeout value to wait for merge operations to complete.

Note: Depending on the data structure, this can be the number of collected containers or the number of merging values within the collected containers.

Returns:

the number of collected merge values

isMergeable

protected boolean isMergeable(C container)

Determines if the container should be merged.

Can be overridden if there are additional restrictions beside the merge policy, if a container is mergeable or not.

Returns:

true if the container is mergeable, false otherwise