org.apache.giraph.ooc.policy

Interface OutOfCoreOracle

All Known Implementing Classes:

FixedPartitionsOracle, MemoryEstimatorOracle, SimpleGCMonitoringOracle, ThresholdBasedOracle

public interface OutOfCoreOracle

Interface for any out-of-core oracle. An out-of-core oracle is the brain of the out-of-core mechanism, determining/deciding on out-of-core actions (load or store) that should happen. Note: any class implementing this interface should have one and only one constructor taking only two arguments of types ImmutableClassesGiraphConfiguration and OutOfCoreEngine

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	OutOfCoreOracle.IOAction Different types of IO actions that can potentially lead to a more desired state of computation for out-of-core mechanism.

Method Summary

Modifier and Type	Method and Description
boolean	approve(IOCommand command) Whether a command is appropriate to bring the memory to a more desired state.
void	commandCompleted(IOCommand command) Notification of command completion.
void	gcCompleted(com.sun.management.GarbageCollectionNotificationInfo gcInfo) Notification of GC completion.
OutOfCoreOracle.IOAction[]	getNextIOActions() Get the next set of viable IO actions to help bring memory to a more desired state.
void	startIteration() Called at the beginning of a superstep.

Method Detail

getNextIOActions

OutOfCoreOracle.IOAction[] getNextIOActions()

Get the next set of viable IO actions to help bring memory to a more desired state.

Returns:

an array of viable IO actions, sorted from highest priority to lowest priority

approve

boolean approve(IOCommand command)

Whether a command is appropriate to bring the memory to a more desired state. A command is not executed unless it is approved by the oracle. This method is specially important where there are multiple IO threads performing IO operations for the out-of-core mechanism. The approval becomes significantly important to prevent all IO threads from performing identical command type, if that is a necessity. For instance, execution of a particular command type by only one thread may bring the memory to a desired state, and the rest of IO threads may perform other types of commands.

Parameters:

command - the IO command that is about to execute

Returns:

'true' if the command is approved for execution. 'false' if the command should not be executed

commandCompleted

void commandCompleted(IOCommand command)

Notification of command completion. Oracle may update its status and commit the changes a command may cause.

Parameters:

command - the IO command that is completed

gcCompleted

void gcCompleted(com.sun.management.GarbageCollectionNotificationInfo gcInfo)

Notification of GC completion. Oracle may take certain decisions based on GC information (such as amount of time it took, memory it reclaimed, etc.)

Parameters:

gcInfo - GC information

startIteration

void startIteration()

Called at the beginning of a superstep.