org.gridgain.grid.spi.collision.jobstealing
Class GridJobStealingCollisionSpi

java.lang.Object
  org.gridgain.grid.spi.GridSpiAdapter
      org.gridgain.grid.spi.collision.jobstealing.GridJobStealingCollisionSpi

All Implemented Interfaces:

GridCollisionSpi, GridJobStealingCollisionSpiMBean, GridSpi, GridSpiManagementMBean

@GridSpiInfo(author="GridGain Systems",
             url="www.gridgain.org",
             email="support@gridgain.com",
             version="x.x")
@GridSpiMultipleInstancesSupport(value=true)
public class GridJobStealingCollisionSpi
extends GridSpiAdapter
implements GridCollisionSpi, GridJobStealingCollisionSpiMBean

Collision SPI that supports job stealing from over-utilized nodes to under-utilized nodes. This SPI is especially useful if you have some jobs within task complete fast, and others sitting in the waiting queue on slower nodes. In such case, the waiting jobs will be stolen from slower node and moved to the fast under-utilized node.

The design and ideas for this SPI are significantly influenced by Java Fork/Join Framework authored by Doug Lea and planned for Java 7. GridJobStealingCollisionSpi took similar concepts and applied them to the grid (as opposed to within VM support planned in Java 7).

Quite often grids are deployed across many computers some of which will always be more powerful than others. This SPI helps you avoid jobs being stuck at a slower node, as they will be stolen by a faster node. In the following picture when Node₃ becomes free, it steals Job₁₃ and Job₂₃ from Node₁ and Node₂ respectively.

Note that this SPI must always be used in conjunction with GridJobStealingFailoverSpi. The responsibility of Job Stealing Failover SPI is to properly route stolen jobs to the nodes that initially requested (stole) these jobs. The SPI maintains a counter of how many times a jobs was stolen and hence traveled to another node. GridJobStealingCollisionSpi checks this counter and will not allow a job to be stolen if this counter exceeds a certain threshold GridJobStealingCollisionSpi.setMaximumStealingAttempts(int).

Configuration

In order to use this SPI, you should configure your grid instance to use GridJobStealingCollisionSpi either from Spring XML file or directly. The following configuration parameters are supported:

Mandatory

This SPI has no mandatory configuration parameters.

Optional

The following configuration parameters are optional:

• Maximum number of active jobs that will be allowed by this SPI to execute concurrently (see GridJobStealingCollisionSpi.setActiveJobsThreshold(int)).
• Maximum number of waiting jobs. Once waiting queue size goes below this number, this SPI will attempt to steal jobs from over-utilized nodes by sending "steal" requests (see GridJobStealingCollisionSpi.setWaitJobsThreshold(int)).
• Steal message expire time. If no response was received from a node to which steal request was sent, then request will be considered lost and will be resent, potentially to another node (see GridJobStealingCollisionSpi.setMessageExpireTime(long)).
• Maximum number of stealing attempts for the job (see GridJobStealingCollisionSpi.setMaximumStealingAttempts(int)).
• Whether stealing enabled or not (see GridJobStealingCollisionSpi.setStealingEnabled(boolean)).
• Enables stealing to/from only nodes that have these attributes set (see GridJobStealingCollisionSpi.setStealingAttributes(Map)).

Below is example of configuring this SPI from Java code:

 GridJobStealingCollisionSpi spi = new GridJobStealingCollisionSpi();

 // Configure number of waiting jobs
 // in the queue for job stealing.
 spi.setWaitJobsThreshold(10);

 // Configure message expire time (in milliseconds).
 spi.setMessageExpireTime(500);

 // Configure stealing attempts number.
 spi.setMaximumStealingAttempts(10);

 // Configure number of active jobs that are allowed to execute
 // in parallel. This number should usually be equal to the number
 // of threads in the pool (default is 100).
 spi.setActiveJobsThreshold(50);

 // Enable stealing.
 spi.setStealingEnabled(true);

 // Set stealing attribute to steal from/to nodes that have it.
 spi.setStealingAttributes(Collections.singletonMap("node.segment", "foobar"));

 GridConfigurationAdapter cfg = new GridConfigurationAdapter();

 // Override default Collision SPI.
 cfg.setCollisionSpi(spi);
 

Here is an example of how this SPI can be configured from Spring XML configuration:

 <property name="collisionSpi">
     <bean class="org.gridgain.grid.spi.collision.jobstealing.GridJobStealingCollisionSpi">
         <property name="activeJobsThreshold" value="100"/>
         <property name="waitJobsThreshold" value="0"/>
         <property name="messageExpireTime" value="1000"/>
         <property name="maximumStealingAttempts" value="10"/>
         <property name="stealingEnabled" value="true"/>
         <property name="stealingAttributes">
             <map>
                 <entry key="node.segment" value="foobar"/>
             </map>
         </property>
     </bean>
 </property>
 

For information about Spring framework visit www.springframework.org



See Also:

Documentation
Email Support
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Issue Tracking

Author: 2005-2008 Copyright © GridGain Systems. All Rights Reserved. ver. 2.1.0

	Nikita Ivanov, GridGain Systems nivanov@gridgain.com
	Dmitriy Setrakyan, GridGain Systems dsetrakyan@gridgain.com
	Alexander Magdenko, GridGain Systems amagdenko@gridgain.com
	Boris Suchodoev, GridGain Systems bsuchodoev@gridgain.com
	Denis Kharlamov, GridGain Systems dkharlamov@gridgain.com
	close

Field Summary

static int	DFLT_ACTIVE_JOBS_THRESHOLD Default number of parallel jobs allowed (value is 95 which is slightly less same as default value of threads in the execution thread pool to allow some extra threads for system processing).
static int	DFLT_MAX_STEALING_ATTEMPTS Maximum number of attempts to steal job by another node (default is 5).
static long	DFLT_MSG_EXPIRE_TIME Default steal message expire time in milliseconds (value is 1000).
static int	DFLT_WAIT_JOBS_THRESHOLD Default threshold of waiting jobs.
static String	THIEF_NODE_ATTR Job context attribute for storing thief node UUID (this attribute is used in job stealing failover SPI).

Constructor Summary

GridJobStealingCollisionSpi()

Method Summary

int	getActiveJobsThreshold() Gets number of jobs that can be executed in parallel.
protected List<String>	getConsistentAttributeNames() Returns back list of attributes that should be consistent for this SPI.
int	getCurrentActiveJobsCount() Gets current number of jobs that are being executed.
int	getCurrentJobsToStealCount() Gets current number of jobs to be stolen.
int	getCurrentWaitJobsCount() Gets current number of jobs that wait for the execution.
int	getMaximumStealingAttempts() Gets maximum number of attempts to steal job by another node.
long	getMessageExpireTime() Message expire time configuration parameter.
Map<String,Serializable>	getNodeAttributes() This method is called before SPI starts (before method GridSpi.spiStart(String) is called). It allows SPI implementation to add attributes to a local node. Kernel collects these attributes from all SPI implementations loaded up and then passes it to discovery SPI so that they can be exchanged with other nodes.
Map<String,? extends Serializable>	getStealingAttributes() Configuration parameter to enable stealing to/from only nodes that have these attributes set (see GridNode.getAttribute(String) and GridConfiguration.getUserAttributes() methods).
int	getTotalStolenJobsCount() Gets total number of stolen jobs.
int	getWaitJobsThreshold() Gets job count threshold at which this node will start stealing jobs from other nodes.
boolean	isStealingEnabled() Gets flag indicating whether this node should attempt to steal jobs from other nodes.
void	onCollision(Collection<GridCollisionJobContext> waitJobs, Collection<GridCollisionJobContext> activeJobs) This is a callback called when either new grid job arrived or executing job finished its execution.
void	onContextDestroyed() Callback invoked prior to stopping grid before SPI context is destroyed. Once this method is complete, grid will begin shutdown sequence. Use this callback for de-initialization logic that may involve SPI context. Note that invoking SPI context after this callback is complete is considered illegal and may produce unknown results. If GridSpiAdapter is used for SPI implementation, then it will replace actual context with dummy no-op context which is usually good-enough since grid is about to shut down.
void	onContextInitialized(GridSpiContext spiCtx) Callback invoked when SPI context is initialized. SPI implementation may store SPI context for future access. This method is invoked after GridSpi.spiStart(String) method is completed, so SPI should be fully functional at this point. Use this method for post-start initialization, such as subscribing a discovery listener, sending a message to remote node, etc...
void	setActiveJobsThreshold(int activeJobsThreshold) Sets number of jobs that are allowed to be executed in parallel on this node.
void	setExternalCollisionListener(GridCollisionExternalListener listener) Listener to be set for notification of external collision events (e.g. job stealing).
void	setMaximumStealingAttempts(int maxStealingAttempts) Sets maximum number of attempts to steal job by another node.
void	setMessageExpireTime(long msgExpireTime) Message expire time configuration parameter.
void	setStealingAttributes(Map<String,? extends Serializable> stealAttrs) Configuration parameter to enable stealing to/from only nodes that have these attributes set (see GridNode.getAttribute(String) and GridConfiguration.getUserAttributes() methods).
void	setStealingEnabled(boolean isStealingEnabled) Sets flag indicating whether this node should attempt to steal jobs from other nodes.
void	setWaitJobsThreshold(int waitJobsThreshold) Sets wait jobs threshold.
void	spiStart(String gridName) This method is called to start SPI.
void	spiStop() This method is called to stop SPI.
String	toString()

Methods inherited from class org.gridgain.grid.spi.GridSpiAdapter

assertParameter, configInfo, createSpiAttributeName, getAuthor, getGridGainHome, getLocalNodeId, getName, getSpiContext, getStartTimestamp, getStartTimestampFormatted, getUpTime, getUpTimeFormatted, getVendorEmail, getVendorUrl, getVersion, registerMBean, setName, setSpiContext, startInfo, startStopwatch, stopInfo, unregisterMBean

Methods inherited from class java.lang.Object

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

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

getName

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

getAuthor, getGridGainHome, getLocalNodeId, getName, getStartTimestamp, getStartTimestampFormatted, getUpTime, getUpTimeFormatted, getVendorEmail, getVendorUrl, getVersion

Field Detail

DFLT_MAX_STEALING_ATTEMPTS

public static final int DFLT_MAX_STEALING_ATTEMPTS

Maximum number of attempts to steal job by another node (default is 5).

See Also:

Constant Field Values

DFLT_ACTIVE_JOBS_THRESHOLD

public static final int DFLT_ACTIVE_JOBS_THRESHOLD

Default number of parallel jobs allowed (value is 95 which is slightly less same as default value of threads in the execution thread pool to allow some extra threads for system processing).

See Also:

Constant Field Values

DFLT_MSG_EXPIRE_TIME

public static final long DFLT_MSG_EXPIRE_TIME

Default steal message expire time in milliseconds (value is 1000). Once this time is elapsed and no response for steal message is received, the message is considered lost and another steal message will be generated, potentially to another node.

See Also:

Constant Field Values

DFLT_WAIT_JOBS_THRESHOLD

public static final int DFLT_WAIT_JOBS_THRESHOLD

Default threshold of waiting jobs. If number of waiting jobs exceeds this threshold, then waiting jobs will become available to be stolen (value is 0).

See Also:

Constant Field Values

THIEF_NODE_ATTR

public static final String THIEF_NODE_ATTR

Job context attribute for storing thief node UUID (this attribute is used in job stealing failover SPI).

See Also:

Constant Field Values

Constructor Detail

GridJobStealingCollisionSpi

public GridJobStealingCollisionSpi()

Method Detail

setActiveJobsThreshold

@GridSpiConfiguration(optional=true)
public void setActiveJobsThreshold(int activeJobsThreshold)

Sets number of jobs that are allowed to be executed in parallel on this node. Node that this attribute may be different for different grid nodes as stronger nodes may be able to execute more jobs in parallel.

If not provided, default value is GridJobStealingCollisionSpi.DFLT_ACTIVE_JOBS_THRESHOLD.

Parameters:

activeJobsThreshold - Maximum number of jobs to be executed in parallel.

getActiveJobsThreshold

public int getActiveJobsThreshold()

Gets number of jobs that can be executed in parallel.

Specified by:

getActiveJobsThreshold in interface GridJobStealingCollisionSpiMBean

Returns:

Number of jobs that can be executed in parallel.

setWaitJobsThreshold

@GridSpiConfiguration(optional=true)
public void setWaitJobsThreshold(int waitJobsThreshold)

Sets wait jobs threshold. If number of jobs in the waiting queue goes below (or equal to) this threshold, then implementation will attempt to steal jobs from other, more over-loaded nodes.

Note this value may be different (but does not have to be) for different nodes in the grid. You may wish to give stronger nodes a smaller waiting threshold so they can start stealing jobs from other nodes sooner.

If not provided, default value is GridJobStealingCollisionSpi.DFLT_WAIT_JOBS_THRESHOLD.

Parameters:

waitJobsThreshold - Default job priority.

getWaitJobsThreshold

public int getWaitJobsThreshold()

Gets job count threshold at which this node will start stealing jobs from other nodes.

Specified by:

getWaitJobsThreshold in interface GridJobStealingCollisionSpiMBean

Returns:

Job count threshold.

setMessageExpireTime

@GridSpiConfiguration(optional=true)
public void setMessageExpireTime(long msgExpireTime)

Message expire time configuration parameter. If no response is received from a busy node to a job stealing request, then implementation will assume that message never got there, or that remote node does not have this node included into topology of any of the jobs it has. In any case, job steal request will be resent (potentially to another node).

If not provided, default value is GridJobStealingCollisionSpi.DFLT_MSG_EXPIRE_TIME.

Parameters:

msgExpireTime - Message expire time.

getMessageExpireTime

public long getMessageExpireTime()

Message expire time configuration parameter. If no response is received from a busy node to a job stealing message, then implementation will assume that message never got there, or that remote node does not have this node included into topology of any of the jobs it has.

Specified by:

getMessageExpireTime in interface GridJobStealingCollisionSpiMBean

Returns:

Message expire time.

setStealingEnabled

@GridSpiConfiguration(optional=true)
public void setStealingEnabled(boolean isStealingEnabled)

Sets flag indicating whether this node should attempt to steal jobs from other nodes. If false, then this node will steal allow jobs to be stolen from it, but won't attempt to steal any jobs from other nodes.

Default value is true.

Parameters:

isStealingEnabled - Flag indicating whether this node should attempt to steal jobs from other nodes

isStealingEnabled

public boolean isStealingEnabled()

Gets flag indicating whether this node should attempt to steal jobs from other nodes. If false, then this node will steal allow jobs to be stolen from it, but won't attempt to steal any jobs from other nodes.

Default value is true.

Specified by:

isStealingEnabled in interface GridJobStealingCollisionSpiMBean

Returns:

Flag indicating whether this node should attempt to steal jobs from other nodes.

getMaximumStealingAttempts

public int getMaximumStealingAttempts()

Gets maximum number of attempts to steal job by another node. If not specified, GridJobStealingCollisionSpi.DFLT_MAX_STEALING_ATTEMPTS value will be used.

Specified by:

getMaximumStealingAttempts in interface GridJobStealingCollisionSpiMBean

Returns:

Maximum number of attempts to steal job by another node.

setMaximumStealingAttempts

@GridSpiConfiguration(optional=true)
public void setMaximumStealingAttempts(int maxStealingAttempts)

Sets maximum number of attempts to steal job by another node. If not specified, GridJobStealingCollisionSpi.DFLT_MAX_STEALING_ATTEMPTS value will be used.

Note this value must be identical for all grid nodes in the grid.

Parameters:

maxStealingAttempts - Maximum number of attempts to steal job by another node.

setStealingAttributes

@GridSpiConfiguration(optional=true)
public void setStealingAttributes(Map<String,? extends Serializable> stealAttrs)

Configuration parameter to enable stealing to/from only nodes that have these attributes set (see GridNode.getAttribute(String) and GridConfiguration.getUserAttributes() methods).

Parameters:

stealAttrs - Node attributes to enable job stealing for.

getStealingAttributes

public Map<String,? extends Serializable> getStealingAttributes()

Configuration parameter to enable stealing to/from only nodes that have these attributes set (see GridNode.getAttribute(String) and GridConfiguration.getUserAttributes() methods).

Specified by:

getStealingAttributes in interface GridJobStealingCollisionSpiMBean

Returns:

Node attributes to enable job stealing for.

getCurrentWaitJobsCount

public int getCurrentWaitJobsCount()

Gets current number of jobs that wait for the execution.

Specified by:

getCurrentWaitJobsCount in interface GridJobStealingCollisionSpiMBean

Returns:

Number of jobs that wait for execution.

getCurrentActiveJobsCount

public int getCurrentActiveJobsCount()

Gets current number of jobs that are being executed.

Specified by:

getCurrentActiveJobsCount in interface GridJobStealingCollisionSpiMBean

Returns:

Number of active jobs.

getTotalStolenJobsCount

public int getTotalStolenJobsCount()

Gets total number of stolen jobs.

Specified by:

getTotalStolenJobsCount in interface GridJobStealingCollisionSpiMBean

Returns:

Number of stolen jobs.

getCurrentJobsToStealCount

public int getCurrentJobsToStealCount()

Gets current number of jobs to be stolen. This is outstanding requests number.

Specified by:

getCurrentJobsToStealCount in interface GridJobStealingCollisionSpiMBean

Returns:

Number of jobs to be stolen.

getNodeAttributes

public Map<String,Serializable> getNodeAttributes()
                                           throws GridSpiException

This method is called before SPI starts (before method GridSpi.spiStart(String) is called). It allows SPI implementation to add attributes to a local node. Kernel collects these attributes from all SPI implementations loaded up and then passes it to discovery SPI so that they can be exchanged with other nodes.

Specified by:

getNodeAttributes in interface GridSpi

Overrides:

getNodeAttributes in class GridSpiAdapter

Throws:

GridSpiException - Throws in case of any error.

Returns:

Map of local node attributes this SPI wants to add.

spiStart

public void spiStart(String gridName)
              throws GridSpiException

This method is called to start SPI. After this method returns successfully kernel assumes that SPI is fully operational.

Specified by:

spiStart in interface GridSpi

Throws:

GridSpiException - Throws in case of any error during SPI start.

Parameters:

gridName - Name of grid instance this SPI is being started for (null for default grid).

spiStop

public void spiStop()
             throws GridSpiException

This method is called to stop SPI. After this method returns kernel assumes that this SPI is finished and all resources acquired by it are released. Note that this method can be called at any point including during recovery of failed start. It should make no assumptions on what state SPI will be in when this method is called.

Specified by:

spiStop in interface GridSpi

Throws:

GridSpiException - Thrown in case of any error during SPI stop.

setExternalCollisionListener

public void setExternalCollisionListener(GridCollisionExternalListener listener)

Listener to be set for notification of external collision events (e.g. job stealing). Once grid receives such notification, it will immediately invoke collision SPI.

GridGain uses this listener to enable job stealing from overloaded to underloaded nodes. However, you can also utilize it, for instance, to provide time based collision resolution. To achieve this, you most likely would mark some job by setting a certain attribute in job context (see GridJobContext) for a job that requires time-based scheduling and set some timer in your SPI implementation that would wake up after a certain period of time. Once this period is reached, you would notify this listener that a collision resolution should take place. Then inside of your collision resolution logic, you would find the marked waiting job and activate it.

Note that most collision SPI's may not have external collisions. In that case, they should simply ignore this method and do nothing when listener is set.

Specified by:

setExternalCollisionListener in interface GridCollisionSpi

Parameters:

listener - Listener for external collision events.

onContextInitialized

public void onContextInitialized(GridSpiContext spiCtx)
                          throws GridSpiException

Callback invoked when SPI context is initialized. SPI implementation may store SPI context for future access.

This method is invoked after GridSpi.spiStart(String) method is completed, so SPI should be fully functional at this point. Use this method for post-start initialization, such as subscribing a discovery listener, sending a message to remote node, etc...

Specified by:

onContextInitialized in interface GridSpi

Overrides:

onContextInitialized in class GridSpiAdapter

Throws:

GridSpiException - If context initialization failed (grid will be stopped).

Parameters:

spiCtx - Spi context.

onContextDestroyed

public void onContextDestroyed()

Callback invoked prior to stopping grid before SPI context is destroyed. Once this method is complete, grid will begin shutdown sequence. Use this callback for de-initialization logic that may involve SPI context. Note that invoking SPI context after this callback is complete is considered illegal and may produce unknown results.

If GridSpiAdapter is used for SPI implementation, then it will replace actual context with dummy no-op context which is usually good-enough since grid is about to shut down.

Specified by:

onContextDestroyed in interface GridSpi

Overrides:

onContextDestroyed in class GridSpiAdapter

onCollision

public void onCollision(Collection<GridCollisionJobContext> waitJobs,
                        Collection<GridCollisionJobContext> activeJobs)

This is a callback called when either new grid job arrived or executing job finished its execution. When new job arrives it is added to the end of the wait list and this method is called. When job finished its execution, it is removed from the active list and this method is called (i.e., when grid job is finished it will not appear in any list in collision resolution).

Implementation of this method should act on two lists, each of which contains collision job contexts that define a set of operations available during collision resolution. Refer to GridCollisionJobContext documentation for more information.

Specified by:

onCollision in interface GridCollisionSpi

Parameters:

waitJobs - Ordered collection of collision contexts for jobs that are currently waiting for execution. It can be empty but never null. Note that a new newly arrived job, if any, will always be represented by the last item in this list.

activeJobs - Ordered collection of collision contexts for jobs that are currently executing. It can be empty but never null.

getConsistentAttributeNames

protected List<String> getConsistentAttributeNames()

Returns back list of attributes that should be consistent for this SPI. Consistency means that remote node has to have the same attribute with the same value.

Overrides:

getConsistentAttributeNames in class GridSpiAdapter

Returns:

List or attribute names.

toString

public String toString()

Overrides:

toString in class Object