Package org.apache.ignite.spi.failover.jobstealing

## Class JobStealingFailoverSpi

- java.lang.Object
- - org.apache.ignite.spi.IgniteSpiAdapter
  - - org.apache.ignite.spi.failover.jobstealing.JobStealingFailoverSpi

- All Implemented Interfaces:
    `FailoverSpi`, `IgniteSpi`

      @IgniteSpiMultipleInstancesSupport(true)
      @IgniteSpiConsistencyChecked(optional=true)
      public class JobStealingFailoverSpi
      extends IgniteSpiAdapter
      implements FailoverSpi

  Job stealing failover SPI needs to always be used in conjunction with `JobStealingCollisionSpi` SPI. When `JobStealingCollisionSpi` receives a steal request and rejects jobs so they can be routed to the appropriate node, it is the responsibility of this `JobStealingFailoverSpi` SPI to make sure that the job is indeed re-routed to the node that has sent the initial request to steal it.

  `JobStealingFailoverSpi` knows where to route a job based on the `JobStealingCollisionSpi.THIEF_NODE_ATTR` job context attribute (see `ComputeJobContext`). Prior to rejecting a job, `JobStealingCollisionSpi` will populate this attribute with the ID of the node that wants to steal this job. Then `JobStealingFailoverSpi` will read the value of this attribute and route the job to the node specified.

  If failure is caused by a node crash, and not by steal request, then this SPI behaves identically to `AlwaysFailoverSpi`, and tries to find the next balanced node to fail-over a job to.

  # Configuration

  ## Mandatory

  This SPI has no mandatory configuration parameters.

  ## Optional

  This SPI has following optional configuration parameters:
  - Maximum failover attempts for a single job (see `setMaximumFailoverAttempts(int)`).
  Here is a Java example on how to configure grid with `JobStealingFailoverSpi`.

       JobStealingFailoverSpi spi = new JobStealingFailoverSpi();

       // Override maximum failover attempts.
       spi.setMaximumFailoverAttempts(5);

       IgniteConfiguration cfg = new IgniteConfiguration();

       // Override default failover SPI.
       cfg.setFailoverSpiSpi(spi);

       // Starts grid.
       G.start(cfg);

  Here is an example of how to configure `JobStealingFailoverSpi` from Spring XML configuration file.

       <property name="failoverSpi">
           <bean class="org.apache.ignite.spi.failover.jobstealing.JobStealingFailoverSpi">
               <property name="maximumFailoverAttempts" value="5"/>
           </bean>
       </property>

  For information about Spring framework visit www.springframework.org

  See Also:
    `FailoverSpi`

- - ### Field Summary

    Fields
    Modifier and Type | Field | Description
    --- | --- | ---
    `static int` | `DFLT_MAX_FAILOVER_ATTEMPTS` | Maximum number of attempts to execute a failed job on another node (default is `5`).

    - ### Fields inherited from class org.apache.ignite.spi.IgniteSpiAdapter

      `ignite, igniteInstanceName`

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `JobStealingFailoverSpi()` |

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `ClusterNode` | `failover​(FailoverContext ctx, List<ClusterNode> top)` | This method is called when method `ComputeTask.result(org.apache.ignite.compute.ComputeJobResult, List)` returns value `ComputeJobResultPolicy.FAILOVER` policy indicating that the result of job execution must be failed over.
    `protected List<String>` | `getConsistentAttributeNames()` | Returns back a list of attributes that should be consistent for this SPI.
    `int` | `getMaximumFailoverAttempts()` | See `setMaximumFailoverAttempts(int)`.
    `Map<String,​Object>` | `getNodeAttributes()` | This method is called before SPI starts (before method `IgniteSpi.spiStart(String)` is called).
    `int` | `getTotalFailedOverJobsCount()` | Get total number of jobs that were failed over including stolen ones.
    `int` | `getTotalStolenJobsCount()` | Get total number of jobs that were stolen.
    `JobStealingFailoverSpi` | `setMaximumFailoverAttempts​(int maxFailoverAttempts)` | Sets maximum number of attempts to execute a failed job on another node.
    `JobStealingFailoverSpi` | `setName​(String name)` | Sets SPI name.
    `void` | `spiStart​(String igniteInstanceName)` | This method is called to start SPI.
    `void` | `spiStop()` | This method is called to stop SPI.
    `String` | `toString()`

    - ### Methods inherited from class org.apache.ignite.spi.IgniteSpiAdapter

      `addTimeoutObject, assertParameter, checkConfigurationConsistency0, clientFailureDetectionTimeout, configInfo, createSpiAttributeName, failureDetectionTimeout, failureDetectionTimeoutEnabled, failureDetectionTimeoutEnabled, getExceptionRegistry, getLocalNode, getName, getSpiContext, ignite, initFailureDetectionTimeout, injectables, injectResources, isNodeStopping, onBeforeStart, onClientDisconnected, onClientReconnected, onContextDestroyed, onContextDestroyed0, onContextInitialized, onContextInitialized0, registerMBean, removeTimeoutObject, started, 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.apache.ignite.spi.IgniteSpi

      `getName, onClientDisconnected, onClientReconnected, onContextDestroyed, onContextInitialized`

- - ### Field Detail

    - #### DFLT_MAX_FAILOVER_ATTEMPTS

          public static final int DFLT_MAX_FAILOVER_ATTEMPTS

      Maximum number of attempts to execute a failed job on another node (default is `5`).
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### JobStealingFailoverSpi

          public JobStealingFailoverSpi()

  - ### Method Detail

    - #### getMaximumFailoverAttempts

          public int getMaximumFailoverAttempts()

      See `setMaximumFailoverAttempts(int)`.
      Returns:
        Maximum number of attempts to execute a failed job on another node.

    - #### setMaximumFailoverAttempts

          @IgniteSpiConfiguration(optional=true)
          public JobStealingFailoverSpi setMaximumFailoverAttempts​(int maxFailoverAttempts)

      Sets maximum number of attempts to execute a failed job on another node. If job gets stolen and thief node exists then it is not considered as failed job. If not specified, `DFLT_MAX_FAILOVER_ATTEMPTS` value will be used.

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

      Parameters:
        `maxFailoverAttempts` - Maximum number of attempts to execute a failed job on another node.
      Returns:
        `this` for chaining.

    - #### getTotalFailedOverJobsCount

          public int getTotalFailedOverJobsCount()

      Get total number of jobs that were failed over including stolen ones.
      Returns:
        Total number of failed over jobs.

    - #### getTotalStolenJobsCount

          public int getTotalStolenJobsCount()

      Get total number of jobs that were stolen.
      Returns:
        Total number of stolen jobs.

    - #### getNodeAttributes

          public Map<String,​Object> getNodeAttributes()
                                                     throws IgniteSpiException

      This method is called before SPI starts (before method `IgniteSpi.spiStart(String)` is called). It allows SPI implementation to add attributes to a local node. Kernal 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 `IgniteSpi`
      Overrides:
        `getNodeAttributes` in class `IgniteSpiAdapter`
      Returns:
        Map of local node attributes this SPI wants to add.
      Throws:
        `IgniteSpiException` - Throws in case of any error.

    - #### spiStart

          public void spiStart​(String igniteInstanceName)
                        throws IgniteSpiException

      This method is called to start SPI. After this method returns successfully kernel assumes that SPI is fully operational.
      Specified by:
        `spiStart` in interface `IgniteSpi`
      Parameters:
        `igniteInstanceName` - Name of Ignite instance this SPI is being started for (`null` for default Ignite instance).
      Throws:
        `IgniteSpiException` - Throws in case of any error during SPI start.

    - #### spiStop

          public void spiStop()
                       throws IgniteSpiException

      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 `IgniteSpi`
      Throws:
        `IgniteSpiException` - Thrown in case of any error during SPI stop.

    - #### failover

          public ClusterNode failover​(FailoverContext ctx,
                                      List<ClusterNode> top)

      This method is called when method `ComputeTask.result(org.apache.ignite.compute.ComputeJobResult, List)` returns value `ComputeJobResultPolicy.FAILOVER` policy indicating that the result of job execution must be failed over. Implementation of this method should examine failover context and choose one of the grid nodes from supplied `topology` to retry job execution on it. For best performance it is advised that `FailoverContext.getBalancedNode(List)` method is used to select node for execution of failed job.
      Specified by:
        `failover` in interface `FailoverSpi`
      Parameters:
        `ctx` - Failover context.
        `top` - Collection of all grid nodes within task topology (may include failed node).
      Returns:
        New node to route this job to or `null` if new node cannot be picked. If job failover fails (returns `null`) the whole task will be failed.

    - #### getConsistentAttributeNames

          protected List<String> getConsistentAttributeNames()

      Returns back a 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 `IgniteSpiAdapter`
      Returns:
        List or attribute names.

    - #### setName

          public JobStealingFailoverSpi setName​(String name)

      Sets SPI name.
      Overrides:
        `setName` in class `IgniteSpiAdapter`
      Parameters:
        `name` - SPI name.
      Returns:
        `this` for chaining.

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`