org.apache.ignite.spi.failover.always

## Class AlwaysFailoverSpi

- java.lang.Object
- - org.apache.ignite.spi.IgniteSpiAdapter
  - - org.apache.ignite.spi.failover.always.AlwaysFailoverSpi

- All Implemented Interfaces:
    FailoverSpi, IgniteSpi

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

  Failover SPI that always reroutes a failed job to another node. Note, that at first an attempt will be made to reroute the failed job to a node that was not part of initial split for a better chance of success. If no such nodes are available, then an attempt will be made to reroute the failed job to the nodes in the initial split minus the node the job is failed on. If none of the above attempts succeeded, then the job will not be failed over and `null` will be returned.

  # Configuration

  This SPI is default failover SPI and does not have to be explicitly configured unless configuration parameters need to be changed.

  ## 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)`). If maximum failover attempts is reached, then job will not be failed-over and, hence, will fail.
  Here is a Java example how to configure grid with `AlwaysFailoverSpi` failover SPI.

       AlwaysFailoverSpi spi = new AlwaysFailoverSpi();

       // 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 `AlwaysFailoverSpi` from Spring XML configuration file.

       <property name="failoverSpi">
           <bean class="org.apache.ignite.spi.failover.always.AlwaysFailoverSpi">
               <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 and Description
    --- | ---
    `static String` | `AFFINITY_CALL_ATTEMPT` Name of job context attribute containing number of affinity call attempts.
    `static int` | `DFLT_MAX_FAILOVER_ATTEMPTS` Maximum number of attempts to execute a failed job on another node (default is `5`).
    `static String` | `FAILED_NODE_LIST_ATTR` Name of job context attribute containing all nodes a job failed on.
    `static String` | `MAX_FAILOVER_ATTEMPT_ATTR` Maximum attempts attribute key should be the same on all nodes.

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

      `ignite, igniteInstanceName`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `AlwaysFailoverSpi()`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and 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` | `getTotalFailoverJobsCount()` Get total number of jobs that were failed over.
    `AlwaysFailoverSpi` | `setMaximumFailoverAttempts(int maxFailoverAttempts)` Sets maximum number of attempts to execute a failed job on another node.
    `AlwaysFailoverSpi` | `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

    - #### FAILED_NODE_LIST_ATTR

          public static final String FAILED_NODE_LIST_ATTR

      Name of job context attribute containing all nodes a job failed on.
      See Also:
        `ComputeJobContext`, Constant Field Values

    - #### AFFINITY_CALL_ATTEMPT

          public static final String AFFINITY_CALL_ATTEMPT

      Name of job context attribute containing number of affinity call attempts.
      See Also:
        Constant Field Values

    - #### MAX_FAILOVER_ATTEMPT_ATTR

          public static final String MAX_FAILOVER_ATTEMPT_ATTR

      Maximum attempts attribute key should be the same on all nodes.
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### AlwaysFailoverSpi

          public AlwaysFailoverSpi()

  - ### 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 AlwaysFailoverSpi setMaximumFailoverAttempts(int maxFailoverAttempts)

      Sets maximum number of attempts to execute a failed job on another node. If not specified, `DFLT_MAX_FAILOVER_ATTEMPTS` value will be used.
      Parameters:
        `maxFailoverAttempts` - Maximum number of attempts to execute a failed job on another node.
      Returns:
        `this` for chaining.

    - #### getTotalFailoverJobsCount

          public int getTotalFailoverJobsCount()

      Get total number of jobs that were failed over.
      Returns:
        Total number of failed over 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 AlwaysFailoverSpi 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`

2021 Copyright © Apache Software Foundation
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Ignite Database and Caching Platform | : ver. 2.11.0
Release Date | : September 11 2021