org.apache.ignite.spi.collision.fifoqueue

## Class FifoQueueCollisionSpi

- java.lang.Object
- - org.apache.ignite.spi.IgniteSpiAdapter
  - - org.apache.ignite.spi.collision.fifoqueue.FifoQueueCollisionSpi

- All Implemented Interfaces:
    CollisionSpi, IgniteSpi

      @IgniteSpiMultipleInstancesSupport(value=true)
      public class FifoQueueCollisionSpi
      extends IgniteSpiAdapter
      implements CollisionSpi

  This class provides implementation for Collision SPI based on FIFO queue. Jobs are ordered as they arrived and only `getParallelJobsNumber()` number of jobs is allowed to execute in parallel. Other jobs will be buffered in the passive queue.

  # Configuration

  ## Mandatory

  This SPI has no mandatory configuration parameters.

  ## Optional

  This SPI has following optional configuration parameters:
  - Number of jobs that can execute in parallel (see `setParallelJobsNumber(int)`). This number should usually be set to the number of threads in the execution thread pool.

  ## Java Example

  `FifoQueueCollisionSpi` can be configured as follows:

       FifoQueueCollisionSpi colSpi = new FifoQueueCollisionSpi();

       // Execute all jobs sequentially by setting parallel job number to 1.
       colSpi.setParallelJobsNumber(1);

       IgniteConfiguration cfg = new IgniteConfiguration();

       // Override default collision SPI.
       cfg.setCollisionSpi(colSpi);

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

  ## Spring Example

  `FifoQueueCollisionSpi` can be configured from Spring XML configuration file:

       <bean id="grid.custom.cfg" class="org.apache.ignite.configuration.IgniteConfiguration" singleton="true">
             ...
             <property name="collisionSpi">
                 <bean class="org.apache.ignite.spi.collision.fifoqueue.FifoQueueCollisionSpi">
                     <property name="parallelJobsNumber" value="1"/>
                 </bean>
             </property>
             ...
       </bean>

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `DFLT_PARALLEL_JOBS_NUM` Default number of parallel jobs allowed (set to number of cores times 2).
    `static int` | `DFLT_WAIT_JOBS_NUM` Default waiting jobs number.

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

      `ignite, igniteInstanceName`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `FifoQueueCollisionSpi()`

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `int` | `getCurrentActiveJobsNumber()` Gets current number of jobs that are active, i.e.
    `int` | `getCurrentHeldJobsNumber()` Gets number of currently `'held'` jobs.
    `int` | `getCurrentRunningJobsNumber()` Gets number of currently running (not `'held`) jobs.
    `int` | `getCurrentWaitJobsNumber()` Gets current number of jobs that wait for the execution.
    `int` | `getParallelJobsNumber()` See `setParallelJobsNumber(int)`
    `int` | `getWaitingJobsNumber()` See `setWaitingJobsNumber(int)`
    `void` | `onCollision(CollisionContext ctx)` This is a callback called: new grid job arrived executing job finished its execution topology changed periodically (on `EventType.EVT_NODE_METRICS_UPDATED`) When new job arrives it is added to the end of the wait list and this method is called.
    `void` | `setExternalCollisionListener(CollisionExternalListener lsnr)` Listener to be set for notification of external collision events (e.g. job stealing).
    `FifoQueueCollisionSpi` | `setName(String name)` Sets SPI name.
    `FifoQueueCollisionSpi` | `setParallelJobsNumber(int parallelJobsNum)` Sets number of jobs that can be executed in parallel.
    `FifoQueueCollisionSpi` | `setWaitingJobsNumber(int waitJobsNum)` Sets maximum number of jobs that are allowed to wait in waiting queue.
    `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, getConsistentAttributeNames, getExceptionRegistry, getLocalNode, getName, getNodeAttributes, 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, getNodeAttributes, onClientDisconnected, onClientReconnected, onContextDestroyed, onContextInitialized`

- - ### Field Detail

    - #### DFLT_PARALLEL_JOBS_NUM

          public static final int DFLT_PARALLEL_JOBS_NUM

      Default number of parallel jobs allowed (set to number of cores times 2).

    - #### DFLT_WAIT_JOBS_NUM

          public static final int DFLT_WAIT_JOBS_NUM

      Default waiting jobs number. If number of waiting jobs exceeds this number, jobs will be rejected. Default value is `Integer.MAX_VALUE`.
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### FifoQueueCollisionSpi

          public FifoQueueCollisionSpi()

  - ### Method Detail

    - #### getParallelJobsNumber

          public int getParallelJobsNumber()

      See `setParallelJobsNumber(int)`
      Returns:
        Number of jobs that can be executed in parallel.

    - #### setParallelJobsNumber

          @IgniteSpiConfiguration(optional=true)
          public FifoQueueCollisionSpi setParallelJobsNumber(int parallelJobsNum)

      Sets number of jobs that can be executed in parallel.
      Parameters:
        `parallelJobsNum` - Parallel jobs number.
      Returns:
        `this` for chaining.

    - #### getWaitingJobsNumber

          public int getWaitingJobsNumber()

      See `setWaitingJobsNumber(int)`
      Returns:
        Maximum allowed number of waiting jobs.

    - #### setWaitingJobsNumber

          @IgniteSpiConfiguration(optional=true)
          public FifoQueueCollisionSpi setWaitingJobsNumber(int waitJobsNum)

      Sets maximum number of jobs that are allowed to wait in waiting queue. If number of waiting jobs ever exceeds this number, excessive jobs will be rejected.
      Parameters:
        `waitJobsNum` - Waiting jobs number.
      Returns:
        `this` for chaining.

    - #### getCurrentWaitJobsNumber

          public int getCurrentWaitJobsNumber()

      Gets current number of jobs that wait for the execution.
      Returns:
        Number of jobs that wait for execution.

    - #### getCurrentActiveJobsNumber

          public int getCurrentActiveJobsNumber()

      Gets current number of jobs that are active, i.e. `'running + held'` jobs.
      Returns:
        Number of active jobs.

    - #### getCurrentRunningJobsNumber

          public int getCurrentRunningJobsNumber()

      Gets number of currently running (not `'held`) jobs.
      Returns:
        Number of currently running (not `'held`) jobs.

    - #### getCurrentHeldJobsNumber

          public int getCurrentHeldJobsNumber()

      Gets number of currently `'held'` jobs.
      Returns:
        Number of currently `'held'` jobs.

    - #### 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.

    - #### setExternalCollisionListener

          public void setExternalCollisionListener(CollisionExternalListener lsnr)

      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.

      Ignite 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 `ComputeJobContext`) 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 might 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 `CollisionSpi`
      Parameters:
        `lsnr` - Listener for external collision events.

    - #### onCollision

          public void onCollision(CollisionContext ctx)

      This is a callback called:
      - new grid job arrived
      - executing job finished its execution
      - topology changed
      - periodically (on `EventType.EVT_NODE_METRICS_UPDATED`)
      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 all lists, each of which contains collision job contexts that define a set of operations available during collision resolution. Refer to `CollisionContext` and `CollisionJobContext` documentation for more information.

      Specified by:
        `onCollision` in interface `CollisionSpi`
      Parameters:
        `ctx` - Collision context which contains all collision lists.

    - #### setName

          public FifoQueueCollisionSpi 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`

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Ignite Database and Caching Platform | : ver. 2.12.0
Release Date | : January 10 2022