Package org.apache.ignite.spi.loadbalancing.adaptive

## Interface AdaptiveLoadProbe

- All Known Implementing Classes:
    `AdaptiveCpuLoadProbe`, `AdaptiveJobCountLoadProbe`, `AdaptiveProcessingTimeLoadProbe`

      public interface AdaptiveLoadProbe

  Pluggable implementation of node load probing. Implementations of this can be configured to be used with `AdaptiveLoadBalancingSpi` by setting `AdaptiveLoadBalancingSpi.setLoadProbe(AdaptiveLoadProbe)` configuration parameter.

  Note that if `getLoad(org.apache.ignite.cluster.ClusterNode, int)` returns a value of `0`, then implementation will assume that load value is simply not available and will try to calculate an average of load values for other nodes. If such average cannot be obtained (all node load values are `0`), then a value of `1` will be used.

  By default, `AdaptiveCpuLoadProbe` probing implementation is used.

  # Example

  Here is an example of how probing can be implemented to use number of active and waiting jobs as probing mechanism:

       public class FooBarLoadProbe implements GridAdaptiveLoadProbe {
           // Flag indicating whether to use average value or current.
           private int useAvg = true;

           public FooBarLoadProbe(boolean useAvg) {
               this.useAvg = useAvg;
           }

           // Calculate load based on number of active and waiting jobs.
           public double getLoad(ClusterNode node, int jobsSentSinceLastUpdate) {
               GridNodeMetrics metrics = node.getMetrics();

               if (useAvg) {
                   double load = metrics.getAverageActiveJobs() + metrics.getAverageWaitingJobs();

                   if (load > 0) {
                       return load;
                   }
               }

               return metrics.getCurrentActiveJobs() + metrics.getCurrentWaitingJobs();
           }
       }

  Below is an example of how a probe shown above would be configured with `AdaptiveLoadBalancingSpi` SPI:

       <property name="loadBalancingSpi">
           <bean class="org.apache.ignite.spi.loadBalancing.adaptive.GridAdaptiveLoadBalancingSpi">
               <property name="loadProbe">
                   <bean class="foo.bar.FooBarLoadProbe">
                       <constructor-arg value="true"/>
                   </bean>
               </property>
           </bean>
       </property>

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `double` | `getLoad​(ClusterNode node, int jobsSentSinceLastUpdate)` | Calculates load value for a given node.

- - ### Method Detail

    - #### getLoad

          double getLoad​(ClusterNode node,
                         int jobsSentSinceLastUpdate)

      Calculates load value for a given node. Specific implementations would usually take into account some of the values provided by `ClusterNode.metrics()` method. For example, load can be calculated based on job execution time or number of active jobs, or CPU/Heap utilization.

      Note that if this method returns a value of `0`, then implementation will assume that load value is simply not available and will try to calculate an average of load values for other nodes. If such average cannot be obtained (all node load values are `0`), then a value of `1` will be used.

      Parameters:
        `node` - Grid node to calculate load for.
        `jobsSentSinceLastUpdate` - Number of jobs sent to this node since last metrics update. This parameter may be useful when implementation takes into account the current job count on a node.
      Returns:
        Non-negative load value for the node (zero and above).