org.gridgain.grid.spi.loadbalancing

Interface GridLoadBalancingSpi

All Superinterfaces:

GridSpi

All Known Implementing Classes:

GridAdaptiveLoadBalancingSpi, GridRoundRobinLoadBalancingSpi, GridWeightedRandomLoadBalancingSpi

public interface GridLoadBalancingSpi
extends GridSpi

Load balancing SPI provides the next best balanced node for job execution. This SPI is used either implicitly or explicitly whenever a job gets mapped to a node during GridComputeTask.map(List, Object) invocation.

Coding Examples

If you are using GridComputeTaskSplitAdapter then load balancing logic is transparent to your code and is handled automatically by the adapter. Here is an example of how your task could look:

 public class MyFooBarTask extends GridComputeTaskSplitAdapter<Object,Object> {
    @Override
    protected Collection<? extends GridComputeJob> split(int gridSize, Object arg) throws GridException {
        List<MyFooBarJob> jobs = new ArrayList<MyFooBarJob>(gridSize);

        for (int i = 0; i < gridSize; i++) {
            jobs.add(new MyFooBarJob(arg));
        }

        // Node assignment via load balancer
        // happens automatically.
        return jobs;
    }
    ...
 }
 

If you need more fine-grained control over how some jobs within task get mapped to a node and use, for example, affinity load balancing for some other jobs within task, then you should use GridComputeTaskAdapter. Here is an example of how your task could look. Note that in this case we manually inject load balancer and use it to pick the best node. Doing it in such way would allow user to map some jobs manually and for others use load balancer.

 public class MyFooBarTask extends GridComputeTaskAdapter<String,String> {
    // Inject load balancer.
    @GridLoadBalancerResource
    GridComputeLoadBalancer balancer;

    // Map jobs to grid nodes.
    public Map<? extends GridComputeJob, GridNode> map(List<GridNode> subgrid, String arg) throws GridException {
        Map<MyFooBarJob, GridNode> jobs = new HashMap<MyFooBarJob, GridNode>(subgrid.size());

        // In more complex cases, you can actually do
        // more complicated assignments of jobs to nodes.
        for (int i = 0; i < subgrid.size(); i++) {
            // Pick the next best balanced node for the job.
            GridComputeJob myJob = new MyFooBarJob(arg);

            jobs.put(myJob, balancer.getBalancedNode(myJob, null));
        }

        return jobs;
    }

    // Aggregate results into one compound result.
    public String reduce(List<GridComputeJobResult> results) throws GridException {
        // For the purpose of this example we simply
        // concatenate string representation of every
        // job result
        StringBuilder buf = new StringBuilder();

        for (GridComputeJobResult res : results) {
            // Append string representation of result
            // returned by every job.
            buf.append(res.getData().toString());
        }

        return buf.toString();
    }
 }
 

GridGain comes with the following load balancing SPI implementations out of the box:

• GridRoundRobinLoadBalancingSpi - default
• GridAdaptiveLoadBalancingSpi
• GridWeightedRandomLoadBalancingSpi

NOTE: this SPI (i.e. methods in this interface) should never be used directly. SPIs provide internal view on the subsystem and is used internally by GridGain kernal. In rare use cases when access to a specific implementation of this SPI is required - an instance of this SPI can be obtained via Grid.configuration() method to check its configuration properties or call other non-SPI methods. Note again that calling methods from this interface on the obtained instance can lead to undefined behavior and explicitly not supported.

Method Summary

Methods

Modifier and Type	Method and Description
GridNode	getBalancedNode(GridComputeTaskSession ses, List<GridNode> top, GridComputeJob job) Gets balanced node for specified job within given task session.

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

getName, getNodeAttributes, onContextDestroyed, onContextInitialized, spiStart, spiStop

Method Detail

getBalancedNode

GridNode getBalancedNode(GridComputeTaskSession ses,
                       List<GridNode> top,
                       GridComputeJob job)
                         throws GridException

Gets balanced node for specified job within given task session.

Parameters:

ses - Grid task session for currently executing task.

top - Topology of task nodes from which to pick the best balanced node for given job.

job - Job for which to pick the best balanced node.

Returns:

Best balanced node for the given job within given task session.

Throws:

GridException - If failed to get next balanced node.