org.gridgain.grid.spi.loadbalancing
Interface GridLoadBalancingSpi
- All Superinterfaces:
- GridSpi, GridSpiJsonConfigurable
- All Known Implementing Classes:
- GridAdaptiveLoadBalancingSpi, GridRoundRobinLoadBalancingSpi, GridWeightedRandomLoadBalancingSpi
public interface GridLoadBalancingSpi
- extends GridSpi, GridSpiJsonConfigurable
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 GridTask.map(List, Object)
invocation.
If you are using GridTaskSplitAdapter 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 GridTaskSplitAdapter<Object,Object> {
@Override
protected Collection<? extends GridJob> 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
GridTaskAdapter. 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 GridTaskAdapter<String,String> {
// Inject load balancer.
@GridLoadBalancerResource
GridLoadBalancer balancer;
// Map jobs to grid nodes.
public Map<? extends GridJob, 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.
jobs.put(new MyFooBarJob(arg), balancer.getBalancedNode())
}
return jobs;
}
// Aggregate results into one compound result.
public String reduce(List<GridJobResult> results) throws GridException {
// For the purpose of this example we simply
// concatenate string representation of every
// job result
StringBuilder buf = new StringBuilder();
for (GridJobResult res : results) {
// Append string representation of result
// returned by every job.
buf.append(res.getData().string());
}
return buf.string();
}
}
GridGain comes with the following load balancing SPI implementations out of the box:
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.
-
getBalancedNode
GridNode getBalancedNode(GridTaskSession ses,
List<GridNode> top,
GridJob job)
throws GridException
- Gets balanced node for specified job within given task session.
- Throws:
GridException - If failed to get next balanced node.- 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.
