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| <h2 title="Interface ComputeLoadBalancer" class="title">Interface ComputeLoadBalancer</h2> |
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| <pre>public interface <span class="strong">ComputeLoadBalancer</span></pre> |
| <div class="block">Load balancer is used for finding the best balanced node according |
| to load balancing policy. Internally load balancer will |
| query the <a href="../../../../org/apache/ignite/spi/loadbalancing/LoadBalancingSpi.html" title="interface in org.apache.ignite.spi.loadbalancing"><code>LoadBalancingSpi</code></a> |
| to get the balanced node. |
| <p> |
| Load balancer can be used <i>explicitly</i> from inside <a href="../../../../org/apache/ignite/compute/ComputeTask.html#map(java.util.List,%20T)"><code>ComputeTask.map(List, Object)</code></a> |
| method when you implement <a href="../../../../org/apache/ignite/compute/ComputeTask.html" title="interface in org.apache.ignite.compute"><code>ComputeTask</code></a> interface directly or use |
| <a href="../../../../org/apache/ignite/compute/ComputeTaskAdapter.html" title="class in org.apache.ignite.compute"><code>ComputeTaskAdapter</code></a>. If you use <a href="../../../../org/apache/ignite/compute/ComputeTaskSplitAdapter.html" title="class in org.apache.ignite.compute"><code>ComputeTaskSplitAdapter</code></a> then |
| load balancer is accessed <i>implicitly</i> by the adapter so you don't have |
| to use it directly in your logic. |
| <h1 class="header">Coding Examples</h1> |
| If you are using <a href="../../../../org/apache/ignite/compute/ComputeTaskSplitAdapter.html" title="class in org.apache.ignite.compute"><code>ComputeTaskSplitAdapter</code></a> then load balancing logic |
| is transparent to your code and is handled automatically by the adapter. |
| Here is an example of how your task will look: |
| <pre name="code" class="java"> |
| public class MyFooBarTask extends ComputeTaskSplitAdapter<String> { |
| @Override |
| protected Collection<? extends ComputeJob> split(int gridSize, String arg) throws IgniteCheckedException { |
| 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; |
| } |
| ... |
| } |
| </pre> |
| If you need more fine-grained control over how some jobs within task get mapped to a node |
| and use affinity load balancing for some other jobs within task, then you should use |
| <a href="../../../../org/apache/ignite/compute/ComputeTaskAdapter.html" title="class in org.apache.ignite.compute"><code>ComputeTaskAdapter</code></a>. Here is an example of how your task will 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. |
| <pre name="code" class="java"> |
| public class MyFooBarTask extends ComputeTaskAdapter<String, String> { |
| // Inject load balancer. |
| @LoadBalancerResource |
| ComputeLoadBalancer balancer; |
| |
| // Map jobs to grid nodes. |
| public Map<? extends ComputeJob, ClusterNode> map(List<ClusterNode> subgrid, String arg) throws IgniteCheckedException { |
| Map<MyFooBarJob, ClusterNode> jobs = new HashMap<MyFooBarJob, ClusterNode>(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. |
| ComputeJob myJob = new MyFooBarJob(arg); |
| |
| jobs.put(myJob, balancer.getBalancedNode(myJob, null)); |
| } |
| |
| return jobs; |
| } |
| |
| // Aggregate results into one compound result. |
| public String reduce(List<ComputeJobResult> results) throws IgniteCheckedException { |
| // For the purpose of this example we simply |
| // concatenate string representation of every |
| // job result |
| StringBuilder buf = new StringBuilder(); |
| |
| for (ComputeJobResult res : results) { |
| // Append string representation of result |
| // returned by every job. |
| buf.append(res.getData().toString()); |
| } |
| |
| return buf.toString(); |
| } |
| } |
| </pre></div> |
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| <h3>Method Summary</h3> |
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| <caption><span>Methods</span><span class="tabEnd"> </span></caption> |
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| <th class="colLast" scope="col">Method and Description</th> |
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| <td class="colFirst"><code><a href="../../../../org/apache/ignite/cluster/ClusterNode.html" title="interface in org.apache.ignite.cluster">ClusterNode</a></code></td> |
| <td class="colLast"><code><strong><a href="../../../../org/apache/ignite/compute/ComputeLoadBalancer.html#getBalancedNode(org.apache.ignite.compute.ComputeJob,%20java.util.Collection)">getBalancedNode</a></strong>(<a href="../../../../org/apache/ignite/compute/ComputeJob.html" title="interface in org.apache.ignite.compute">ComputeJob</a> job, |
| <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Collection.html?is-external=true" title="class or interface in java.util">Collection</a><<a href="../../../../org/apache/ignite/cluster/ClusterNode.html" title="interface in org.apache.ignite.cluster">ClusterNode</a>> exclNodes)</code> |
| <div class="block">Gets the next balanced node according to the underlying load balancing policy.</div> |
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| <h4>getBalancedNode</h4> |
| <pre>@Nullable |
| <a href="../../../../org/apache/ignite/cluster/ClusterNode.html" title="interface in org.apache.ignite.cluster">ClusterNode</a> getBalancedNode(<a href="../../../../org/apache/ignite/compute/ComputeJob.html" title="interface in org.apache.ignite.compute">ComputeJob</a> job, |
| @Nullable |
| <a href="http://docs.oracle.com/javase/7/docs/api/java/util/Collection.html?is-external=true" title="class or interface in java.util">Collection</a><<a href="../../../../org/apache/ignite/cluster/ClusterNode.html" title="interface in org.apache.ignite.cluster">ClusterNode</a>> exclNodes) |
| throws <a href="../../../../org/apache/ignite/IgniteException.html" title="class in org.apache.ignite">IgniteException</a></pre> |
| <div class="block">Gets the next balanced node according to the underlying load balancing policy.</div> |
| <dl><dt><span class="strong">Parameters:</span></dt><dd><code>job</code> - Job to get the balanced node for.</dd><dd><code>exclNodes</code> - Optional collection of nodes that should be excluded from balanced nodes. |
| If collection is <code>null</code> or empty - no nodes will be excluded.</dd> |
| <dt><span class="strong">Returns:</span></dt><dd>Next balanced node.</dd> |
| <dt><span class="strong">Throws:</span></dt> |
| <dd><code><a href="../../../../org/apache/ignite/IgniteException.html" title="class in org.apache.ignite">IgniteException</a></code> - If any error occurred when finding next balanced node.</dd></dl> |
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