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* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
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package org.apache.ignite.spi.loadbalancing.roundrobin;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import org.apache.ignite.IgniteLogger;
import org.apache.ignite.cluster.ClusterNode;
import org.apache.ignite.compute.ComputeJob;
import org.apache.ignite.compute.ComputeTaskSession;
import org.apache.ignite.events.Event;
import org.apache.ignite.events.JobEvent;
import org.apache.ignite.events.TaskEvent;
import org.apache.ignite.internal.managers.eventstorage.GridLocalEventListener;
import org.apache.ignite.internal.util.typedef.internal.A;
import org.apache.ignite.internal.util.typedef.internal.S;
import org.apache.ignite.internal.util.typedef.internal.U;
import org.apache.ignite.lang.IgniteUuid;
import org.apache.ignite.resources.LoggerResource;
import org.apache.ignite.spi.IgniteSpiAdapter;
import org.apache.ignite.spi.IgniteSpiConfiguration;
import org.apache.ignite.spi.IgniteSpiContext;
import org.apache.ignite.spi.IgniteSpiException;
import org.apache.ignite.spi.IgniteSpiMBeanAdapter;
import org.apache.ignite.spi.IgniteSpiMultipleInstancesSupport;
import org.apache.ignite.spi.loadbalancing.LoadBalancingSpi;
import org.jetbrains.annotations.Nullable;
import org.jsr166.ConcurrentHashMap8;
import static org.apache.ignite.events.EventType.EVT_JOB_MAPPED;
import static org.apache.ignite.events.EventType.EVT_TASK_FAILED;
import static org.apache.ignite.events.EventType.EVT_TASK_FINISHED;
/**
* This SPI iterates through nodes in round-robin fashion and pick the next
* sequential node. Two modes of operation are supported: per-task and global
* (see {@link #setPerTask(boolean)} configuration). Global mode is used be default.
* <p>
* When configured in per-task mode, implementation will pick a random node at the
* beginning of every task execution and then sequentially iterate through all
* nodes in topology starting from the picked node. For cases when split size
* is equal to the number of nodes, this mode guarantees that all nodes will
* participate in the split.
* <p>
* When configured in global mode, a single sequential queue of nodes is maintained for
* all tasks and the next node in the queue is picked every time. In this mode (unlike in
* {@code per-task} mode) it is possible that even if split size may be equal to the
* number of nodes, some jobs within the same task will be assigned to the same node if
* multiple tasks are executing concurrently.
* <h1 class="header">Coding Example</h1>
* If you are using {@link org.apache.ignite.compute.ComputeTaskSplitAdapter} 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<Object, Object> {
* @Override
* protected Collection<? extends ComputeJob> split(int gridSize, Object 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
* {@link org.apache.ignite.compute.ComputeTaskAdapter}. 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.
* jobs.put(new MyFooBarJob(arg), balancer.getBalancedNode())
* }
*
* 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().string());
* }
*
* return buf.string();
* }
* }
* </pre>
* <p>
* <h1 class="header">Configuration</h1>
* In order to use this load balancer, you should configure your grid instance
* to use {@link RoundRobinLoadBalancingSpi} either from Spring XML file or
* directly. The following configuration parameters are supported:
* <h2 class="header">Mandatory</h2>
* This SPI has no mandatory configuration parameters.
* <h2 class="header">Optional</h2>
* The following configuration parameters are optional:
* <ul>
* <li>
* Flag that indicates whether to use {@code per-task} or global
* round-robin modes described above (see {@link #setPerTask(boolean)}).
* </li>
* </ul>
* Below is Java configuration example:
* <pre name="code" class="java">
* RoundRobinLoadBalancingSpi spi = new RoundRobinLoadBalancingSpi();
*
* // Configure SPI to use global round-robin mode.
* spi.setPerTask(false);
*
* IgniteConfiguration cfg = new IgniteConfiguration();
*
* // Override default load balancing SPI.
* cfg.setLoadBalancingSpi(spi);
*
* // Starts grid.
* G.start(cfg);
* </pre>
* Here is how you can configure {@link RoundRobinLoadBalancingSpi} using Spring XML configuration:
* <pre name="code" class="xml">
* <property name="loadBalancingSpi">
* <bean class="org.apache.ignite.spi.loadBalancing.roundrobin.RoundRobinLoadBalancingSpi">
* <!-- Set to global round-robin mode. -->
* <property name="perTask" value="false"/>
* </bean>
* </property>
* </pre>
* <p>
* <img src="http://ignite.apache.org/images/spring-small.png">
* <br>
* For information about Spring framework visit <a href="http://www.springframework.org/">www.springframework.org</a>
*/
@IgniteSpiMultipleInstancesSupport(true)
public class RoundRobinLoadBalancingSpi extends IgniteSpiAdapter implements LoadBalancingSpi {
/** Grid logger. */
@LoggerResource
private IgniteLogger log;
/** */
private RoundRobinGlobalLoadBalancer balancer;
/** */
private boolean isPerTask;
/** */
private final Map<IgniteUuid, RoundRobinPerTaskLoadBalancer> perTaskBalancers =
new ConcurrentHashMap8<>();
/** Event listener. */
private final GridLocalEventListener lsnr = new GridLocalEventListener() {
@Override public void onEvent(Event evt) {
if (evt.type() == EVT_TASK_FAILED ||
evt.type() == EVT_TASK_FINISHED)
perTaskBalancers.remove(((TaskEvent)evt).taskSessionId());
else if (evt.type() == EVT_JOB_MAPPED) {
RoundRobinPerTaskLoadBalancer balancer =
perTaskBalancers.get(((JobEvent)evt).taskSessionId());
if (balancer != null)
balancer.onMapped();
}
}
};
/**
* See {@link #setPerTask(boolean)}.
*
* @return Configuration parameter indicating whether a new round robin order should
* be created for every task. Default is {@code false}.
*/
public boolean isPerTask() {
return isPerTask;
}
/**
* Configuration parameter indicating whether a new round robin order should be
* created for every task. If {@code true} then load balancer is guaranteed
* to iterate through nodes sequentially for every task - so as long as number
* of jobs is less than or equal to the number of nodes, jobs are guaranteed to
* be assigned to unique nodes. If {@code false} then one round-robin order
* will be maintained for all tasks, so when tasks execute concurrently, it
* is possible for more than one job within task to be assigned to the same
* node.
* <p>
* Default is {@code false}.
*
* @param isPerTask Configuration parameter indicating whether a new round robin order should
* be created for every task. Default is {@code false}.
* @return {@code this} for chaining.
*/
@IgniteSpiConfiguration(optional = true)
public RoundRobinLoadBalancingSpi setPerTask(boolean isPerTask) {
this.isPerTask = isPerTask;
return this;
}
/** {@inheritDoc} */
@Override public void spiStart(@Nullable String igniteInstanceName) throws IgniteSpiException {
startStopwatch();
if (log.isDebugEnabled())
log.debug(configInfo("isPerTask", isPerTask));
registerMBean(igniteInstanceName, new RoundRobinLoadBalancingSpiMBeanImpl(this),
RoundRobinLoadBalancingSpiMBean.class);
balancer = new RoundRobinGlobalLoadBalancer(log);
// Ack ok start.
if (log.isDebugEnabled())
log.debug(startInfo());
}
/** {@inheritDoc} */
@Override public void spiStop() throws IgniteSpiException {
balancer = null;
perTaskBalancers.clear();
unregisterMBean();
// Ack ok stop.
if (log.isDebugEnabled())
log.debug(stopInfo());
}
/** {@inheritDoc} */
@Override protected void onContextInitialized0(IgniteSpiContext spiCtx) throws IgniteSpiException {
if (!isPerTask)
balancer.onContextInitialized(spiCtx);
else {
if (!getSpiContext().isEventRecordable(EVT_TASK_FAILED, EVT_TASK_FINISHED, EVT_JOB_MAPPED))
throw new IgniteSpiException("Required event types are disabled: " +
U.gridEventName(EVT_TASK_FAILED) + ", " +
U.gridEventName(EVT_TASK_FINISHED) + ", " +
U.gridEventName(EVT_JOB_MAPPED));
getSpiContext().addLocalEventListener(lsnr, EVT_TASK_FAILED, EVT_TASK_FINISHED, EVT_JOB_MAPPED);
}
}
/** {@inheritDoc} */
@Override protected void onContextDestroyed0() {
if (!isPerTask) {
if (balancer != null)
balancer.onContextDestroyed();
}
else {
IgniteSpiContext spiCtx = getSpiContext();
if (spiCtx != null)
spiCtx.removeLocalEventListener(lsnr);
}
}
/** {@inheritDoc} */
@Override public ClusterNode getBalancedNode(ComputeTaskSession ses, List<ClusterNode> top, ComputeJob job) {
A.notNull(ses, "ses", top, "top");
if (isPerTask) {
// Note that every session operates from single thread which
// allows us to use concurrent map and avoid synchronization.
RoundRobinPerTaskLoadBalancer taskBalancer = perTaskBalancers.get(ses.getId());
if (taskBalancer == null)
perTaskBalancers.put(ses.getId(), taskBalancer = new RoundRobinPerTaskLoadBalancer());
return taskBalancer.getBalancedNode(top);
}
return balancer.getBalancedNode(top);
}
/**
* THIS METHOD IS USED ONLY FOR TESTING.
*
* @param ses Task session.
* @return Internal list of nodes.
*/
List<UUID> getNodeIds(ComputeTaskSession ses) {
if (isPerTask) {
RoundRobinPerTaskLoadBalancer balancer = perTaskBalancers.get(ses.getId());
if (balancer == null)
return Collections.emptyList();
List<UUID> ids = new ArrayList<>();
for (ClusterNode node : balancer.getNodes()) {
ids.add(node.id());
}
return ids;
}
return balancer.getNodeIds();
}
/** {@inheritDoc} */
@Override public RoundRobinLoadBalancingSpi setName(String name) {
super.setName(name);
return this;
}
/** {@inheritDoc} */
@Override public String toString() {
return S.toString(RoundRobinLoadBalancingSpi.class, this);
}
/**
* MBean implementation for RoundRobinLoadBalancingSpi.
*/
private class RoundRobinLoadBalancingSpiMBeanImpl extends IgniteSpiMBeanAdapter
implements RoundRobinLoadBalancingSpiMBean {
/** {@inheritDoc} */
RoundRobinLoadBalancingSpiMBeanImpl(IgniteSpiAdapter spiAdapter) {
super(spiAdapter);
}
/** {@inheritDoc} */
@Override public boolean isPerTask() {
return RoundRobinLoadBalancingSpi.this.isPerTask();
}
}
}