/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* 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.
*/
package org.apache.ignite.spi.loadbalancing.adaptive;
import org.apache.ignite.cluster.ClusterNode;
/**
* Pluggable implementation of node load probing. Implementations
* of this can be configured to be used with {@link AdaptiveLoadBalancingSpi}
* by setting {@link AdaptiveLoadBalancingSpi#setLoadProbe(AdaptiveLoadProbe)}
* configuration parameter.
* <p>
* Note that if {@link #getLoad(org.apache.ignite.cluster.ClusterNode, int)} returns a value of {@code 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 {@code 0}), then a value
* of {@code 1} will be used.
* <p>
* By default, {@link AdaptiveCpuLoadProbe} probing implementation is used.
* <p>
* <h1 class="header">Example</h1>
* Here is an example of how probing can be implemented to use
* number of active and waiting jobs as probing mechanism:
* <pre name="code" class="java">
* 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();
* }
* }
* </pre>
* Below is an example of how a probe shown above would be configured with {@link AdaptiveLoadBalancingSpi}
* SPI:
* <pre name="code" class="xml">
* <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>
* </pre>
*/
public interface AdaptiveLoadProbe {
/**
* Calculates load value for a given node. Specific implementations would
* usually take into account some of the values provided by
* {@link org.apache.ignite.cluster.ClusterNode#metrics()} method. For example, load can be calculated
* based on job execution time or number of active jobs, or CPU/Heap utilization.
* <p>
* Note that if this method returns a value of {@code 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 {@code 0}), then a value
* of {@code 1} will be used.
*
* @param node Grid node to calculate load for.
* @param 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.
* @return Non-negative load value for the node (zero and above).
*/
public double getLoad(ClusterNode node, int jobsSentSinceLastUpdate);
}