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package org.apache.camel.processor.loadbalancer; |
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import java.util.HashMap; |
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import java.util.Iterator; |
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import java.util.List; |
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import java.util.Map; |
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import org.apache.camel.Exchange; |
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import org.apache.camel.Expression; |
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import org.apache.camel.Processor; |
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public class StickyLoadBalancer extends QueueLoadBalancer { |
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private Expression<Exchange> correlationExpression; |
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private QueueLoadBalancer loadBalancer; |
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private int numberOfHashGroups = 64 * 1024; |
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private Map<Object, Processor> stickyMap = new HashMap<Object, Processor>(); |
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public StickyLoadBalancer(Expression<Exchange> correlationExpression) { |
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this(correlationExpression, new RoundRobinLoadBalancer()); |
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} |
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public StickyLoadBalancer(Expression<Exchange> correlationExpression, QueueLoadBalancer loadBalancer) { |
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this.correlationExpression = correlationExpression; |
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this.loadBalancer = loadBalancer; |
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} |
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protected synchronized Processor chooseProcessor(List<Processor> processors, Exchange exchange) { |
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Object value = correlationExpression.evaluate(exchange); |
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Object key = getStickyKey(value); |
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Processor processor; |
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synchronized (stickyMap) { |
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processor = stickyMap.get(key); |
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if (processor == null) { |
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processor = loadBalancer.chooseProcessor(processors, exchange); |
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stickyMap.put(key, processor); |
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} |
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} |
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return processor; |
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} |
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@Override |
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public void removeProcessor(Processor processor) { |
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synchronized (stickyMap) { |
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Iterator<Map.Entry<Object, Processor>> iter = stickyMap.entrySet().iterator(); |
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while (iter.hasNext()) { |
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Map.Entry<Object, Processor> entry = iter.next(); |
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if (processor.equals(entry.getValue())) { |
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iter.remove(); |
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} |
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} |
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} |
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super.removeProcessor(processor); |
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} |
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public int getNumberOfHashGroups() { |
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return numberOfHashGroups; |
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} |
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public void setNumberOfHashGroups(int numberOfHashGroups) { |
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this.numberOfHashGroups = numberOfHashGroups; |
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} |
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protected Object getStickyKey(Object value) { |
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int hashCode = 37; |
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if (value != null) { |
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hashCode = value.hashCode(); |
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} |
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if (numberOfHashGroups > 0) { |
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hashCode = hashCode % numberOfHashGroups; |
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} |
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return hashCode; |
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} |
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} |