001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.camel.model.loadbalancer;
018
019import java.util.ArrayList;
020import java.util.List;
021import javax.xml.bind.annotation.XmlAccessType;
022import javax.xml.bind.annotation.XmlAccessorType;
023import javax.xml.bind.annotation.XmlAttribute;
024import javax.xml.bind.annotation.XmlElement;
025import javax.xml.bind.annotation.XmlRootElement;
026import javax.xml.bind.annotation.XmlTransient;
027
028import org.apache.camel.model.LoadBalancerDefinition;
029import org.apache.camel.processor.loadbalancer.CircuitBreakerLoadBalancer;
030import org.apache.camel.processor.loadbalancer.LoadBalancer;
031import org.apache.camel.spi.Metadata;
032import org.apache.camel.spi.RouteContext;
033import org.apache.camel.util.ObjectHelper;
034
035/**
036 * Circuit break load balancer
037 * <p/>
038 * The Circuit Breaker load balancer is a stateful pattern that monitors all calls for certain exceptions.
039 * Initially the Circuit Breaker is in closed state and passes all messages.
040 * If there are failures and the threshold is reached, it moves to open state and rejects all calls until halfOpenAfter
041 * timeout is reached. After this timeout is reached, if there is a new call, it will pass and if the result is
042 * success the Circuit Breaker will move to closed state, or to open state if there was an error.
043 *
044 * @deprecated use Hystrix EIP instead which is the popular Netflix implementation of circuit breaker
045 */
046@Metadata(label = "eip,routing,loadbalance,circuitbreaker")
047@XmlRootElement(name = "circuitBreaker")
048@XmlAccessorType(XmlAccessType.FIELD)
049@Deprecated
050public class CircuitBreakerLoadBalancerDefinition extends LoadBalancerDefinition {
051    @XmlTransient
052    private List<Class<?>> exceptionTypes = new ArrayList<Class<?>>();
053    @XmlElement(name = "exception")
054    private List<String> exceptions = new ArrayList<String>();
055    @XmlAttribute
056    private Long halfOpenAfter;
057    @XmlAttribute
058    private Integer threshold;
059
060    public CircuitBreakerLoadBalancerDefinition() {
061    }
062
063    @Override
064    protected int getMaximumNumberOfOutputs() {
065        // we can only support 1 output
066        return 1;
067    }
068
069    @Override
070    protected LoadBalancer createLoadBalancer(RouteContext routeContext) {
071        CircuitBreakerLoadBalancer answer;
072
073        List<Class<?>> classes = new ArrayList<Class<?>>();
074        if (!exceptionTypes.isEmpty()) {
075            classes.addAll(exceptionTypes);
076        } else if (!exceptions.isEmpty()) {
077            for (String name : exceptions) {
078                Class<?> type = routeContext.getCamelContext().getClassResolver().resolveClass(name);
079                if (type == null) {
080                    throw new IllegalArgumentException("Cannot find class: " + name + " in the classpath");
081                }
082                if (!ObjectHelper.isAssignableFrom(Throwable.class, type)) {
083                    throw new IllegalArgumentException("Class is not an instance of Throwable: " + type);
084                }
085                classes.add(type);
086            }
087        }
088        if (classes.isEmpty()) {
089            answer = new CircuitBreakerLoadBalancer();
090        } else {
091            answer = new CircuitBreakerLoadBalancer(classes);
092        }
093
094        if (getHalfOpenAfter() != null) {
095            answer.setHalfOpenAfter(getHalfOpenAfter());
096        }
097        if (getThreshold() != null) {
098            answer.setThreshold(getThreshold());
099        }
100        return answer;
101    }
102
103    public Long getHalfOpenAfter() {
104        return halfOpenAfter;
105    }
106
107    /**
108     * The timeout in millis to use as threshold to move state from closed to half-open or open state
109     */
110    public void setHalfOpenAfter(Long halfOpenAfter) {
111        this.halfOpenAfter = halfOpenAfter;
112    }
113
114    public Integer getThreshold() {
115        return threshold;
116    }
117
118    /**
119     * Number of previous failed messages to use as threshold to move state from closed to half-open or open state
120     */
121    public void setThreshold(Integer threshold) {
122        this.threshold = threshold;
123    }
124
125    public List<String> getExceptions() {
126        return exceptions;
127    }
128
129    /**
130     * A list of class names for specific exceptions to monitor.
131     * If no exceptions is configured then all exceptions is monitored
132     */
133    public void setExceptions(List<String> exceptions) {
134        this.exceptions = exceptions;
135    }
136
137    public List<Class<?>> getExceptionTypes() {
138        return exceptionTypes;
139    }
140
141    /**
142     * A list of specific exceptions to monitor.
143     * If no exceptions is configured then all exceptions is monitored
144     */
145    public void setExceptionTypes(List<Class<?>> exceptionTypes) {
146        this.exceptionTypes = exceptionTypes;
147    }
148
149    @Override
150    public String toString() {
151        return "CircuitBreakerLoadBalancer";
152    }
153}