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JAX-RS:

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Failover

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Starting from CXF 2.4.1,

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CXF

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JAX-RS

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clients

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can

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be

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configured

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them

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to

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become

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failover-capable.
Core CXF Failover and Load Distribution features are supported.

Failover

Proxies and WebClients can be configured to failover to alternate addresses in case of connection-related failures.
Sequential and Random strategies are supported and implementers can build more sophisticated failover features by retrieving
alternate addresses from locators and other intermediaries.

Spring

Code Block

	xml
	xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxrs="http://cxf.apache.org/jaxrs"
       xmlns:clustering="http://cxf.apache.org/clustering"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"/>
    
    <util:list id="addressList">
        <value>http://localhost:${testutil.ports.Server.1}/rest</value>
        <value>http://localhost:${testutil.ports.Server.2}/rest</value>
        <value>http://localhost:${testutil.ports.Server.3}/rest</value>
    </util:list>

    <bean id="SequentialAddresses" class="org.apache.cxf.clustering.SequentialStrategy">
        <property name="alternateAddresses">
            <ref bean="addressList"/>
        </property>
    </bean>

    <bean id="RandomAddresses" class="org.apache.cxf.clustering.RandomStrategy">
        <property name="alternateAddresses">
            <ref bean="addressList"/>
        </property>
    </bean>

    <jaxrs:client id="failoverSequential" address="http://localhost:8080/initialAddress">
       <jaxrs:features>
           <clustering:failover>
                <clustering:strategy>
                    <ref bean="SequentialAddresses"/>
                </clustering:strategy>
            </clustering:failover>
       </jaxrs:features>
    </jaxrs:client>

    <jaxrs:client id="failoverRandom" address="http://localhost:8080/initialAddress">
       <jaxrs:features>
           <clustering:failover>
                <clustering:strategy>
                    <ref bean="RandomAddresses"/>
                </clustering:strategy>
            </clustering:failover>
       </jaxrs:features>
    </jaxrs:client>

    <bean id="myWebClient" class="org.apache.cxf.jaxrs.client.JAXRSClientFactoryBean" 
factory-method="createWebClient"> 
        <property name="address" value="http://some.base.url.that.responds/" /> 
        <property name="features">
            <ref bean="failover1"/> 
        </property>  
    </bean> 
</beans>

Code

Code Block

	java
	java

org.apache.cxf.jaxrs.features.clustering.FailoverFeature feature = 
    new org.apache.cxf.jaxrs.features.clustering.FailoverFeature();
List<String> alternateAddresses = new ArrayList<String>();
// addresses are alternate addresses provided at start-up
for (String s : address) {
    alternateAddresses.add(s);
}
SequentialStrategy strategy = new SequentialStrategy();
strategy.setAlternateAddresses(alternateAddresses);
feature.setStrategy(strategy);

JAXRSClientFactoryBean bean = new JAXRSClientFactoryBean();
bean.setAddress("http://localhost:8080/inactive-replica");
List<Feature> features = new ArrayList<Feature>();
features.add(feature);
bean.setFeatures(features);

// create proxy:
bean.create(BookStore.class);
// create web client
bean.createWebClient();

Circuit Breakers Failover

The recent addition to CXF failover features is the implementation based on circuit breakers, more precisely Apache Zest (https://zest.apache.org/) library. It is available starting from CXF 3.2.0.

The configuration is very similar to the regular failover strategy, the only difference is usage of clustering:circuit-breaker-failover element.

Spring

Code Block

	xml
	xml


Core CXF Failover and Load Distribution features are supported.
     

h1. Failover

Proxies and WebClients can be configured to failover to alternate addresses in case of connection-related failures.
Sequential and Random strategies are supported and implementers can build more sophisticated failover features by retrieving
alternate addresses from locators and other intermediaries.

h2. Spring 

{code:xml}

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxrs="http://cxf.apache.org/jaxrs"
       xmlns:clustering="http://cxf.apache.org/clustering"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"/>
    
    <util:list id="addressList">
        <value>http://localhost:${testutil.ports.Server.1}/rest</value>
        <value>http://localhost:${testutil.ports.Server.2}/rest</value>
        <value>http://localhost:${testutil.ports.Server.3}/rest</value>
    </util:list>

    <bean id="SequentialAddresses" class="org.apache.cxf.clustering.SequentialStrategy">
        <property name="alternateAddresses">
            <ref bean="addressList"/>
        </property>
    </bean>

    <bean id="RandomAddresses" class="org.apache.cxf.clustering.RandomStrategy">
        <property name="alternateAddresses">
            <ref bean="addressList"/>
        </property>
    </bean>

    <jaxrs:client id="failoverSequential" address="http://localhost:8080/initialAddress">
       <jaxrs:features>
           <clustering:failover>circuit-breaker-failover threshold="1" timeout="60000">
                <clustering:strategy>
                    <ref bean="SequentialAddresses"/>
                </clustering:strategy>
            </clustering:circuit-breaker-failover>
       </jaxrs:features>
    </jaxrs:client>

    <jaxrs:client id="failoverRandom" address="http://localhost:8080/initialAddress">
       <jaxrs:features>
           <clustering:failover>circuit-breaker-failover threshold="1" timeout="60000">
                <clustering:strategy>
                    <ref bean="RandomAddresses"/>
                </clustering:strategy>
            </clustering:circuit-breaker-failover>
       </jaxrs:features>
    </jaxrs:client>

    <bean id="myWebClient" class="org.apache.cxf.jaxrs.client.JAXRSClientFactoryBean" 
factory-method="createWebClient"> 
        <property name="address" value="http://some.base.url.that.responds/" /> 
        <property name="features">
            <ref bean="failover1"/> 
        </property>  
    </bean> 
</beans>
{code}


h2. Code

{code:java}

Circuit breakers have recommended themselves as a proven strategy to handle and monitor the failures related to external service calls, giving the external systems a time to recover by preventing endless retries or time-outing. For that reason, two configuration parameters could be tuned:

threshold: the error threshold to open the circuit breaker
timeout: the timeout to wait before trying the next invocation

Code

Code Block

	java
	java

org.apache.cxf.jaxrs.features.clustering.FailoverFeatureCircuitBreakerFailoverFeature feature = 
    new org.apache.cxf.jaxrs.features.clustering.FailoverFeatureCircuitBreakerFailoverFeature(1, 60000);
List<String> alternateAddresses = new ArrayList<String>();
// addresses are alternate addresses provided at start-up
for (String s : address) {
    alternateAddresses.add(s);
}
SequentialStrategy strategy = new SequentialStrategy();
strategy.setAlternateAddresses(alternateAddresses);
feature.setStrategy(strategy);

JAXRSClientFactoryBean bean = new JAXRSClientFactoryBean();
bean.setAddress("http://localhost:8080/inactive-replica");
List<Feature> features = new ArrayList<Feature>();
features.add(feature);
bean.setFeatures(features);

// create proxy:
bean.create(BookStore.class);
// create web client
bean.createWebClient();

Load Distribution

CXF Load Distribution feature is a failover feature which can iterate where alternate addresses not only in case of failures but also after a successful invocation has been done.

Example:

Code Block

	xml
	xml


{code}

h1. Load Distribution 

CXF Load Distribution feature is a failover feature which can iterate where alternate addresses not only in case of failures but also after a successful invocation has been done.

Example:
{code:xml}
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxrs="http://cxf.apache.org/jaxrs"
       xmlns:clustering="http://cxf.apache.org/clustering"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
    <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"/>
    
    <util:list id="addressList">
        <value>http://localhost:${testutil.ports.Server.1}/rest</value>
        <value>http://localhost:${testutil.ports.Server.2}/rest</value>
        <value>http://localhost:${testutil.ports.Server.3}/rest</value>
    </util:list>

    <bean id="SequentialAddresses" class="org.apache.cxf.clustering.SequentialStrategy">
        <property name="alternateAddresses">
            <ref bean="addressList"/>
        </property>
    </bean>

    
    <jaxrs:client id="loadDistributorClient" address="http://localhost:8080/initialAddress">
       <jaxrs:features>
           <clustering:loadDistributor>
                <clustering:strategy>
                    <ref bean="RandomAddresses"/>
                </clustering:strategy>
            </clustering:loadDistributor>
       </jaxrs:features>
    </jaxrs:client>

the selector can be set from code like this:

Code Block

	java
	java

{code} 

the selector can be set from code like this:
{code:java}
org.apache.cxf.jaxrs.features.clustering.FailoverFeature feature = 
    new org.apache.cxf.jaxrs.features.clustering.FailoverFeature();
feature.setSelector(new org.apache.cxf.clustering.LoadDistributorTargetSelector());
{code}

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