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Failover and Load Distributor Feature

Failover

The CXF Failover feature allows to configure CXF frontend clients to retry a call when the target endpoint becomes unavailable.
A number of retry strategies available: a client can iterate sequentially over the alternative addresses or chose them randomly.
Every strategy can be configured to do a delay between selecting the addresses.

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxws="http://cxf.apache.org/jaxws"
       xmlns:clustering="http://cxf.apache.org/clustering"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.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:${testutil.ports.Server.1}/services1</value>
        <value>http://localhost:${testutil.ports.Server.2}/services2</value>
        <value>http://localhost:${testutil.ports.Server.3}/services3</value>
    </util:list>

    <bean id="SequentialAddresses" class="org.apache.cxf.clustering.SequentialStrategy">
        <property name="alternateAddresses">
            <ref bean="addressList"/>
        </property>
        <!-- delay a retry for 1/10 of a second -->
        <property name="delayBetweenRetries" value="100"/>
    </bean>

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

    <!-- other jaxws:client attributes and elements are omitted for brewity -->
    
    <jaxws:client id="clientWithSeqFailoverSupport" address="http://localhost:8080/services">
       <jaxws:features>
           <clustering:failover>
                <clustering:strategy>
                    <ref bean="SequentialAddresses"/>
                </clustering:strategy>
            </clustering:failover>
       </jaxws:features>
    </jaxws:client>

    <!-- other jaxws:client attributes and elements are omitted for brewity -->

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

</beans>

Note, org.apache.cxf.clustering.RetryStrategy can be used to retry the same, last address for a limited number of times, before switching to the next address. Use RetryStrategy 'maxNumberOfRetries' property. RetryStrategy currently uses a sequential algorithm for selecting the addresses.

Load Distribution

Load Distributor Feature is a Failover feature which can allow the clients to iterate over alternative addresses on every new call, irrespectively of whether the last call has reached its target or not. It can help with the controlling the traffic originating from CXF clients at individual servers.

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:jaxws="http://cxf.apache.org/jaxws"
       xmlns:clustering="http://cxf.apache.org/clustering"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.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:${testutil.ports.Server.1}/services1</value>
        <value>http://localhost:${testutil.ports.Server.2}/services2</value>
        <value>http://localhost:${testutil.ports.Server.3}/services3</value>
    </util:list>

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

    <!-- other jaxws:client attributes and elements are omitted for brewity -->
    
    <jaxws:client id="clientWithLoadDistributor" address="http://localhost:8080/services">
       <jaxws:features>
           <clustering:loadDistributor>
                <clustering:strategy>
                    <ref bean="SequentialAddresses"/>
                </clustering:strategy>
            </clustering:loadDistributor>
       </jaxws:features>
    </jaxws:client>
</beans>

Configuring JAX-RS clients

JAX-RS clients are configured exactly as JAX-WS clients are, please see this page for more info.

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