Executor-Based Remoting

Executor Based Remoting uses Executors to provided remoting capabilities on top of the Space. Executor Based Remoting allows for direct invocation of services in an asynchronous manner in a broadcast or routed manner. Executor Remoting works with services that are deployed in a Processing Unit and execute within a collocated space.

The Executor Proxy

The executor-proxy should be created on the client side to interact with the remote service. It can be created via Spring namespace, Spring Bean or via API.

The executor-proxy include the following properties:

Example:

<bean id="dataProcessor" class="org.openspaces.remoting.ExecutorSpaceRemotingProxyFactoryBean">
    <property name="gigaSpace" ref="gigaSpace" />
    <property name="timeout" value="60000" />

    <property name="serviceInterface" value="org.openspaces.example.data.common.IDataProcessor" />
    <property name="broadcast" value="true" />

    <property name="remoteInvocationAspect">
        <bean class="eg.MyRemoteInvocationAspect" />
    </property>

    <property name="metaArgumentsHandler">
        <bean class="eg.MyMetaArgumentsHandler" />
    </property>

    <property name="remoteResultReducer">
        <bean class="eg.MyRemoteResultReducer" />
    </property>

    <property name="remoteRoutingHandler">
        <bean class="org.openspaces.example.data.feeder.support.DataRemoteRoutingHandler"/>
    </property>
</bean>

Defining the Contract

In order to support remoting, the first step is to define the contract between the client and the server. In our case, the contract is a simple Java interface. Here is an example:

public interface IDataProcessor {

    /**
     * Process a given Data object, returning the processed Data object.
     */
    Data processData(Data data);
}

Implementing the Contract

Next, an implementation of this contract needs to be provided. This implementation will "live" on the server side. Here is a sample implementation:

@RemotingService
public class DataProcessor implements IDataProcessor {

    public Data processData(Data data) {
        data.setProcessor(true);
        return data;
    }
}

public class DataProcessor implements IDataProcessor {

    public Data processData(Data data) {
        data.setProcessor(true);
        return data;
    }
}

The XML tab corresponds to exporting the service using an xml configuration (explained in the next section). The Annotation tab corresponds to exporting the service using annotations.

Exporting the Service Over the Space

The next step is exporting the service over the space. Exporting the service is done on the server side. As with other Spring remoting support, exporting the service and the mechanism of exporting the service is a configuration-time decision. Here is an example of a Spring XML configuration:

<!-- Support @RemotingService component scanning -->
<context:component-scan base-package="com.demo"/>

<!-- Support the @RemotingService annotation on a service-->
<os-remoting:annotation-support />

<os-core:embedded-space id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<os-remoting:service-exporter id="serviceExporter" />

<os-core:embedded-space id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<bean id="dataProcessor" class="DataProcessor" />

<os-remoting:service-exporter id="serviceExporter">
     <os-remoting:service ref="dataProcessor"/>
</os-remoting:service-exporter>

<bean id="space" class="org.openspaces.core.space.EmbeddedSpaceFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="DataProcessor" />

<bean id="serviceExporter" class="org.openspaces.remoting.SpaceRemotingServiceExporter">
    <property name="services">
        <list>
            <ref bean="dataProcessor" />
        </list>
    </property>
</bean>

The name/id of the SpaceRemotingServiceExporter bean is important when using Executor Based Remoting. By default, the Task representing the remote invocation searches for a service exporter named serviceExporter, otherwise, it uses the first bean that is of the type SpaceRemotingServiceExporter.

Using the Service on the Client Side

In order to use the exported IDataProcessor on the client side, beans should use the IDataProcessor interface directly:

public class DataRemoting {

    private IDataProcessor dataProcessor;

    public void setDataProcessor(IDataProcessor dataProcessor) {
        this.dataProcessor = dataProcessor;

    }
}

Configuring the IDataProcessor proxy can done in the following manner:

<os-core:space-proxy  id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<os-remoting:executor-proxy id="dataProcessor" giga-space="gigaSpace"
                   interface="org.openspaces.example.data.common.IDataProcessor">
</os-remoting:executor-proxy>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

<bean id="space" class="org.openspaces.core.space.SpaceProxyFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="org.openspaces.remoting.ExecutorSpaceRemotingProxyFactoryBean">
    <property name="gigaSpace" ref="gigaSpace" />
    <property name="serviceInterface" value="org.openspaces.example.data.common.IDataProcessor" />
</bean>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

SpaceProxyConfigurer configurer = new SpaceProxyConfigurer("space");

GigaSpace gigaSpace = new GigaSpaceConfigurer(configurer).gigaSpace();

IDataProcessor dataProcessor = new ExecutorRemotingProxyConfigurer<IDataProcessor>(gigaSpace, IDataProcessor.class)
                               .proxy();

DataRemoting dataRemoting = new DataRemoting();

dataRemoting.setDataProcessor(dataProcessor);

The example above uses the executor-proxy bean in order to create the remoting proxy which can later be injected into the DataRemoting object. OpenSpaces remoting also allows injection of the remoting proxy into the remoting service property using annotations. Here is an example of annotating the DataRemoting class:

public class DataRemoting {

    @ExecutorProxy
    private IDataProcessor dataProcessor;

    // ...
}

If there are more than one GigaSpace beans defined within the application context, the ID of the giga-space bean should be defined explicitly on the annotations via the name attribute.

In order to enable this feature, the following element needs to be added to the application context XML:

<os-remoting:annotation-support />

<bean id="space" class="org.openspaces.remoting.RemotingAnnotationBeanPostProcessor" />

Remote Routing Handler

Many times, space remoting is done by exporting services in a space with a partitioned cluster topology. The service is exported when working directly with a cluster member (and not against the whole space cluster). When working with such a topology, the client side remoting automatically generates a random routing index value. In order to control the routing index, the following interface can be implemented:

public interface RemoteRoutingHandler<T> {

    /**
     * Returns the routing field value based on the remoting invocation. If <code>null</code>
     * is returned, will use internal calcualtion of the routing index.
     */
    T computeRouting(SpaceRemotingInvocation remotingEntry);
}

Here is a sample implementation which uses the first parameter Data object type as the routing index.

public class DataRemoteRoutingHandler implements RemoteRoutingHandler<Long> {

    public Long computeRouting(SpaceRemotingInvocation remotingEntry) {
        if (remotingEntry.getMethodName().equals("processData")) {
            Data data = (Data) remotingEntry.getArguments()[0];
            return data.getType();
        }
        return null;
    }
}

Finally, the wiring is done in the following manner:

<os-core:space-proxy  id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<os-remoting:executor-proxy id="dataProcessor" giga-space="gigaSpace"
                   interface="org.openspaces.example.data.common.IDataProcessor">
    <os-remoting:routing-handler>
        <bean class="org.openspaces.example.data.feeder.support.DataRemoteRoutingHandler"/>
    </os-remoting:routing-handler>
</os-remoting:executor-proxy>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

<bean id="space" class="org.openspaces.core.space.SpaceProxyFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="org.openspaces.remoting.ExecutorSpaceRemotingProxyFactoryBean">
    <property name="gigaSpace" ref="gigaSpace" />
    <property name="serviceInterface" value="org.openspaces.example.data.common.IDataProcessor" />
    <property name="remoteRoutingHandler">
        <bean class="org.openspaces.example.data.feeder.support.DataRemoteRoutingHandler"/>
    </property>
</bean>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

SpaceProxyConfigurer configurer = new SpaceProxyConfigurer("space");

GigaSpace gigaSpace = new GigaSpaceConfigurer(configurer).gigaSpace();

IDataProcessor dataProcessor = new ExecutorRemotingProxyConfigurer<IDataProcessor>(gigaSpace, IDataProcessor.class)
                               .remoteRoutingHandler(new DataRemoteRoutingHandler())
                               .proxy();

DataRemoting dataRemoting = new DataRemoting();

dataRemoting.setDataProcessor(dataProcessor);

Routing Annotation

The option, above, using the remote routing handler is very handy when not using annotations (broadcasting). OpenSpaces remoting also supports the @Routing annotation in order to define which parameter controls the routing. Here is an example:

public interface MyService {

    void doSomething(@Routing int param1, int param2);
}

In the example above, the routing is done using the param1 value. In complex objects, a method name can be specified to be invoked on the parameter, in order to get the actual routing index. Here is an example:

public interface MyService {

    void doSomething(@Routing("getProperty") Value param1, int param2);
}

In the example, the getProperty method is called on the Value object, and its return value is subsequently used to extract the routing index.

Asynchronous Execution

OpenSpaces executor remoting supports asynchronous execution of remote services using the AsyncFuture interface (which extends the java.util.concurrent.Future interface). Since the remoting implementation is asynchronous by nature, a Future can be used to execute remote services asynchronously.

Since the definition of the interface acts as the contract between the client and the server, asynchronous invocation requires the interface to also support the same business method, returning a Future or AsyncFuture instead of its actual return value. The asynchronous nature is only relevant on the client side, provided by the asynchronous nature of OpenSpaces remoting. There are two options to implement such behavior:

Different Service Interfaces

The client and the server can have a different service interface definition under the same package and under the same name. The server includes the actual implementation:

public interface SimpleService {

    String say(String message);

    int calc(int value1, int value2);
}

The client has the same method except it returns a future:

public interface SimpleService {

    AsyncFuture<String> say(String message);

    int calc(int value1, int value2);
}

In the above example, the say() method uses a Future in order to receive the result, while the calc method remains synchronous.

Single Service Interface

Both the client and server share the same interface, with the interface holding both synchronous and asynchronous services. Here is an example:

public interface SimpleService {

    String say(String message);

    AsyncFuture<String> asyncSay(String message);
}

In the above case, the server implementation does not need to implement the asyncSay method (simply return null for the asyncSay method). The client side can choose which service to invoke. You should note the naming convention and the signature of the asynchronous method in this case. If the regular method looks as follows: T doSomething(String arg), T being the return value type, then the asynchronous method should have the following signature: Future<T> asyncDoSomething(String arg). In other words, the regular method should be prefixed with async and the return value should be a Future of the original return value (unless it's void, in which case it stays void).

Server Side Services Injection

Each parameter of a remote service can be dynamically injected as if it were a bean defined within the server side (where the service is actually executed) context. This allows you to utilize server side resources and state, within the actual invocation. In order to enable such injection the service interface should either be annotated with AutowireArguments annotation, or implement the marker interface AutowireArgumentsMarker. Let's see an example:

@AutowireArguments
public interface MyService {

    void doSomething(Value param1);
}

The above service exposes a service which accepts a Value as a parameter. The Value parameter, if needed, can be injected dynamically with server side resources and state. For example, if the server side execution needs to be aware of the ClusterInfo, the Value parameter can implement the ClusterInfoAware interface. Here is what it looks like:

public class Value implements ClusterInfoAware {

    private transient ClusterInfo clusterInfo;

    public void setClusterInfo(ClusterInfo clusterInfo) {
        this.clusterInfo = clusterInfo;
    }
}

Another example is injecting another service that is defined in the server side directly into the parameter, for example, using Spring @Autowired annotation.

public class Value implements ClusterInfoAware {

    @Autowired
    private transient AnotherService anotherService;
}

Transactional Execution

Executor remoting supports transactional execution of services. On the client side, if there is an ongoing declarative transaction during the service invocation (a Space based transaction), the service will be executed under the same transaction. The transaction itself is passed to the server and any Space related operations (performed using GigaSpace) will be executed under the same transaction. The transaction lifecycle itself is controlled on the client side (declaratively) and is committed / rolled back only on the client side. (Note, exceptions on the server side will simply propagate to the client side, and will cause a rollback only if the client "decides" so.)

When using broadcast with executor remoting, a declarative distributed transaction must be used and not a local (or JTA one). Also note, the GigaSpace instance that is used internally by the executor remoting invocation must be configured with a transaction manager (as is the case for enabling transaction execution with any other GigaSpace based operation).

Here is a simple example how the Client and the Service should be configured:

Client pu.xml

<context:component-scan base-package="com.demo"/>
<os-core:space-proxy id="space" space-name="mySpace"/>

<os-core:distributed-tx-manager id="myTransactionManager" />
<os-core:giga-space id="gigaspace" space="space"  tx-manager="myTransactionManager"/>
<tx:annotation-driven transaction-manager="myTransactionManager" />

<os-remoting:executor-proxy id="myService" giga-space="gigaspace" interface="com.demo.IMyService" broadcast="true">
<os-remoting:result-reducer>
    <bean class="com.demo.MyRemoteResultReducer" />
    </os-remoting:result-reducer>
    </os-remoting:executor-proxy>

<bean id="callingBean" class="com.demo.ClientWarrper">
           <property name="client" ref="client"/>
</bean>

<bean id="client" class="com.demo.Client">
       <property name="myService" ref="myService" />
       <property name="gigaspace" ref="gigaspace" />
</bean>

Client Implementation

@Transactional(readOnly = true , value="myTransactionManager")
public class Client{
    GigaSpace gigaspace ;
    IMyService myService ;

    public static void main(String[] args) {
    }

    @Transactional(propagation=Propagation.REQUIRES_NEW , value="myTransactionManager")
    public void doTX() throws Exception
    {
        MyData myObj = new MyData(1);
        gigaspace.write(myObj);

        System.out.println("Client - TX:" + gigaspace.getCurrentTransaction());
        boolean ret = myService.doTX();
        System.out.println("Service Call Done! - Result:"+ret);
    }
}

Service pu.xml

<context:component-scan base-package="com.demo"/>
<os-remoting:annotation-support />
<os-core:embedded-space id="space" space-name="mySpace"/>
<os-core:giga-space id="gigaSpace" space="space"/>
<os-remoting:service-exporter id="serviceExporter" />

Service Implementation

@RemotingService
@Transactional(readOnly = true)
public class MyService implements IMyService {
    public MyService()  {}
    @Autowired
    GigaSpace gigaSpace;

    @Transactional(propagation=Propagation.SUPPORTS)
    public boolean doTX()
    {
        MyData myObj = new MyData(2);
        gigaSpace.write(myObj);
        System.out.println("Service - TX:" + gigaSpace.getCurrentTransaction());
    }
}

Execution Aspects

Space based remoting allows you to inject "aspects" that can wrap the invocation of a remote method on the client side, as well as wrapping the execution of an invocation on the server side.

The Client Invocation Aspect

The client invocation aspect interface is shown below. You should implement this interface and wire and instance of the implementing class to the client side remote proxy, as explained below:

public interface RemoteInvocationAspect<T> {

    /**
     * The aspect is called instead of the actual remote invocation. The methodInvocation can
     * be used to access any method related information. The remoting invoker passed can be used
     * to actually invoke the remote invocation.
     */
    T invoke(MethodInvocation methodInvocation, RemotingInvoker remotingInvoker) throws Throwable;
}

An implementation of such an aspect can be configured as follows:

<os-core:space-proxy  id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<os-remoting:executor-proxy id="dataProcessor" giga-space="gigaSpace"
                   interface="org.openspaces.example.data.common.IDataProcessor">
    <os-remoting:aspect>
        <bean class="eg.MyRemoteInvocationAspect" />
    </os-remoting:aspect>
</os-remoting:executor-proxy>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

<bean id="space" class="org.openspaces.core.space.SpaceProxyFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="org.openspaces.remoting.ExecutorSpaceRemotingProxyFactoryBean">
    <property name="gigaSpace" ref="gigaSpace" />
    <property name="serviceInterface" value="org.openspaces.example.data.common.IDataProcessor" />
    <property name="remoteInvocationAspect">
        <bean class="eg.MyRemoteInvocationAspect" />
    </property>
</bean>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

SpaceProxyConfigurer configurer = new SpaceProxyConfigurer("space");

GigaSpace gigaSpace = new GigaSpaceConfigurer(configurer).gigaSpace();

IDataProcessor dataProcessor = new ExecutorRemotingProxyConfigurer<IDataProcessor>(gigaSpace, IDataProcessor.class)
                               .remoteInvocationAspect(new MyRemoteInvocationAspect())
                               .proxy();

DataRemoting dataRemoting = new DataRemoting();

dataRemoting.setDataProcessor(dataProcessor);

The instance of the class that implements the RemoteInvocationAspect interface will be called by the framework prior to the invocation on the client side. Note that it is up to the aspect implementation to decide whether or not the call should proceed. If the aspect implementation decides to proceed with the call it should call method.invoke() on the provided method argument. Otherwise the call to the server will not be performed.

The Server Invocation Aspect

The server side invocation aspect interface is shown below. You should implement this interface and wire and instance of the implementing class to the server side service exporter (this is the component that is responsible for exposing your service bean to remote clients):

public interface ServiceExecutionAspect {

    /**
     * A service execution callback allows you to wrap the execution of "server side" service. If
     * actual execution of the service is needed, the <code>invoke</code> method will need to
     * be called on the passed <code>Method</code> using the service as the actual service to
     * invoke it on, and {@link SpaceRemotingInvocation#getArguments()} as the method arguments.
     *
     * <p>As an example: <code>method.invoke(service, invocation.getArguments())</code>.
     */
    Object invoke(SpaceRemotingInvocation invocation, Method method, Object service)
                                  throws InvocationTargetException, IllegalAccessException;
}

An implementation of such an aspect can be configured as follows:

<os-core:embedded-space id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<bean id="dataProcessor" class="DataProcessor" />

<os-remoting:service-exporter id="serviceExporter">
     <os-remoting:aspect>
         <bean class="eg.MyServiceExecutionAspect" />
     </os-remoting:aspect>
     <os-remoting:service ref="dataProcessor"/>
</os-remoting:service-exporter>

<bean id="space" class="org.openspaces.core.space.EmbeddedSpaceFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="DataProcessor" />

<bean id="serviceExporter" class="org.openspaces.remoting.SpaceRemotingServiceExporter">
    <property name="serviceExecutionAspect">
         <bean class="eg.MyServiceExecutionAspect" />
    </property>
    <property name="services">
        <list>
            <ref bean="dataProcessor" />
        </list>
    </property>
</bean>

The instance of the class that implements the ServiceExecutionAspect interface will be called by the framework prior to the invocation of the service bean on the server side. Note that it is up to the aspect implementation to decide whether or not the call should proceed. If the aspect implementation decides to proceed with the call it should call method.invoke() on the provided method argument. Otherwise the call to the service bean will not be performed.

The Metadata Handler

When executing a service using Space based remoting, a set of one or more metadata arguments (in the form of a java.lang.Object array) can be passed to the server with the remote invocation. This feature is very handy when you want to pass certain metadata with every remote call that is not part of the arguments of the method you call. A prime example for using meta arguments is security – i.e. passing security credentials as meta arguments, and using a server side aspect to authorize the execution or to log who actually called the method.

To create the meta arguments on the client side you should implement the following interface and inject an instance of the implementing class to the client side proxy:

public interface MetaArgumentsHandler {

    /**
     * Meta argument handler can control the meta data objects that will be used
     * for the remote invocation.
     */
    Object[] obtainMetaArguments(SpaceRemotingInvocation remotingEntry);
}

The following snippets show how to plug a custom meta arguments handler to the client side remote proxy. The Object array returned by the implementation of the MetaArgumentsHandler interface will be sent along with the invocation to server side.

<os-core:space-proxy  id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<os-remoting:executor-proxy id="dataProcessor" giga-space="gigaSpace"
                   interface="org.openspaces.example.data.common.IDataProcessor">
    <os-remoting:meta-arguments-handler>
        <bean class="eg.MyMetaArgumentsHandler" />
    </os-remoting:meta-arguments-handler>
</os-remoting:executor-proxy>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

<bean id="space" class="org.openspaces.core.space.SpaceProxyFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="org.openspaces.remoting.ExecutorSpaceRemotingProxyFactoryBean">
    <property name="gigaSpace" ref="gigaSpace" />
    <property name="serviceInterface" value="org.openspaces.example.data.common.IDataProcessor" />
    <property name="metaArgumentsHandler">
        <bean class="eg.MyMetaArgumentsHandler" />
    </property>
</bean>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>

SpaceProxyConfigurer configurer = new SpaceProxyConfigurer("space");

GigaSpace gigaSpace = new GigaSpaceConfigurer(configurer).gigaSpace();

IDataProcessor dataProcessor = new ExecutorRemotingProxyConfigurer<IDataProcessor>(gigaSpace, IDataProcessor.class)
                               .metaArgumentsHandler(new MyMetaArgumentsHandler())
                               .proxy();

DataRemoting dataRemoting = new DataRemoting();

dataRemoting.setDataProcessor(dataProcessor);

The way to access the meta arguments on the server side is to configure a server side execution aspect by implementing the ServiceExecutionAspect and wiring it on the server side as shown above. To access the meta arguments, you should call SpaceRemotingInvocation.getMetaArguments() on the invocation argument provided to the server side aspect.

Broadcast Remoting

When using executor remoting, a remote invocation can be broadcasted to all active (primary) cluster members. Each Service instance is invoked and return a result to its called which in turn reduce these and pass the final result to the application.

• The First phase involves the Service invocation:

  

• The Second phase involves reducing the results retrieved from the Services:

  

The configuration of enabling broadcasting is done on the client level, by setting the broadcast flag to true:

<os-core:space-proxy id="space" space-name="mySpace"/>

<os-core:giga-space id="gigaSpace" space="space"/>

<os-remoting:executor-proxy id="dataProcessor" giga-space="gigaSpace"
                   interface="org.openspaces.example.data.common.IDataProcessor" broadcast="true">
    <os-remoting:result-reducer ref="remoteResultReducer" />
</os-remoting:executor-proxy>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>
<bean id="remoteResultReducer" class="MyRemoteResultReducer" />

<bean id="space" class="org.openspaces.core.space.SpaceProxyFactoryBean">
    <property name="name" value="space" />
</bean>

<bean id="gigaSpace" class="org.openspaces.core.GigaSpaceFactoryBean">
    <property name="space" ref="space" />
</bean>

<bean id="dataProcessor" class="org.openspaces.remoting.ExecutorSpaceRemotingProxyFactoryBean">
    <property name="gigaSpace" ref="gigaSpace" />
    <property name="serviceInterface" value="org.openspaces.example.data.common.IDataProcessor" />
    <property name="broadcast" value="true" />
    <property name="remoteResultReducer" ref="remoteResultReducer"/>
</bean>

<bean id="dataRemoting" class="DataRemoting">
    <property name="dataProcessor" ref="dataProcessor" />
</bean>
<bean id="remoteResultReducer" class="MyRemoteResultReducer" />

SpaceProxyConfigurer configurer = new SpaceProxyConfigurer("space");

GigaSpace gigaSpace = new GigaSpaceConfigurer(configurer).gigaSpace();

MyRemoteResultReducer myRemoteResultReducer = new MyRemoteResultReducer();
IDataProcessor dataProcessor = new ExecutorRemotingProxyConfigurer<IDataProcessor>(gigaSpace, IDataProcessor.class)
                               .broadcast(true)
                   .remoteResultReducer(myRemoteResultReducer)
                               .proxy();

DataRemoting dataRemoting = new DataRemoting();

dataRemoting.setDataProcessor(dataProcessor);

The Remote Result Reducer

When broadcasting remote invocations to all active cluster members, and the remote method returns a result, on the client side an array of all remote results needs to be processed. By default, the first result is returned, and it can be overridden using the return-first-result flag (which will then return the array of responses). The executor remoting proxy allows for a pluggable remote result reducer that can reduce a collection of remoting results into a single one. Here is the defined interface:

public interface RemoteResultReducer<T, Y> {

    /**
     * Reduces a list of Space remoting invocation results to an Object value. Can use
     * the provided remote invocation to perform different reduce operations, for example
     * based on the {@link SpaceRemotingInvocation#getMethodName()}.
     *
     * <p>An exception thrown from the reduce operation will be propagated to the client.
     *
     * @param results            A list of results from (usually) broadcast sync remote invocation.
     * @param remotingInvocation The remote invocation
     * @return A reduced return value (to the calling client)
     * @throws Exception An exception that will be propagated to the client
     */
    T reduce(SpaceRemotingResult<Y>[] results, SpaceRemotingInvocation remotingInvocation) throws Exception;
}

Failover

In case of a Primary Backup clusters and Partitioned Sync2Backup clusters, when there is failure of primary space partition, remoting request is transparently forwarded to the backup.

Executor proxy is aware of each partition in the cluster and connection with the failed primary partition will get interrupted/disconnected in case of a failure. Proxy recognizes failure and redirects the request to the backup partition. When the backup becomes ready (any warmup code that needs to run and is ready to accept operations), it will accept this request and process the request. All of this failover behavior is done within the GigaSpaces proxy code and client does not need any extra logic. For more information refer to Proxy Connectivity.

If the backup space does not become ready to accept requests within the configured number of retries, execute request will fail with an Exception. In case of a broadcast request, SpaceRemotingResult for failed partition will have an exception. Following example shows how to inspect for exceptions in Reducer,

public class DataProcessorServiceReducer implements RemoteResultReducer<Integer, Integer>{

    public Integer reduce(SpaceRemotingResult<Integer>[] results,
                               SpaceRemotingInvocation sri) throws Exception {
        int total_result =0;
        for (SpaceRemotingResult<Integer> result : results)
        {
            if (result.getException() == null) {
                int temp_result = result.getResult().intValue();
                total_result +=  temp_result ;
            } else {
                System.out.println("Exception on the Server: "
                                                   + result.getException().getMessage());
                result.getException().printStackTrace();
            }

        }
        return total_result/results.length  ;
    }
}

Considerations

If the remote method is called frequently or large complex objects are used as return types, it is recommended to implement optimized serialization such as Externalizable for the returned value object or use libraries such as kryo.

Working Examples

The repository located here provides both a service exporter and a service consumer. Test code dispatches a remoted request right here.