import org.opendaylight.yangtools.yang.binding.RpcService;
/**
- * Base interface defining contract for retrieving MD-SAL
- * version of RpcServices
+ * Provides access to registered Remote Procedure Call (RPC) service implementations. The RPCs are
+ * defined in YANG models.
+ * <p>
+ * RPC implementations are registered using the {@link RpcProviderRegistry}.
*
*/
public interface RpcConsumerRegistry extends BindingAwareService {
/**
- * Returns a session specific instance (implementation) of requested
- * YANG module implementation / service provided by consumer.
+ * Returns an implementation of a requested RPC service.
*
- * @return Session specific implementation of service
+ * <p>
+ * The returned instance is not an actual implementation of the RPC service
+ * interface, but a proxy implementation of the interface that forwards to
+ * an actual implementation, if any.
+ * <p>
+ *
+ * The following describes the behavior of the proxy when invoking RPC methods:
+ * <ul>
+ * <li>If an actual implementation is registered with the MD-SAL, all invocations are
+ * forwarded to the registered implementation.</li>
+ * <li>If no actual implementation is registered, all invocations will fail by
+ * throwing {@link IllegalStateException}.</li>
+ * <li>Prior to invoking the actual implementation, the method arguments are are validated.
+ * If any are invalid, an {@link IllegalArgumentException} is thrown.
+ * </ul>
+ *
+ * The returned proxy is automatically updated with the most recent
+ * registered implementation.
+ * <p>
+ * The generated RPC method APIs require implementors to return a {@link java.util.concurrent.Future Future}
+ * instance that wraps the {@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult}. Since
+ * RPC methods may be implemented asynchronously, callers should avoid blocking on the
+ * {@link java.util.concurrent.Future Future} result. Instead, it is recommended to use
+ * {@link com.google.common.util.concurrent.JdkFutureAdapters#listenInPoolThread(java.util.concurrent.Future)}
+ * or {@link com.google.common.util.concurrent.JdkFutureAdapters#listenInPoolThread(java.util.concurrent.Future, java.util.concurrent.Executor)}
+ * to listen for Rpc Result. This will asynchronously listen for future result in executor and
+ * will not block current thread.
+ *
+ * <pre>
+ * final Future<RpcResult<SomeRpcOutput>> future = someRpcService.someRpc( ... );
+ * Futures.addCallback(JdkFutureAdapters.listenInThreadPool(future), new FutureCallback<RpcResult<SomeRpcOutput>>() {
+ *
+ * public void onSuccess(RpcResult<SomeRpcOutput> result) {
+ * // process result ...
+ * }
+ *
+ * public void onFailure(Throwable t) {
+ * // RPC failed
+ * }
+ * );
+ * </pre>
+ * @param serviceInterface the interface of the RPC Service. Typically this is an interface generated
+ * from a YANG model.
+ * @return the proxy for the requested RPC service. This method never returns null.
*/
- <T extends RpcService> T getRpcService(Class<T> module);
+ <T extends RpcService> T getRpcService(Class<T> serviceInterface);
}
import org.opendaylight.yangtools.yang.binding.RpcService;
/**
- * Interface defining provider's access to the Rpc Registry which could be used
- * to register their implementations of service to the MD-SAL.
+ * Provides a registry for Remote Procedure Call (RPC) service implementations. The RPCs are
+ * defined in YANG models.
+ * <p>
+ * There are 2 types of RPCs:
+ * <ul>
+ * <li>Global</li>
+ * <li>Routed</li>
+ * </ul>
*
- * @author ttkacik
+ * <h2>Global RPC</h2>
+ * <p>
+ * An RPC is global if there is intended to be only 1 registered implementation. A global RPC is not
+ * explicitly declared as such, essentially any RPC that is not defined to be routed is considered global.
+ * <p>
+ * Global RPCs are registered using the
+ * {@link #addRpcImplementation(Class, RpcService)} method.
*
+ * <h2>Routed RPC</h2>
+ * <p>
+ * MD-SAL supports routing of RPC between multiple implementations where the appropriate
+ * implementation is selected at run time based on the content of the RPC message as described in
+ * YANG model.
+ * <p>
+ * RPC routing is based on:
+ * <ul>
+ * <li><b>Route identifier</b> -
+ * An {@link org.opendaylight.yangtools.yang.binding.InstanceIdentifier InstanceIdentifier} value
+ * which is part of the RPC input. This value is used to select the correct
+ * implementation at run time.</li>
+ * <li><b>Context Type</b> - A YANG-defined construct which constrains the subset of
+ * valid route identifiers for a particular RPC.</li>
+ * </ul>
+ *
+ * <h3>Context type</h3>
+ * <p>
+ * A context type is modeled in YANG using a combination of a YANG <code>identity</code>
+ * and Opendaylight specific extensions from <code>yang-ext</code> module. These extensions are:
+ * <ul>
+ * <li><b>context-instance</b> - This is used in the data tree part of a YANG model to
+ * define a context type that associates nodes with a specified context <code>identity</code>.
+ * Instance identifiers that reference these nodes are valid route identifiers for RPCs that
+ * reference this context type.</li>
+ * <li><b>context-reference</b> - This is used in RPC input to mark a leaf of type
+ * <code>instance-identifier</code> as a reference to the particular context type defined by the
+ * specified context <code>identity</code>. The value of this
+ * leaf is used by the RPC broker at run time to route the RPC request to the correct implementation.
+ * Note that <code>context-reference</code> may only be used on leaf elements of type
+ * <code>instance-identifier</code> or a type derived from <code>instance-identifier</code>.</li>
+ * </ul>
+ *
+ *
+ * <h3>Routed RPC example</h3>
+ * <p>
+ * <h5>1. Defining a Context Type</h5>
+ * <p>
+ * The following snippet declares a simple YANG <code>identity</code> named <code>example-context</code>:
+ *
+ * <pre>
+ * module example {
+ * ...
+ * identity example-context {
+ * description "Identity used to define an example-context type";
+ * }
+ * ...
+ * }
+ * </pre>
+ * <p>
+ * We then use the declared identity to define a context type by using it in combination
+ * with the <code>context-instance</code> YANG extension. We'll associate the context type
+ * with a list element in the data tree. This defines the set of nodes whose instance
+ * identifiers are valid for the <code>example-context</code> context type.
+ * <p>
+ * The following YANG snippet imports the <code>yang-ext</code> module and defines the list
+ * element named <code>item</code> inside a container named <code>foo</code>:
+ *
+ * <pre>
+ * module foo {
+ * ...
+ * import yang-ext {prefix ext;}
+ * ...
+ * container foo {
+ * list item {
+ * key "id";
+ * leaf id {type string;}
+ * ext:context-instance "example-context";
+ * }
+ * }
+ * ...
+ * }
+ * </pre>
+ * <p>
+ * The statement <code>ext:context-instance "example-context";</code> inside the list element
+ * declares that any instance identifier referencing <code>item</code> in the data
+ * tree is valid for <code>example-context</code>. For example, the following instance
+ * identifier:
+ * <pre>
+ * InstanceIdentifier.create(Foo.class).child(Item.class,new ItemKey("Foo"))
+ * </pre>
+ * is valid for <code>example-context</code>. However the following:
+ * <pre>
+ * InstanceIdentifier.create(Example.class)
+ * </pre>
+ * is not valid.
+ * <p>
+ * So using an <code>identity</code> in combination with <code>context-instance</code> we
+ * have effectively defined a context type that can be referenced in a YANG RPC input.
+ *
+ * <h5>2. Defining an RPC to use the Context Type</h5>
+ * <p>
+ * To define an RPC to be routed based on the context type we need to add an input leaf element
+ * that references the context type which will hold an instance identifier value to be
+ * used to route the RPC.
+ * <p>
+ * The following snippet defines an RPC named <code>show-item</code> with 2 leaf elements
+ * as input: <code>item</code> of type <code>instance-identifier</code> and <code>description</code>:
+ *
+ * <pre>
+ * module foo {
+ * ...
+ * import yang-ext {prefix ext;}
+ * ...
+ * rpc show-item {
+ * input {
+ * leaf item {
+ * type instance-identifier;
+ * ext:context-reference example-context;
+ * }
+ * leaf description {
+ * type "string";
+ * }
+ * }
+ * }
+ * }
+ * </pre>
+ * <p>
+ * We mark the <code>item</code> leaf with a <code>context-reference</code> statement that
+ * references the <code>example-context</code> context type. RPC calls will then be routed
+ * based on the instance identifier value contained in <code>item</code>. Only instance
+ * identifiers that point to a <code>foo/item</code> node are valid as input.
+ * <p>
+ * The generated RPC Service interface for the module is:
+ *
+ * <pre>
+ * interface FooService implements RpcService {
+ * Future<RpcResult<Void>> showItem(ShowItemInput input);
+ * }
+ * </pre>
+ * <p>
+ * For constructing the RPC input, there are generated classes ShowItemInput and ShowItemInputBuilder.
+ *
+ * <h5>3. Registering a routed RPC implementation</h5>
+ * <p>
+ * To register a routed implementation for the <code>show-item</code> RPC, we must use the
+ * {@link #addRoutedRpcImplementation(Class, RpcService)} method. This
+ * will return a {@link RoutedRpcRegistration} instance which can then be used to register /
+ * unregister routed paths associated with the registered implementation.
+ * <p>
+ * The following snippet registers <code>myImpl</code> as the RPC implementation for an
+ * <code>item</code> with key <code>"foo"</code>:
+ * <pre>
+ * // Create the instance identifier path for item "foo"
+ * InstanceIdentifier path = InstanceIdentifier.create(Foo.class).child(Item.class, new ItemKey("foo"));
+ *
+ * // Register myImpl as the implementation for the FooService RPC interface
+ * RoutedRpcRegistration reg = rpcRegistry.addRoutedRpcImplementation(FooService.class, myImpl);
+ *
+ * // Now register for the context type and specific path ID. The context type is specified by the
+ * // YANG-generated class for the example-context identity.
+ * reg.registerPath(ExampleContext.class, path);
+ * </pre>
+ * <p>
+ * It is also possible to register the same implementation for multiple paths:
+ *
+ * <pre>
+ * InstanceIdentifier one = InstanceIdentifier.create(Foo.class).child(Item.class, new ItemKey("One"));
+ * InstanceIdentifier two = InstanceIdentifier.create(Foo.class).child(Item.class, new ItemKey("Two"));
+ *
+ * RoutedRpcRegistration reg = rpcRegistry.addRoutedRpcImplementation(FooService.class, myImpl);
+ * reg.registerPath(ExampleContext.class, one);
+ * reg.registerPath(ExampleContext.class, two);
+ * </pre>
+ *
+ * <p>
+ * When another client invokes the <code>showItem(ShowItemInput)</code> method on the proxy instance
+ * retrieved via {@link RpcConsumerRegistry#getRpcService(Class)}, the proxy will inspect the
+ * arguments in ShowItemInput, extract the InstanceIdentifier value of the <code>item</code> leaf and select
+ * the implementation whose registered path matches the InstanceIdentifier value of the <code>item</code> leaf.
+ *
+ * <h2>Notes for RPC Implementations</h2>
+ *
+ * <h3>RpcResult</h3>
+ * <p>
+ * The generated interfaces require implementors to return
+ * {@link java.util.concurrent.Future Future}<{@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult}<{RpcName}Output>> instances.
+ *
+ * Implementations should do processing of RPC calls asynchronously and update the
+ * returned {@link java.util.concurrent.Future Future} instance when processing is complete.
+ * However using {@link com.google.common.util.concurrent.Futures#immediateFuture(Object) Futures.immediateFuture}
+ * is valid only if the result is immediately available and asynchronous processing is unnecessary and
+ * would only introduce additional complexity.
+ *
+ * <p>
+ * The {@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult} is a generic
+ * wrapper for the RPC output payload, if any, and also allows for attaching error or
+ * warning information (possibly along with the payload) should the RPC processing partially
+ * or completely fail. This is intended to provide additional human readable information
+ * for users of the API and to transfer warning / error information across the system
+ * so it may be visible via other external APIs such as Restconf.
+ * <p>
+ * It is recommended to use the {@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult}
+ * for conveying appropriate error information
+ * on failure rather than purposely throwing unchecked exceptions if at all possible.
+ * While unchecked exceptions will fail the returned {@link java.util.concurrent.Future Future},
+ * using the intended RpcResult to convey the error information is more user-friendly.
*/
public interface RpcProviderRegistry extends //
RpcConsumerRegistry, //
RouteChangePublisher<RpcContextIdentifier, InstanceIdentifier<?>> {
/**
- * Registers a global RpcService implementation.
+ * Registers a global implementation of the provided RPC service interface.
+ * All methods of the interface are required to be implemented.
+ *
+ * @param serviceInterface the YANG-generated interface of the RPC Service for which to register.
+ * @param implementation "the implementation of the RPC service interface.
+ * @return an RpcRegistration instance that should be used to unregister the RPC implementation
+ * when no longer needed by calling {@link RpcRegistration#close()}.
*
- * @param type
- * @param implementation
- * @return
+ * @throws IllegalStateException
+ * if the supplied RPC interface is a routed RPC type.
*/
- <T extends RpcService> RpcRegistration<T> addRpcImplementation(Class<T> type, T implementation)
+ <T extends RpcService> RpcRegistration<T> addRpcImplementation(Class<T> serviceInterface, T implementation)
throws IllegalStateException;
/**
+ * Registers an implementation of the given routed RPC service interface.
+ * <p>
+ * See the {@link RpcProviderRegistry class} documentation for information and example on
+ * how to use routed RPCs.
*
- * Register a Routed RpcService where routing is determined on annotated
- * (in YANG model) context-reference and value of annotated leaf.
- *
- * @param type
- * Type of RpcService, use generated interface class, not your
- * implementation class
- * @param implementation
- * Implementation of RpcService
- * @return Registration object for routed Rpc which could be used to unregister
+ * @param serviceInterface the YANG-generated interface of the RPC Service for which to register.
+ * @param implementation the implementation instance to register.
+ * @return a RoutedRpcRegistration instance which can be used to register paths for the RPC
+ * implementation via invoking {@link RoutedRpcRegistration#registerPath(....).
+ * {@link RoutedRpcRegistration#close()} should be called to unregister the implementation
+ * and all previously registered paths when no longer needed.
*
* @throws IllegalStateException
+ * if the supplied RPC interface is not a routed RPC type.
*/
- <T extends RpcService> RoutedRpcRegistration<T> addRoutedRpcImplementation(Class<T> type, T implementation)
+ <T extends RpcService> RoutedRpcRegistration<T> addRoutedRpcImplementation(Class<T> serviceInterface,
+ T implementation)
throws IllegalStateException;
}
Code Review / controller.git / commitdiff