2 * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.controller.sal.binding.api;
10 import org.opendaylight.controller.md.sal.common.api.routing.RouteChangePublisher;
11 import org.opendaylight.controller.sal.binding.api.BindingAwareBroker.RoutedRpcRegistration;
12 import org.opendaylight.controller.sal.binding.api.BindingAwareBroker.RpcRegistration;
13 import org.opendaylight.controller.sal.binding.api.rpc.RpcContextIdentifier;
14 import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
15 import org.opendaylight.yangtools.yang.binding.RpcService;
18 * Provides a registry for Remote Procedure Call (RPC) service implementations. The RPCs are
19 * defined in YANG models.
21 * There are 2 types of RPCs:
29 * An RPC is global if there is intended to be only 1 registered implementation. A global RPC is not
30 * explicitly declared as such, essentially any RPC that is not defined to be routed is considered global.
32 * Global RPCs are registered using the
33 * {@link #addRpcImplementation(Class, RpcService)} method.
37 * MD-SAL supports routing of RPC between multiple implementations where the appropriate
38 * implementation is selected at run time based on the content of the RPC message as described in
41 * RPC routing is based on:
43 * <li><b>Route identifier</b> -
44 * An {@link org.opendaylight.yangtools.yang.binding.InstanceIdentifier InstanceIdentifier} value
45 * which is part of the RPC input. This value is used to select the correct
46 * implementation at run time.</li>
47 * <li><b>Context Type</b> - A YANG-defined construct which constrains the subset of
48 * valid route identifiers for a particular RPC.</li>
51 * <h3>Context type</h3>
53 * A context type is modeled in YANG using a combination of a YANG <code>identity</code>
54 * and Opendaylight specific extensions from <code>yang-ext</code> module. These extensions are:
56 * <li><b>context-instance</b> - This is used in the data tree part of a YANG model to
57 * define a context type that associates nodes with a specified context <code>identity</code>.
58 * Instance identifiers that reference these nodes are valid route identifiers for RPCs that
59 * reference this context type.</li>
60 * <li><b>context-reference</b> - This is used in RPC input to mark a leaf of type
61 * <code>instance-identifier</code> as a reference to the particular context type defined by the
62 * specified context <code>identity</code>. The value of this
63 * leaf is used by the RPC broker at run time to route the RPC request to the correct implementation.
64 * Note that <code>context-reference</code> may only be used on leaf elements of type
65 * <code>instance-identifier</code> or a type derived from <code>instance-identifier</code>.</li>
69 * <h3>Routed RPC example</h3>
71 * <h4>1. Defining a Context Type</h4>
73 * The following snippet declares a simple YANG <code>identity</code> named <code>example-context</code>:
78 * identity example-context {
79 * description "Identity used to define an example-context type";
85 * We then use the declared identity to define a context type by using it in combination
86 * with the <code>context-instance</code> YANG extension. We'll associate the context type
87 * with a list element in the data tree. This defines the set of nodes whose instance
88 * identifiers are valid for the <code>example-context</code> context type.
90 * The following YANG snippet imports the <code>yang-ext</code> module and defines the list
91 * element named <code>item</code> inside a container named <code>foo</code>:
96 * import yang-ext {prefix ext;}
101 * leaf id {type string;}
102 * ext:context-instance "example-context";
109 * The statement <code>ext:context-instance "example-context";</code> inside the list element
110 * declares that any instance identifier referencing <code>item</code> in the data
111 * tree is valid for <code>example-context</code>. For example, the following instance
114 * InstanceIdentifier.create(Foo.class).child(Item.class,new ItemKey("Foo"))
116 * is valid for <code>example-context</code>. However the following:
118 * InstanceIdentifier.create(Example.class)
122 * So using an <code>identity</code> in combination with <code>context-instance</code> we
123 * have effectively defined a context type that can be referenced in a YANG RPC input.
125 * <h5>2. Defining an RPC to use the Context Type</h5>
127 * To define an RPC to be routed based on the context type we need to add an input leaf element
128 * that references the context type which will hold an instance identifier value to be
129 * used to route the RPC.
131 * The following snippet defines an RPC named <code>show-item</code> with 2 leaf elements
132 * as input: <code>item</code> of type <code>instance-identifier</code> and <code>description</code>:
137 * import yang-ext {prefix ext;}
142 * type instance-identifier;
143 * ext:context-reference example-context;
153 * We mark the <code>item</code> leaf with a <code>context-reference</code> statement that
154 * references the <code>example-context</code> context type. RPC calls will then be routed
155 * based on the instance identifier value contained in <code>item</code>. Only instance
156 * identifiers that point to a <code>foo/item</code> node are valid as input.
158 * The generated RPC Service interface for the module is:
161 * interface FooService implements RpcService {
162 * Future<RpcResult<Void>> showItem(ShowItemInput input);
166 * For constructing the RPC input, there are generated classes ShowItemInput and ShowItemInputBuilder.
168 * <h5>3. Registering a routed RPC implementation</h5>
170 * To register a routed implementation for the <code>show-item</code> RPC, we must use the
171 * {@link #addRoutedRpcImplementation(Class, RpcService)} method. This
172 * will return a {@link RoutedRpcRegistration} instance which can then be used to register /
173 * unregister routed paths associated with the registered implementation.
175 * The following snippet registers <code>myImpl</code> as the RPC implementation for an
176 * <code>item</code> with key <code>"foo"</code>:
178 * // Create the instance identifier path for item "foo"
179 * InstanceIdentifier path = InstanceIdentifier.create(Foo.class).child(Item.class, new ItemKey("foo"));
181 * // Register myImpl as the implementation for the FooService RPC interface
182 * RoutedRpcRegistration reg = rpcRegistry.addRoutedRpcImplementation(FooService.class, myImpl);
184 * // Now register for the context type and specific path ID. The context type is specified by the
185 * // YANG-generated class for the example-context identity.
186 * reg.registerPath(ExampleContext.class, path);
189 * It is also possible to register the same implementation for multiple paths:
192 * InstanceIdentifier one = InstanceIdentifier.create(Foo.class).child(Item.class, new ItemKey("One"));
193 * InstanceIdentifier two = InstanceIdentifier.create(Foo.class).child(Item.class, new ItemKey("Two"));
195 * RoutedRpcRegistration reg = rpcRegistry.addRoutedRpcImplementation(FooService.class, myImpl);
196 * reg.registerPath(ExampleContext.class, one);
197 * reg.registerPath(ExampleContext.class, two);
201 * When another client invokes the <code>showItem(ShowItemInput)</code> method on the proxy instance
202 * retrieved via {@link RpcConsumerRegistry#getRpcService(Class)}, the proxy will inspect the
203 * arguments in ShowItemInput, extract the InstanceIdentifier value of the <code>item</code> leaf and select
204 * the implementation whose registered path matches the InstanceIdentifier value of the <code>item</code> leaf.
206 * <h2>Notes for RPC Implementations</h2>
210 * The generated interfaces require implementors to return
211 * {@link java.util.concurrent.Future Future}<{@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult}<{RpcName}Output>> instances.
213 * Implementations should do processing of RPC calls asynchronously and update the
214 * returned {@link java.util.concurrent.Future Future} instance when processing is complete.
215 * However using {@link com.google.common.util.concurrent.Futures#immediateFuture(Object) Futures.immediateFuture}
216 * is valid only if the result is immediately available and asynchronous processing is unnecessary and
217 * would only introduce additional complexity.
220 * The {@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult} is a generic
221 * wrapper for the RPC output payload, if any, and also allows for attaching error or
222 * warning information (possibly along with the payload) should the RPC processing partially
223 * or completely fail. This is intended to provide additional human readable information
224 * for users of the API and to transfer warning / error information across the system
225 * so it may be visible via other external APIs such as Restconf.
227 * It is recommended to use the {@link org.opendaylight.yangtools.yang.common.RpcResult RpcResult}
228 * for conveying appropriate error information
229 * on failure rather than purposely throwing unchecked exceptions if at all possible.
230 * While unchecked exceptions will fail the returned {@link java.util.concurrent.Future Future},
231 * using the intended RpcResult to convey the error information is more user-friendly.
233 public interface RpcProviderRegistry extends //
234 RpcConsumerRegistry, //
235 RouteChangePublisher<RpcContextIdentifier, InstanceIdentifier<?>> {
237 * Registers a global implementation of the provided RPC service interface.
238 * All methods of the interface are required to be implemented.
240 * @param serviceInterface the YANG-generated interface of the RPC Service for which to register.
241 * @param implementation "the implementation of the RPC service interface.
242 * @return an RpcRegistration instance that should be used to unregister the RPC implementation
243 * when no longer needed by calling {@link RpcRegistration#close()}.
245 * @throws IllegalStateException
246 * if the supplied RPC interface is a routed RPC type.
248 <T extends RpcService> RpcRegistration<T> addRpcImplementation(Class<T> serviceInterface, T implementation)
249 throws IllegalStateException;
252 * Registers an implementation of the given routed RPC service interface.
254 * See the {@link RpcProviderRegistry class} documentation for information and example on
255 * how to use routed RPCs.
257 * @param serviceInterface the YANG-generated interface of the RPC Service for which to register.
258 * @param implementation the implementation instance to register.
259 * @return a RoutedRpcRegistration instance which can be used to register paths for the RPC
260 * implementation via invoking RoutedRpcRegistration#registerPath(Class, InstanceIdentifer).
261 * {@link RoutedRpcRegistration#close()} should be called to unregister the implementation
262 * and all previously registered paths when no longer needed.
264 * @throws IllegalStateException
265 * if the supplied RPC interface is not a routed RPC type.
267 <T extends RpcService> RoutedRpcRegistration<T> addRoutedRpcImplementation(Class<T> serviceInterface,
269 throws IllegalStateException;