/*
* Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 which accompanies this distribution,
* and is available at http://www.eclipse.org/legal/epl-v10.html
*/
package org.opendaylight.controller.sal.binding.api;
import org.opendaylight.controller.md.sal.common.api.routing.RouteChangePublisher;
import org.opendaylight.controller.sal.binding.api.BindingAwareBroker.RoutedRpcRegistration;
import org.opendaylight.controller.sal.binding.api.BindingAwareBroker.RpcRegistration;
import org.opendaylight.controller.sal.binding.api.rpc.RpcContextIdentifier;
import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
import org.opendaylight.yangtools.yang.binding.RpcService;
/**
* 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>
*
* <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>
* <h4>1. Defining a Context Type</h4>
* <p>
* The following snippet declares a simple YANG <code>identity</code> named <code>example-context</code>:
*
* {@code
* module example {
* ...
* identity example-context {
* description "Identity used to define an example-context type";
* }
* ...
* }
* }
* <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>:
*
* {@code
* module foo {
* ...
* import yang-ext {prefix ext;}
* ...
* container foo {
* list item {
* key "id";
* leaf id {type string;}
* ext:context-instance "example-context";
* }
* }
* ...
* }
* }
* <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 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()}.
*
* @throws IllegalStateException
* if the supplied RPC interface is a routed RPC type.
*/
<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.
*
* @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 RoutedRpcRegistration#registerPath(Class, InstanceIdentifer).
* {@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> serviceInterface,
T implementation)
throws IllegalStateException;
}