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/*
* Copyright 2016 The gRPC Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.ratis.thirdparty.io.grpc;
import java.util.concurrent.Executor;
/**
* Carries credential data that will be propagated to the server via request metadata for each RPC.
*
* This is used by {@link CallOptions#withCallCredentials} and {@code withCallCredentials()} on
* the generated stub, for example:
*
* FooGrpc.FooStub stub = FooGrpc.newStub(channel);
* response = stub.withCallCredentials(creds).bar(request);
*
*
* The contents and nature of this class (and whether it remains an abstract class) is
* experimental, in that it can change. However, we are guaranteeing stability for the
* name. That is, we are guaranteeing stability for code to be returned a reference and
* pass that reference to gRPC for usage. However, code may not call or implement the {@code
* CallCredentials} itself if it wishes to only use stable APIs.
*/
public abstract class CallCredentials {
/**
* Pass the credential data to the given {@link CallCredentials.MetadataApplier}, which will
* propagate it to the request metadata.
*
*
It is called for each individual RPC, within the {@link Context} of the call, before the
* stream is about to be created on a transport. Implementations should not block in this
* method. If metadata is not immediately available, e.g., needs to be fetched from network, the
* implementation may give the {@code applier} to an asynchronous task which will eventually call
* the {@code applier}. The RPC proceeds only after the {@code applier} is called.
*
* @param requestInfo request-related information
* @param appExecutor The application thread-pool. It is provided to the implementation in case it
* needs to perform blocking operations.
* @param applier The outlet of the produced headers. It can be called either before or after this
* method returns.
*/
public abstract void applyRequestMetadata(
RequestInfo requestInfo, Executor appExecutor, CallCredentials.MetadataApplier applier);
/**
* Should be a noop but never called; tries to make it clearer to implementors that they may break
* in the future.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1914")
public abstract void thisUsesUnstableApi();
/**
* The outlet of the produced headers. Not thread-safe.
*
*
Exactly one of its methods must be called to make the RPC proceed.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1914")
public abstract static class MetadataApplier {
/**
* Called when headers are successfully generated. They will be merged into the original
* headers.
*/
public abstract void apply(Metadata headers);
/**
* Called when there has been an error when preparing the headers. This will fail the RPC.
*/
public abstract void fail(Status status);
}
/**
* The request-related information passed to {@code CallCredentials.applyRequestMetadata()}.
*/
@ExperimentalApi("https://github.com/grpc/grpc-java/issues/1914")
public abstract static class RequestInfo {
/**
* The method descriptor of this RPC.
*/
public abstract MethodDescriptor getMethodDescriptor();
/**
* The security level on the transport.
*/
public abstract SecurityLevel getSecurityLevel();
/**
* Returns the authority string used to authenticate the server for this call.
*/
public abstract String getAuthority();
/**
* Returns the transport attributes.
*/
@Grpc.TransportAttr
public abstract Attributes getTransportAttrs();
}
}