Add GenericInterceptor to help writing client interceptors

pull/12613/head
Mehrdad Afshari 7 years ago
parent e954dff656
commit ef4d4e8904
  1. 325
      src/csharp/Grpc.Core/Interceptors/GenericInterceptor.cs

@ -0,0 +1,325 @@
#region Copyright notice and license
// Copyright 2018 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.
#endregion
using System;
using System.Threading;
using System.Threading.Tasks;
using Grpc.Core.Internal;
namespace Grpc.Core.Interceptors
{
/// <summary>
/// Provides a base class for generic interceptor implementations that raises
/// events and hooks to control the RPC lifecycle.
/// </summary>
public abstract class GenericInterceptor : Interceptor
{
/// <summary>
/// Provides hooks through which an invocation should be intercepted.
/// </summary>
public sealed class ClientCallArbitrator<TRequest, TResponse>
where TRequest : class
where TResponse : class
{
internal ClientCallArbitrator<TRequest, TResponse> Freeze()
{
return (ClientCallArbitrator<TRequest, TResponse>)MemberwiseClone();
}
/// <summary>
/// Override the context for the outgoing invocation.
/// </summary>
public ClientInterceptorContext<TRequest, TResponse> Context { get; set; }
/// <summary>
/// Override the request for the outgoing invocation for non-client-streaming invocations.
/// </summary>
public TRequest UnaryRequest { get; set; }
/// <summary>
/// Delegate that intercepts a response from a non-server-streaming invocation and optionally overrides it.
/// </summary>
public Func<TResponse, TResponse> OnUnaryResponse { get; set; }
/// <summary>
/// Delegate that intercepts each request message for a client-streaming invocation and optionally overrides each message.
/// </summary>
public Func<TRequest, TRequest> OnRequestMessage { get; set; }
/// <summary>
/// Delegate that intercepts each response message for a server-streaming invocation and optionally overrides each message.
/// </summary>
public Func<TResponse, TResponse> OnResponseMessage { get; set; }
/// <summary>
/// Callback that gets invoked when response stream is finished.
/// </summary>
public Action OnResponseStreamEnd { get; set; }
/// <summary>
/// Callback that gets invoked when request stream is finished.
/// </summary>
public Action OnRequestStreamEnd { get; set; }
}
/// <summary>
/// Intercepts an outgoing call from the client side.
/// Derived classes that intend to intercept outgoing invocations from the client side should
/// override this and return the appropriate hooks in the form of a ClientCallArbitrator instance.
/// </summary>
/// <param name="context">The context of the outgoing invocation.</param>
/// <param name="clientStreaming">True if the invocation is client-streaming.</param>
/// <param name="serverStreaming">True if the invocation is server-streaming.</param>
/// <param name="request">The request message for client-unary invocations, null otherwise.</param>
/// <typeparam name="TRequest">Request message type for the current invocation.</typeparam>
/// <typeparam name="TResponse">Response message type for the current invocation.</typeparam>
/// <returns>
/// The derived class should return an instance of ClientCallArbitrator to control the trajectory
/// as they see fit, or null if it does not intend to pursue the invocation any further.
/// </returns>
protected virtual ClientCallArbitrator<TRequest, TResponse> InterceptCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, bool clientStreaming, bool serverStreaming, TRequest request)
where TRequest : class
where TResponse : class
{
return null;
}
/// <summary>
/// Intercepts a blocking invocation of a simple remote call and dispatches the events accordingly.
/// </summary>
public override TResponse BlockingUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, BlockingUnaryCallContinuation<TRequest, TResponse> continuation)
{
var arbitrator = InterceptCall(context, false, false, request)?.Freeze();
context = arbitrator?.Context ?? context;
request = arbitrator?.UnaryRequest ?? request;
var response = continuation(request, context);
if (arbitrator?.OnUnaryResponse != null)
{
response = arbitrator.OnUnaryResponse(response);
}
return response;
}
/// <summary>
/// Intercepts an asynchronous invocation of a simple remote call and dispatches the events accordingly.
/// </summary>
public override AsyncUnaryCall<TResponse> AsyncUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncUnaryCallContinuation<TRequest, TResponse> continuation)
{
var arbitrator = InterceptCall(context, false, false, request)?.Freeze();
context = arbitrator?.Context ?? context;
request = arbitrator?.UnaryRequest ?? request;
var response = continuation(request, context);
if (arbitrator?.OnUnaryResponse != null)
{
response = new AsyncUnaryCall<TResponse>(response.ResponseAsync.ContinueWith(unaryResponse => arbitrator.OnUnaryResponse(unaryResponse.Result)),
response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
}
return response;
}
/// <summary>
/// Intercepts an asynchronous invocation of a streaming remote call and dispatches the events accordingly.
/// </summary>
public override AsyncServerStreamingCall<TResponse> AsyncServerStreamingCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, AsyncServerStreamingCallContinuation<TRequest, TResponse> continuation)
{
var arbitrator = InterceptCall(context, false, true, request)?.Freeze();
context = arbitrator?.Context ?? context;
request = arbitrator?.UnaryRequest ?? request;
var response = continuation(request, context);
if (arbitrator?.OnResponseMessage != null || arbitrator?.OnResponseStreamEnd != null)
{
response = new AsyncServerStreamingCall<TResponse>(
new WrappedClientStreamReader<TResponse>(response.ResponseStream, arbitrator.OnResponseMessage, arbitrator.OnResponseStreamEnd),
response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
}
return response;
}
/// <summary>
/// Intercepts an asynchronous invocation of a client streaming call and dispatches the events accordingly.
/// </summary>
public override AsyncClientStreamingCall<TRequest, TResponse> AsyncClientStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncClientStreamingCallContinuation<TRequest, TResponse> continuation)
{
var arbitrator = InterceptCall(context, true, false, null)?.Freeze();
context = arbitrator?.Context ?? context;
var response = continuation(context);
if (arbitrator?.OnRequestMessage != null || arbitrator?.OnResponseStreamEnd != null || arbitrator?.OnUnaryResponse != null)
{
var requestStream = response.RequestStream;
if (arbitrator?.OnRequestMessage != null || arbitrator?.OnRequestStreamEnd != null)
{
requestStream = new WrappedClientStreamWriter<TRequest>(response.RequestStream, arbitrator.OnRequestMessage, arbitrator.OnRequestStreamEnd);
}
var responseAsync = response.ResponseAsync;
if (arbitrator?.OnUnaryResponse != null)
{
responseAsync = response.ResponseAsync.ContinueWith(unaryResponse => arbitrator.OnUnaryResponse(unaryResponse.Result));
}
response = new AsyncClientStreamingCall<TRequest, TResponse>(requestStream, responseAsync, response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
}
return response;
}
/// <summary>
/// Intercepts an asynchronous invocation of a duplex streaming call and dispatches the events accordingly.
/// </summary>
public override AsyncDuplexStreamingCall<TRequest, TResponse> AsyncDuplexStreamingCall<TRequest, TResponse>(ClientInterceptorContext<TRequest, TResponse> context, AsyncDuplexStreamingCallContinuation<TRequest, TResponse> continuation)
{
var arbitrator = InterceptCall(context, true, true, null)?.Freeze();
context = arbitrator?.Context ?? context;
var response = continuation(context);
if (arbitrator?.OnRequestMessage != null || arbitrator?.OnRequestStreamEnd != null || arbitrator?.OnResponseMessage != null || arbitrator?.OnResponseStreamEnd != null)
{
var requestStream = response.RequestStream;
if (arbitrator?.OnRequestMessage != null || arbitrator?.OnRequestStreamEnd != null)
{
requestStream = new WrappedClientStreamWriter<TRequest>(response.RequestStream, arbitrator.OnRequestMessage, arbitrator.OnRequestStreamEnd);
}
var responseStream = response.ResponseStream;
if (arbitrator?.OnResponseMessage != null || arbitrator?.OnResponseStreamEnd != null)
{
responseStream = new WrappedClientStreamReader<TResponse>(response.ResponseStream, arbitrator.OnResponseMessage, arbitrator.OnResponseStreamEnd);
}
response = new AsyncDuplexStreamingCall<TRequest, TResponse>(requestStream, responseStream, response.ResponseHeadersAsync, response.GetStatus, response.GetTrailers, response.Dispose);
}
return response;
}
/// <summary>
/// Server-side handler for intercepting unary calls.
/// </summary>
/// <typeparam name="TRequest">Request message type for this method.</typeparam>
/// <typeparam name="TResponse">Response message type for this method.</typeparam>
public override Task<TResponse> UnaryServerHandler<TRequest, TResponse>(TRequest request, ServerCallContext context, UnaryServerMethod<TRequest, TResponse> continuation)
{
return continuation(request, context);
}
/// <summary>
/// Server-side handler for intercepting client streaming call.
/// </summary>
/// <typeparam name="TRequest">Request message type for this method.</typeparam>
/// <typeparam name="TResponse">Response message type for this method.</typeparam>
public override Task<TResponse> ClientStreamingServerHandler<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, ServerCallContext context, ClientStreamingServerMethod<TRequest, TResponse> continuation)
{
return continuation(requestStream, context);
}
/// <summary>
/// Server-side handler for intercepting server streaming calls.
/// </summary>
/// <typeparam name="TRequest">Request message type for this method.</typeparam>
/// <typeparam name="TResponse">Response message type for this method.</typeparam>
public override Task ServerStreamingServerHandler<TRequest, TResponse>(TRequest request, IServerStreamWriter<TResponse> responseStream, ServerCallContext context, ServerStreamingServerMethod<TRequest, TResponse> continuation)
{
return continuation(request, responseStream, context);
}
/// <summary>
/// Server-side handler for intercepting bidi streaming calls.
/// </summary>
/// <typeparam name="TRequest">Request message type for this method.</typeparam>
/// <typeparam name="TResponse">Response message type for this method.</typeparam>
public override Task DuplexStreamingServerHandler<TRequest, TResponse>(IAsyncStreamReader<TRequest> requestStream, IServerStreamWriter<TResponse> responseStream, ServerCallContext context, DuplexStreamingServerMethod<TRequest, TResponse> continuation)
{
return continuation(requestStream, responseStream, context);
}
private class WrappedClientStreamReader<T> : IAsyncStreamReader<T>
{
readonly IAsyncStreamReader<T> reader;
readonly Func<T, T> onMessage;
readonly Action onStreamEnd;
public WrappedClientStreamReader(IAsyncStreamReader<T> reader, Func<T, T> onMessage, Action onStreamEnd)
{
this.reader = reader;
this.onMessage = onMessage;
this.onStreamEnd = onStreamEnd;
}
public void Dispose() => ((IDisposable)reader).Dispose();
private T current;
public T Current
{
get
{
if (current == null)
{
throw new InvalidOperationException("No current element is available.");
}
return current;
}
}
public async Task<bool> MoveNext(CancellationToken token)
{
if (await reader.MoveNext(token))
{
var current = reader.Current;
if (onMessage != null)
{
var mappedValue = onMessage(current);
if (mappedValue != null)
{
current = mappedValue;
}
}
this.current = current;
return true;
}
onStreamEnd?.Invoke();
return false;
}
}
private class WrappedClientStreamWriter<T> : IClientStreamWriter<T>
{
readonly IClientStreamWriter<T> writer;
readonly Func<T, T> onMessage;
readonly Action onResponseStreamEnd;
public WrappedClientStreamWriter(IClientStreamWriter<T> writer, Func<T, T> onMessage, Action onResponseStreamEnd)
{
this.writer = writer;
this.onMessage = onMessage;
this.onResponseStreamEnd = onResponseStreamEnd;
}
public Task CompleteAsync()
{
if (onResponseStreamEnd != null)
{
return writer.CompleteAsync().ContinueWith(x => onResponseStreamEnd());
}
return writer.CompleteAsync();
}
public Task WriteAsync(T message)
{
if (onMessage != null)
{
message = onMessage(message);
}
return writer.WriteAsync(message);
}
public WriteOptions WriteOptions
{
get
{
return writer.WriteOptions;
}
set
{
writer.WriteOptions = value;
}
}
}
}
}
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