ServerCallHandler.cs

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#endregion

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Grpc.Core.Internal;
using Grpc.Core.Logging;
using Grpc.Core.Utils;

namespace Grpc.Core.Internal
{
    internal interface IServerCallHandler
    {
        Task HandleCall(ServerRpcNew newRpc, GrpcEnvironment environment);
    }

    internal class UnaryServerCallHandler<TRequest, TResponse> : IServerCallHandler
        where TRequest : class
        where TResponse : class
    {
        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<UnaryServerCallHandler<TRequest, TResponse>>();

        readonly Method<TRequest, TResponse> method;
        readonly UnaryServerMethod<TRequest, TResponse> handler;

        public UnaryServerCallHandler(Method<TRequest, TResponse> method, UnaryServerMethod<TRequest, TResponse> handler)
        {
            this.method = method;
            this.handler = handler;
        }

        public async Task HandleCall(ServerRpcNew newRpc, GrpcEnvironment environment)
        {
            var asyncCall = new AsyncCallServer<TRequest, TResponse>(
                method.ResponseMarshaller.Serializer,
                method.RequestMarshaller.Deserializer,
                environment);

            asyncCall.Initialize(newRpc.Call);
            var finishedTask = asyncCall.ServerSideCallAsync();
            var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
            var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);

            Status status;
            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
            try
            {
                Preconditions.CheckArgument(await requestStream.MoveNext());
                var request = requestStream.Current;
                // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
                Preconditions.CheckArgument(!await requestStream.MoveNext());
                var result = await handler(request, context);
                status = context.Status;
                await responseStream.WriteAsync(result);
            } 
            catch (Exception e)
            {
                Logger.Error(e, "Exception occured in handler.");
                status = HandlerUtils.StatusFromException(e);
            }
            try
            {
                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
            }
            catch (OperationCanceledException)
            {
                // Call has been already cancelled.
            }
            await finishedTask;
        }
    }

    internal class ServerStreamingServerCallHandler<TRequest, TResponse> : IServerCallHandler
        where TRequest : class
        where TResponse : class
    {
        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<ServerStreamingServerCallHandler<TRequest, TResponse>>();

        readonly Method<TRequest, TResponse> method;
        readonly ServerStreamingServerMethod<TRequest, TResponse> handler;

        public ServerStreamingServerCallHandler(Method<TRequest, TResponse> method, ServerStreamingServerMethod<TRequest, TResponse> handler)
        {
            this.method = method;
            this.handler = handler;
        }

        public async Task HandleCall(ServerRpcNew newRpc, GrpcEnvironment environment)
        {
            var asyncCall = new AsyncCallServer<TRequest, TResponse>(
                method.ResponseMarshaller.Serializer,
                method.RequestMarshaller.Deserializer,
                environment);

            asyncCall.Initialize(newRpc.Call);
            var finishedTask = asyncCall.ServerSideCallAsync();
            var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
            var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);

            Status status;
            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
            try
            {
                Preconditions.CheckArgument(await requestStream.MoveNext());
                var request = requestStream.Current;
                // TODO(jtattermusch): we need to read the full stream so that native callhandle gets deallocated.
                Preconditions.CheckArgument(!await requestStream.MoveNext());
                await handler(request, responseStream, context);
                status = context.Status;
            }
            catch (Exception e)
            {
                Logger.Error(e, "Exception occured in handler.");
                status = HandlerUtils.StatusFromException(e);
            }

            try
            {
                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
            }
            catch (OperationCanceledException)
            {
                // Call has been already cancelled.
            }
            await finishedTask;
        }
    }

    internal class ClientStreamingServerCallHandler<TRequest, TResponse> : IServerCallHandler
        where TRequest : class
        where TResponse : class
    {
        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<ClientStreamingServerCallHandler<TRequest, TResponse>>();

        readonly Method<TRequest, TResponse> method;
        readonly ClientStreamingServerMethod<TRequest, TResponse> handler;

        public ClientStreamingServerCallHandler(Method<TRequest, TResponse> method, ClientStreamingServerMethod<TRequest, TResponse> handler)
        {
            this.method = method;
            this.handler = handler;
        }

        public async Task HandleCall(ServerRpcNew newRpc, GrpcEnvironment environment)
        {
            var asyncCall = new AsyncCallServer<TRequest, TResponse>(
                method.ResponseMarshaller.Serializer,
                method.RequestMarshaller.Deserializer,
                environment);

            asyncCall.Initialize(newRpc.Call);
            var finishedTask = asyncCall.ServerSideCallAsync();
            var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
            var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);

            Status status;
            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
            try
            {
                var result = await handler(requestStream, context);
                status = context.Status;
                try
                {
                    await responseStream.WriteAsync(result);
                }
                catch (OperationCanceledException)
                {
                    status = Status.DefaultCancelled;
                }
            }
            catch (Exception e)
            {
                Logger.Error(e, "Exception occured in handler.");
                status = HandlerUtils.StatusFromException(e);
            }

            try
            {
                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
            }
            catch (OperationCanceledException)
            {
                // Call has been already cancelled.
            }
            await finishedTask;
        }
    }

    internal class DuplexStreamingServerCallHandler<TRequest, TResponse> : IServerCallHandler
        where TRequest : class
        where TResponse : class
    {
        static readonly ILogger Logger = GrpcEnvironment.Logger.ForType<DuplexStreamingServerCallHandler<TRequest, TResponse>>();

        readonly Method<TRequest, TResponse> method;
        readonly DuplexStreamingServerMethod<TRequest, TResponse> handler;

        public DuplexStreamingServerCallHandler(Method<TRequest, TResponse> method, DuplexStreamingServerMethod<TRequest, TResponse> handler)
        {
            this.method = method;
            this.handler = handler;
        }

        public async Task HandleCall(ServerRpcNew newRpc, GrpcEnvironment environment)
        {
            var asyncCall = new AsyncCallServer<TRequest, TResponse>(
                method.ResponseMarshaller.Serializer,
                method.RequestMarshaller.Deserializer,
                environment);

            asyncCall.Initialize(newRpc.Call);
            var finishedTask = asyncCall.ServerSideCallAsync();
            var requestStream = new ServerRequestStream<TRequest, TResponse>(asyncCall);
            var responseStream = new ServerResponseStream<TRequest, TResponse>(asyncCall);

            Status status;
            var context = HandlerUtils.NewContext(newRpc, asyncCall.Peer, responseStream, asyncCall.CancellationToken);
            try
            {
                await handler(requestStream, responseStream, context);
                status = context.Status;
            }
            catch (Exception e)
            {
                Logger.Error(e, "Exception occured in handler.");
                status = HandlerUtils.StatusFromException(e);
            }
            try
            {
                await responseStream.WriteStatusAsync(status, context.ResponseTrailers);
            }
            catch (OperationCanceledException)
            {
                // Call has been already cancelled.
            }
            await finishedTask;
        }
    }

    internal class NoSuchMethodCallHandler : IServerCallHandler
    {
        public static readonly NoSuchMethodCallHandler Instance = new NoSuchMethodCallHandler();

        public async Task HandleCall(ServerRpcNew newRpc, GrpcEnvironment environment)
        {
            // We don't care about the payload type here.
            var asyncCall = new AsyncCallServer<byte[], byte[]>(
                (payload) => payload, (payload) => payload, environment);
            
            asyncCall.Initialize(newRpc.Call);
            var finishedTask = asyncCall.ServerSideCallAsync();
            var responseStream = new ServerResponseStream<byte[], byte[]>(asyncCall);

            await responseStream.WriteStatusAsync(new Status(StatusCode.Unimplemented, "No such method."), Metadata.Empty);
            await finishedTask;
        }
    }

    internal static class HandlerUtils
    {
        public static Status StatusFromException(Exception e)
        {
            var rpcException = e as RpcException;
            if (rpcException != null)
            {
                // use the status thrown by handler.
                return rpcException.Status;
            }

            // TODO(jtattermusch): what is the right status code here?
            return new Status(StatusCode.Unknown, "Exception was thrown by handler.");
        }

        public static ServerCallContext NewContext<TRequest, TResponse>(ServerRpcNew newRpc, string peer, ServerResponseStream<TRequest, TResponse> serverResponseStream, CancellationToken cancellationToken)
            where TRequest : class
            where TResponse : class
        {
            DateTime realtimeDeadline = newRpc.Deadline.ToClockType(GPRClockType.Realtime).ToDateTime();

            return new ServerCallContext(
                newRpc.Method, newRpc.Host, peer, realtimeDeadline,
                newRpc.RequestMetadata, cancellationToken, serverResponseStream.WriteResponseHeadersAsync, serverResponseStream);
        }
    }
}