eShopOnContainers 知多少[11]：服务间通信之gRPC

引言

最近翻看最新3.0 eShopOncontainers源码，发现其在架构选型中补充了 gRPC 进行服务间通信。那就索性也写一篇，作为系列的补充。

gRPC

老规矩，先来理一下gRPC的基本概念。gRPC是Google开源的RPC框架，比肩dubbo、thrift、brpc。其优势在于：
1. 基于proto buffer：二进制协议，具有高性能的序列化机制。相较于JSON（文本协议）而言，首先从数据包上就有60%-80%的减小，其次其解包速度仅需要简单的数学运算完成，无需复杂的词法语法分析，具有8倍以上的性能提升。
2. 支持数据流。
3. 基于proto 文件：可以更方便的在客户端和服务端之间进行交互。
4. gRPC语言无关性： 所有服务都是使用原型文件定义的。这些文件基于protobuffer语言，并定义服务的接口。基于原型文件，可以为每种语言生成用于创建服务端和客户端的代码。其中protoc编译工具就支持将其生成C #代码。从.NET Core 3 中，gRPC在工具和框架中深度集成，开发者会有更好的开发体验。

gRPC 在 eShopOncontainers 的应用

首先来理一下eShopOncontainers 中服务间同步通信的技术选型，主要还是是基于HTTP/REST，gRPC作为补充。

在eShopOncontainers中Ordering API、Catalog API、Basket API微服务通过gRPC端点暴露服务。其中Mobile Shopping、Web Shopping BFFs使用gRPC客户端访问服务。以下以Ordering API gRPC 服务举例说明。

订单微服务中定义了一个gRPC服务，用于从购物车创建订单。

服务端实现

proto文件定义如下：

syntax = "proto3";
option csharp_namespace = "GrpcOrdering";
package OrderingApi;
service OrderingGrpc {
  rpc CreateOrderDraftFromBasketData(CreateOrderDraftCommand) returns (OrderDraftDTO) {}
}
message CreateOrderDraftCommand {
  string buyerId = 1;
    repeated BasketItem items = 2;
}
message BasketItem {
    string id = 1;
    int32 productId = 2;
    string productName = 3;
    double unitPrice = 4;
    double oldUnitPrice = 5;
    int32 quantity = 6;
    string pictureUrl = 7;
}
message OrderDraftDTO {
    double total = 1;
    repeated OrderItemDTO orderItems = 2;
}
message OrderItemDTO {
    int32 productId = 1;
    string productName = 2;
    double unitPrice = 3;
    double discount = 4;
    int32 units = 5;
    string pictureUrl = 6;
}

服务实现，主要是借助Mediator充当CommandBus进行命令分发，具体实现如下：

namespace GrpcOrdering
{
    public class OrderingService : OrderingGrpc.OrderingGrpcBase
    {
        private readonly IMediator _mediator;
        private readonly ILogger<OrderingService> _logger;

        public OrderingService(IMediator mediator, ILogger<OrderingService> logger)
        {
            _mediator = mediator;
            _logger = logger;
        }

        public override async Task<OrderDraftDTO> CreateOrderDraftFromBasketData(CreateOrderDraftCommand createOrderDraftCommand, ServerCallContext context)
        {
            _logger.LogInformation("Begin gRPC call from method {Method} for ordering get order draft {CreateOrderDraftCommand}", context.Method, createOrderDraftCommand);
            _logger.LogTrace(
                "----- Sending command: {CommandName} - {IdProperty}: {CommandId} ({@Command})",
                createOrderDraftCommand.GetGenericTypeName(),
                nameof(createOrderDraftCommand.BuyerId),
                createOrderDraftCommand.BuyerId,
                createOrderDraftCommand);

            var command = new AppCommand.CreateOrderDraftCommand(
                            createOrderDraftCommand.BuyerId,
                            this.MapBasketItems(createOrderDraftCommand.Items));
            var data = await _mediator.Send(command);

            if (data != null)
            {
                context.Status = new Status(StatusCode.OK, $" ordering get order draft {createOrderDraftCommand} do exist");

                return this.MapResponse(data);
            }
            else
            {
                context.Status = new Status(StatusCode.NotFound, $" ordering get order draft {createOrderDraftCommand} do not exist");
            }

            return new OrderDraftDTO();
        }

        public OrderDraftDTO MapResponse(AppCommand.OrderDraftDTO order)
        {
            var result = new OrderDraftDTO()
            {
                Total = (double)order.Total,
            };

            order.OrderItems.ToList().ForEach(i => result.OrderItems.Add(new OrderItemDTO()
            {
                Discount = (double)i.Discount,
                PictureUrl = i.PictureUrl,
                ProductId = i.ProductId,
                ProductName = i.ProductName,
                UnitPrice = (double)i.UnitPrice,
                Units = i.Units,
            }));

            return result;
        }

        public IEnumerable<ApiModels.BasketItem> MapBasketItems(RepeatedField<BasketItem> items)
        {
            return items.Select(x => new ApiModels.BasketItem()
            {
                Id = x.Id,
                ProductId = x.ProductId,
                ProductName = x.ProductName,
                UnitPrice = (decimal)x.UnitPrice,
                OldUnitPrice = (decimal)x.OldUnitPrice,
                Quantity = x.Quantity,
                PictureUrl = x.PictureUrl,
            });
        }
    }
}

同时，服务端还要注册gRPC的请求处理管道：

app.UseEndpoints(endpoints =>
{
    endpoints.MapDefaultControllerRoute();
    endpoints.MapControllers();
    endpoints.MapGrpcService<OrderingService>();
});

客户端调用

接下来看下客户端[web.bff.shopping]怎么消费的：

public class OrderingService : IOrderingService
    {
        private readonly UrlsConfig _urls;
        private readonly ILogger<OrderingService> _logger;
        public readonly HttpClient _httpClient;

        public OrderingService(HttpClient httpClient, IOptions<UrlsConfig> config, ILogger<OrderingService> logger)
        {
            _urls = config.Value;
            _httpClient = httpClient;
            _logger = logger;
        }
        public async Task<OrderData> GetOrderDraftAsync(BasketData basketData)
        {
            return await GrpcCallerService.CallService(_urls.GrpcOrdering, async channel =>
            {
                var client = new OrderingGrpc.OrderingGrpcClient(channel);
                _logger.LogDebug(" gRPC client created, basketData={@basketData}", basketData);
                var command = MapToOrderDraftCommand(basketData);
                var response = await client.CreateOrderDraftFromBasketDataAsync(command);
                _logger.LogDebug(" gRPC response: {@response}", response);

                return MapToResponse(response, basketData);
            });
        }
        private OrderData MapToResponse(GrpcOrdering.OrderDraftDTO orderDraft, BasketData basketData)
        {
            if (orderDraft == null)
            {
                return null;
            }
            var data = new OrderData
            {
                Buyer = basketData.BuyerId,
                Total = (decimal)orderDraft.Total,
            };

            orderDraft.OrderItems.ToList().ForEach(o => data.OrderItems.Add(new OrderItemData
            {
                Discount = (decimal)o.Discount,
                PictureUrl = o.PictureUrl,
                ProductId = o.ProductId,
                ProductName = o.ProductName,
                UnitPrice = (decimal)o.UnitPrice,
                Units = o.Units,
            }));
            return data;
        }

        private CreateOrderDraftCommand MapToOrderDraftCommand(BasketData basketData)
        {
            var command = new CreateOrderDraftCommand
            {
                BuyerId = basketData.BuyerId,
            };

            basketData.Items.ForEach(i => command.Items.Add(new BasketItem
            {
                Id = i.Id,
                OldUnitPrice = (double)i.OldUnitPrice,
                PictureUrl = i.PictureUrl,
                ProductId = i.ProductId,
                ProductName = i.ProductName,
                Quantity = i.Quantity,
                UnitPrice = (double)i.UnitPrice,
            }));

            return command;
        }
    }

其中，GrpcCallerService是对gRPC Client的一层封装，主要是为了解决未启用TLS无法使用gRPC的问题。

不启用TLS使用gRPC

我们已经知道gRpc 是基于HTTP2.0 协议。然而，连接的建立，默认并不是一步到位直接基于HTTP2.0建立连接的。客户端是先基于HTTP1.1进行协议协商，协商成功后，确认服务端支持HTTP2.0后，才会建立HTT2.0连接，协议协商需要TLS的ALPN协议来实现。流程如下：

这意味着，默认情况下，您需要启用TLS协议才能完成HTTP2.0协议协商，进而才能使用gRPC。

然而，在微服务架构中，并不是所有服务都需要启用安全传输层协议，尤其是微服务间的内部调用。那么在微服务内部如何使用gRPC进行通信呢？

客户端绕过协议协商，直连HTTP2.0（前提是：服务端必须支持HTTP2.0）。

服务端配置如下：

WebHost.CreateDefaultBuilder(args)
    .ConfigureKestrel(options =>
    {
        options.Listen(IPAddress.Any, ports.httpPort, listenOptions =>
        {
            listenOptions.Protocols = HttpProtocols.Http1AndHttp2; //同时监听协议HTTP1，HTTP2
        });
        options.Listen(IPAddress.Any, ports.gRPCPort, listenOptions =>
        {
            listenOptions.Protocols = HttpProtocols.Http2; // gRPC端口仅监听HTTP2.0
        });

    })

客户端需要添加以下设置，这些设置只能在客户端开始时设置一次：

AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);
AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2Support", true);

知道了这些，再回过来看GrpcCallerService的实现，就一目了然了。

public static class GrpcCallerService
{
    public static async Task<TResponse> CallService<TResponse>(string urlGrpc, Func<GrpcChannel, Task<TResponse>> func)
    {
        AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);
        AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2Support", true);

        var channel = GrpcChannel.ForAddress(urlGrpc);

        /*
        using var httpClientHandler = new HttpClientHandler
        {
            ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => { return true; }
        };
        */

        Log.Information(@"Creating gRPC client base address urlGrpc ={@urlGrpc}, 
                          BaseAddress={@BaseAddress} ", urlGrpc, channel.Target);

        try
        {
            return await func(channel);
        }
        catch (RpcException e)
        {
            Log.Error("Error calling via gRPC: {Status} - {Message}", e.Status, e.Message);
            return default;
        }
        finally
        {
            AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", false);
            AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2Support", false);
        }
    }

    public static async Task CallService(string urlGrpc, Func<GrpcChannel, Task> func)
    {
        AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true);
        AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2Support", true);

        /*
        using var httpClientHandler = new HttpClientHandler
        {
            ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => { return true; }
        };
        */

        var channel = GrpcChannel.ForAddress(urlGrpc);

        Log.Debug("Creating gRPC client base address {@httpClient.BaseAddress} ", channel.Target);

        try
        {
            await func(channel);
        }
        catch (RpcException e)
        {
            Log.Error("Error calling via gRPC: {Status} - {Message}", e.Status, e.Message);
        }
        finally
        {
            AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", false);
            AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2Support", false);
        }
    }
}

最后

本文简要介绍了 eShopOnContainers 如何通过集成 gRPC 来完善服务间同步通信机制，希望对你在对微服务进行RPC相关技术选型时有一定的启示和帮助。

参考资料：

1. HTTP2.0笔记之连接建立
2. eShopOnContainers/wiki/gRPC
3. Google Protocol Buffer 的使用和原理