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 _logger;
public OrderingService(IMediator mediator, ILogger logger)
{
_mediator = mediator;
_logger = logger;
}
public override async Task 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 MapBasketItems(RepeatedField 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();
});
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 _logger;
public readonly HttpClient _httpClient;
public OrderingService(HttpClient httpClient, IOptions config, ILogger logger)
{
_urls = config.Value;
_httpClient = httpClient;
_logger = logger;
}
public async Task 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：
![eShopOnContainers 知多少[11]：服务间通信之gRPC_第1张图片](http://img.e-com-net.com/image/info8/b7665157712742d1ac554665d94b7011.jpg)
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 CallService(string urlGrpc, Func> 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 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：
- HTTP2.0笔记之连接建立
- eShopOnContainers/wiki/gRPC
- Google Protocol Buffer 的使用和原理