服务调用是什么

在分布式应用程序中的服务之间进行调用会涉及到许多挑战。例如：

维护其他服务的地址。
如何安全地调用服务。
在发生短暂的暂时性错误时如何处理重试。
分布式应用程序调用链路追踪。

服务调用构建块通过使用 Dapr 挎斗作为服务的反向代理来解决这些难题。

工作原理

由于调用经过Sidecar，Dapr 可以注入一些有其他行为：

失败时自动重试调用。
通过相互 (mTLS) 身份验证（包括自动证书滚动更新），在服务之间进行调用。
使用访问控制策略控制客户端可以执行的操作。
捕获服务间所有调用的跟踪和指标，以提供分布式调用链路追踪与诊断。

任何应用程序都可以通过使用 Dapr 中内置的本机 Invoke API 来调用 Dapr Sidecar。可以通过 HTTP 或 gRPC 调用 API。使用以下 URL 调用 HTTP API：

http://localhost:<dapr-port>/v1.0/invoke/<application-id>/method/<method-name>

<dapr-port> Dapr 正在侦听的 HTTP 端口。
<application-id> 要调用的服务的应用程序 ID。
<method-name> 要在远程服务上调用的方法的名称。

项目演示

我们使用.NET5创建两个WebAPI项目：BackEnd和FrontEnd，通过FrontEnd调用BackEnd

指定BackEnd默认启动端口5000

        public static IHostBuilder CreateHostBuilder(string[] args) =>

            Host.CreateDefaultBuilder(args)

                .ConfigureWebHostDefaults(webBuilder =>

                {

                    webBuilder.UseStartup<Startup>().UseUrls("http://*:5000");

                });

通过Dapr CLI启动BackEnd，指定sidecar端口为3511，默认为3500，指定app-port是5000，与BackEnd默认端口保持一致

dapr run --dapr-http-port 3511 --app-port 5000 --app-id backend dotnet  .\BackEnd\bin\Debug\net5.0\BackEnd.dll

C:\demo\test\DaprBackEnd>dapr run --dapr-http-port 3511 --app-port 5000 --app-id backend dotnet  .\BackEnd\bin\Debug\net5.0\BackEnd.dll

Starting Dapr with id backend. HTTP Port: 3511. gRPC Port: 30204

time="2021-09-23T14:14:08.3785429+08:00" level=info msg="starting Dapr Runtime -- version 1.4.0 -- commit ed969edc72b3934fffb481f079b736f3588e373a" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.3831089+08:00" level=info msg="log level set to: info" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.3831089+08:00" level=info msg="metrics server started on :30205/" app_id=backend instance=chesterchen-lap scope=dapr.metrics type=log ver=1.4.0

time="2021-09-23T14:14:08.3861203+08:00" level=info msg="standalone mode configured" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.3861203+08:00" level=info msg="app id: backend" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.3871107+08:00" level=info msg="mTLS is disabled. Skipping certificate request and tls validation" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4115681+08:00" level=info msg="local service entry announced: backend -> 10.32.193.9:30209" app_id=backend instance=chesterchen-lap scope=dapr.contrib type=log ver=1.4.0

time="2021-09-23T14:14:08.4115681+08:00" level=info msg="Initialized name resolution to mdns" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4127024+08:00" level=info msg="loading components" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4160224+08:00" level=info msg="component loaded. name: pubsub, type: pubsub.redis/v1" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4160224+08:00" level=info msg="waiting for all outstanding components to be processed" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4187042+08:00" level=info msg="component loaded. name: statestore, type: state.redis/v1" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4187042+08:00" level=info msg="all outstanding components processed" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4192486+08:00" level=info msg="enabled gRPC tracing middleware" app_id=backend instance=chesterchen-lap scope=dapr.runtime.grpc.api type=log ver=1.4.0

time="2021-09-23T14:14:08.4192486+08:00" level=info msg="enabled gRPC metrics middleware" app_id=backend instance=chesterchen-lap scope=dapr.runtime.grpc.api type=log ver=1.4.0

time="2021-09-23T14:14:08.4192486+08:00" level=info msg="API gRPC server is running on port 30204" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4197888+08:00" level=info msg="enabled metrics http middleware" app_id=backend instance=chesterchen-lap scope=dapr.runtime.http type=log ver=1.4.0

time="2021-09-23T14:14:08.4197888+08:00" level=info msg="enabled tracing http middleware" app_id=backend instance=chesterchen-lap scope=dapr.runtime.http type=log ver=1.4.0

time="2021-09-23T14:14:08.4202954+08:00" level=info msg="http server is running on port 3511" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.420335+08:00" level=info msg="The request body size parameter is: 4" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.420335+08:00" level=info msg="enabled gRPC tracing middleware" app_id=backend instance=chesterchen-lap scope=dapr.runtime.grpc.internal type=log ver=1.4.0

time="2021-09-23T14:14:08.4225403+08:00" level=info msg="enabled gRPC metrics middleware" app_id=backend instance=chesterchen-lap scope=dapr.runtime.grpc.internal type=log ver=1.4.0

time="2021-09-23T14:14:08.4230868+08:00" level=info msg="internal gRPC server is running on port 30209" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.4230868+08:00" level=info msg="application protocol: http. waiting on port 5000.  This will block until the app is listening on that port." app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Now listening on: http://[::]:5000

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Application started. Press Ctrl+C to shut down.

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Hosting environment: Production

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Content root path: C:\demo\test\DaprBackEnd

time="2021-09-23T14:14:08.7252681+08:00" level=info msg="application discovered on port 5000" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[1]

== APP ==       Request starting HTTP/1.1 GET http://127.0.0.1:5000/dapr/config application/json -

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[2]

== APP ==       Request finished HTTP/1.1 GET http://127.0.0.1:5000/dapr/config application/json - - 404 0 - 17.3850ms

time="2021-09-23T14:14:08.7693649+08:00" level=info msg="application configuration loaded" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:14:08.7699003+08:00" level=info msg="actor runtime started. actor idle timeout: 1h0m0s. actor scan interval: 30s" app_id=backend instance=chesterchen-lap scope=dapr.runtime.actor type=log ver=1.4.0

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[1]

== APP ==       Request starting HTTP/1.1 GET http://127.0.0.1:5000/dapr/subscribe application/json -

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[2]

time="2021-09-23T14:14:08.7736383+08:00" level=info msg="dapr initialized. Status: Running. Init Elapsed 387.518ms" app_id=backend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

== APP ==       Request finished HTTP/1.1 GET http://127.0.0.1:5000/dapr/subscribe application/json - - 404 0 - 0.1789ms

time="2021-09-23T14:14:08.7888444+08:00" level=info msg="placement tables updated, version: 0" app_id=backend instance=chesterchen-lap scope=dapr.runtime.actor.internal.placement type=log ver=1.4.0

Updating metadata for app command: dotnet .\BackEnd\bin\Debug\net5.0\BackEnd.dll

You're up and running! Both Dapr and your app logs will appear here.

现在修改FrontEnd里Demo，指定启动端口5001

        public static IHostBuilder CreateHostBuilder(string[] args) =>

            Host.CreateDefaultBuilder(args)

                .ConfigureWebHostDefaults(webBuilder =>

                {

                    webBuilder.UseStartup<Startup>().UseUrls("http://*:5001");

                });

引入Nuget包 Dapr.Client，新建DaprController

1.使用 HttpClient调用HTTP服务

using Dapr.Client;

using Microsoft.AspNetCore.Mvc;

using Microsoft.Extensions.Logging;

using System.Collections.Generic;

using System.Net.Http;

using System.Threading.Tasks;

namespace FrontEnd.Controllers

{

    [ApiController]

    [Route("[controller]")]

    public class DaprController : ControllerBase

    {

        private readonly ILogger<DaprController> _logger;

        public DaprController(ILogger<DaprController> logger)

        {

            _logger = logger;

        }

        // 通过HttpClient调用BackEnd

        [HttpGet]

        public async Task<ActionResult> GetAsync()

        {

            using var httpClient = DaprClient.CreateInvokeHttpClient();

            var result = await httpClient.GetAsync("http://backend/WeatherForecast");

            var resultContent = string.Format("result is {0} {1}", result.StatusCode, await result.Content.ReadAsStringAsync());

            return Ok(resultContent);

        }

    }

}

GetAsync API中通过DaprClient.CreateInvokeHttpClient()新建了HttpClient,通过GetAsync方法调用了backend服务中的WeatherForecastAPI。

Sidecar使用可插接式名称解析组件来解析服务BackEnd的地址。在自承载模式下，Dapr 使用 mdn来查找它。在 Kubernetes 模式下运行时，Kubernetes DNS 服务将确定地址。

2.使用 DaprClient调用HTTP服务

        // 通过DaprClient调用BackEnd

        [HttpGet("get2")]

        public async Task<ActionResult> Get2Async()

        {

            using var daprClient = new DaprClientBuilder().Build();

            var result = await daprClient.InvokeMethodAsync<IEnumerable<WeatherForecast>>(HttpMethod.Get, "backend", "WeatherForecast");

            return Ok(result);

        }

DaprController中新增API Get2Async

3.使用注入方式调用 DaprClient

首先引入Nuget包Dapr.AspNetCore，然后在Startup.cs注入Dapr

        public void ConfigureServices(IServiceCollection services)

        {

            services.AddControllers().AddDapr();

        }

新建DaprDIController

using Dapr.Client;

using Microsoft.AspNetCore.Mvc;

using Microsoft.Extensions.Logging;

using System.Collections.Generic;

using System.Net.Http;

using System.Threading.Tasks;

namespace FrontEnd.Controllers

{

    [Route("[controller]")]

    [ApiController]

    public class DaprDIController : ControllerBase

    {

        private readonly ILogger<DaprDIController> _logger;

        private readonly DaprClient _daprClient;

        public DaprDIController(ILogger<DaprDIController> logger, DaprClient daprClient)

        {

            _logger = logger;

            _daprClient = daprClient;

        }

        [HttpGet()]

        public async Task<ActionResult> GetAsync()

        {

            var result = await _daprClient.InvokeMethodAsync<IEnumerable<WeatherForecast>>(HttpMethod.Get, "backend", "WeatherForecast");

            return Ok(result);

        }

    }

}

以上代码通过注入方式注入DaprClient

4.使用DaprClient同样可以调用GRPC

await daprClient.InvokeMethodGrpcAsync<Order, OrderConfirmation>("orderservice", "submitOrder", order);

与HTTP调用方式一致，不再为GRPC新建server

通过Dapr CLI启动FrontEnd，指定sidecar端口为3501，默认为3500，指定app-port是5001，与FrontEnd默认端口保持一致

dapr run --dapr-http-port 3501 --app-port 5001  --app-id frontend dotnet  .\FrontEnd\bin\Debug\net5.0\FrontEnd.dll

C:\demo\test\DaprBackEnd>dapr run --dapr-http-port 3501 --app-port 5001  --app-id frontend dotnet  .\FrontEnd\bin\Debug\net5.0\FrontEnd.dll

Starting Dapr with id frontend. HTTP Port: 3501. gRPC Port: 1045

time="2021-09-23T14:15:24.5222236+08:00" level=info msg="starting Dapr Runtime -- version 1.4.0 -- commit ed969edc72b3934fffb481f079b736f3588e373a" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5269659+08:00" level=info msg="log level set to: info" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5269659+08:00" level=info msg="metrics server started on :1046/" app_id=frontend instance=chesterchen-lap scope=dapr.metrics type=log ver=1.4.0

time="2021-09-23T14:15:24.5302603+08:00" level=info msg="standalone mode configured" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5302904+08:00" level=info msg="app id: frontend" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5302904+08:00" level=info msg="mTLS is disabled. Skipping certificate request and tls validation" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.559128+08:00" level=info msg="local service entry announced: frontend -> 10.32.193.9:1051" app_id=frontend instance=chesterchen-lap scope=dapr.contrib type=log ver=1.4.0

time="2021-09-23T14:15:24.559128+08:00" level=info msg="Initialized name resolution to mdns" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.560108+08:00" level=info msg="loading components" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5641089+08:00" level=info msg="component loaded. name: pubsub, type: pubsub.redis/v1" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5641089+08:00" level=info msg="waiting for all outstanding components to be processed" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5671082+08:00" level=info msg="component loaded. name: statestore, type: state.redis/v1" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5671082+08:00" level=info msg="all outstanding components processed" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5671082+08:00" level=info msg="enabled gRPC tracing middleware" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.grpc.api type=log ver=1.4.0

time="2021-09-23T14:15:24.5671082+08:00" level=info msg="enabled gRPC metrics middleware" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.grpc.api type=log ver=1.4.0

time="2021-09-23T14:15:24.5671082+08:00" level=info msg="API gRPC server is running on port 1045" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5684039+08:00" level=info msg="enabled metrics http middleware" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.http type=log ver=1.4.0

time="2021-09-23T14:15:24.5700491+08:00" level=info msg="enabled tracing http middleware" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.http type=log ver=1.4.0

time="2021-09-23T14:15:24.5700491+08:00" level=info msg="http server is running on port 3501" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5705931+08:00" level=info msg="The request body size parameter is: 4" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5705931+08:00" level=info msg="enabled gRPC tracing middleware" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.grpc.internal type=log ver=1.4.0

time="2021-09-23T14:15:24.5705931+08:00" level=info msg="enabled gRPC metrics middleware" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.grpc.internal type=log ver=1.4.0

time="2021-09-23T14:15:24.5711294+08:00" level=info msg="internal gRPC server is running on port 1051" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.5711294+08:00" level=info msg="application protocol: http. waiting on port 5001.  This will block until the app is listening on that port." app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Now listening on: http://[::]:5001

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Application started. Press Ctrl+C to shut down.

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Hosting environment: Production

== APP == info: Microsoft.Hosting.Lifetime[0]

== APP ==       Content root path: C:\demo\test\DaprBackEnd

time="2021-09-23T14:15:24.8729143+08:00" level=info msg="application discovered on port 5001" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[1]

== APP ==       Request starting HTTP/1.1 GET http://127.0.0.1:5001/dapr/config application/json -

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[2]

== APP ==       Request finished HTTP/1.1 GET http://127.0.0.1:5001/dapr/config application/json - - 404 0 - 19.0408ms

time="2021-09-23T14:15:24.9188354+08:00" level=info msg="application configuration loaded" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.9193692+08:00" level=info msg="actor runtime started. actor idle timeout: 1h0m0s. actor scan interval: 30s" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.actor type=log ver=1.4.0

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[1]

== APP ==       Request starting HTTP/1.1 GET http://127.0.0.1:5001/dapr/subscribe application/json -

== APP == info: Microsoft.AspNetCore.Hosting.Diagnostics[2]

== APP ==       Request finished HTTP/1.1 GET http://127.0.0.1:5001/dapr/subscribe application/json - - 404 0 - 0.2000ms

time="2021-09-23T14:15:24.9236093+08:00" level=info msg="dapr initialized. Status: Running. Init Elapsed 393.349ms" app_id=frontend instance=chesterchen-lap scope=dapr.runtime type=log ver=1.4.0

time="2021-09-23T14:15:24.9393948+08:00" level=info msg="placement tables updated, version: 0" app_id=frontend instance=chesterchen-lap scope=dapr.runtime.actor.internal.placement type=log ver=1.4.0

Updating metadata for app command: dotnet .\FrontEnd\bin\Debug\net5.0\FrontEnd.dll

You're up and running! Both Dapr and your app logs will appear here.

测试调用

1.浏览器地址栏输入

http://localhost:3501/v1.0/invoke/frontend/method/dapr

http://localhost:3501/v1.0/invoke/frontend/method/dapr/get2

http://localhost:3501/v1.0/invoke/frontend/method/DaprDI

可以看到正常响应

2.DaprCLI测试调用

打开cmd输入

dapr invoke --app-id frontend --verb "GET" --method dapr

也可以看到调用成功

C:\Users\chesterychen>dapr invoke --app-id frontend --verb "GET" --method dapr

result is OK [{"date":"2021-09-24T14:20:51.2386681+08:00","temperatureC":47,"temperatureF":116,"summary":"Mild"},{"date":"2021-09-25T14:20:51.2386705+08:00","temperatureC":50,"temperatureF":121,"summary":"Mild"},{"date":"2021-09-26T14:20:51.2386707+08:00","temperatureC":34,"temperatureF":93,"summary":"Hot"},{"date":"2021-09-27T14:20:51.2386708+08:00","temperatureC":42,"temperatureF":107,"summary":"Bracing"},{"date":"2021-09-28T14:20:51.2386709+08:00","temperatureC":-19,"temperatureF":-2,"summary":"Warm"}]

App invoked successfully

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Dapr微服务应用开发系列3：服务调用构件块
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Dapr实战（二） 服务调用