Teach you to learn dapr - 4 Service invocation

Introduce

By using a service call , Your application can use standard gRPC or HTTP The protocol is reliable with other applications 、 Communicate safely .

Why not use it directly HttpClientFactory Well

Ask a few questions first ：

• How to discover and invoke methods of different services
• How to call other services safely , And apply access control to the method
• How to handle retry and transient errors
• How to use distributed tracking metrics to view call graphs to diagnose problems in production

At this point you will find these things HttpClientFactory I didn't help you finish it , These are essential capabilities in microservices , Next, let's look at what the service call does

How service invocation works

Let's first look at the call sequence between two services

1. service A To service B To launch a HTTP/gRPC Call to . The call went to the local Dapr sidecar

2. Dapr Use the name resolution component to discover the service B The location of

3. Dapr Forward the message to the service B Of Dapr sidecar

   notes : Dapr sidecar All calls between are made through gRPC To improve performance . Only services and Dapr sidecar The call between can be HTTP or gRPC

4. service B Of Dapr sidecar Forward the request to the service B A specific endpoint on the ( Or method ) . service B Then run its business logic code

5. service B Send a response to the service A. The response will go to the service B Of Dapr sidecar

6. Dapr Forward the response to the service A Of Dapr sidecar

7. service A Receiving response

Namespace scope

By default , Other services calling the same namespace can directly use AppID（ The assumption is ：nodeapp）

localhost:3500/v1.0/invoke/nodeapp/method/neworder

Service invocation also supports cross namespace invocation , On all supported hosting platforms ,Dapr AppID follow FQDN Format , This includes the target namespace .

FQDN：(Fully Qualified Domain Name) Fully qualified domain name ： Name with both host name and domain name .（ By means of symbols “.”）

for example ： The host name is bigserver, Domain name is mycompany.com, that FQDN Namely bigserver.mycompany.com

​ ** notes ：**FQDN Through the symbol . To splice domain names , That explains AppID Why not use symbols ., If you don't remember here , There should be many friends who will step on the pit

​ such as .net Developers are used to using A.B.C To name the project , but AppID Need to put . Switch to - And all words should also be lowercase （a-b-c）, It is suggested to turn it into an agreement to abide by

For example, call namespace ：production,AppID：nodeapp

localhost:3500/v1.0/invoke/nodeapp.production/method/neworder

This is in K8s Cross namespace calls in clusters are particularly useful

Inter service security

Through mutual on the hosting platform (mTLS) Authentication , Including passage Dapr Sentry Automatic certificate transfer for services , To ensure that Dapr Security for all calls between applications . The following figure shows a self managed application .

Access control

Applications can control which other applications can call them , And what they are authorized to do through access policies . This enables you to restrict sensitive applications with personal information from being accessed by unauthorized applications , And combine service to service secure communication , Provides soft multi tenant deployment .

Specific access control will be introduced in subsequent chapters

retry

In case of call failure and transient error , Service call execution auto retry , And execute... Within the fallback period .

** notes ：** Automatic retry , On by default , You can turn it off . But if it's not related and the business doesn't support idempotence, it's dangerous . It is suggested that the service interface should be designed to support idempotent , This is also a standard choice in microservices .

The errors causing the retry are :

Network error , Including endpoint unavailability and connection rejection .

Due to calling / The called Dapr sidecars Authentication error caused by updating certificate on .

The fallback interval for each call retry is 1 second , At most 3 Time . adopt gRPC And target Sidecar The timeout for the connection is 5 second

Pluggable service discovery

Dapr Can run on a variety of managed platforms . To enable service discovery and service invocation ,Dapr Use pluggable name resolution components . for example ,K8s The name resolution component uses K8s DNS Service to resolve the location of other applications running in the cluster . Self managed machines can use mDNS Name resolution component . Consul The name resolution component can be used in any managed environment , Include K8s Or self managed environment

Focus on , Self managed machines use mDNS, In the development environment, the following articles will recommend VS Seamless development experience on , Is based on mDNS Of

But it has a little problem , We have solved . You just need to develop a console program , be based on Minimal API happy F5 That's all right.

The suggestion is not understood yet Minimal API My little partner can study it , It's delicious

Use mDNS Perform polling load balancing

A picture is worth a thousand words , Just use mDNS Call in turn

Observability tracking and indicators

By default , All calls between applications are tracked , And collect indicators , To provide application insight and diagnostics , This is particularly important in production scenarios . This provides you with call graphs and metrics for calls between services .

The service call API and gRPC agent

pythonapp adopt Dapr sidecar call nodeapp, Through service invocation API And gRPC The proxy is still the calling process seen above , It has nothing to do with language

Use HTTP Call the service

establish Assignment.Server

establish ASP.NET Core empty project , And modify it launchSettings.json, Let's start HTTP The boot port of becomes 5000

profiles.Assignment.Server.applicationUrl To change the value of "https://localhost:6000;http://localhost:5000"

modify Program.cs file

var builder = WebApplication.CreateBuilder(args);var app = builder.Build();app.MapPost("/", () => Console.WriteLine("Hello!"));app.MapGet("/Hello1", () =>{    Console.WriteLine("Hello World1!");    return $"\"Hello World1!\"";});app.MapPost("/Hello2", () => Console.WriteLine("Hello World2!"));app.Map("/Hello3", () => Console.WriteLine("Hello World3!"));app.Run();

There is a total of 4 A service

• / ：Post Method , Print Hello!

• /Hello1：Get Method , Print Hello World1!, return Hello World1!

  ** notes ：** The returned type is Json character string , convenient SDK Deserialization

• /Hello2：Post Method , Print Hello World2!

• /Hello3： No suffix means that all methods are adapted , Print Hello World3!

First use Dapr CLI So let's verify that

function Assignment.Server： In the catalog dapr-study-room\Assignment04\Assignment.Server Open the command line tool , And execute the following command

dapr run --app-id assignment-server --app-port 5000 dotnet watch

Careful friends should find that it is a little different from the command in the previous article ,dontet run Turned into dotnet watch, This turns on the thermal overload , Convenient debugging

Call the service ： Open a new command line tool , And execute the following command

dapr invoke --app-id assignment-server --method /dapr invoke --app-id assignment-server --method Hello1dapr invoke --app-id assignment-server --method Hello2dapr invoke --app-id assignment-server --method Hello3

You can find 4 All commands were called successfully , however Assignment.Server The output is a little unexpected

== APP == Hello!== APP == Hello World2!== APP == Hello World3!

Yes , No, Hello World1!, Then what shall I do? ？ We put Hello1 Change your order

dapr invoke --app-id assignment-server --method Hello1 --verb GET

invoke The output of the call is except App invoked successfully There is another line besides Hello World1!

meanwhile Assignment.Server Your output is correct

== APP == Hello World1!

besides invoke There are also some parameters , such as --data,--data-file, Like to study Dapr CLI My little partner can continue to try . But in general SDK That's all right.

establish Assignment.Client

HTTP The service call

establish Console Application project , Use NuGet Package manager add Dapr.Client SDK, And modify it Program.cs file

using Dapr.Client;var appId = "assignment-server";var client = new DaprClientBuilder().Build();await client.InvokeMethodAsync(appId, "/");var resp = await client.InvokeMethodAsync<string>(HttpMethod.Get, appId, "Hello1");Console.WriteLine($"Hello1 Response: {resp}");await client.InvokeMethodAsync(appId, "Hello2");await client.InvokeMethodAsync(appId, "Hello3");

Look at a few details

• DaprClient It's from DaprClinetBuilder Build Coming out

  There is another way to use DaprClient, adopt DI

  First of all, you need to add Dapr.AspNetCore NuGet package

  Then there began to be branches , If it was before Web API It can be done in Startup.cs file ConfigureServices Method to add a line of code

  services.AddControllers().AddDapr();

  If you use Minimal API The default is No Controllers Of , That can be in var builder = WebApplication.CreateBuilder(args); Then add a line of code

  builder.Services.AddDaprClient();

  Successfully injected , stay Constructors perhaps [FromServices] Have fun in the

• HttpMethod.Post I didn't specify , The default is Post

• HttpMethod.Get When , The return value will be automatically used Json Deserialization

  Don't like Json？ Can pass DaprClient.CreateInvokeHttpClient structure HttpClient, Smart, you must know what to do later

notes ：

1. Minimal API Though fragrant , But new , So not all functions support , For example, directly mapping state management from parameters , Have to wait Minimal API Support Model Binder Later and SDK Only when synchronization is supported 2. DaprClient yes TCP Of , It's also thread safe , You can reuse it boldly , If not DI You don't need to build frequently DaprClient

Verification call succeeded

Open the directory using the command line tool dapr-study-room\Assignment04\Assignment.Client, And then execute the command

dotnet run

If you don't use VS Code Terminal PowerShell perform dapr run You may encounter the following errors

Even if you don't encounter it, it is recommended to learn how to support non default ports

An exception occurred while invoking method: '/' on app-id: 'assignment-server' ---> System.Net.Http.HttpRequestException:  Because the target computer actively refuses , Unable to connect . (127.0.0.1:3500) ---> System.Net.Sockets.SocketException (10061):  Because the target computer actively refuses , Unable to connect .

Because it uses dapr run There was no designation of dapr http port, And default client What I visited was 3500 port

There are two solutions ：

1. modify Assignment.Server Launch parameters , increase --dapr-http-port 3500, This method does not cure the symptoms , Because we may start multiple services in the future

   dapr run --app-id assignment-server --app-port 5000 --dapr-http-port 3500 dotnet watch

2. modify Assignment.Client Environment variables of

   First, execute dapr list Check the port , Take the following as an example ,HTTP PORT yes 51460

   APP ID HTTP PORT GRPC PORT APP PORT COMMAND AGE CREATED PID

   assignment-server 51460 51461 5000 dotnet watch 7s 2021-10-29 14:13.49 11676

   modify Assignment.Client Start parameter of , Pay attention to the 51460 Change to your own port , Use PowerShell Execute the following command

   $Env:DAPR_HTTP_PORT = 51460dotnet run

Execute it again dotnet run You can see the correct output

Hello1 Response: Hello World1!

gRPC The service call

It's too long , Draw inferences from one instance . It's called InvokeMethodGrpcAsync, then dapr-http-port Switch to dapr-grpc-port,DAPR_HTTP_PORT Switch to DAPR_GRPC_PORT

View tracking

Remember dapr init When docker There is a zipkin Well , adopt zipkin You can take a look at the call trace , Open the following address through the browser

http://localhost:9411/

The page is empty

Follow the steps to see

Just click on the end of a line of data SHOW, You can see the call details

Source code of this chapter

Assignment04

https://github.com/doddgu/dapr-study-room

We are acting , New framework 、 New ecology

Our goal is The freedom of the 、 Easy-to-use 、 Highly malleable 、 functional 、 Robust .

So we learn from Building blocks Design concept of , Working on a new framework MASA Framework, What are its characteristics ？

• Native support Dapr, And allow Dapr Replace with traditional means of communication
• Unlimited architecture , Single application 、SOA、 Micro services support
• Support .Net Native framework , Reduce the burden of learning , In addition to the concepts that must be introduced in a specific field , Insist on not making new wheels
• Rich ecological support , In addition to the framework, there are component libraries 、 Authority Center 、 Configuration center 、 Troubleshooting center 、 A series of products such as Alarm Center
• Unit test coverage of the core code base 90%+
• Open source 、 free 、 Community driven
• What is the ？ We are waiting for you , Come together and discuss

After several months of production project practice , Completed POC, At present, the previous accumulation is being refactored into new open source projects

At present, the source code has been synchronized to Github（ The document site is under planning , Will gradually improve ）：

MASA.BuildingBlocks

MASA.Contrib

MASA.Utils

MASA.EShop

BlazorComponent

MASA.Blazor

QQ Group ：7424099

Wechat group ： Plus technology operation wechat （MasaStackTechOps）, Remarks , Invite in

Reprinted from ：（ guiguzi ）