使用sam框架可以在部署serverless应用之前，在本地调试application是否符合预期

sam框架安装

serverless应用是lambda函数，事件源和其他资源的组合

使用sam能够基于docker容器在本地测试lambda函数

安装sam

wget https://github.com/aws/aws-sam-cli/releases/latest/download/aws-sam-cli-linux-x86_64.zip
unzip aws-sam-cli-linux-x86_64.zip -d sam-installation
sudo ./sam-installation/install --update
sam --version

示例程序中三个比较重要的文件

 sam-app/
   ├── README.md
   ├── events/
   │   └── event.json
   ├── hello_world/
   │   ├── __init__.py
   │   ├── app.py            #Contains your AWS Lambda handler logic.
   │   └── requirements.txt  #Contains any Python dependencies the application requires, used for sam build
   ├── template.yaml         #Contains the AWS SAM template defining your application's AWS resources.
   └── tests/
       └── unit/
           ├── __init__.py
           └── test_handler.py

• template.yaml：包含Amazon SAM定义应用程序的模板Amazon资源的费用
• hello_world/app.py：包含实际的 Lambda 处理程序逻辑
• hello_world/requirements.txt：包含应用程序所需的任何 Python 依赖项，用于sam build

测试和调试serverless

测试和调试无服务器应用程序

本地调用lambda

sam local invoke对应lambda命令aws lambda invoke

$ sam local invoke "Ratings" -e event.json
$ echo '{"message": "Hey, are you there?" }' | sam local invoke --event - "Ratings"

注意：如果函数包含layer，本地调用或测试时层包将下载并缓存在本地

sam本地调用主要通过template.yaml识别函数

$ sam build
Build Succeeded
Built Artifacts  : .aws-sam/build
Built Template   : .aws-sam/build/template.yaml

使用官方image构建lambda镜像，将构建完毕的

$ echo '{"message": "Hey, are you there?" }' | sam local invoke "HelloWorldFunction"
Invoking app.lambda_handler (python3.7)
Image was not found.
Removing rapid images for repo public.ecr.aws/sam/emulation-python3.7
Building image.....
Skip pulling image and use local one: public.ecr.aws/sam/emulation-python3.7:rapid-1.66.0-x86_64.

Mounting xxxxx/.aws-sam/build/HelloWorldFunction as /var/task:ro,delegated inside runtime container
START RequestId: c95f8298-2ff8-4eed-ab34-8ba730ac62f1 Version: $LATEST
END RequestId: c95f8298-2ff8-4eed-ab34-8ba730ac62f1
REPORT RequestId: c95f8298-2ff8-4eed-ab34-8ba730ac62f1  Init Duration: 2.54 ms  Duration: 111.97 ms     Billed Duration: 112 ms      Memory Size: 128 MB     Max Memory Used: 128 MB
{"statusCode": 200, "body": "{\"message\": \"hello world\"}"}
SAM CLI update available (1.68.0); (1.66.0 installed)
To download: https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/serverless-sam-cli-install.html

本地调用apigateway

使用sam local start-api在本地启动api，可以热重载。sam识别template.yaml模板中。

默认sam使用lambda代理集成，并支持http api 和 rest api

示例程序如下

import json
import requests

def lambda_handler(event, context):
    try:
        ip = requests.get("http://checkip.amazonaws.com/")
    except requests.RequestException as e:
        print(e)
        raise e
    
    return {
        "statusCode": 200,
        "body": json.dumps({
            "message": "hello world",
            "location": ip.text.replace("\n", "")
        }),
    }

示例模板如下

AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Description: rating app
Globals:
  Function:
    Timeout: 3
    MemorySize: 128
Resources:
  Ratings:
    Type: AWS::Serverless::Function
    Properties:
      Handler: ratings.lambda_handler
      Runtime: python3.7
      Architectures:
      - x86_64
      Events:
        Api:
          Type: Api
          Properties:
            Path: /ratings
            Method: get
      CodeUri: Ratings
    Metadata:
      SamResourceId: Ratings

当访问对应的api时，会启动构建，并将代码通过挂载卷的方式挂载到容器中

$ sam local start-api
Mounting Ratings at http://127.0.0.1:3000/ratings [GET]
You can now browse to the above endpoints to invoke your functions. You do not need to restart/reload SAM CLI while working on your functions, changes will be reflected instantly/automatically. If you used sam build before running local commands, you will need to re-run sam build for the changes to be picked up. You only need to restart SAM CLI if you update your AWS SAM template
2023-01-09 15:19:21  * Running on http://127.0.0.1:3000/ (Press CTRL+C to quit)
Invoking ratings.lambda_handler (python3.7)
Skip pulling image and use local one: public.ecr.aws/sam/emulation-python3.7:rapid-1.66.0-x86_64.

Mounting /home/ec2-user/efs/aws-sam-test/ratingdemo/.aws-sam/build/Ratings as /var/task:ro,delegated inside runtime container
START RequestId: a5b6a479-c011-4139-b142-98c0e88a0e6c Version: $LATEST
END RequestId: a5b6a479-c011-4139-b142-98c0e88a0e6c
REPORT RequestId: a5b6a479-c011-4139-b142-98c0e88a0e6c  Init Duration: 0.13 ms  Duration: 592.02 ms     Billed Duration: 593 ms  Memory Size: 128 MB     Max Memory Used: 128 MB
No Content-Type given. Defaulting to 'application/json'.
2023-01-09 15:19:25 127.0.0.1 - - [09/Jan/2023 15:19:25] "GET /ratings HTTP/1.1" 200 -

此外，sam还提供了模拟lambda终端节点，生成模拟事件的命令

sam local start-lambda
sam local generate-event s3 put

可以使用vscode插件方便管理和编写lambda函数

https://docs.aws.amazon.com/zh_cn/toolkit-for-vscode/latest/userguide/remote-lambda.html

sam集成codedeploy部署lambda

使 Lambda 码部署和Amazon无服务器应用程序模型

将应用程序规范文件添加到 CodeDeploy 的 revision

sam本身能够将将代码打包为lambda函数，并通过蓝绿部署的方式发布。sam使用cloudformation创建lambda函数和codedeploy，同时完成版本切换和蓝绿发布

打包并部署命令如下

sam package \
  --template-file template.yml \
  --output-template-file package.yml \
  --s3-bucket s3://xxxxx/xxxx
  
$ sam deploy \
  --template-file package.yml \
  --stack-name my-date-time-app \
  --capabilities CAPABILITY_IAM

实例代码的template.yaml文件，注释的非常清楚，需要注意以下几点

• 函数的资源类型为AWS::Serverless::Function，AWS::Serverless是cloudformation提供的官方宏，实质是对lambda函数写法的简化，cfn会将模板转换并扩展为兼容的cfn模板

  AWSTemplateFormatVersion : '2010-09-09'
  Transform: AWS::Serverless-2016-10-31
  Resources:
    myDateTimeFunction:
      Type: AWS::Serverless::Function
      Properties:
        Handler: myDateTimeFunction.handler
        Runtime: nodejs16.x
        AutoPublishAlias: live
  	  ...
        DeploymentPreference:  
            Type: Linear10PercentEvery1Minute
            Hooks:
              PreTraffic: !Ref beforeAllowTraffic
              PostTraffic: !Ref afterAllowTraffic
  

• 当在serverless中指定AutoPublishAlias时，lambda函数会创建alias，检测函数变化并通过名为live的别名部署

• DeploymentPreference是独属于sam的属性，启用该属性后转换的cfn模板会创建codedeploy 应用，部署组和角色对lambda，同时可以在hook中指定流量切换前后的测试函数。测试函数在lambda控制台上显示为关联函数

测试函数的主要逻辑在于

• 调用主函数（函数名通过环境变量传入）
• 将调用结果回传codedeploy（需要使用事件中的deploymentId和lifecycleEventHookExecutionId参数）

'use strict';
const AWS = require('aws-sdk');
const codedeploy = new AWS.CodeDeploy({ apiVersion: '2014-10-06' });
var lambda = new AWS.Lambda();

exports.handler = (event, context, callback) => {
    console.log("Entering PreTraffic Hook!");
    var deploymentId = event.DeploymentId;
    var lifecycleEventHookExecutionId = event.LifecycleEventHookExecutionId;
    var functionToTest = process.env.NewVersion;
    var lambdaParams = {
        FunctionName: functionToTest,
        Payload: "{\"option\": \"time\"}",
        InvocationType: "RequestResponse"
    };
    var lambdaResult = "Failed";
    // Invoke the updated Lambda function.
    lambda.invoke(lambdaParams, function (err, data) {
        if (err) {	// an error occurred
            console.log(err, err.stack);
            lambdaResult = "Failed";
        }
        else {	// successful response
            var result = JSON.parse(data.Payload);
            console.log("Result: " + JSON.stringify(result));
            console.log("statusCode: " + result.statusCode);
            if (result.statusCode != "400") {
                console.log("Validation succeeded");
                lambdaResult = "Succeeded";
            }
            else {
                console.log("Validation failed");
            }

            var params = {
                deploymentId: deploymentId,
                lifecycleEventHookExecutionId: lifecycleEventHookExecutionId,
                status: lambdaResult
            };

            codedeploy.putLifecycleEventHookExecutionStatus(params, function (err, data) {
                if (err) {
                    // Validation failed.
                    console.log("CodeDeploy Status update failed");
                    console.log(err, err.stack);
                    callback("CodeDeploy Status update failed");
                } else {
                    // Validation succeeded.
                    console.log("CodeDeploy status updated successfully");
                    callback(null, "CodeDeploy status updated successfully");
                }
            });
        }
    });
}

生成的codedeploy修订如下，即通过将别名指向不同版本完成流量切换

{
  "version": "0.0",
  "Resources": [
    {
      "my-date-time-app-myDateTimeFunction-L7EvikmOAZm9": {
        "Type": "AWS::Lambda::Function",
        "Properties": {
          "Name": "my-date-time-app-myDateTimeFunction-L7EvikmOAZm9",
          "Alias": "live",
          "CurrentVersion": "1",
          "TargetVersion": "2"
        }
      }
    }
  ],
  "Hooks": [
    {
      "BeforeAllowTraffic": "CodeDeployHook_beforeAllowTraffic"
    },
    {
      "AfterAllowTraffic": "CodeDeployHook_afterAllowTraffic"
    }
  ]
}

• serverless模板转换后的serverless函数会转化成普通的lambda函数资源，通过alias资源的update策略，当函数版本变化时触发codedeploy操作

    myDateTimeFunctionAliaslive:
      Type: 'AWS::Lambda::Alias'
      UpdatePolicy:
        CodeDeployLambdaAliasUpdate:
          ApplicationName:
            Ref: ServerlessDeploymentApplication
          DeploymentGroupName:
            Ref: myDateTimeFunctionDeploymentGroup
          BeforeAllowTrafficHook:
            Ref: beforeAllowTraffic
          AfterAllowTrafficHook:
            Ref: afterAllowTraffic
      Properties:
        Name: live
        FunctionName:
          Ref: myDateTimeFunction
        FunctionVersion:
          'Fn::GetAtt':
            - myDateTimeFunctionVersion368eb951f6
            - Version
  

• 部署配置为Linear10PercentEvery1Minute，即codedeploy的流量切换为线性每分钟切换10%