[云] Deploying Your First Serverless Application

• Goal:

• Hands-on lab to get started with Serverless

• Agenda:

• Deploying Your First Serverless Application

• Assignment Introduction

Create and test function in AWS Lambda

• Let's create an addition function using AWS Lambda.

• To create the addition function:

• Navigate to the AWS Lambda console and click "Create function.“

• Select "Author from scratch," name your function, choose Python 3.12 as the runtime, and select the LabRole execution role from the list of existing roles.

• Implement the addition function within the provided lambda_function.py template.

• Deploy the function.

• The addition function is provided in the next slide.

•

Our addition function

import json
 
def lambda_handler(event, context):
    json_input = event
    if 'body' in event: # it can be an external request via API gateway
        json_input = json.loads(event['body'])
    if 'a' in json_input and 'b' in json_input:
        a = int(json_input['a'])
        b = int(json_input['b'])
        return a + b
    else:
        return "No input found"

Code explanation

def lambda_handler(event, context):
The lambda_handler is the entry point for any AWS Lambda function.

event: 
This parameter contains the input data for the function. 
This data is sent to the function when it's invoked.

context: 
This parameter provides information about the invocation, function, 
and execution environment.

if 'body' in event:
This checks if the event dictionary contains a key named body. 
This is crucial because AWS API Gateway 
(a common way to trigger Lambda functions) 
often sends data within a body key.

Add trigger

• To add an API Gateway trigger:

• Go to your function's overview page and click "Add trigger.“

• Select "API Gateway" as the trigger source.

• Create a new API: choose "HTTP API" as the API type and "Open" as the security setting.

• Click "Add.“

Check API endpoint

Invoke function via API

• Send POST requests

curl --header "Content-Type: application/json" --request POST --data "{\"a\": \"2\", \"b\": \"3\"}" <API endpoint>

• Expected response :

• What we got:

{"message":"Internal Server Error"}

• Why is this? AWS Lambda functions that are triggered by API Gateway must return a specific structure, including statusCode and body . Without this structure, the API Gateway may return a 500 Internal Server Error.

• Let’s modify our response format!

import json
 
def lambda_handler(event, context):
    # Initialize response
    response = {
        'statusCode': 200,
        'body': ''
    }
 
    json_input = event
    if 'body' in event: # it can be an external request via API gateway
        json_input = json.loads(event['body'])
    if 'a' in json_input and 'b' in json_input:
        a = int(json_input['a'])
        b = int(json_input['b'])
        result = a + b
        response['body'] = json.dumps({'result': result})
        return response
    else:
        response['body'] = json.dumps({'error': 'No input found'})
        return response

• Comprehensive Error Handling: Introduced try-except blocks to catch and handle different errors (JSON parsing, missing parameters, and unexpected errors).

• More Informative Error Responses: Specific error messages for different failure scenarios.

• What we’ll do:

• Develop a Lambda function for simple ML model inference.

• Deploy a machine learning model as a serverless application using AWS Lambda and API Gateway.

• Analyze the cold start phenomenon associated with serverless functions.

• Environments used:

• Local machine

• AWS console

• Google Colab

Locust for load testing

目标：

实践实验：入门无服务器计算

议程：

部署您的第一个无服务器应用程序
作业介绍

创建和测试 AWS Lambda 函数

让我们使用 AWS Lambda 创建一个加法函数。

要创建加法函数：

导航到 AWS Lambda 控制台并点击“创建函数”。
选择“从头开始创建”，为您的函数命名，选择 Python 3.12 作为运行时，并从现有角色列表中选择 LabRole 执行角色。
在提供的 lambda_function.py 模板中实现加法函数。
部署函数。
加法函数代码

import json

def lambda_handler(event, context):
    json_input = event
    if 'body' in event:  # 通过 API 网关的外部请求可能带有 body
        json_input = json.loads(event['body'])
    if 'a' in json_input and 'b' in json_input:
        a = int(json_input['a'])
        b = int(json_input['b'])
        return a + b
    else:
        return "未找到输入"

lambda_handler 是任何 AWS Lambda 函数的入口。

event: 包含函数的输入数据。此数据是在函数被调用时发送的。
context: 提供关于调用、函数和执行环境的信息。

if 'body' in event:

此处检查 event 字典中是否包含名为 body 的键。
这很重要，因为 AWS API Gateway（触发 Lambda 函数的常见方式）通常会在 body 键中发送数据。

添加触发器

添加 API Gateway 触发器：
- 转到函数的概览页面，点击“添加触发器”。
- 选择“API Gateway”作为触发源。
- 创建一个新 API：选择“HTTP API”作为 API 类型，并选择“开放”作为安全设置。
- 点击“添加”。

检查 API 端点

通过 API 调用函数

发送 POST 请求

curl --header "Content-Type: application/json" --request POST --data "{\"a\": \"2\", \"b\": \"3\"}" <API 端点>

我直接用curl会报错：

PS C:\Users\Eric1> curl --header "Content-Type: application/json" --request POST --data "{\"a\": \"2\", \"b\": \"3\"}" https://qgb4uu66o3.execute-api.us-east-1.amazonaws.com/default/myFirstLambda
Invoke-WebRequest : 找不到接受实际参数“Content-Type: application/json”的位置形式参数。
所在位置 行:1 字符: 1
+ curl --header "Content-Type: application/json" --request POST --data  ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Invoke-WebRequest]，ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.PowerShell.Commands.InvokeWebRequestCommand

PS C:\Users\Eric1> Invoke-RestMethod -Uri "https://qgb4uu66o3.execute-api.us-east-1.amazonaws.com/default/myFirstLambda" -Method Post -Body '{"a": "2", "b": "3"}' -ContentType "application/json"

result
------
     5

预期响应：
- 5
实际得到：
- {"message":"Internal Server Error"}

很神奇，后来又好了：

C:\Users\Eric1>curl --header "Content-Type: application/json" --request POST --data "{\"a\": \"2\", \"b\": \"3\"}" https://qgb4uu66o3.execute-api.us-east-1.amazonaws.com/default/MyAddition
{"result": 5}

为什么会这样？ 通过 API Gateway 触发的 AWS Lambda 函数必须返回特定的结构，包括 statusCode 和 body。如果没有这种结构，API Gateway 可能会返回 500 内部服务器错误。

我们来修改我们的响应格式！

import json

def lambda_handler(event, context):
    # 初始化响应
    response = {
        'statusCode': 200,
        'body': ''
    }

    json_input = event
    if 'body' in event:  # 通过 API 网关的外部请求可能带有 body
        json_input = json.loads(event['body'])
    if 'a' in json_input and 'b' in json_input:
        a = int(json_input['a'])
        b = int(json_input['b'])
        result = a + b
        response['body'] = json.dumps({'result': result})
        return response
    else:
        response['body'] = json.dumps({'error': '未找到输入'})
        return response

更全面的错误处理: 引入了 try-except 块来捕获和处理不同的错误（JSON 解析、缺少参数和意外错误）。
更具信息性的错误响应: 针对不同的失败场景提供了特定的错误消息。

我们接下来会做什么：