使用 sam 在本地调试 aws lambda 程序

假如每次修改了 lambda 程序, 都要打成 zip 包, 上传到 aws 后台看, 才能看到运行状况. 那这样效率过低了.

让人兴奋的是, 有这个工具, sam cli, 能够用它在本地调试 lambda 程序

Installation

---

前提

在本地用 sam cli 运行 serverless 程序必须安装和运行 docker. sam cli 用环境变量 DOCKER_HSOT 和 docker 进程链接

• macOS: Docker for Mac
• Windows: Docker for Windows
• Linux: yum install docker

使用 pip 安装 sam cli

在 aws 文档估计没人更新, 仍是只有 npm 安装 sam cli 的说明. npm 安装下来的是旧 sam cli. 因此这里, 我推荐使用 sam cli 最新的版本, 也就是用 pip 安装出来的版本

要求 python 2.7

pip install --user aws-sam-cli

检查是否安装成功

sam --version SAM CLI, version 0.3.0

Usage

---

继续沿用以上一篇文章 S3 事件触发的例子, 若是没有看过的, 建议先看 使用 aws lambda 开发无服务器程序

1. 代码例子

from __future__ import print_function

import json
import urllib
import boto3

print('Loading function')

s3 = boto3.client('s3')

def lambda_handler(event, context):
    # Get the object from the event and show its content type
    bucket = event['Records'][0]['s3']['bucket']['name']
    key = urllib.unquote_plus(event['Records'][0]['s3']['object']['key'].encode('utf8'))
    try:
        response = s3.get_object(Bucket=bucket, Key=key)
        print("CONTENT TYPE: " + response['ContentType'])
        return response['ContentType']
    except Exception as e:
        print(e)
        print('Error getting object {} from bucket {}. Make sure they exist and your bucket is in the same region as this function.'.format(key, bucket))
        raise e
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2. 初始目录

3. 创建测试用例

sam local generate-event s3 --region us-east-1 --bucket test4lambda --key lambda-test.txt > event.json
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S3 的 bucket(test4lambda) 和 key(lambda-test.txt) 须要提早建好

生成以下用例

{
    "Records": [
        {
            "eventVersion": "2.0", 
            "eventName": "ObjectCreated:Put", 
            "eventTime": "1970-01-01T00:00:00.000Z", 
            "userIdentity": {
                "principalId": "EXAMPLE"
            }, 
            "eventSource": "aws:s3", 
            "requestParameters": {
                "sourceIPAddress": "127.0.0.1"
            }, 
            "s3": {
                "configurationId": "testConfigRule", 
                "object": {
                    "eTag": "0123456789abcdef0123456789abcdef", 
                    "key": "lambda-test.txt", 
                    "sequencer": "0A1B2C3D4E5F678901", 
                    "size": 1024
                }, 
                "bucket": {
                    "ownerIdentity": {
                        "principalId": "EXAMPLE"
                    }, 
                    "name": "test4lambda", 
                    "arn": "arn:aws:s3:::test4lambda"
                }, 
                "s3SchemaVersion": "1.0"
            }, 
            "responseElements": {
                "x-amz-id-2": "EXAMPLE123/5678abcdefghijklambdaisawesome/mnopqrstuvwxyzABCDEFGH", 
                "x-amz-request-id": "EXAMPLE123456789"
            }, 
            "awsRegion": "us-east-1"
        }
    ]
}
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4. 编写 yaml 配置文件

固然, 不须要手写, 能够到 lambda 后台导出.

4.1 导出函数

4.2 下载 AWS SAM 文件

4.3 获得的配置文件以下

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: >-
  An Amazon S3 trigger that retrieves metadata for the object that has been
  updated.
Resources:
 myTest1:
 Type: 'AWS::Serverless::Function'
 Properties:
 Handler: lambda_function.lambda_handler
 Runtime: python2.7
 CodeUri: .
 Description: >-
        An Amazon S3 trigger that retrieves metadata for the object that has
        been updated.
 MemorySize: 128
 Timeout: 3
 Role: 'arn:aws:iam::851829110870:role/service-role/lambdaTest'
 Events:
 BucketEvent1:
 Type: S3
 Properties:
 Bucket:
 Ref: Bucket1
 Events:
 - 's3:ObjectCreated:*'
 Tags:
        'lambda-console:blueprint': s3-get-object-python
 Bucket1:
 Type: 'AWS::S3::Bucket'
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4.4 最终的三个文件以下:

运行

---

sam local invoke myTest1 -e event.json -t myTest1.yaml
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居然提示 "time out after 3 seconds"

解决方法: 在 myTest1.yaml 找到 Timeout 字段, 改为 30

再次运行, 成功输出 "text/plain", 也就是 python 代码那句 print 语句的结果

结语

---

一个本地调试 lambda 的环境就这样完成了. sam 还有不少功能, 更多学习, 能够执行如下两个命令

➜ sam --help
Usage: sam [OPTIONS] COMMAND [ARGS]...

  AWS Serverless Application Model (SAM) CLI

  The AWS Serverless Application Model extends AWS CloudFormation to provide
  a simplified way of defining the Amazon API Gateway APIs, AWS Lambda
  functions, and Amazon DynamoDB tables needed by your serverless
  application. You can find more in-depth guide about the SAM specification
  here: https://github.com/awslabs/serverless-application-model.

Options:
  --debug    Turn on debug logging
  --version  Show the version and exit.
  --help     Show this message and exit.

Commands:
  init      Initialize a serverless application with a...
  package   Package an AWS SAM application. This is an alias for 'aws cloudformation package'.
  local     Run your Serverless application locally for...
  validate  Validate an AWS SAM template.
  deploy    Deploy an AWS SAM application. This is an alias for 'aws cloudformation deploy'.
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➜ sam local generate-event --help
Usage: sam local generate-event [OPTIONS] COMMAND [ARGS]...

  Generate an event

Options:
  --help  Show this message and exit.

Commands:
  api       Generates a sample Amazon API Gateway event
  dynamodb  Generates a sample Amazon DynamoDB event
  kinesis   Generates a sample Amazon Kinesis event
  s3        Generates a sample Amazon S3 event
  schedule  Generates a sample scheduled event
  sns       Generates a sample Amazon SNS event
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