使用 sam 在本地調試 aws lambda 程序

假如每次修改了 lambda 程序, 都要打成 zip 包, 上傳到 aws 後臺看, 才能看到運行狀況. 那這樣效率過低了.

讓人興奮的是, 有這個工具, sam cli, 能夠用它在本地調試 lambda 程序

Installation

---

前提

在本地用 sam cli 運行 serverless 程序必須安裝和運行 docker. sam cli 用環境變量 DOCKER_HSOT 和 docker 進程鏈接

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

使用 pip 安裝 sam cli

在 aws 文檔估計沒人更新, 仍是隻有 npm 安裝 sam cli 的說明. npm 安裝下來的是舊 sam cli. 因此這裏, 我推薦使用 sam cli 最新的版本, 也就是用 pip 安裝出來的版本

要求 python 2.7

pip install --user aws-sam-cli

檢查是否安裝成功

sam --version SAM CLI, version 0.3.0

Usage

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繼續沿用以上一篇文章 S3 事件觸發的例子, 若是沒有看過的, 建議先看 使用 aws lambda 開發無服務器程序

1. 代碼例子

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. 初始目錄

3. 創建測試用例

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) 須要提早建好

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. 編寫 yaml 配置文件

固然, 不須要手寫, 能夠到 lambda 後臺導出.

4.1 導出函數

4.2 下載 AWS SAM 文件

4.3 獲得的配置文件以下

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 最終的三個文件以下:

運行

---

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

解決方法: 在 myTest1.yaml 找到 Timeout 字段, 改爲 30

再次運行, 成功輸出 "text/plain", 也就是 python 代碼那句 print 語句的結果

結語

---

一個本地調試 lambda 的環境就這樣完成了. sam 還有不少功能, 更多學習, 能夠執行如下兩個命令

➜ 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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