Lambda@Edgeを使って画像をリサイズしてみた

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.14.2
BuildVersion:	18C54
$ docker --version
Docker version 18.09.0, build 4d60db4

.
├── Dockerfile
├── dist
│   ├── origin-response-function.zip 
│   └── viewer-request-function.zip
├── lambda
│   ├── origin-response-function
│   │   └── index.js
│   └── viewer-request-function
│       └── index.js
└── template.yaml

mkdir resize-lambda-edge && cd resize-lambda-edge
mkdir -p dist lambda/origin-response-function lambda/viewer-request-function
touch Dockerfile lambda/origin-response-function/index.js lambda/viewer-request-function/index.js template.yaml

FROM amazonlinux

WORKDIR /tmp
#install the dependencies
RUN yum -y install gcc-c++ && yum -y install findutils

RUN touch ~/.bashrc && chmod +x ~/.bashrc

RUN curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.33.5/install.sh | bash

RUN source ~/.bashrc && nvm install 6.10

WORKDIR /build

'use strict';

const http = require('http');
const https = require('https');
const querystring = require('querystring');

const AWS = require('aws-sdk');
const S3 = new AWS.S3({
  signatureVersion: 'v4',
});
const Sharp = require('sharp');

// set the S3 endpoints
const BUCKET = '<image-bucket>';

exports.handler = (event, context, callback) => {
  let response = event.Records[0].cf.response;

  console.log("Response status code :%s", response.status);

  //check if image is not present
  if (response.status == 404) {

    let request = event.Records[0].cf.request;
    let params = querystring.parse(request.querystring);

    // if there is no dimension attribute, just pass the response
    if (!params.d) {
      callback(null, response);
      return;
    }

    // read the dimension parameter value = width x height and split it by 'x'
    let dimensionMatch = params.d.split("x");

    // read the required path. Ex: uri /images/100x100/webp/image.jpg
    let path = request.uri;

    // read the S3 key from the path variable.
    // Ex: path variable /images/100x100/webp/image.jpg
    let key = path.substring(1);

    // parse the prefix, width, height and image name
    // Ex: key=images/200x200/webp/image.jpg
    let prefix, originalKey, match, width, height, requiredFormat, imageName;
    let startIndex;

    try {
      match = key.match(/(.*)\/(\d+)x(\d+)\/(.*)\/(.*)/);
      prefix = match[1];
      width = parseInt(match[2], 10);
      height = parseInt(match[3], 10);

      // correction for jpg required for 'Sharp'
      requiredFormat = match[4] == "jpg" ? "jpeg" : match[4];
      imageName = match[5];
      originalKey = prefix + "/" + imageName;
    }
    catch (err) {
      // no prefix exist for image..
      console.log("no prefix present..");
      match = key.match(/(\d+)x(\d+)\/(.*)\/(.*)/);
      width = parseInt(match[1], 10);
      height = parseInt(match[2], 10);

      // correction for jpg required for 'Sharp'
      requiredFormat = match[3] == "jpg" ? "jpeg" : match[3]; 
      imageName = match[4];
      originalKey = imageName;
    }
    console.log(BUCKET)
    console.log(originalKey)
    // get the source image file
    S3.getObject({ Bucket: BUCKET, Key: originalKey }).promise()
      // perform the resize operation
      .then(data => Sharp(data.Body)
        .resize(width, height)
        .toFormat(requiredFormat)
        .toBuffer()
      )
      .then(buffer => {
        // save the resized object to S3 bucket with appropriate object key.
        S3.putObject({
            Body: buffer,
            Bucket: BUCKET,
            ContentType: 'image/' + requiredFormat,
            CacheControl: 'max-age=31536000',
            Key: key,
            StorageClass: 'STANDARD'
        }).promise()
        // even if there is exception in saving the object we send back the generated
        // image back to viewer below
        .catch(() => { console.log("Exception while writing resized image to bucket")});

        // generate a binary response with resized image
        response.status = 200;
        response.body = buffer.toString('base64');
        response.bodyEncoding = 'base64';
        response.headers['content-type'] = [{ key: 'Content-Type', value: 'image/' + requiredFormat }];
        callback(null, response);
      })
    .catch( err => {
      console.log("Exception while reading source image :%j",err);
      console.log(BUCKET);
      console.log(originalKey);
    });
  } // end of if block checking response statusCode
  else {
    // allow the response to pass through
    callback(null, response);
  }
};

'use strict';

const querystring = require('querystring');

// defines the allowed dimensions, default dimensions and how much variance from allowed
// dimension is allowed.

const variables = {
        allowedDimension : [ {w:100,h:100}, {w:200,h:200}, {w:300,h:300}, {w:400,h:400} ],
        defaultDimension : {w:200,h:200},
        variance: 20,
        webpExtension: 'webp'
  };

exports.handler = (event, context, callback) => {
    const request = event.Records[0].cf.request;
    const headers = request.headers;

    // parse the querystrings key-value pairs. In our case it would be d=100x100
    const params = querystring.parse(request.querystring);

    // fetch the uri of original image
    let fwdUri = request.uri;

    // if there is no dimension attribute, just pass the request
    if(!params.d){
        callback(null, request);
        return;
    }
    // read the dimension parameter value = width x height and split it by 'x'
    const dimensionMatch = params.d.split("x");

    // set the width and height parameters
    let width = dimensionMatch[1];
    let height = dimensionMatch[2];

    // parse the prefix, image name and extension from the uri.
    // In our case /images/image.jpg

    const match = fwdUri.match(/(.*)\/(.*)\.(.*)/);

    let prefix = match[1];
    let imageName = match[2];
    let extension = match[3];

    // define variable to be set to true if requested dimension is allowed.
    let matchFound = false;

    // calculate the acceptable variance. If image dimension is 105 and is within acceptable
    // range, then in our case, the dimension would be corrected to 100.
    let variancePercent = (variables.variance/100);

    for (let dimension of variables.allowedDimension) {
        let minWidth = dimension.w - (dimension.w * variancePercent);
        let maxWidth = dimension.w + (dimension.w * variancePercent);
        if(width >= minWidth && width <= maxWidth){
            width = dimension.w;
            height = dimension.h;
            matchFound = true;
            break;
        }
    }
    // if no match is found from allowed dimension with variance then set to default
    //dimensions.
    if(!matchFound){
        width = variables.defaultDimension.w;
        height = variables.defaultDimension.h;
    }

    // read the accept header to determine if webP is supported.
    let accept = headers['accept']?headers['accept'][0].value:"";

    let url = [];
    // build the new uri to be forwarded upstream
    url.push(prefix);
    url.push(width+"x"+height);
  
    // check support for webp
    if (accept.includes(variables.webpExtension)) {
        url.push(variables.webpExtension);
    }
    else{
        url.push(extension);
    }
    url.push(imageName+"."+extension);

    fwdUri = url.join("/");

    // final modified url is of format /images/200x200/webp/image.jpg
    request.uri = fwdUri;
    callback(null, request);
};

AWSTemplateFormatVersion: 2010-09-09

Transform: AWS::Serverless-2016-10-31

Resources:
  ImageBucket:
    Type: AWS::S3::Bucket
    DeletionPolicy: Retain
    Properties:
      AccessControl: PublicRead
      BucketName: <image-bucket>

  ImageBucketPolicy:
    Type: AWS::S3::BucketPolicy
    Properties:
      Bucket: !Ref ImageBucket
      PolicyDocument:
        Statement:
            - Action:
                - s3:GetObject
              Effect: Allow
              Principal: "*"
              Resource: !Sub arn:aws:s3:::${ImageBucket}/*
            - Action:
                - s3:PutObject
              Effect: Allow
              Principal:
                AWS: !GetAtt EdgeLambdaRole.Arn
              Resource: !Sub arn:aws:s3:::${ImageBucket}/*
            - Action:
                - s3:GetObject
              Effect: Allow
              Principal:
                AWS: !GetAtt EdgeLambdaRole.Arn
              Resource: !Sub arn:aws:s3:::${ImageBucket}/*

  EdgeLambdaRole:
    Type: "AWS::IAM::Role"
    Properties:
      AssumeRolePolicyDocument:
        Version: "2012-10-17"
        Statement:
            Effect: "Allow"
            Principal:
              Service:
                - "lambda.amazonaws.com"
                - "edgelambda.amazonaws.com"
            Action:
              - "sts:AssumeRole"
      Path: "/service-role/"
      ManagedPolicyArns:
        - "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"

  ViewerRequestFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: s3://<code-bucket>/viewer-request-function.zip
      Handler: index.handler
      Runtime: nodejs6.10
      MemorySize: 128
      Timeout: 1
      Role: !GetAtt EdgeLambdaRole.Arn

  ViewerRequestFunctionVersion:
    Type: "AWS::Lambda::Version"
    Properties:
      FunctionName: !Ref ViewerRequestFunction
      Description: "A version of ViewerRequestFunction"

  OriginResponseFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: s3://<code-bucket>/origin-response-function.zip
      Handler: index.handler
      Runtime: nodejs6.10
      MemorySize: 512
      Timeout: 5
      Role: !GetAtt EdgeLambdaRole.Arn

  OriginResponseFunctionVersion:
    Type: "AWS::Lambda::Version"
    Properties:
      FunctionName: !Ref OriginResponseFunction
      Description: "A version of OriginResponseFunction"

  MyDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        Origins:
        - DomainName: !Sub ${ImageBucket}.s3.amazonaws.com
          Id: myS3Origin
          S3OriginConfig: {}
        Enabled: 'true'
        Comment: distribution for content delivery
        DefaultRootObject: index.html
        DefaultCacheBehavior:
          TargetOriginId: myS3Origin
          LambdaFunctionAssociations:
            - EventType: 'viewer-request'
              LambdaFunctionARN: !Ref ViewerRequestFunctionVersion
            - EventType: 'origin-response'
              LambdaFunctionARN: !Ref OriginResponseFunctionVersion
          ForwardedValues:
            QueryString: 'true'
            QueryStringCacheKeys:
              - d
            Cookies:
              Forward: 'none'
          ViewerProtocolPolicy: allow-all
          MinTTL: '100'
          SmoothStreaming: 'false'
          Compress: 'true'
        PriceClass: PriceClass_All
        ViewerCertificate:
          CloudFrontDefaultCertificate: 'true'

Outputs:
  ImageBucket:
    Value: !Ref ImageBucket
    Export:
      Name: !Sub "${AWS::StackName}-ImageBucket"

  MyDistribution:
    Value: !Ref MyDistribution
    Export:
      Name: !Sub "${AWS::StackName}-MyDistribution"

export IMAGE_BUCKET=[任意のバケット名]
export CODE_BUCKET=[任意のバケット名]

# バケット名を置換する
sed -i ".orig" "s/<image-bucket>/${IMAGE_BUCKET}/g" template.yaml  lambda/origin-response-function/index.js
sed -i ".orig" "s/<code-bucket>/${CODE_BUCKET}/g" template.yaml

docker build --tag amazonlinux:nodejs .

docker run --rm --volume ${PWD}/lambda/origin-response-function:/build amazonlinux:nodejs /bin/bash -c "source ~/.bashrc; npm init -f -y; npm install sharp --save; npm install querystring --save; npm install --only=prod"
docker run --rm --volume ${PWD}/lambda/viewer-request-function:/build amazonlinux:nodejs /bin/bash -c "source ~/.bashrc; npm init -f -y; npm install querystring --save; npm install --only=prod"

cd lambda/origin-response-function && zip -FS -x "*.orig" -q -r ../../dist/origin-response-function.zip * && cd ../..
cd lambda/viewer-request-function && zip -FS -x "*.orig" -q -r ../../dist/viewer-request-function.zip * && cd ../..

# Lambda@Edgeで使用するLambda関数はバージニア北部(us-east-1)で作成する必要があります｡その為､リージョンを明示して作業しています｡

aws --region us-east-1 s3 mb s3://${CODE_BUCKET}
aws s3 cp dist/origin-response-function.zip s3://${CODE_BUCKET}/
aws s3 cp dist/viewer-request-function.zip s3://${CODE_BUCKET}/

# CloudFrontを作成するので､約20分かかります｡
aws --region us-east-1 cloudformation deploy --template-file template.yaml --stack-name resize-lambda-edge2 --capabilities CAPABILITY_IAM

# サンプル画像をDLしてS3にPUT
curl -L http://www.cor-art.com/best/tenkei/down/SA001.JPG -o image.jpg
aws s3 cp image.jpg s3://images${IMAGE_BUCKET}/images/

# 作成されたCloudFrontのDomainNameを確認する｡
aws cloudfront list-distributions