AWS SAM Demo - Automatic Rollback for AWS Lambda with AWS CodeDeploy

aws-sam-automatic-rollback-demo.md

How to Build and Deploy Serverless Apps [AWS Summit]

This demo was presented at the AWS Summit @ Cape Town on Jul 12th.

You can find the slides here.

What's included in this Gist?

• index.js: The node.js code used for AWS Lambda
• sam_template.yaml: The AWS SAM template in YAML format (i.e. CloudFormation)
• scripts: Four scripts used to showcase the live deployment rollback.
  • script_deploy.sh: It packages and deploys the AWS SAM template, then it shows the ENDPOINT Output
  • script_poll.sh: It polls a given URL forever and stores responses and timings in a txt file
  • script_tail.sh: It tails the txt file that contains responses and timings to show live responses
  • script_stats.sh: It reads the txt file and counts OK and KO responses to show some statistics

Feel free to reach out to me on Twitter if you need help or if you just want to say hi :)

index.js

'use strict';

const AWS = require('aws-sdk');
const dynamo = new AWS.DynamoDB.DocumentClient();

const tableName = process.env.TABLE_NAME;

const createResponse = (statusCode, msg) => {
    return {
        statusCode: statusCode,
        body: JSON.stringify({message: msg})
    }
};

const dbGet = (params) => { return dynamo.get(params).promise() };

exports.test = (event, context, callback) => {

    // throw new Error("KO");
    
    let params = {
        TableName: tableName,
        Key: {
            id: "test"
        }
    };
    
    dbGet(params).then( (data) => {
        if (!data.Item) {
            return callback(null, createResponse(404, "ITEM NOT FOUND"));
        }
        callback(null, createResponse(200, data.Item.message));
    }).catch( (err) => { 
        console.log(`GET ITEM FAILED WITH ERROR: ${err}`);
        callback(null, createResponse(500, err));
    });
};

sam_template.yaml

AWSTemplateFormatVersion: '2010-09-09'
Transform: 'AWS::Serverless-2016-10-31'
Description: Safe deployments Demo
Resources:

  Table:
    Type: AWS::Serverless::SimpleTable

  TestFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: index.test
      Runtime: nodejs6.10
      CodeUri: ./
      Policies: AmazonDynamoDBReadOnlyAccess
      Environment:
        Variables:
          TABLE_NAME: !Ref Table
      Events:
        GetResource:
          Type: Api
          Properties:
            Path: /test
            Method: get
      
      AutoPublishAlias: live
      DeploymentPreference:
        Type: Linear10PercentEvery1Minute
        Alarms:
          - !Ref AliasErrorMetricGreaterThanZeroAlarm
          - !Ref LatestVersionErrorMetricGreaterThanZeroAlarm

  AliasErrorMetricGreaterThanZeroAlarm:
    Type: AWS::CloudWatch::Alarm
    DependsOn: TestFunction
    Properties:
      AlarmName: !Sub alarm-sam-demo-alias-${TestFunction}
      AlarmDescription: "deployment alarm to check for errors in the function"
      ComparisonOperator: GreaterThanOrEqualToThreshold
      Dimensions:
        - Name: FunctionName
          Value: !Ref TestFunction
      EvaluationPeriods: 1
      MetricName: Errors
      Namespace: AWS/Lambda
      Period: 60
      Statistic: Sum
      Threshold: 1

  LatestVersionErrorMetricGreaterThanZeroAlarm:
    Type: AWS::CloudWatch::Alarm
    DependsOn: TestFunction
    Properties:
      AlarmName: !Sub alarm-sam-demo-latestversion-${TestFunction}
      AlarmDescription: "alarm to check for errors in the function"
      ComparisonOperator: GreaterThanOrEqualToThreshold
      TreatMissingData: missing
      Dimensions:
        - Name: FunctionName
          Value: !Ref TestFunction
        - Name: Resource
          Value: !Join [":", [!Ref TestFunction, !Select ["7", !Split [":", !Ref TestFunction.Version]]]]
      EvaluationPeriods: 1
      MetricName: Errors
      Namespace: AWS/Lambda
      Period: 60
      Statistic: Sum
      Threshold: 1
  
Outputs:
  ENDPOINT:
    Description: "API endpoint URL for Prod environment"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/test"

script_deploy.sh

#!/bin/bash

# variables
TEMPLATE_IN=sam_template.yaml
TEMPLATE_OUT=template-packaged.yaml
S3_BUCKET=serverless-sam-demos
STACK_NAME=ServerlessSAMDemo
REGION=eu-west-1

# package (upload artifact to S3)
echo "SAM is now packaging..."
sam package --template-file $TEMPLATE_IN --s3-bucket $S3_BUCKET --output-template-file $TEMPLATE_OUT --region $REGION

# deploy (CloudFormation changesets)
echo "SAM is now deploying..."
sam deploy --template-file $TEMPLATE_OUT --stack-name $STACK_NAME --capabilities CAPABILITY_IAM --region $REGION

# fetch and show CloudFormation output
ENDPOINT=$(aws cloudformation describe-stacks --stack-name $STACK_NAME --region $REGION --query 'Stacks[0].Outputs[?OutputKey==`ENDPOINT`].OutputValue' --output text)
echo "ENDPOINT: $ENDPOINT"

script_poll.sh

#!/bin/bash

# loop forever
for ((;;))
    do
        # print a same-line dot
        echo -e ".\c"
        # fetch the given URL and append the response to a txt file
        curl $1 -w " (%{time_total}s) \n" >> data.txt 2>/dev/null
    done

script_stats.sh

#!/bin/bash

# count lines
KO=$(grep "Internal server error" data.txt  | wc -l)
OK=$(grep "OK" data.txt  | wc -l)
# compute percntage
PERCKO=$(echo "$KO * 100 / ($KO + $OK)" | bc)
PERCOK=$(echo "$OK * 100 / ($KO + $OK)" | bc)
# show stats
echo "OK requests: $OK ($PERCOK%)"
echo "KO requests: $KO ($PERCKO%)"

script_tail.sh

#!/bin/bash

# empty file
echo "" > data.txt 

# tail and wait for new daata
tail -F data.txt