Do more with less code in a serverless world

There are many software engineering practices that can and should be applied to Lambda functions: Single Responsibility Principle (from SOLID), You Ain't Gonna Need It (YAGNI), Keep It Simply Stupid (KISS). In this presentation, I'll go through the different ways to apply those principles in the AWS serverless world and even to avoid the usage of Lambda functions sometimes.

Transcript

1. Less is more
   Do more with less code in a serverless world
   Jerome Van Der Linden
   Geneva Serverless Meetup - 26/05/2020
   

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2. About me
   • In a previous life, ”Mr Cut Cut” (M. Coupe coupe)
   • Developer & software craftsman
   • And now, Solutions Architect @ AWS
   2
   linkedin.com/in/jeromevdl/
   Jerome Van Der Linden
   

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3. Few principles
   Clean Code
   

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4. SOLID
   4
   S Single Responsibility Principle
   O Open / closed Principle
   L Liskov substitution Principle
   I Interface segregation Principle
   D Dependency Inversion Principle
   

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5. Single Responsibility Principle
   5
   “A class or module should have one,
   and only one, reason to be changed”
   - Robert C. Martin, aka Uncle Bob
   

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6. YAGNI (You Ain’t Gonna Need It)
   6
   Just because you can,
   doesn’t mean you should…
   

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7. KISS
   7
   

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8. 8
   And many more…
   Clean Code
   DRY
   Don’t Repeat Yourself
   Law of Demeter
   Broken window
   theory
   Boy scout rule
   Not invented here
   

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9. How to apply those principles?
   In the serverless world
   

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10. Serverless World?
    10
    Serverless == FAAS
    Function As A Service
    

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11. Serverless World?
    11
    Serverless ⊃ FAAS
    Function As A Service
    

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12. AWS Serverless world
    12
    AWS
    Lambda
    AWS
    Fargate
    Amazon
    API Gateway
    Amazon
    SNS
    Amazon
    SQS
    COMPUTE
    DATA STORES
    INTEGRATION
    Amazon Aurora
    Serverless
    Amazon
    S3
    Amazon
    DynamoDB
    Amazon
    EventBridge
    FAAS
    AWS
    Step Functions
    AWS
    AppSync
    

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13. Single Responsibility Principle
    ü Do’s ✘ Don’ts *
    - Input validation
    - Business logic /!\
    - Transform data
    - Return result
    - Event/Input Filtering
    - Transport data
    - Orchestration & long
    transactions
    - Retry/Failure handling
    * Most of the time
    

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14. Event Filtering
    15
    SNS
    Topic
    Publisher
    if event_type == 'order_created’:
    lambda_client.invoke('OrderCreation', ...)
    elif event_type == 'order_placed’:
    lambda_client.invoke('OrderPlacement', ...)
    elif event_type == 'order_cancelled’:
    lambda_client.invoke('OrderCancelation', ...)
    OrderCreation
    OrderPlacement
    OrderCancellation
    {
    "event_type": "order_placed",
    "order": {
    "id": "232134",
    "amount": "2341,45",
    "stock_ref": "AMZN”
    }
    }
    the wrong way
    function code
    Input event
    OrderFiltering
    

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15. Event Filtering with SNS
    16
    OrderCreation
    OrderPlacement
    OrderCancellation
    Publisher
    OrderCreationEvent:
    Type: AWS::SNS::Subscription
    Properties:
    TopicArn: 'arn:aws:sns:eu-central-1:123456789:OrdersTopic’
    Protocol: lambda
    Endpoint: 'arn:aws:lambda:eu-central-1:123456789:function:OrderCreation’
    FilterPolicy:
    event_type:
    - order_created
    SNS
    Topic
    https://docs.aws.amazon.com/sns/latest/dg/sns-subscription-filter-policies.html
    Cloudformation template
    {
    "event_type": [
    "order_created"
    ]
    }
    Filter policy
    

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16. Event Filtering with SNS
    17
    OrderCreation
    OrderPlacement
    OrderCancellation
    Publisher
    OrderPlacementEvent:
    Type: AWS::SNS::Subscription
    Properties:
    TopicArn: 'arn:aws:sns:eu-central-1:123456789:OrdersTopic’
    Protocol: lambda
    Endpoint: 'arn:aws:lambda:eu-central-1:123456789:function:OrderPlacement’
    FilterPolicy:
    event_type:
    - order_placed
    SNS
    Topic
    Cloudformation template
    

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17. Event Filtering with SNS
    18
    OrderCreation
    OrderPlacement
    OrderCancellation
    Publisher
    OrderCancellationEvent:
    Type: AWS::SNS::Subscription
    Properties:
    TopicArn: 'arn:aws:sns:eu-central-1:123456789:OrdersTopic’
    Protocol: lambda
    Endpoint: 'arn:aws:lambda:eu-central-1:123456789:function:OrderCancellation’
    FilterPolicy:
    event_type:
    - order_cancelled
    SNS
    Topic
    Cloudformation template
    

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18. Event Filtering with EventBridge
    19
    https://aws.amazon.com/blogs/compute/reducing-custom-code-by-using-advanced-rules-in-amazon-eventbridge/
    {
    "Source": "custom.myATMapp",
    "EventBusName": "default",
    "DetailType": "transaction",
    "Time": "Wed Jan 29 2020 08:03:18 GMT-0500",
    "Detail":{
    "action": "withdrawal",
    "location": "NY-NYC-001",
    "amount": 300,
    "result": "approved",
    "transactionId": "123456",
    "cardPresent": true,
    "partnerBank": "Example Bank",
    "remainingFunds": 722.34
    }
    }
    {
    "source": [ "custom.myATMapp" ],
    "detail-type": [ "transaction" ],
    "detail": {
    "amount": [ { "numeric": [ ">", 300 ] } ]
    }
    }
    {
    "source": [ "custom.myATMapp" ],
    "detail-type": [ "transaction" ],
    "detail": {
    "location": [ { "prefix": "NY-NYC-" } ]
    }
    }
    {
    "source": [ "custom.myATMapp" ],
    "detail-type": [ "transaction" ],
    "detail": {
    "partnerBank": [ { "exists": true } ]
    }
    }
    {
    "source": [ "custom.myATMapp" ],
    "detail-type": [ "transaction" ],
    "detail": {
    "result": [ "approved" ],
    "partnerBank": [ { "exists": false } ],
    "location": [ { "anything-but": "NY-NYC-002" }]
    }
    }
    

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19. Orchestration
    20
    the wrong way
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    

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20. Simple orchestration with Lambda destinations
    21
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    Lambda Destinations
    

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21. Simple orchestration with Lambda destinations
    22
    Amazon SNS
    Amazon
    EventBridge
    Amazon
    Cloudwatch Logs
    Amazon S3
    Amazon SES
    AWS Config
    Amazon
    CloudFormation
    AWS
    CodeCommit
    A
    S
    Y
    N
    C
    "DestinationConfig": {
    "onSuccess": {
    "Destination": "arn:aws:lambda:..."
    },
    "onFailure": {
    "Destination": "arn:aws:sqs:..."
    }
    }
    Cloudformation template
    Amazon SNS
    Amazon
    EventBridge
    Amazon
    SQS
    AWS Lambda
    if success:
    return {...}
    else:
    raise Exception(‘Failure', {...})
    function code
    Lambda function
    A
    S
    Y
    N
    C
    

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22. Advanced orchestration with Step Functions
    23
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    

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23. Advanced orchestration with Step Functions
    24
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    {
    "StartAt": "SimpleInvocation",
    "States": {
    "SimpleInvocation": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:eu-central-
    1:123456789012:function:HelloFunction",
    "Next": "Choose1or2"
    },
    

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24. Advanced orchestration with Step Functions
    25
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "Choose1or2": {
    "Type": "Choice",
    "Choices": [
    {
    "Variable": "$.foo”,
    "NumericEquals": 1,
    "Next": "Lambda1"
    },
    {
    "Variable": "$.foo",
    "NumericEquals": 2,
    "Next": "ParallelInvocation"
    }
    ],
    "Default": "Unmatched"
    },
    

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25. Advanced orchestration with Step Functions
    26
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "Lambda1": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:eu-
    central-1:123456789012:function:Lambda1",
    "Next": "SuccessOrFailure"
    },
    

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26. Advanced orchestration with Step Functions
    27
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "SuccessOrFailure": {
    "Type": "Choice",
    "Choices": [
    {
    "Variable": "$.status",
    "StringEquals": "SUCCESS",
    "Next": "SendNotification"
    },
    {
    "Variable": "$.status",
    "StringEquals": "FAILURE",
    "Next": "QueueError"
    }
    ],
    "Default": "Unmatched"
    }
    

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27. Advanced orchestration with Step Functions
    28
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "SendNotification": {
    "Type": "Succeed"
    },
    "QueueError": {
    "Type": "Fail"
    },
    

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28. Advanced orchestration with Step Functions
    29
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "ParallelInvocation": {
    "Type": "Parallel",
    "Branches": [
    {
    "StartAt": "SendApprovalRequest",
    "States": {
    "SendApprovalRequest": {
    // ...
    }
    },
    {
    "StartAt": "Loop",
    "States": {
    "Loop": {
    // ...
    }
    }
    }
    

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29. Advanced orchestration with Step Functions
    30
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "SendApprovalRequest": {
    "Type": "Task",
    "Resource":
    "arn:aws:states:::lambda:invoke.waitForTaskToken",
    "Parameters": {
    "FunctionName": "sendMailForApprovalFunction",
    "Payload": {
    "step.$": "$$.State.Name",
    "model.$": "$.data",
    "token.$": "$$.Task.Token"
    }
    },
    "ResultPath": "$.output",
    "Next": "Approved",
    "Catch": [
    {
    "ErrorEquals": [ "rejected" ],
    "ResultPath": "$.reason",
    "Next": "Rejected"
    }
    ]
    }
    SendTaskSuccess
    SendTaskFailure
    

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30. Advanced orchestration with Step Functions
    31
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    "Loop": {
    "Type": "Map",
    "ItemsPath": "$.loopItems",
    "Iterator": {
    "StartAt": "LoopLambda",
    "States": {
    "LoopLambda": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:us-east-
    1:123456789012:function:LoopFunction",
    "End": true
    }
    }
    },
    "End": true
    }
    

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31. Advanced orchestration with Step Functions
    32
    invoke
    invoke
    if (…
    )
    invoke //
    else
    if (success)
    Notify with SNS
    n * invoke
    if (failure)
    Enqueue error
    notify with SNS
    need approval
    App…
    

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32. TL;DR Single Responsibility Principle
    33
    èKeep your code focused on the business
    This is not the responsibility of a to do orchestration
    

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33. You ain’t gonna need it
    34
    Welcome in the “functionless” world !
    

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34. API Gateway Service Proxy
    35
    

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35. Ex: insert data in DynamoDB
    36
    Resource: /comments
    HTTP Method: POST
    HTTP Request Body: {
    "pageId": "example-page-id",
    "userName": "ExampleUserName",
    "message": "Example comment to be added."
    }
    Table: Comments
    commentId: String
    userName: String
    message: String
    pageId: String
    PK: commentId
    API Gateway DynamoDB
    Lambda
    var AWS = require('aws-sdk');
    var ddb = new AWS.DynamoDB({apiVersion: '2012-08-10'});
    exports.handler = async function(event, context) {
    var params = {
    TableName: 'Comments’,
    Item: {
    'commentId' : {
    S: 'randomid’
    },
    'pageId' : {
    S: event.pageId
    },
    'userName' : {
    S: event.userName
    },
    'message' : {
    S: event.message
    }
    }
    };
    ddb.putItem(params, function(err, data) {
    if (err) {
    console.log("Error", err);
    } else {
    console.log("Success", data);
    }
    });
    }
    

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36. Ex: insert data in DynamoDB
    37
    Resource: /comments
    HTTP Method: POST
    HTTP Request Body: {
    "pageId": "example-page-id",
    "userName": "ExampleUserName",
    "message": "Example comment to be added."
    }
    Table: Comments
    commentId: String
    userName: String
    message: String
    pageId: String
    PK: commentId
    API Gateway DynamoDB
    

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37. Ex: insert data in DynamoDB
    38
    Resource: /comments
    HTTP Method: POST
    HTTP Request Body: {
    "pageId": "example-page-id",
    "userName": "ExampleUserName",
    "message": "Example comment to be added."
    }
    Table: Comments
    commentId: String
    userName: String
    message: String
    pageId: String
    PK: commentId
    API Gateway DynamoDB
    

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38. Ex: insert data in DynamoDB
    39
    Resource: /comments
    HTTP Method: POST
    HTTP Request Body: {
    "pageId": "example-page-id",
    "userName": "ExampleUserName",
    "message": "Example comment to be added."
    }
    Table: Comments
    commentId: String
    userName: String
    message: String
    pageId: String
    PK: commentId
    API Gateway DynamoDB
    

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39. Ex: insert data in DynamoDB
    40
    Resource: /comments
    HTTP Method: POST
    HTTP Request Body: {
    "pageId": "example-page-id",
    "userName": "ExampleUserName",
    "message": "Example comment to be added."
    }
    Table: Comments
    commentId: String
    userName: String
    message: String
    pageId: String
    PK: commentId
    API Gateway DynamoDB
    

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40. Ex: insert data in DynamoDB
    41
    Resource: /comments
    HTTP Method: POST
    HTTP Request Body: {
    "pageId": "example-page-id",
    "userName": "ExampleUserName",
    "message": "Example comment to be added."
    }
    Table: Comments
    commentId: String
    userName: String
    message: String
    pageId: String
    PK: commentId
    API Gateway DynamoDB
    

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41. Use with caution
    42
    • Not a generic design pattern, not
    always applicable
    • Apply when the lambda is a
    passthrough (no business code, just
    mapping)
    • Mapping can sometimes be complex
    (Velocity Template Language)
    

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42. Step Function integrations
    43
    "QueueError": {
    "Type": "Task",
    "Resource": "arn:aws:states:::sqs:sendMessage",
    "Parameters": {
    "QueueUrl": "https://sqs.eu-central-1.amazonaws.com/123456789012/myQueue",
    "MessageBody.$": "$.input.message"
    },
    "End": true
    },
    "SendNotification": {
    "Type": "Task",
    "Resource": "arn:aws:states:::sns:publish",
    "Parameters": {
    "TopicARN": "arn:aws:sns:eu-central-
    1:123456789012:myTopic",
    "Subject": "Lambda1 has successfully finish its job",
    "Message.$" : "$.input.message"
    },
    "End": true
    },
    SQS
    SNS
    

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43. Step Function integrations
    44
    AWS Batch Amazon DynamoDB Amazon ECS / Fargate Amazon EMR AWS Glue
    Amazon SageMaker Amazon SNS Amazon SQS AWS Step Functions
    AWS Lambda
    AWS CodeBuild
    

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44. TL;DR You Ain’t Gonna Need It
    45
    è is not always needed
    You can save costs and
    optimize performance
    when functions are just passthrough/mapping
    

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45. Keep it simple stupid
    46
    Lighten your functions
    

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46. Keep your functions simple & stupid
    nano functions
    API GW
    /res1
    /res2
    /res3
    = 1 handler (1 function)
    = 1 file
    Not that stupid
    so they need
    sisters to do the job !
    

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47. Keep your functions simple & stupid
    nano functions
    API GW
    /res1
    /res2
    /res3
    = 1 handler (1 function)
    = 1 file
    function-lith
    API GW
    /{proxy}
    /res1
    /res2
    /res3
    That’s really not simple & stupid!
    = 1 handler (1 function)
    = 1 file
    

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48. Keep your functions simple & stupid
    nano functions
    API GW
    /res1
    /res2
    /res3
    function-lith
    API GW
    /{proxy}
    /res1
    /res2
    /res3
    = 1 handler (1 function)
    = 1 file
    fat functions
    API GW
    /res1
    /res2
    /res3
    = 3 handlers (3 functions)
    = 1 file
    = 1 handler (1 function)
    = 1 file
    

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49. Keep your functions simple & stupid
    50
    nano functions
    API GW
    /res1
    /res2
    /res3
    function-lith
    API GW
    /{proxy}
    /res1
    /res2
    /res3
    fat functions
    = 1 handler (1 function)
    = 1 file
    API GW
    = 3 handler (3 functions)
    = 1 file
    micro functions
    API GW
    /res1
    /res2
    /res3
    /res1
    /res2
    /res3
    = 1 handler (1 function)
    = 1 file
    = 1 handler (1 function)
    = 1 file
    

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50. Keep your functions simple & stupid
    https://github.com/cdk-patterns/serverless/tree/master/the-lambda-trilogy
    Potential duplicated code ++
    Cognitive burden ++
    Coupled functions
    Coupled deployments
    nano functions
    API GW
    /res1
    /res2
    /res3
    function-lith
    API GW
    /{proxy}
    /res1
    /res2
    /res3
    fat functions
    = 1 handler (1 function)
    = 1 file
    API GW
    = 3 handler (3 functions)
    = 1 file
    micro functions
    /res1
    /res2
    /res3
    = 1 handler (1 function)
    = 1 file
    API GW
    /res1
    /res2
    /res3
    = 1 handler (1 function)
    = 1 file
    Stupidity Complexity
    FAAS?
    Longer cold starts ++
    Risk of blast radius
    Framework dependent
    Longer cold starts
    Risk of blast radius
    Potential duplicated code
    Cognitive burden
    

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51. TL;DR Keep it simple stupid
    52
    Lighter functions
    =
    Easier to test and maintain
    Faster to start: less cold start
    More scalable: higher throughput
    More secure: less permission needed
    

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52. Conclusion
    No function is easier to manage
    than ‘no function’
    – me
    è If you can do better without a
    function, just do it
    è Else, apply software
    craftsmanship principles
    (clean code, tests, code reviews…)
    “No server is easier to
    manage than ‘no server’”
    – Werner Vogels
    

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53. Thank You
    @jeromevdl
    https://tinyurl.com/ydeowzut
    2-minutes survey:
    

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54. Appendix
    

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55. AWSTemplateFormatVersion: 2010-09-09
    Resources:
    API:
    Type: AWS::ApiGateway::RestApi
    Properties:
    Name: !Sub ${AWS::StackName}-api-
    ${AWS::AccountId}
    APIDeployment:
    Type: AWS::ApiGateway::Deployment
    Properties:
    RestApiId: !Ref API
    StageName: prod
    DependsOn:
    - ListBucketAPI
    APIBucketResource:
    Type: AWS::ApiGateway::Resource
    Properties:
    ParentId: !GetAtt API.RootResourceId
    PathPart: "{bucket}"
    RestApiId: !Ref API
    ListBucketAPI:
    Type: AWS::ApiGateway::Method
    Properties:
    HttpMethod: GET
    ResourceId: !Ref APIBucketResource
    RestApiId: !Ref API
    AuthorizationType: NONE
    Integration:
    Credentials: 'arn:aws:iam::1234567890:role/role-demo-api-gw-s3-integration’
    IntegrationHttpMethod: GET
    IntegrationResponses:
    - StatusCode: "200"
    PassthroughBehavior: WHEN_NO_MATCH
    RequestParameters:
    integration.request.header.Content-Type: method.request.header.Content-Type
    integration.request.header.x-amz-acl: "'authenticated-read’”
    integration.request.path.bucket: method.request.path.bucket
    Type: AWS
    Uri: !Sub arn:aws:apigateway:${AWS::Region}:s3:path/{bucket}
    MethodResponses:
    - StatusCode: "200"
    RequestParameters:
    method.request.path.bucket: true
    method.request.header.Content-Type: false
    API Gateway & S3 sample
    https://docs.aws.amazon.com/apigateway/latest/developerguide/integrating-api-with-aws-services-s3.html
    

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56. 57
    Advanced orchestration with Step Functions
    {
    "StartAt": "SimpleInvocation",
    "States": {
    "SimpleInvocation": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:eu-central-1:123456789012:function:HelloFunction",
    "Next": "Choose1or2"
    },
    "Choose1or2": {
    "Type": "Choice",
    "Choices": [
    {
    "Variable": "$.foo",
    "NumericEquals": 1,
    "Next": "Lambda1"
    },
    {
    "Variable": "$.foo",
    "NumericEquals": 2,
    "Next": "ParallelInvocation"
    }
    ],
    "Default": "Unmatched"
    },
    "Lambda1": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:eu-central-1:123456789012:function:Lambda1",
    "Next": "SuccessOrFailure"
    },
    "SuccessOrFailure": {
    "Type": "Choice",
    "Choices": [
    {
    "Variable": "$.status",
    "StringEquals": "SUCCESS",
    "Next": "SendNotification"
    },
    {
    "Variable": "$.status",
    "StringEquals": "FAILURE",
    "Next": "QueueError"
    }
    ],
    "Default": "Unmatched"
    },
    "SendNotification": {
    "Type": "Succeed"
    },
    "QueueError": {
    "Type": "Fail"
    },
    "ParallelInvocation": {
    "Type": "Parallel",
    "Branches": [
    {
    "StartAt": "SendApprovalRequest",
    "States": {
    "SendApprovalRequest": {
    "Type": "Task",
    "Resource": "arn:aws:states:::lambda:invoke.waitForTaskToken",
    "Parameters": {
    "FunctionName": "sendMailForApprovalFunction",
    "Payload": {
    "step.$": "$$.State.Name",
    "model.$": "$.data",
    "token.$": "$$.Task.Token"
    }
    },
    "ResultPath": "$.output",
    "Next": "Approved",
    "Catch": [
    {
    "ErrorEquals": [ "rejected" ],
    "ResultPath": "$.reason",
    "Next": "Rejected"
    }
    ]
    },
    "Approved": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:eu-central-1:123456789012:function:Lambda1",
    "End": true
    },
    "Rejected": {
    "Type": "Fail"
    }
    }
    },
    {
    "StartAt": "Loop",
    "States": {
    "Loop": {
    "Type": "Map",
    "ItemsPath": "$.loopItems",
    "Iterator": {
    "StartAt": "LoopLambda",
    "States": {
    "LoopLambda": {
    "Type": "Task",
    "Resource": "arn:aws:lambda:us-east-1:123456789012:function:LoopFunction",
    "End": true
    }
    }
    },
    "End": true
    }
    }
    }
    ],
    "End": true
    },
    "Unmatched": {
    "Type": "Fail",
    "Error": "DefaultStateError",
    "Cause": "No Matches!"
    }
    }
    }
    

    View Slide