© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building Advanced Serverless Applications with AWS Step Functions Danilo Poccia Technical Evangelist [email protected] @danilop danilop 

λ λ λ DBMS λ λ λ λ λ λ λ λ λ Queue Modern serverless app 

Modern serverless app 

"I want to sequence functions" "I want to select functions based on data" "I want to retry functions" "I want try/catch/finally" Functions into apps "I have code that runs for hours" "I want to run functions in parallel" 

Coordination must-haves • Scales out • Doesn’t lose state • Deals with errors/timeouts • Easy to build & operate • Auditable 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. 

Application Lifecycle in AWS Step Functions Visualize in the Console Define in JSON Monitor Executions 

Define in JSON and Then Visualize in the Console { "Comment": "Hello World Example", "StartAt" : "HelloWorld", "States" : { "HelloWorld" : { "Type" : "Task", "Resource" : "${lambdaArn}", "End" : true } } } 

Execute One or One Million Start End HelloWorld Start End HelloWorld Start End HelloWorld Start End HelloWorld Start End HelloWorld Start End HelloWorld Start End HelloWorld Start End HelloWorld 

Maximum Execution Time AWS Lambda Functions 5 minutes AWS Step Functions State Machines 1 year 

Monitor Executions from the Console 

Seven State Types Task A single unit of work Choice Adds branching logic Parallel Fork and join the data across tasks Wait Delay for a specified time Fail Stops an execution and marks it as a failure Succeed Stops an execution successfully Pass Passes its input to its output 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. ExtractImageMetadata ImageTypeCheck TransformMetadata Rekognition Thumbnail StoreMetadata Start End Synchronous task Task: a single unit of work Synchronous: Lambda { "ExtractImageMetadata": { "Type": "Task", "Resource": "arn:aws:lambda:mars-ter …", … } } 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. ExtractImageMetadata TransformMetadata Rekognition Thumbnail StoreMetadata Start End Task: a single unit of work Asynchronous: "Activity Task", Polled by workers { "ExtractImageMetadata": { "Type": "Task", "Resource": "arn:aws:states:mars-ter …", … } } Asynchronous task 

API actions on activity task Register Activity Task - Returns ARN Poll For task (by ARN) Report Success Report Failure Report Heartbeat 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. O pen Source A pache License https://states-language.net/spec.html 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Integrate with other AWS services • Create state machines and activities with AWS CloudFormation • Call AWS Step Functions with Amazon API Gateway • Start state machines in response to events, or on a schedule, with Amazon CloudWatch Events • Monitor state machine executions with Amazon CloudWatch • Log API calls with AWS CloudTrail • Start state machine using AWS Lambda 

Build Visual Workflows from State Types Task Choice Fail Parallel 

Serverless Human Approval Tasks https://aws.amazon.com/blogs/compute/ implementing-serverless-manual-approval-steps-in-aws-step-functions-and-amazon-api-gateway/ 

Image Recognition and Processing Backend Task Choice Fail Parallel https://github.com/awslabs/lambda-refarch-imagerecognition 

Amazon EBS Snapshot Management State Machine State Machine create-snapshot complete event copy-snapshot complete event Primary Region DR Region Parallel State Choice Tag Snapshot Count Snapshots CopyToDRRegion Success State Delete Snapshots Choice Tag SnapshotCopy Count Snapshots Pass State Delete Snapshots Notification Topic Errors Sent to SNS Notification Topic Errors Sent to SNS https://github.com/awslabs/aws-step-functions-ebs-snapshot-mgmt 1. Tag 2. Count 3. Copy to DR region 4. Delete Expired Whenever a new EBS snapshot completes: State Machines invoked by Amazon CloudWatch Events 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Demo: AWS Step Functions 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. © 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Case Studies 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Vending Pass problem 1. Thirsty consumer presents card, can buy a drink with Vending Pass or debit 2. But mobile wallet display can get out of sync under certain conditions 3. 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Vending Pass problem • Just wait for backend to catch up • Create a two-step state machine: • Wait (90 seconds) • Update mobile wallet • Cheap and simple! 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. • Transcode 350 clips/day into 14 formats, fast • It’s all done with FFmpeg. The processing time is just about 100% of the video length • Aargh! Video processing problem 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. • Derive keyframe locations within the source • Split the source at the keyframes • Process segments (typically 0.5 sec per) in parallel • Concatenate segments • Elapsed time: ~20 min down to ~2 minutes Video processing solution 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Details How to get from Lambda to Amazon S3: ffmpeg -f concat –safe 0 -I filelist.ffcat –c copy pipe:0 | aws s3 cp – s3://output-bucket/output-file.mp4 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Details 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Let’s peek at the code! "Init": { "Type": "Pass", "ResultPath": "$.operation", "Result": "prepare-split", "Next": "PrepareSplit" }, "PrepareSplit": { "Type": "Task", "Resource": "arn:…:ffmpeg-18HFP9FXFL6P", "Next": "SplitPrepared" }, "SplitPrepared": { "Type": "Pass", "ResultPath": "$.operation", "Result": "perform-split", "Next": "PerformSplit" }, "PerformSplit": { "Type": "Task", "Resource": "arn:…:ffmpeg-18HFP9FXFL6P", "Next": "SplitPerformed" }, "SplitPerformed": { "Type": "Pass", "ResultPath": "$.operation", "Result": "poll-results", "Next": "PreparePoll" }, "PreparePoll": { "Type": "Pass", "ResultPath": "$.pollstatus", "Result": "Submitted", "Next": "WaitForResults" } Hmm…the same function, throughout 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Let’s peek at the code! "WaitForResults": { "Type": "Choice", "Choices": [ { "Variable": "$.pollstatus", "StringEquals": "Complete", "Next": "SegmentsCompleteState" }, { "Variable": "$.pollstatus", "StringEquals": "Progressing", "Next": "loop_wait_using_seconds" }, { "Variable": "$.pollstatus", "StringEquals": "Submitted", "Next": "loop_wait_using_seconds" } ] } "loop_wait_using_seconds": { "Type": "Wait", "Seconds": 3, "Next": "loop" }, "loop": { "Type": "Task", "Resource": "arn:…:ffmpeg-18HFP9FXFL6P", "Next": "WaitForResults" }, "SegmentsCompleteState": { "Type": "Pass", "ResultPath": "$.operation", "Result": "concat", "Next": "CompleteState" }, "CompleteState": { "Type": "Task", "Resource": " arn:…:ffmpeg-18HFP9FXFL6P", "End": true } Counts the segments, sets $.pollstatus Stitches segments together 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Takeaways Use Amazon S3 data events to trigger parallel Lambda processing: win Use Amazon S3 URLs to stream video to Lambda: win Scaling to 1,000 Lambdas, rather than 1,000 EC2 instances: win Process video segments in parallel: win 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. 1. Sometimes Lambda is best, sometimes ECS 2. Previously, all tied together with pub/sub and procedural code 3. Aargh! Media transcoding problem 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. 1. Use state machines to pick execution engine 2. Use CloudWatch Events for messaging and triggering Step Functions Media transcoding solution 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Let’s peek at the code! "Encoder Decider": { "Type": "Choice", "Default": "Run ECS Encoder", "Choices": [ { "Next": "Run Lambda Encoder", "And": [ { "Variable": "$.asset.size", "NumericLessThanEquals": 2000000000 }, { "Variable": "$.asset.duration_ms", "NumericLessThanEquals": 10000 } ] } ] } Hmm…maybe "Default" should have been called "Else" 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Let’s peek at the code! "Run ECS Encoder": { "Type": "Task", "Resource": "arn:…SubmitECSTask", "Retry": [ { "ErrorEquals": [ "NoResourceInCluster" ], "IntervalSeconds": 5, "MaxAttempts": 720, "BackoffRate": 1.0 } ], "ResultPath": "$.task", "Next": "Wait X Seconds" } Hmm…every 5 seconds, for an hour?! "Wait X Seconds": { "Type": "Wait", "SecondsPath": "$.task.wait_time", "Next": "Get ECS Task Status" }, "Get ECS Task Status": { "Type": "Task", "Resource": "arn:…ECSTaskStatus", "Next": "ECS Task Complete?", "ResultPath": "$.task.status" } 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Let’s peek at the code! "ECS Task Complete?": { "Type": "Choice", "Choices": [ { "And": [ { "Variable": "$.task.status", "StringEquals": "FAILED" }, { "Variable": "$.task.attempt", "NumericGreaterThanEquals": 3 } ], "Next": "Fire Failed Event" }, { "Variable": "$.task.status", "StringEquals": "FAILED", "Next": "Run ECS Encoder" }, { "Variable": "$.task.status", "StringEquals": "SUCCEEDED", "Next": "Fire Successful Event" } ], "Default": "Wait X Seconds" }, "Fire Successful Event": { "Type": "Task", "Resource": "aws:…SendSuccessfulEvent", "End": true }, "Fire Failed Event": { "Type": "Task", "Resource": "aws:…SendFailedEvent", "End": true } These fire CloudWatch Events 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Takeaways Passing a correlation ID through a complex serverless app: win SAM to make code changes auditable: win Code Pipeline for CI/CD: win CloudWatch Events pattern matching: win 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. More state machines Image Recognition and Processing Backend EBS Snapshot Management https://aws.amazon.com/step-functions/getting-started 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. What are you building? #stepfunctions https://console.aws.amazon.com/states/ 

© 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. © 2018, Amazon Web Services, Inc. or its Affiliates. All rights reserved. Building Advanced Serverless Applications with AWS Step Functions Danilo Poccia Technical Evangelist [email protected] @danilop danilop