Building Advanced Serverless Applications

1. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
Paul Maddox
Developer Technologies, AWS
April 2018
Building Advanced Serverless Applications
with AWS Step Functions (starting 15:45)
Twitter: @paulmaddox
Email: pmaddox@amazon.com

2. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
About me
Paul Maddox
Developer Technologies
Amazon Web Services
• 16 years of dev, SRE, and systems architecture background
• 7 of 7 AWS certifications
• Developer: Go/Java/C/Node
• Creator of AWS SAM Local
Twitter: @paulmaddox
Email: pmaddox@amazon.com
@paulmaddox

3. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
"Serverless requires me to
develop in a completely different
way"
Myth Busting Time…

4. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
"Serverless isn't for
advanced applications"
Myth Busting Time…

5. λλ
λ
DBMS
λ
λ
λ
λ
λ
λ λ
λ
λ
Queue
Modern
serverless
app

6. Modern
serverless
app

7. "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"

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

9. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
“Any sufficiently complicated model class contains an
ad-hoc, informally-specified, bug-ridden, slow
implementation of half of a state machine.”
http://raganwald.com/2018/02/23/forde.html

10. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
The problem is that you almost never create an object
fully formed with all the behaviour it is ever going to
need, rather you build it up over time.
https://www.skorks.com/2011/09/why-developers-never-use-state-machines/

11. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.

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

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

14. 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

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

16. Monitor Executions from the Console

17. 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

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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 …",
…
}
}

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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

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

21. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
O
pen
Source
A
pache
License
https://states-language.net/spec.html

22. © 2017, 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

23. Build Visual Workflows from State Types
Task
Choice
Fail
Parallel

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

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

26. 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

27. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.© 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
Who's using this in production?

28. © 2017, 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.

29. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
Vending Pass problem
• Use Step Functions to co-
ordinate and verify state
• Cheap and simple!

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• 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

31. © 2017, 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

32. © 2017, 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

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Details

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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

35. © 2017, 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

36. © 2017, 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

37. © 2017, 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

38. © 2017, 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

39. © 2017, 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"

40. © 2017, 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"
}

41. © 2017, 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

42. © 2017, 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: winCloudWatch
Events pattern
matching: win

43. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
More state machines
Image Recognition and Processing BackendEBS Snapshot Management
https://aws.amazon.com/step-functions/getting-started

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What are you building? #stepfunctions
https://console.aws.amazon.com/states/

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Thank you!
Twitter: @paulmaddox
Email: pmaddox@amazon.com@paulmaddox