Learning Objectives: - Learn how to build and operate serverless applications using Step Functions state machines - See reference architectures, blueprints, and example use cases to get started quickly - Know how to integrate Step Functions with other AWS services to develop and deploy applications faster Are you building a serverless application with two or more Lambda functions? AWS Step Functions makes it easy to coordinate multiple functions and microservices as a series of steps using visual workflows. You create Step Functions state machines to specify and reliably step through the functions of your application at scale. In this deep-dive session, we will show how to use AWS CloudFormation and the AWS Serverless Application Model to deploy Step Functions state machines, AWS Lambda functions, and IAM roles and policies. We will demonstrate how Step Functions state machines orchestrate state transitions and error handling, and how state input/output works.

1. © 2017, Amazon Web Services, Inc. or its Affiliates. All rights reserved.
Andy Katz, Senior Product Manager
July 2017
Serverless Orchestration
With AWS Step Functions

2. FROM MONOLITHS TO MICROSERVICES TO FUNCTIONS
2
Enterprise
Resource
Planning
𝝺Finance
Inventory
Manu-
facturing
𝝺
𝝺 𝝺
Sales
AWS STEP FUNCTIONS

3. TURNING FUNCTIONS INTO APPS
3AWS STEP FUNCTIONS

4. “I WANT TO SEQUENCE FUNCTIONS”
4AWS STEP FUNCTIONS

5. “I WANT TO RUN FUNCTIONS IN PARALLEL”
5AWS STEP FUNCTIONS

6. “I WANT TO SELECT FUNCTIONS BASED ON DATA”
6AWS STEP FUNCTIONS
?

7. IS THIS YOU?
7AWS STEP FUNCTIONS
“I WANT TO RETRY
FUNCTIONS”
“I WANT
TRY / CATCH / FINALLY”
“I HAVE CODE THAT RUNS FOR HOURS”

8. COORDINATION BY FUNCTION CHAINING
8AWS STEP FUNCTIONS

9. COORDINATION BY DATABASE
9AWS STEP FUNCTIONS

10. COORDINATION BY QUEUES
10AWS STEP FUNCTIONS

11. COORDINATION “MUST HAVES”
11AWS STEP FUNCTIONS
Scales Out Does Not Lose
State
Handles
Errors/Timeouts
Easy to Build/Operate Auditable

12. AWS STEP FUNCTIONS
12AWS STEP FUNCTIONS
…makes it easy to coordinate the
components of distributed applications
using visual workflows

13. BENEFITS OF AWS STEP FUNCTIONS
13AWS STEP FUNCTIONS
Diagnose and
debug problems
faster
Adapt to change
Easy to connect and
coordinate
distributed components
and microservices to
quickly create apps
Manages the
operations and
infrastructure of
service coordination
to ensure availability
at scale, and
under failure
Productivity Agility Resilience

14. APPLICATION LIFE CYCLE IN AWS STEP FUNCTIONS
14AWS STEP FUNCTIONS
Visualize in the
Console
Define in JSON Monitor
Executions

15. DEFINE IN JSON AND THEN VISUALIZE IN THE CONSOLE
15AWS STEP FUNCTIONS
{
”Comment”: “Hello World Example",
"StartAt” : "HelloWorld”,
"States” : {
"HelloWorld” : {
"Type” : "Task",
"Resource” :
"arn:aws:lambda:REGION:ACCOUNT_ID:function:FUNCTION_NAME
”,
"End” : true
}
}
}

16. EXECUTE ONE OR A MILLION
16AWS STEP FUNCTIONS
Start
End
HelloWorld
Start
End
HelloWorld
Start
End
HelloWorld
Start
End
HelloWorld
Start
End
HelloWorld
Start
End
HelloWorld
Start
End
HelloWorld
Start
End
HelloWorld

17. MONITOR EXECUTIONS FROM THE CONSOLE
17AWS STEP FUNCTIONS

18. USE THROUGH THE API
18AWS STEP FUNCTIONS
Create
Upload state machines defined in JSON
Register activity workers
StartExecution Returns Execution ID
StopExecution
Stops a running state machine with
Execution ID
List All state machines, executions, and activities
Describe
Individual state machines, executions, and
activities

19. SEVEN STATE TYPES
19AWS STEP FUNCTIONS
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

20. BUILD VISUAL WORKFLOWS USING STATE TYPES
20AWS STEP FUNCTIONS
Task
Choice
Fail
ParallelMountains
People
Snow

21. TASK STATES: POLL OR PUSH
21AWS STEP FUNCTIONS
AWS Lambda
…On-premises
AWS container, EC2
instance, or… Long poll
Push

22. TASK STATE: DISPATCH WORK
22AWS STEP FUNCTIONS
{
"StartAt": "HelloWorld",
"States": {
"HelloWorld": {
"Type": "Task",
"Resource":"arn:aws:lambda:REGION:
ACCOUNT_ID:function:FUNCTION_NAME",
"End": true
}
}
}

23. RETRY FAILURES OF TASK STATES
23AWS STEP FUNCTIONS
"HelloWorld": {
"Type": "Task",
…
"Retry": [
{
"ErrorEquals": [”States.TaskFailed"],
"IntervalSeconds": 1,
"MaxAttempts": 2,
"BackoffRate": 2.0
},
… ]

24. CATCH FAILURES OF TASK STATES
24AWS STEP FUNCTIONS
"HelloWorld": {
"Type": "Task",
…
"Catch": [
{
"ErrorEquals": [”AllYourBaseAreBelongToUs"],
"Next": "CustomErrorFallback"
},
{
"ErrorEquals": ["States.TaskFailed"],
"Next": "ReservedTypeFallback"
… ]
{

25. CATCH FAILURE OF TASK STATE
25AWS STEP FUNCTIONS

26. FUNCTION ERROR HANDLING: PYTHON
26AWS STEP FUNCTIONS
{
"StartAt": "Create Account",
"States": {
"CreateAccount": {
"Type": "Task",
"Resource": "arn:aws:lambda:us-east-1:123456789012:function:CreateAccount",
"Next": "Send Welcome Email",
"Catch": [
{
"ErrorEquals": ["AccountAlreadyExistsException"],
"Next": "Suggest AccountName"
}
]
},
…
}
def create_account(event, context):
class AccountAlreadyExistsException(Exception):
pass
raise AccountAlreadyExistsException('Account is in use!')

27. CHOICE STATE FOR BRANCHING LOGIC
27AWS STEP FUNCTIONS
"ChoiceState": {
"Type" : "Choice",
"Choices": [
{
"Variable": "$.foo",
"NumericEquals": 1,
"Next": "FirstMatchState"
},
{
"Variable": "$.foo",
"NumericEquals": 2,
… ]

28. PARALLEL STATES TO FORK AND JOIN PROCESSES
28AWS STEP FUNCTIONS
"Parallel": {
"Type": "Parallel",
"Next": "Final State",
"Branches": [
{
"StartAt": "Wait 20s",
"States": {
"Wait 20s": {
"Type": "Wait",
"Seconds": 20,
"End": true
}
... ]

29. WAIT STATE FOR TIMED DELAY
29AWS STEP FUNCTIONS
"wait_using_seconds": {
"Type": "Wait",
"Seconds": 10,
"Next": "wait_using_timestamp"
},
"wait_using_timestamp": {
"Type": "Wait",
"Timestamp": "2015-09-
04T01:59:00Z",
"Next": "wait_using_timestamp_path"
},
…

30. SIX BLUEPRINTS IN THE CONSOLE
30AWS STEP FUNCTIONS

31. CUSTOMER USE CASES
31AWS STEP FUNCTIONS
• Workflow/Order management
• Batch processing
• Shell-script replacement
• Enterprise application workflows
• Data gathering and processing

32. SYNCHRONIZE S3 BUCKETS
32AWS STEP FUNCTIONShttps://aws.amazon.com/blogs/compute/synchronizing-
amazon-s3-buckets-using-aws-step-functions/

33. DATA PROCESSING WITH AWS BATCH OR AMAZON EMR
33AWS STEP FUNCTIONS
https://tinyurl.com/ybvcwysc

34. SCHEDULE STARTS ON CLOUDWATCH EVENTS
34AWS STEP FUNCTIONS

35. EVENT DRIVEN EBS SNAPSHOT MANAGEMENT
35AWS STEP FUNCTIONS
https://github.com/awslabs/aws-step-functions-ebs-snapshot-
mgmt

36. HUMAN APPROVAL TASKS
36AWS STEP FUNCTIONS
https://aws.amazon.com/step-functions/getting-started/

37. ANATOMY OF A STATE
37AWS STEP FUNCTIONS
State [x]"InputPath" "ResultPath" "OutputPath"
Input
Output
InputPath and OutputPath processes JSON
ResultPath places results into JSON

38. INPUT PROCESSING
38AWS STEP FUNCTIONS
{
"title": "Numbers to add",
"numbers": [ 3, 4 ]
}
{
"Type": "Task",
"InputPath": "$.numbers",
"Resource": "arn:aws:lambda…"
…
[ 3, 4 ]
Raw input:
State spec:
Task input:

39. WHAT HAPPENS WHEN…
39AWS STEP FUNCTIONS
Q: InputPath not provided?
A: State gets raw input as-is.
Q: InputPath is null?
A: State gets an empty JSON object: {}
Q: InputPath produces plural output?
A: State gets it wrapped in a JSON array.

40. RESULT PLACEMENT
40AWS STEP FUNCTIONS
{
"title": "Numbers to add",
"numbers": [ 3, 4 ]
}
{
"Type": "Task",
"InputPath": "$.numbers",
"ResultPath": "$.sum”,
…
Raw input:
State spec:
Output:
{
"title": "Numbers to add",
"numbers": [ 3, 4 ],
"sum": 7
}

41. OUTPUT PROCESSING
41AWS STEP FUNCTIONS
{
"title": "Numbers to add",
"numbers": [ 3, 4 ]
}
{
"Type": "Task",
"InputPath": "$.numbers",
"ResultPath": "$.sum”,
"OutputPath": “$.title, $.sum”
Raw input:
State spec:
Output:
{
"title": "Numbers to add",
"sum": 7
}

42. WHAT HAPPENS WHEN…
42AWS STEP FUNCTIONS
Q: ResultPath not provided?
A: Input discarded, raw output used.
Q: ResultPath is null?
A: State input is state output.
Q: ResultPath produces plural output?
A: Not allowed, validator won’t accept.

43. (DEMO)

44. AWS INTEGRATION
44AWS STEP FUNCTIONS
• AWS CloudFormation
• AWS CloudTrail
• Amazon CloudWatch
• Amazon CloudWatch Events
• Amazon API Gateway

45. COMMON PATTERNS
45AWS STEP FUNCTIONS
• Use Choice states for looping
• Use Pass states to inject values into state
• Manage API uncertainty with Retries
• Use Step Functions where shell scripts would make you nervous
• Parallelize where possible
• Write mini Lambda-functions for JSON mangling
• Generate state machine JSON from building blocks

46. TIPS
46AWS STEP FUNCTIONS
• Don’t try/catch too much at the Lambda level.
• Don’t call Lambda from Lambda without asking:
Can this be done by Step Functions?
• Do decompose larger applications/scripts into an SFN state machine and a
set of Lambda functions.
• Do use SAM to manage many small Lambda functions.
• Do automate your state machine JSON builds.

47. Thank you!
Console: https://aws.amazon.com/step-functions
Resources: https://aws.amazon.com/step-functions/getting-started