© 2016, Amazon Web Services, Inc. or its Affiliates. All rights reserved.

Tim Bray, Senior Principal Engineer

December 1, 2016

NEW LAUNCH!

Serverless Apps with

AWS Step Functions

SVR201

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λDBMS

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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 by method call

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Coordination by function chaining

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Coordination by database

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Coordination by queues

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Coordination must-haves

• Scales out

• Doesn’t lose state

• Deals with errors/timeouts

• Easy to build & operate

• Auditable

“State Machine”(noun)

1. A concept used by CompSci

profs for torturing

undergrads, full of arcane

math.

2. A practical way to build and

manage modern Serverless

Cloud apps.

Dictionary

“I want to sequence functions”

AWS Step Functions, we can easily change and iterate on the application workflow of our food delivery service in order to optimize operations and continually improve delivery times. AWS Step Functions lets us dynamically scale the steps in our food delivery algorithm so we can manage spikes in customer orders and meet demand.

Mathias Nitzsche, CTO, foodpanda

“

var Twit = require('twit');

var T = new Twit(require('botfiles/config.js'));

exports.handler = function myBot(event, context, callback) {

var list = event.inputList;

var textToTweet = list.shift();

var output = { inputList: list }

T.post('statuses/update',

{ status: textToTweet }, function(err, reply) {

if (err) {

console.log('error:', err); context.fail();

} else {

console.log('tweet:', reply); callback(null, output);

}

});

};

(Demo)

How it works – API-level

Create State Machine – input is a

machine spec in a JSON DSL

Run Machine – input JSON blob,

returns Execution ID

List Executions

Describe Execution

Stop Execution

How it works – API-level

Create State Machine – input is a

machine spec in a JSON DSL

Run Machine – input JSON blob,

returns Execution ID

List Executions

Describe Execution

Stop Execution

https://states-language.net/spec

“I want to select functions based on data”

With AWS Step Functions, it was easy to build a multi-step product

updating system to ensure our database and website always have the

latest price and availability information.

AWS Step Functions let us replace a manual updating process with an

automated series of steps, including built-in retry conditions and error

handling, so we can reliably scale before a big show, and keep pace

with rapidly changing fashions.

Jared Browarnik, CTO, TheTake

“

"ChoiceState": {

"Type" : "Choice",

"Choices": [

{

"Variable": "$.productSource",

"StringEquals": "screen-scrape",

"Next": "ScreenScrapeState"

},{

"Variable": "$.productSource",

"StringEquals": "vendor-a",

"Next": "VendorA"

},{

"Variable": "$.productSource",

"StringEquals": "vendor-b",

"Next": "VendorB"

},

{

"Variable": "$.productSource",

"StringEquals": "vendor-c",

"Next":"VendorC"

},{

"Variable": "$.productSource",

"StringEquals": "updateProduct",

"Next":"UpdateProduct"

}

],

"Default": "ScreenScrapeState”

}

“I want to retry functions”

We get transient errors from a RESTful

service we depend on, once every four

or five times we call it. But if we keep

retrying, it eventually works.

“

{

"Comment": "Call out to a RESTful service",

"StartAt": "Call out",

"States": {

"Call out": {

"Type": "Task",

"Resource":

"arn:aws:lambda:eu-central-1:123456789012:function:RestCallout",

"Retry": [

{ "ErrorEquals": [ "HandledError" ], "MaxAttempts": 10 }

],

"End": true

}

}

}

(Demo)

“I want to run functions in parallel”

We want to send the captured image to

three OCR providers and take the result

with the highest confidence value.“

"Send for OCR": {

"Type": "Parallel",

"Next": "Pick result",

"Branches": [

{

"StartAt": "Prep1",

"States": {

"Prep1": {

"Type": "Pass",

"Result": { "inputList": [ "OCR Provider 1" ] },

"Next": "Go1"

},

"Go1": {

"Type": "Task",

"Resource": "arn:aws:lambda:eu-central-1:123456789012:function:StatesBot",

"End": true

}

}

Where does transient application

state live?

In the machine, in JSON texts

passing from state to state.A:

Q:

Input processing

{

"title": "Numbers to add",

"numbers": [ 3, 4 ]

}

{

"Type": "Task",

"InputPath": "$.numbers",

"Resource": "arn:aws:lambda…"

…

[ 3, 4 ]

Raw input:

State spec:

Task input:

Input processing

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.

Result placement{

"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

}

Result placement

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.

“I want try/catch/finally”

AWS Step Functions makes it simple to coordinate information

from many different infrastructure systems using easy to design

workflows and create a more intelligent monitoring system for our

Platform as a Service (PaaS).

With AWS Step Functions, we can reliably automate monitoring

decisions and actions in order to reduce human intervention by

over 60%, which improves infrastructure operation productivity and

customer application availability on our platform.

Pedro Pimenta, VP R&D, OutSystems

“

13 AWS Lambda Task States

6 Choice States

1 Fail State

“I want try/catch/finally”

"Access Media": {

"Type": "Task",

"Resource": "arn:aws:lambda:eu-central-1:123456789012:function:FindMedia",

"TimeoutSeconds": 2,

"Next": "Graceful Exit",

"Retry": [

{

"ErrorEquals": [ "States.Timeout" ],

"IntervalSeconds": 2, "MaxAttempts": 2, "BackoffRate": 1.5

}

],

"Catch": [

{ "ErrorEquals": [ "States.ALL" ], "Next": "Clean Up" }

]

},

“I have code that runs for hours”

We need to gather data from our

production line, in units of 8-hour shifts.“

More APIs

Register Activity Task - Returns ARN

Poll For task (by ARN)

Report Success

Report Failure

Report Heartbeat

"NextShift": {

"Type": "Wait",

"TimestampPath": "$.ShiftStart",

"Next": "Gather Plant Data"

},

"Gather Plant Data": {

"Type": "Task",

"Resource":

"arn:aws:states:ap-northeast-1:123456789012:activity:PlWatch",

"TimeoutSeconds": 30000,

"HeartBeatSeconds": 120,

"Next": "Clean up"

}

“I want to sequence functions”

“I want to select functions based on data”

“I want to retry functions”

“I want try/catch/finally”

Is this you?

“I have code that runs for hours”

“I want to run functions in parallel”

2.5¢

How much?

per thousand

state transitions

4,000 free

transitions/month

Free tier:

Related Sessions

• CMP319: Building Distributed Applications with AWS

Step Functions (Thursday, 5:30 PM, Venetian, L4, Delfino 4004)

• In the hallway outside this room, starting now!

Thank you!

timbray@amazon.com

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