The Twelve-Factor App Methodology introduces best practices for building modern, cloud-native applications. In this session you'll learn how to directly apply the Twelve-Factor methodology to modern application development with Lambda and Amazon API Gateway. As you'll see, many of these factors are not only directly applicable to serverless applications and can be applied to various architectures and solutions.

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Twelve-factor app methodology
and modern applications
Uri Segev
Principal Solutions Architect
Amazon Web Services
D E V 3 0 8
Oren Reuveni
Solutions Architect
Amazon Web Services

2. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
Agenda
• What is the “12 Factor app”?
• What do we mean by “Serverless”?
• 12 Factor in a serverless app
• Demo
• Takeaways

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The “12 Factor” model & serverless applications
• Methodology for building modern applications
• A popular best practice for both developers and operations engineers
• Many of the 12 Factor guidelines align directly with best practices for
serverless applications and are improved upon given the nature of
AWS Lambda, Amazon API Gateway, and other AWS services
• However, some of the 12 Factor guidelines don’t directly align with
serverless applications or are interpreted very differently

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What is serverless?
No infrastructure provisioning,
no management
Automatic scaling
Pay for value Highly available and secure

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AWS Lambda
Run code without provisioning or managing servers
Virtually any type of application or backend service
Trigger from other AWS services or call it directly
from any web or mobile app

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Serverless applications
Services (anything)
Changes in
data state
Requests to
endpoints
Changes in
resource state
Event source Function
Node.js
Python
Java
C#
Go
Ruby
Runtime API

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AWS
Lambda
AWS
Fargate
COMPUTE
DATA STORES
INTEGRATION
Amazon Aurora
Serverless
Amazon
S3
Amazon
DynamoDB
Amazon
API Gateway
Amazon
SNS
Amazon
SQS
AWS
Step Functions
AWS
AppSync

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The 12 Factors:
Let’s explore how the 12 Factors apply to a serverless application:
1. Codebase
2. Dependencies
3. Config
4. Backing services
5. Build, release, run
6. Process
7. Port Binding
8. Concurrency
9. Disposability
10. Dev/prod parity
11. Logs
12. Admin processes
https://12factor.net

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1. Codebase
12Factor: “One codebase tracked in revision control, many deploys”
Serverless Apps: All code should be stored in revision control (a
development best practice).
Same repository should be used for all environments deployed to.
The bounds of an “application” differ in serverless terms:
• If events are shared (i.e., a common Amazon API Gateway) then
Lambda function code for those events should be put in the same
repository
• Otherwise break “services” into their own repositories

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2. Dependencies
12Factor: “Explicitly declare and isolate dependencies”
Serverless Apps: Code that is used by multiple functions should be
packaged into its own library. Include those libs inside your deployment
package or into a AWS Lambda Layer.
Node.js, Python, Ruby
• Use npm/pip to
install libraries
• All dependencies
must be at root
level
• .zip file consisting of
your code and any
dependencies
Java
• Either .zip file with all
code/dependencies,
or standalone .jar
• Use Maven / Eclipse
IDE plugins
• Compiled class &
resource files at root
level, required jars in
/lib directory
C# (.NET Core)
• Either .zip file with
all code /
dependencies, or a
standalone .dll
• Use NuGet /
VisualStudio
plugins
• All assemblies (.dll)
at root level
Go
• .zip file consisting
of your Go binary
and any
dependencies
• Use “go get” to
install
dependencies

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Lambda Layers
Lets functions easily share code: Upload layer
once, reference within any function
Layer can be anything: dependencies, training
data, configuration files, etc
Promote separation of responsibilities, lets
developers iterate faster on writing business logic
Built in support for secure sharing by ecosystem

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3. Config
12Factor: “Store config in the environment”
Serverless Apps: Many ways to do this in serverless applications:
• Lambda environment variables
• API Gateway stage variables
• AWS Systems Manager Parameter Store

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4. Backing services
12Factor: “Treat backing services as attached resources”
Serverless Apps: No differences. Resources that Lambda functions
connect to, such as databases, should have their endpoints and access
credentials made available via config resources or IAM policies

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5. Build, Release, Run
12Factor: “Strictly separate build and run stages”
Serverless Apps: No differences. Development best practices such as
Continuous Integration and Continuous Delivery should be followed.
• Use AWS CodeBuild and AWS CodePipeline to support this:
AWS CodeBuild AWS CodePipeline

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CI/CD for serverless applications
• Source code repository hosts SAM template
• CodePipeline per application
• CodeBuild generates a deployable artifact
• CodePipeline/CodeDeploy deploys to
different environments, with the right
config
CodeBuildCodeCommit CodePipeline
CloudFormation
API Gateway
Lambda
Dev account
Step Functions
DynamoDBCodeDeploy
CloudFormation
API Gateway
Lambda
Test account
Step Functions
DynamoDB
CodeDeploy
CloudFormation
API Gateway
Lambda
Prod account
Step Functions
DynamoDB
CodeDeploy
Tools accountCode account

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6. Process
12Factor: “Execute the app as one or more stateless processes”
Serverless Apps: This is inherent in how Lambda is designed already:
• Lambda Functions should be treated as stateless components
• There is no promise of execution environment re-use between function
invocations
• Data that needs to be kept should be stored in a stateful service such
as a database or cache

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7. Port binding
12Factor: “Export services via port binding”
Serverless Apps: In Lambda/serverless applications this factor doesn’t
apply the same due to a difference in how Lambda Functions are
accessed:
• Instead of a “port” Lambda functions are invoked by an event
• Lambda functions are invoked in 3 ways: synchronously,
asynchronously, and via stream
• Instead of having one function support multiple invocation sources,
create independent functions

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Lambda execution model
Synchronous (push)
AWS Lambda
function
/order
Asynchronous (event)
AWS Lambda
function
reqs
Poll-based
changes
AWS Lambda
service
Function
Amazon
API Gateway
Amazon
SNS
Amazon
S3
Amazon
DynamoDB
Amazon
Kinesis

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8. Concurrency
12Factor: “Scale out via the process model”
Serverless Apps: Doesn’t apply. Lambda functions will scale automatically
based on load.

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9. Disposability
12Factor: “Maximize robustness with fast startup and graceful shutdown”
Serverless Apps:
Shutdown doesn’t apply as Lambda functions and their invocation are
tied directly to incoming events.
Speed at startup does matter:
• Minimize package size to necessities
• Do one thing – smaller package size
• Reuse – initializing clients/instances outside the handler
• Choose the right environment size for optimal operation

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10. Dev/prod parity
12Factor: “Keep dev, staging, and production as similar as possible”
Serverless Apps: This can be made incredibly easy with serverless
applications by:
• Making use of environment/stage variables or Parameter Store for
configuration information, backend resources, etc
• Using Serverless Application Models (SAM) to deploy your application
• Having a CI/CD process and tooling that supports multiple
environments or accounts

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11. Logs
12Factor: “Treat logs as event streams”
Serverless Apps: Logging (as well as Metric collection) are considered a
“universal right” in Lambda:
• Console output automatically collected and sent to Amazon
CloudWatch Logs
• Metrics for Lambda and API Gateway for several key stats are
automatically collected and sent to CloudWatch
• You can easily send more using the CloudWatch SDK

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12. Admin processes
12Factor: “Run admin/management tasks as one-off processes”
Serverless Apps: Doesn’t apply to Lambda since you already limit your
functions based on use case.
True administrative tasks would occur via their own Lambda Functions.

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AWS Serverless Application Model (SAM)
• AWS CloudFormation extension optimized for
serverless
• Special serverless resource types:
• Functions, APIs, SimpleTables and Layers
• CLI tool for local development, debugging,
testing, deploying, and monitoring of
serverless applications
https://aws.amazon.com/serverless/sam

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26. © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
Takeaways
• The 12 factor app methodology can assist with designing modern
applications properly
• Many factors are already built into serverless applications
• Serverless applications assist with focusing on our core business
https://aws.amazon.com/serverless/

27. Thank you!
© 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
Uri Segev
Oren Reuveni
http://bit.ly/2SFkTzT