Making s3 more resilient using lambda@edge

© 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.SUMMIT
Making S3 more resilient
using Lambda@Edge
Júlia Biró, Yann Hamon
Reliability Team
Contentful

Introduction
Júlia Biró
Reliability Engineer
Yann Hamon
Reliability Engineer

Agenda
1. Our goal
2. Proof of concept
3. Going live
4. Improving our Lambda@Edge software platform
5. Review

SUMMIT © 2019, Amazon Web Services, Inc. or its affiliates. All rights reserved.
Our goal

Our file delivery infrastructure

Our goal: multi-region active-active
https://www.youtube.com/watch?v=2e29I3dA8o4

Active-active vs. failover

Current state-of-the-art (?)
Highly available multi region S3 website
Cloudfront distributions - Derek Higgins (2017)
Could work but:
Failover solution
No guaranteed propagation time for
configuration changes in Cloudfront
Manual reset

A possible solution...
Use an origin with DNS Round-Robin?

… that doesn’t work
GET /puppy.jpg HTTP/1.1
Host: examplebucket.s3-us-west-2.amazonaws.com
Date: Mon, 11 Apr 2016 12:00:00 GMT
x-amz-date: Mon, 11 Apr 2016 12:00:00 GMT
Authorization: authorization string

There must be a way...
Dynamically Route Viewer Requests
to Any Origin Using Lambda@Edge
Jake Wells, AWS Blog (Nov. 2017)

A/B Testing with Lambda@Edge

Load-balancing with Lambda@Edge
dns.resolveCname('files-origin.contentful.com', (function(err, result) {
if (result[0].includes('us-east-1')) {
bucketName = 'cf-files.s3.us-east-1.amazonaws.com';
region = 'us-east-1';
} else {
bucketName = 'cf-files.s3.eu-west-1.amazonaws.com';
region = 'eu-west-1';
}
request.origin.s3.region = region;
request.origin.s3.domain = bucketName;
request.headers['host'] = [{key: 'host', value: bucketName}];
}))

Proof of concept

Technology validation
We build a small proof-of-concept. Only 20 lines of code!
Proof: different image with the same path in both regions.
us-east-1 eu-west-1
Learnings:
Our Javascript is not great - we don't do this every day!
We do a DNS resolution on every cache miss

DNS Caching
static async ResolveCname(fqdn) {
let now = Date.now();
let cachedEntry = this.cache[fqdn];
if (cachedEntry && now - cachedEntry.updatedAt < this.defaultTTL) {
return cachedEntry.answers;
}
[...]
DNS lookups add up to 100ms latency to our requests...
But we can cache the results [1]

It works!

Leap of faith
Our team is not used to writing Javascript
Lambda@Edge is a new technology to the
company
High cost of failure
©https://www.iimef.marines.mil/Units/MEF-Support-Battalion/Article/1096888/leap-of-faith/

High cost of failure
Contractual SLAs
100s of requests/second
No graceful degradation
We need safety gear.

Why do we trust our current software platform?
testing deploy-ment
alerting
logging
version
control
monitoring
dash-
boards debugging
perfor-
mance

Production-readiness criteria
Solution-agnostic criteria list
To add an image, select Click
to insert image, and find the
image you want to use.
Gap analysis
Translated for the specific solution

Production-readiness list is an ideal
The goal is to reduce uncertainty and risk RUNNIN' RHINO
Design by Allan Faustino
No need to meet all requirements:
Our existing software platforms did
not meet all requirements
It needs to be a conscious and
documented decision

Risk-aversion

Going live

Going live… gradually
1. Attach the Lambda - new feature turned off completely
2. Feature-flag / dark release
3. Whitelist for some internal test customers
4. Gradually roll out to all traffic
5. Monitor all steps
Big red button: ability to quickly revert
at all times
Expect to meet unknowns.

Our new file delivery infrastructure

Improving our Lambda@Edge
software platform

Migrating a larger service to Lambda@Edge
10 times more requests per second
Full-fledged API, lot of logic
/yadj1kx9rmg0/wtrHxeu3zEoEce2MokCSi/cf6f68efdcf625fdc060607df0f3baef/qu
wowooybuqbl6ntboz3.jpg?fm=jpg&w=250&h=100
Request

TypeScript
JavaScript

Rolling out again
https://commons.wikimedia.org/wiki/File:Pit_stop_raikkonen.jpg
Improved CI
Code review
Rollbacks
Backport tooling
Operational experience

Working with Lambda@Edge
Near-immediate scale-up
Marginal costs
Highly available

Working with Lambda@Edge
But...
Challenging development environment (esp. integration testing)
Logs saved in each region
Our deployment workflow is still manual
TypeScript helped us write safer code
We contributed the Lambda@Edge types to the AWS TypeScript package

Future improvements
Use Geo-routing to forward requests to the closest S3 bucket
Run the DNS resolution outside of the main event loop
Automate deployments

A few months later...

A few months later...
Similar implementations emerged:
Using Amazon CloudFront with Multi-Region Amazon S3 Origins (Sept. 30th, Seldam)
Amazon S3 Region Failover — Part 2: CloudFront S3 origin failover (Oct. 30th, Frias)
Cloudfront origin failover was introduced:
Amazon CloudFront announces support for Origin Failover (Nov. 20th, AWS)
But…
Current solution has proven cheap, fast and stable...
and has laid the groundworks for other multi-region projects.

Takeaways
Lambda@Edge is a cheap, scalable & highly reliable platform to build
stateless APIs
Feature-flagging, canarying, gradual rollouts are easy to use with
Lambda@Edge to reduce risk of large-scale changes
When the cost of failure is high, use production-readiness lists

Thank you!
Júlia Biró, Yann Hamon
julia.biro@contentful.com, yann.hamon@contentful.com

Making s3 more resilient using lambda@edge

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