Learning from Learnings: Anatomy of Three Incidents

Learning from Learnings:
Anatomy of Three Incidents
Randy Shoup
@randyshoup
linkedin.com/in/randyshoup

http://googleappengine.blogspot.com/2012/10/about-todays-app-engine-outage.html
App Engine Outage
Oct 2012

App Engine
Reliability Fixit
• Step 1: Identify the Problem
o All team leads and senior engineers met in a room with a whiteboard
o Enumerated all known and suspected reliability issues
o Too much technical debt had accumulated
o Reliability issues had not been prioritized
o Identify 8-10 themes

• Step 2: Understand the Problem
o Each theme assigned to a senior engineer to investigate
o Timeboxed for 1 week
o After 1 week, all leads came back with
• Detailed list of issues
• Recommended steps to address them
• Estimated order-of-magnitude of effort (1 day, 1 week, 1 month, etc.)
App Engine
Reliability Fixit

• Step 3: Consensus and Prioritization
o Leads discussed themes and prioritized work
o Assigned engineers to tasks
App Engine
Reliability Fixit

• Step 4: Implementation and Follow-up
o Engineers worked on assigned tasks
o Simple spreadsheet of task status, which engineers updated weekly
o Minimal effort from management (~1 hour / week) to summarize progress at
weekly team meeting
App Engine
Reliability Fixit

•  Results
o 10x reduction in reliability issues
o Improved team cohesion and camaraderie
o Broader participation and ownership of the future health of the platform
o Still remembered several years later
App Engine
Reliability Fixit

Stitch Fix Outages
Oct / Nov 2016
• (11/08/2016) Spectre unavailable for ~3 minutes [Shared Database]
• (11/05/2016) Spectre unavailable for ~5 minutes [Shared Database]
• (10/25/2016) All systems unavailable for ~5 minutes [Shared Database]
• (10/21/2016) All systems unavailable for ~3 ½ hours [DDOS attack]
• (10/13/2016) Minx escalation broken for ~2 hours [Zendesk outage]
• (10/11/2016) Label printing unavailable for ~10 minutes [FedEx outage]
• (10/10/2016) Label printing unavailable for ~15 minutes [FedEx outage]

Database Stability
Problems
• 1. Applications contended on common tables
• 2. Scalability limited by database connections
• 3. One application could take down entire company

Stitch Fix
Stability Retrospective
• Step 4: Implementation and Follow-Up
•  Results
@randyshoup

Stability
Solutions
• 1. Focus on expensive queries
o Log
o Eliminate
o Rewrite
o Reduce
• 2. Manage database connections via connection
concentrator
• 3. Stability and Scalability Program
o Ongoing 25% investment in services migration

WeWork
Login Issues
• Problem: Some members unable to log in
• Inconsistent representations across different services in
the system
• Over time, simple system interactions grew increasingly
complex and convoluted
• Not enough graceful degradation or automated repair
@randyshoup

WeWork
Login Retrospective
• Step 4: Implementation and Follow-Up
@randyshoup

Common
Elements
• Unintentional, long-term accumulation of small,
individually reasonable decisions
• “Compelling event” catalyzes long-term change
• Blameless culture makes learning and improvement
possible
• Structured post-incident approach
@randyshoup

If you don’t end up regretting
your early technology
decisions, you probably over-
engineered.

Lessons
•Leadership and Collaboration
•Quality and Discipline
•Driving Change

Blameless
Post-Mortems
• Open and Honest Discussion
o Detect
o Diagnose
o Mitigate
o Remediate
o Prevent
Engineers compete to take personal responsibility (!)
@randyshoup linkedin.com/in/randyshoup

“Finally we can prioritize
fixing that broken system!”

Cross-Functional
Collaboration
• Best decisions made through partnership
• Shared context
o Tradeoffs and implications
o Given common context, well-meaning people generally agree
• “Disagree and Commit”
@randyshoup

15 Million
“Never let a
good crisis go
to waste.”

Quality and reliability are
business concerns
@randyshoup

“Do you have time to do it
twice?”
“We don’t have time to do it
right!”
@randyshoup

The more constrained you are
on time or resources, the more
important it is to build it right
the first time.
@randyshoup

“Do not try to
do everything.
Do one thing
well.”
@randyshoup

Definition of
Done
• Feature complete
• Automated Tests
• Released to Production
• Feature gate turned on
• Monitored

Vicious Cycle
of Technical Debt
Technical
Debt
“No time
to do it
right”
Quick-
and-dirty
@randyshoup

Virtuous Cycle
of Investment
Solid
Foundation
Confidence
Faster and
Better
Quality
Investment
@randyshoup

Funding the
Improvement Program
• Approach 1: Standard project
o Prioritize and fund like any other project
o Works best when project is within one team
• Approach 2: Explicit global investment
o Agree on an up-front investment
(e.g., 25%, 30% of engineering efforts)
o Works best when program is across many teams

Finance
An unexpected ally …
@randyshoup

“If you can’t change your
organization,
change your organization.”
-- Martin Fowler
@randyshoup

We are Hiring!
700 software engineers
globally, in
• New York
• Tel Aviv
• San Francisco
• Seattle
• Shanghai
• Singapore
@randyshoup

Learning from Learnings: Anatomy of Three Incidents

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