Overview
The article discusses a significant incident at Shopify caused by the expiration of Let’s Encrypt’s old root certificate on September 30, 2021, which nearly led to a global outage. It details the incident response, the underlying issues related to internal libraries, and the emergency fix implemented to prevent further disruptions.
What You'll Learn
1
How to respond effectively to certificate expiration incidents in distributed systems
2
Why maintaining up-to-date root certificate stores is critical for service reliability
3
When to implement emergency fixes to mitigate service disruptions
Prerequisites & Requirements
- Understanding of SSL/TLS and certificate management
- Experience with incident response in distributed systems(optional)
Key Questions Answered
What caused the internal certificate errors at Shopify on September 30, 2021?
The internal certificate errors were caused by the expiration of Let’s Encrypt’s old root certificate, which led to issues in services relying on outdated root certificate stores. This incident highlighted the importance of keeping root certificates updated to avoid service disruptions.
How did Shopify respond to the certificate expiration incident?
Shopify's response involved locking deployments to prevent further issues, investigating the certificate errors, and ultimately forking the httpclient library to update the root certificate bundle. This emergency fix allowed them to restore service functionality quickly.
What were the consequences of the certificate expiration for Shopify's services?
The expiration led to various disruptions, including delayed order confirmations and throttled marketing campaigns, as services dependent on data were affected. However, only the canaries in the Shopify monolith experienced issues due to the incident response measures taken.
Why did the certificate expiration issue take 15 minutes to manifest?
The delay was due to HTTP keep-alive connections, which maintained the validity of existing connections until they were broken by Kubernetes pod recreation during deployments, triggering the TLS validation failure only after new connections were established.
Technologies & Tools
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Library
Httpclient
Used for making HTTP connections within Shopify's services, but had outdated root certificates that contributed to the incident.
Orchestration
Kubernetes
Managed the deployment of services and was involved in recreating pods that triggered the TLS validation failures.
Key Actionable Insights
1Implement a monitoring system for root certificate expiration to prevent outages.By proactively tracking certificate expiration dates, teams can avoid last-minute emergencies and ensure that all services remain operational without disruption.
2Regularly update internal libraries that handle HTTP connections to ensure they use the latest root certificates.This practice minimizes the risk of service disruptions caused by outdated dependencies, especially in distributed systems where multiple services interact.
3Lock deployments during critical incidents to prevent cascading failures.This approach allows teams to stabilize the system and investigate issues without introducing new changes that could exacerbate the situation.
Common Pitfalls
1
Failing to update root certificates in dependent libraries can lead to service disruptions.
This often occurs because teams may overlook the importance of maintaining dependencies, leading to outdated trust stores that cannot validate new certificates.
Related Concepts
Certificate Management
Incident Response Strategies
Distributed Systems Reliability