DNS

2 posts about DNS. Every summary links to the original.

Shopify · Aug 5, 2020
An Introduction to DNS Traffic Management
DNS traffic management applies data-driven DNS responses to direct clients to different service endpoints, extending DNS’s basic role of mapping domain names to IP addresses. The post introduces DNS through its history from HOSTS.TXT, explains zones, records, nameservers, root servers, TTL, and negative TTL, then connects caching behavior to routing decisions. Low TTLs can make changes visible sooner, but repeated DNS resolution adds latency: with a one-second resolution time, a 15-second TTL could add 5,760 seconds per day, compared with 1,440 seconds at 60 seconds; resolver behavior can also make delays slightly longer. Use cases include active-passive failover, active-active traffic sharing, progressive green-blue deployments, and location-based routing, while Shopify’s system evolved into an automated, self-served platform serving more than 40 domains across 12 teams and over 100M requests per 24 hours.
2023-10-18
Shopify · Aug 5, 2020
Using DNS Traffic Management to Add Resiliency to Shopify’s Services
Shopify consolidated several team-specific DNS traffic-management approaches that relied on manual changes, pull requests, or provider APIs and had uneven failover, redundancy, and active/active capabilities. The replacement was a fully automated, self-served system for more than 40 domains owned by more than 12 teams and handling more than 100M requests per day. It stores domain configuration in Git, deploys it to two DNS providers, and exposes spy commands for fast updates and failovers. Its traffic-management design uses regionalized matching, endpoint-status filtering, weighted sharing, and fallback layers, while globally matching endpoints ensure an existing domain receives an answer. A later provider migration demonstrated the value of centralized ownership: the team updated Terraform and tooling, moved nameservers incrementally, and kept the change transparent to application owners despite concurrent incidents.
2023-10-18

An Introduction to DNS Traffic Management

DNS traffic management applies data-driven DNS responses to direct clients to different service endpoints, extending DNS’s basic role of mapping domain names to IP addresses. The post introduces DNS through its history from HOSTS.TXT, explains zones, records, nameservers, root servers, TTL, and negative TTL, then connects caching behavior to routing decisions. Low TTLs can make changes visible sooner, but repeated DNS resolution adds latency: with a one-second resolution time, a 15-second TTL could add 5,760 seconds per day, compared with 1,440 seconds at 60 seconds; resolver behavior can also make delays slightly longer. Use cases include active-passive failover, active-active traffic sharing, progressive green-blue deployments, and location-based routing, while Shopify’s system evolved into an automated, self-served platform serving more than 40 domains across 12 teams and over 100M requests per 24 hours.

2023-10-18

Using DNS Traffic Management to Add Resiliency to Shopify’s Services

Shopify consolidated several team-specific DNS traffic-management approaches that relied on manual changes, pull requests, or provider APIs and had uneven failover, redundancy, and active/active capabilities. The replacement was a fully automated, self-served system for more than 40 domains owned by more than 12 teams and handling more than 100M requests per day. It stores domain configuration in Git, deploys it to two DNS providers, and exposes spy commands for fast updates and failovers. Its traffic-management design uses regionalized matching, endpoint-status filtering, weighted sharing, and fallback layers, while globally matching endpoints ensure an existing domain receives an answer. A later provider migration demonstrated the value of centralized ownership: the team updated Terraform and tooling, moved nameservers incrementally, and kept the change transparent to application owners despite concurrent incidents.

2023-10-18