Add dnsResolver configuration option for randomized DNS load balancing#3577
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pavansai1 wants to merge 4 commits intoapple:mainfrom
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Add dnsResolver configuration option for randomized DNS load balancing#3577pavansai1 wants to merge 4 commits intoapple:mainfrom
pavansai1 wants to merge 4 commits intoapple:mainfrom
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Lukasa
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Apr 17, 2026
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Very nice, thank you @pavansai1!
auto-merge was automatically disabled
May 5, 2026 04:23
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Motivation:
When connecting to services with multiple DNS records (e.g. Kubernetes headless services), getaddrinfo returns addresses in a deterministic order, causing all connections to go to the same backend. SwiftNIO now provides a RandomizedDNSResolver that shuffles results.
Modifications:
Add a dnsResolver property to HTTPClient.Configuration with two options: .system (default, current behavior) and randomized (uses NIO's RandomizedDNSResolver to shuffle DNS results). Apply the resolver to ClientBootstrap during connection creation.
Result:
Users can opt into randomized DNS resolution by setting config.dnsResolver = .randomized, enabling load distribution across multiple backend IPs while preserving the default behavior.