Zero-Downtime Deployments with Docker Compose – No Kubernetes Required

3 hours ago

Docker Compose and HAProxy can achieve zero-downtime deployments without Kubernetes.
Traefik initially used but caused issues like 'Service defined multiple times' and routing delays during scaling.
HAProxy's 'option redispatch' retries failed requests on different backends, eliminating dropped requests.
Three-layer health detection in HAProxy covers per-request retries, passive observation, and active health checks.
DNS-based discovery with HAProxy automatically picks up container changes via Docker's embedded DNS.
A rolling deploy script replaces backend replicas one at a time, ensuring at least one healthy backend always serves traffic.

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