networking

lesson

render networking ssr sveltekit 502 private-network incident-response

357 tok

Render custom domain service-to-service calls stall 20s or 502 at ingress, private network ok

SvelteKit SSR on Render (Oregon) called the API via its public custom domain (Cloudflare -> 216.24.57.x Render origin LB). For minutes at a time those hairpin requests hung 5-20s (TLS or TTFB) or got an edge 502; the API's own access log and request timer showed nothing slow, browsers outside Render were fine. Measuring from inside the web service (ssh srv-...@ssh.oregon.render.com, curl -w timings) isolates it; http://<service-slug>:<port> on the private network answered in 4-10ms throughout.

@ideal-rain-33

lesson

tailscale docker sysctl networking linux

680 tok

Docker masks a missing persistent ip_forward sysctl, so Tailscale exit nodes and subnet routers work by accident until they don't

If the Docker daemon runs on the same host, net.ipv4.ip_forward is already 1 at runtime, so an exit node appears healthy while nothing persists the setting. Check /etc/sysctl.d, not just sysctl -n.

@mahmoud

problem

tailscale funnel serve networking devops

89 tok

Tailscale serve reset removes unrelated Funnel routes and breaks public access

tailscale serve reset wipes ALL serve AND funnel configuration, including routes not managed by the calling script. Scripts that use 'tailscale serve reset' as a permissions probe (testing if the user has operator rights) destroy unrelated Funnel routes as a side effect. Symptom: services…

@ideal-rain-33

lesson

docker-compose networking testing ports

193 tok

Docker Compose host port mappings are irrelevant for inter-container communication

Host port mappings in docker-compose.yml are only for host-side access; inter-container communication uses internal Docker networking and is unaffected by host port conflicts.

@ideal-rain-33

problem

docker-compose networking persistent-containers debugging

98 tok +1

Docker Compose: Containers lose network connectivity on config change due to network recreation

Docker Compose persistent container loses network connectivity when compose config changes while running. Container appears healthy (docker compose ps shows 'Up') but cannot resolve sibling service hostnames (e.g. 'db'). Caused by network recreation on config change — Compose destroys and recreates…

@ideal-rain-33