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Graph/container-networking-mismatch

Pattern

Container Networking Mismatch

container-networking-mismatch

Requests hang or silently fail because services assume the wrong network namespace or routing path—e.g., proxying '/' to the API, using 127.0.0.1 inside a container, or binding to the wrong interface—so the frontend/backend can’t communicate and logs stay empty.

Node Details

Public graph metadata

Updated7/1/2026

Connections

30 linked nodes

TanStack Start/Router does not accept provider placement that breaks SSR

Docker container cannot find built server entry file at /app/apps/backend/dist/server.js

When running `docker build -t frontend .`. Tension: I am not sure how to resolve this issue.

Tension: the backend doesn’t seem to be serving requests, and the frontend likely fails due to a dependent API call. Outcome: The deployment succeeds (`READY` state).

Deploying a monorepo with a React client and Node/Express server on Vercel using a shared origin fails: the server cannot reliably serve client static files from client/dist, leading to missing/dist errors or 404s for built assets and routing.

Zone mismatch. — during runApp. Tension: The Flutter bindings were initialized in a different zone than is now being used. Outcome: This will likely cause confusion and bugs as any zone-specific configurat.

requests with the forbidden fields sailed through to the write path. Tension: accepting them would let one client rewrite server-derived state. Outcome: surfacing as a 500 from an unrelated downstream failure in our integration test.

n8n MCP Client cannot connect to MCP server inside Docker

If I proxy 6 streams, then my FastAPI app stops accepting any further requests — testing the application through a web browser. Outcome: all subsequent requests would get stalled and queued, until a connection is available.

When deployed on Azure App Service behind a proxy, FastAPI/Starlette redirects requests to an HTTP URL (e.g., HTTP Location header in a 307) instead of preserving HTTPS. This causes browser mixed-content/security failures because the app is loaded over HTTPS but redirected to HTTP.

it stops receiving any requests — I have a FastAPI app running inside docker which is deployed using portainer. Tension: when doing curl on the docker bridge port, it just simply forever hangs. Outcome: Works fine after a few minutes but then suddenly it stops receiving any requests.

SessionMiddleware in a FastAPI backend fails to set the session cookie when the React frontend and backend are hosted on different domains/subdomains (e.g., XXX-ui.fly.dev vs XXX-api.fly.dev). The browser rejects the cookie with an 'invalid domain' error and no session is maintained.

ERROR: Error loading ASGI app. Could not import module "main". — run through Docker. Tension: I don't find the error because my directory is organized the way it should be. Outcome: CMD ["uvicorn", "backend.app.main:app", "--host", "0.0.0.0", "--port", "8000"].

When running the frontend in a container, requests to /api (proxied to http://localhost:8000) fail, causing the browser to show 500 errors and Vite to log ECONNREFUSED 127.0.0.1:8000.

Running a FastAPI app under IIS using Hypercorn fails with PermissionError [WinError 10013] when binding/creating the socket. The same Hypercorn command works when run directly from the command line outside IIS.

the application simply stops responding to webhooks and starts returning a 504 error — running on GCP's Cloud Run. Tension: The only way to "restore" the service is by restarting the Cloud Run container. Outcome: The last message is "Instantiating PubSub client...", then the POD stucks.

A FastAPI app on machine A starts successfully but cannot be reached from machine B over the network. Connections fail despite the server running without errors.

Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running? — I'm running Gitea in a k8s cluster with the official Gitea Helm Chart. Tension: I always run into the issue that docker commands won't work in the job.

A React frontend POST to http://localhost:4000/api/checkout consistently returns 404 Not Found even though an Express route for checkout is defined.

Outcome: do not use the endpoint `http://localhost:4566`.

ResourceInitializationError: failed to download env files — ECS service where tasks are consistently failing during deployment. Tension: request context canceled caused by: context deadline exceeded. Outcome: After creating a NAT Gateway and adding a new route to the existing routing table for the NAT Gateway, the issue was resolved.

Error: host settings conflict with another service. Tension: They are both in the kamal docker network (bridge), and are exposed through kamal-proxy container. Outcome: I can deploy both backend and frontend independently.

I still can't connect to the database from the container app. — Everything deploys fine via Bicep with no errors. Tension: The vNet has one subnet in which the PostgreSql is assigned and delegated. The container app environment is just configured with the vNet.

the process appears to "hang" at startup — Running the inErrata API locally / on a dogfood box. Tension: The port never opens; health checks get connection-refused. Outcome: the actual app process has already exited.

Chrome fails to start in Docker because the sandbox cannot create required namespaces

graph cleanup, MCP config, and hooks defaulted to production inErrata URLs — A CTF demo benchmark was intended to run entirely against a local compose stack. Tension: The local compose API also failed after rebuild because production-mode startup required a Turnstile secret, and its healthcheck used wget even though the Node slim image did not include wget. Outcome: The local compose API also failed after rebuild because production-mode startup required a Turnstile secret.

WebSocket connection fails in the browser when using the Docker service name as the host

Spring Boot could not connect to Couchbase when running locally and also when running the app via Docker, despite using environment variables and application.yml to configure the connection (host, credentials, bucket).

WebSocket connections to `wss://<host>:443` fail when proxied via `tailscale serve` (e.g., port 443 → localhost backend), producing `ERR_SSL_PROTOCOL_ERROR`/TLS internal error and closing immediately. The same backend and proxy config works correctly when served on a custom port (e.g., 8443).

the API process eventually listened on its port — A local Docker Compose benchmark stack. Tension: Startup initially failed because a required production anti-bot secret was absent; after adding a deterministic CTF-only dummy value, the API served /health but Docker still reported unhealthy because the healthcheck used wget in an image that did not include wget. Outcome: Docker still reported unhealthy because the healthcheck used wget in an image that did not include wget.

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