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Railway Backend Deploy Guide

docs/railway-backend.md

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Railway Backend Deploy Guide

This guide deploys the production FastAPI backend from this monorepo.

1) Prerequisites

  • Railway account + project access
  • Railway CLI installed
  • Logged in locally:
bash
railway login

You can use dashboard or CLI. CLI flow:

bash
cd /path/to/gitdiagram
railway init -n gitdiagram
railway add --service gitdiagram-api
railway link --service gitdiagram-api

3) Set backend environment variables

Required:

  • OPENAI_API_KEY

Recommended:

  • OPENAI_MODEL=gpt-5.4-mini
  • ENVIRONMENT=production
  • WEB_CONCURRENCY=2
  • CORS_ORIGINS=https://gitdiagram.com,https://www.gitdiagram.com,https://<your-vercel-domain>

Optional:

  • GITHUB_PAT (higher GitHub API rate limits for repository fetches)
  • GITHUB_CLIENT_ID
  • GITHUB_PRIVATE_KEY
  • GITHUB_INSTALLATION_ID
  • API_ANALYTICS_KEY

Set variables via CLI:

bash
railway variables --service gitdiagram-api --set "OPENAI_API_KEY=..."
railway variables --service gitdiagram-api --set "OPENAI_MODEL=gpt-5.4-mini"
railway variables --service gitdiagram-api --set "ENVIRONMENT=production"
railway variables --service gitdiagram-api --set "WEB_CONCURRENCY=2"
railway variables --service gitdiagram-api --set "CORS_ORIGINS=https://gitdiagram.com,https://www.gitdiagram.com,https://<your-vercel-domain>"

Do not set PORT manually unless needed. Railway injects it automatically.

4) Deploy backend from backend/

bash
cd /path/to/gitdiagram
railway up --service gitdiagram-api --path-as-root backend

5) Create a public Railway domain

bash
railway domain --service gitdiagram-api

Copy the generated URL, for example: https://gitdiagram-api-production-xxxx.up.railway.app

6) Point Vercel frontend to Railway backend

In your Vercel project environment variables, set:

  • NEXT_PUBLIC_USE_LEGACY_BACKEND=true
  • NEXT_PUBLIC_API_DEV_URL=https://<your-railway-domain>

Then redeploy Vercel.

Note: the variable name includes "LEGACY" for backward compatibility, but this is now the primary external backend path.

7) Verify

  1. Health endpoint:
    • GET https://<your-railway-domain>/healthz
    • expected JSON: {"ok": true, "status": "ok"}
  2. Open your frontend and generate a diagram.
  3. Check Railway logs:
bash
railway logs --service gitdiagram-api