fastapi-deploy

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name: fastapi-deploy description: > Use when this capability is needed. metadata: author: abhayla

Deploy Backend (FastAPI)

Orchestrates backend deployment steps with health verification.

Scope: Local/dev deployment orchestration. For migration authoring, use /fastapi-db-migrate. For post-migration verification, use /db-migrate-verify. For production deployment strategies (canary, blue-green), use /deploy-strategy.

Arguments: $ARGUMENTS

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STEP 1: Pre-flight Checks

cd backend && python --version
python -c "import sys; print('venv:', hasattr(sys, 'real_prefix') or sys.base_prefix != sys.prefix)"
ls -la .env 2>/dev/null || echo "WARNING: .env not found"

If .env is missing, STOP and ask the user — deployment without config will fail silently.

STEP 2: Run Migrations

Skip if --skip-migrate is in $ARGUMENTS.

cd backend && alembic current && alembic upgrade head

If migration fails, STOP and report the error. Do not proceed to seeding or server start with a broken schema.

STEP 3: Seed Data

Skip if --skip-seed is in $ARGUMENTS.

cd backend && ls scripts/seed_*.py 2>/dev/null

If seed scripts are found, run each one:

for script in scripts/seed_*.py; do
  echo "Running: $script"
  python "$script" || echo "WARNING: $script failed"
done

If no seed scripts exist, skip this step silently.

STEP 4: Start/Restart Server

Check if a server process is already running and stop it first:

# Check for existing uvicorn process on the target port
PORT=${PORT:-8000}
lsof -ti:$PORT 2>/dev/null && echo "Port $PORT in use — stopping existing process" && kill $(lsof -ti:$PORT)

Start the server in the background (NOT with --reload — that is for development, not deployment):

cd backend && nohup uvicorn app.main:app --host 0.0.0.0 --port $PORT --workers 2 > uvicorn.log 2>&1 &
echo "Server PID: $!"
sleep 2  # Allow startup time

STEP 5: Health Check

PORT=${PORT:-8000}
HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" http://localhost:$PORT/docs)
echo "Health check: $HTTP_CODE"

If health check returns non-200:

1. Check uvicorn.log for errors: tail -20 backend/uvicorn.log
2. Report the failure with log output
3. If --skip-migrate was NOT set, suggest rolling back: cd backend && alembic downgrade -1

Report

Deploy Summary:
  Migrations: <applied|skipped|failed>
  Seed data:  <N scripts run|skipped|none found>
  Server:     <running on port PORT (PID: N)|failed>
  Health:     <HTTP_CODE — OK|FAILED>
  URL:        http://localhost:PORT/docs
  Log:        backend/uvicorn.log

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CRITICAL RULES

• MUST verify health (Step 5) before reporting success — Why: a running process doesn't mean a working server
• MUST NOT use --reload in deployment — Why: reload is dev-only, blocks the shell, and restarts on file changes
• MUST stop on migration failure — Why: seeding or starting with a broken schema causes data corruption
• MUST check for existing process before starting — Why: port conflicts produce cryptic bind errors
• MUST report rollback path on failure — Why: a failed deploy must be reversible

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Source: abhayla/claude-best-practices — distributed by TomeVault.