python.fastapi.missing_health_check

Stability Medium

Detects FastAPI app without /health, /healthz, /ready, or /ping endpoints.

Why It Matters

Without health checks:

Load balancers can’t route — They don’t know if your service is healthy
Kubernetes can’t manage — Pods aren’t restarted when unhealthy
Deployments break — New versions get traffic before they’re ready
Outages go undetected — Monitoring can’t detect service failures

Health checks are required infrastructure for any production service.

Example

# ❌ Before
from fastapi import FastAPI

app = FastAPI()

@app.get("/api/users")
def get_users():
    return users

Kubernetes, AWS ALB, and other infrastructure have no way to know if this service is healthy.

# ✅ After
from fastapi import FastAPI

app = FastAPI()

@app.get("/health")
def health_check():
    return {"status": "healthy"}

@app.get("/ready")
def readiness_check():
    # Check dependencies
    db_healthy = check_database()
    cache_healthy = check_cache()

    if db_healthy and cache_healthy:
        return {"status": "ready"}
    return JSONResponse(
        status_code=503,
        content={"status": "not_ready"}
    )

@app.get("/api/users")
def get_users():
    return users

What Unfault Detects

FastAPI app without any health endpoint
Health endpoints that don’t return proper status codes
Missing readiness vs liveness distinction

Auto-Fix

Unfault adds a basic /health endpoint. Enhance it with dependency checks for production.

Health Check Types

# Liveness: Is the process running?
# Used by Kubernetes to know when to restart
@app.get("/health")
def liveness():
    return {"status": "alive"}

# Readiness: Is the service ready for traffic?
# Used by load balancers for routing decisions
@app.get("/ready")
def readiness():
    try:
        db.execute("SELECT 1")
        redis.ping()
        return {"status": "ready"}
    except Exception:
        return JSONResponse(status_code=503, content={"status": "not_ready"})

# Startup: Has initialization completed?
# Used by Kubernetes to know when liveness should start
@app.get("/startup")
def startup():
    if app.state.initialized:
        return {"status": "started"}
    return JSONResponse(status_code=503, content={"status": "starting"})

go.graceful_shutdown