Resilience Patterns — JustAPI Docs

JustAPI incorporates enterprise resilience primitives directly in the Rust engine.

Circuit Breakers

Automatically stop calling a failing service when errors exceed a threshold:

app.enable_circuit_breaker(
    failure_threshold=5,      # Open after 5 consecutive failures
    reset_timeout_ms=30000,   # Try again after 30 seconds
)

States: - Closed — Normal operation, requests pass through - Open — Requests fail fast with 503 - Half-Open — Probe request allowed; success → Closed, failure → Open

Request Coalescing

Deduplicate concurrent identical requests so only one hits the backend:

app.enable_request_coalescing(
    headers=["accept"],  # Consider these headers for dedup keys
)

When 100 identical requests arrive simultaneously: - Only 1 request reaches the handler - The response is shared across all 100 callers - Saves backend resources on cacheable/read-only endpoints

Rate Limiting

Global Rate Limiter

app.enable_rate_limiter(max_requests=1000, window_seconds=60)

Per-IP Rate Limiter

app.enable_ip_rate_limiter(max_requests=100, window_seconds=60)

Exceeding limits returns 429 Too Many Requests with Retry-After header.

Bulkhead Pattern

Limit concurrent requests to prevent resource exhaustion:

app.enable_bulkhead(max_concurrent=100)

When the limit is exceeded, requests receive 503 Service Unavailable.

Timeout Middleware

Cancel requests that exceed the time limit:

app.enable_timeout(seconds=30)

Returns 504 Gateway Timeout when exceeded.

Graceful Degradation

app.enable_fallback_middleware(
    fallback_response={"status": "degraded", "message": "Please try again later"},
)

Graceful Shutdown

JustAPI handles SIGINT/SIGTERM automatically:

Stop accepting new connections
Drain in-flight requests (with configurable timeout)
Call plugin on_shutdown() hooks
Close database connections
Exit cleanly

Panic Model

In production, Rust panics abort the process (not unwind). The supervisor (Docker, systemd, K8s) restarts the process immediately:

# Cargo.toml
[profile.release]
panic = "abort"

This avoids undefined behavior across the PyO3 FFI boundary during panics.

Configuration Summary

app = JustAPIApp()

# Resilience
app.enable_circuit_breaker(failure_threshold=5, reset_timeout_ms=30000)
app.enable_request_coalescing(headers=["accept"])
app.enable_rate_limiter(max_requests=1000, window_seconds=60)
app.enable_ip_rate_limiter(max_requests=100, window_seconds=60)
app.enable_bulkhead(max_concurrent=100)
app.enable_timeout(seconds=30)