Generate Synthetic SRE Metrics and Calculate Availability in Python

from datetime import datetime, timedelta
import random

def generate_service_metrics(service_name: str, minutes: int = 30) -> list[dict]:
    """Generate synthetic SRE metrics for a service across recent minutes."""
    metrics = []
    now = datetime.now()
    
    for i in range(minutes):
        timestamp = now - timedelta(minutes=minutes - i)
        metrics.append({
            "service": service_name,
            "timestamp": timestamp.isoformat(),
            "latency_ms": round(random.uniform(50, 300), 2),
            "error_rate": round(random.uniform(0.0, 0.05), 4),
            "requests_per_minute": random.randint(500, 2500)
        })
    return metrics

def calculate_availability(metrics: list[dict]) -> float:
    """Compute SLO availability from error rate (99.9% target)."""
    avg_error_rate = sum(m["error_rate"] for m in metrics) / len(metrics)
    return round((1 - avg_error_rate) * 100, 3)

def summarize_service(metrics: list[dict]) -> dict:
    """Return a beginner-friendly summary of the metric stream."""
    latencies = [m["latency_ms"] for m in metrics]
    total_requests = sum(m["requests_per_minute"] for m in metrics)
    errors = sum(m["error_rate"] * m["requests_per_minute"] for m in metrics)
    
    return {
        "service": metrics[0]["service"],
        "avg_latency_ms": round(sum(latencies) / len(latencies), 2),
        "avg_error_rate": round(sum(m["error_rate"] for m in metrics) / len(metrics), 4),
        "availability_pct": calculate_availability(metrics),
        "total_requests": total_requests,
        "estimated_errors": int(errors),
        "slo_met": calculate_availability(metrics) >= 99.9,
        "sample_size": len(metrics)
    }

if __name__ == "__main__":
    metrics = generate_service_metrics("user-api", minutes=10)
    summary = summarize_service(metrics)
    
    print("First metric sample:")
    print(metrics[0])
    print("\nService summary:")
    for key, value in summary.items():
        print(f"  {key}: {value}")