How to Build a Health Check System with Instance Up and Down Status in Python

from datetime import datetime
import random

class HealthChecker:
    def __init__(self):
        self.status = {}
    
    def mark_up(self, instance_id):
        self.status[instance_id] = {
            "state": "up",
            "last_check": datetime.now().isoformat(),
            "healthy": True
        }
    
    def mark_down(self, instance_id):
        self.status[instance_id] = {
            "state": "down",
            "last_check": datetime.now().isoformat(),
            "healthy": False
        }
    
    def mock_health_check(self, instance_id):
        # Simulate a real health check with some randomness
        is_healthy = random.random() > 0.3
        if is_healthy:
            self.mark_up(instance_id)
        else:
            self.mark_down(instance_id)
        return self.status[instance_id]

    def get_status(self, instance_id):
        return self.status.get(instance_id, {"state": "unknown", "healthy": False})

if __name__ == "__main__":
    checker = HealthChecker()
    
    # Mock health checks for instances
    for instance in ["web-01", "web-02", "db-01"]:
        result = checker.mock_health_check(instance)
        print(f"{instance}: {result['state']} (healthy={result['healthy']})")
    
    # Mark down explicitly
    checker.mark_down("web-02")
    print(f"web-02: {checker.get_status('web-02')['state']}")
    
    # Mark up explicitly
    checker.mark_up("web-02")
    print(f"web-02: {checker.get_status('web-02')['state']}")