How to Mock Replica Lag Monitoring in Python

import time
import random
from datetime import datetime, timedelta

class MockReplicaLagMonitor:
    def __init__(self, replicas=3, base_lag=0.5, jitter=0.2):
        self.replicas = [f"replica-{i}" for i in range(replicas)]
        self.base_lag = base_lag
        self.jitter = jitter
        self.last_write = datetime.now()

    def simulate_write(self):
        self.last_write = datetime.now()
        return f"Write applied at {self.last_write.isoformat()}"

    def check_lag(self):
        results = {}
        for replica in self.replicas:
            lag = max(0.0, self.base_lag + random.uniform(-self.jitter, self.jitter))
            replica_time = self.last_write - timedelta(seconds=lag)
            results[replica] = {
                "lag_seconds": round(lag, 3),
                "replica_last_sync": replica_time.isoformat(),
                "status": "healthy" if lag < 1.0 else "warning" if lag < 2.0 else "critical"
            }
        return results

    def monitor_loop(self, iterations=3, interval=1):
        print(self.simulate_write())
        for i in range(iterations):
            time.sleep(interval)
            statuses = self.check_lag()
            print(f"\nCheck {i + 1}:")
            for replica, info in statuses.items():
                print(f"  {replica}: lag={info['lag_seconds']}s, "
                      f"status={info['status']}, sync={info['replica_last_sync'][:19]}")

if __name__ == "__main__":
    monitor = MockReplicaLagMonitor(replicas=3, base_lag=0.7, jitter=0.5)
    monitor.monitor_loop(iterations=3, interval=1)