Reference library

Observability & SRE

Structured logging, metrics, tracing, health checks, and SLO-friendly instrumentation.

29 matches

How to Track Cache Hit Ratio in Python

Simulate an LRU cache with hit/miss tracking and compute a real-time hit ratio from random access patterns.

import random
import time
from collections import OrderedDict

class LRUCache:
    def __init__(self, capacity: int):
        self.cache = OrderedDict()
        self.capacity = capacity
        self.hits = 0
        self.misses = 0

    def get(self, key):
        if key in self.cache:
            self.hits += 1
     …

13 0 Open

Observability & SRE easy

How to mock Prometheus alert rule thresholds in Python

Simulate a Prometheus alert rule with a configurable threshold and duration window, firing only when the metric exceeds the threshold long enough.

prometheus alerting sre

Python

import time
import random


class MetricsStore:
    def __init__(self):
        self.metrics = {}

    def set_metric(self, name, value, labels=None):
        key = (name, tuple(sorted((labels or {}).items())))
        self.metrics[key] = value

    def get_metric(self, name, labels=None):
        key = (name, tuple(s…

14 0 Open

Observability & SRE easy

How to mock SLI availability success ratio in Python

Simulate request outcomes with deterministic randomness and compute the SLI availability success ratio to check if a target is met.

sli availability monitoring

Python

import random
from collections import defaultdict

def mock_availability(num_requests=1000, target_ratio=0.995):
    """
    Simulate request outcomes and compute the SLI availability success ratio.
    
    Args:
        num_requests: Total number of requests to simulate
        target_ratio: Target availability rati…

14 0 Open

Observability & SRE easy

Mocking a Metrics Gauge's set_value Method in Python

Demonstrates using unittest.mock.Mock with wraps to intercept a gauge's set_value call while verifying arguments and preserving real behavior.

unittest mocking metrics

Python

from unittest.mock import Mock

class MetricsGauge:
    def __init__(self, name):
        self.name = name
        self.value = 0.0

    def set_value(self, new_value):
        self.value = float(new_value)
        return self.value

# Usage demonstration with a mock
gauge = MetricsGauge("cpu_usage")
gauge_mock = Mock…

13 0 Open

Observability & SRE easy

Rotate Log Files by Size in Python

A mock log rotation script that renames log files exceeding a size threshold, appending numbered backups.

log-rotation pathlib file-management

Python

import os
from pathlib import Path

def rotate_logs(directory: str, max_size: int = 100) -> None:
    """Rotate log files that exceed max_size bytes."""
    log_dir = Path(directory)
    for log_file in sorted(log_dir.glob("*.log"), key=lambda p: str(p)):
        if log_file.stat().st_size > max_size:
            for …

13 0 Open

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