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How to Expand a Contract and Migrate Data in Python
Expand an old data contract by renaming fields and adding defaults, then migrate to a final version with deepcopy isolation.
import json
from copy import deepcopy
# Mock data representing a user record (old contract)
old_contract = {
"id": 1,
"name": "Alice",
"email": "alice@example.com",
"age": 30,
"status": "active"
}
# Expanded contract: adds fields with defaults and renames some fields
expand_rules = {
"id": "u…How to Mock Canary Deployment Traffic Split in Python
Simulate a canary deployment's stable/canary traffic split using deterministic request hashing to mock rollout behavior with precise percentage control.
class CanaryDeployment:
def __init__(self, stable_weight: float = 0.9, canary_weight: float = 0.1):
self.stable_weight = stable_weight
self.canary_weight = canary_weight
self.total_weight = stable_weight + canary_weight
def route_request(self, request_id: int) -> str:
"""Route …How to Mock Image Signing Cost in Python
Create a deterministic mock signing cost calculator that predicts resource usage for image signatures before real signing infrastructure is staged.
import math
import struct
def sign_image_cost(image_signature: bytes) -> int:
"""Deterministic mock signing cost based on image signature bytes."""
if not image_signature:
raise ValueError("Empty image signature")
digest = 0
for byte in image_signature:
digest = (digest * 31 + byte) &…How to Mock Kubernetes Secret Mounts in Python
Create and inspect a mock Kubernetes secret volume mount using the official client library and unittest.mock.
import json
from kubernetes import client, config, watch
from unittest.mock import Mock, patch
def create_mock_mount_spec():
"""Create a mock Kubernetes secret volume mount."""
mock_client = Mock()
mock_client.api_version = "v1"
mock_client.kind = "Secret"
mock_client.metadata = {"name": "my-secre…How to Mock Kubernetes Services with a ClusterIP Registry in Python
Simulate Kubernetes service discovery by assigning ClusterIP addresses to dataclass-defined services, with JSON export for inspection or testing.
import json
from dataclasses import dataclass, asdict
from typing import Dict, Optional
@dataclass
class Service:
name: str
namespace: str
cluster_ip: str
selector: Dict[str, str]
port: int
target_port: Optional[int] = None
class ClusterIPServiceRegistry:
_ip_counter = 0
def __init…How to Simulate Blue-Green Deployment Switch in Python
A mock Blue-Green deployment class that deploys new versions to an inactive environment, runs a health check, switches traffic, and supports rollback in Python.
import random
import time
class BlueGreenDeployment:
def __init__(self, initial_env="blue"):
self.environments = {"blue": "v1.0", "green": "v1.0"}
self.active_env = initial_env
self.running = True
def deploy_new_version(self, version, target_env):
if target_env == self.active_…How to Smoke Test a Deployment in Python with unittest.mock
Run a post-deploy smoke test by mocking the deployment status check to verify your health-check logic returns PASS/FAIL.
import unittest
from unittest.mock import Mock, patch
class DeploymentService:
def check_status(self):
return "unknown"
def smoke_test_deploy():
service = DeploymentService()
with patch.object(service, "check_status", return_value="healthy") as mock_check:
status = service.check_status()
…How to mock Kustomize overlay patches in Python
Simulate Kustomize overlay behavior by deep-merging a base Kubernetes manifest with a patch dictionary in pure Python.
import json
SOURCE = {
"apiVersion": "apps/v1",
"kind": "Deployment",
"metadata": {"name": "app", "namespace": "prod"},
"spec": {
"replicas": 3,
"template": {
"spec": {
"containers": [{"name": "app", "image": "nginx:1.19"}]
}
}
}
}
P…How to mock S3 remote backend for Terraform in Python
Simulate a Terraform S3 remote backend using moto to write and read state files, enabling local testing without real AWS.
import boto3
from moto import mock_aws
import json
from pathlib import Path
@mock_aws
def demo_s3_remote_backend():
s3 = boto3.client("s3", region_name="us-east-1")
bucket = "terraform-state-bucket"
key = "env/prod/terraform.tfstate"
s3.create_bucket(Bucket=bucket)
# Simulate Terraform w…Mock ConfigMap Mount Environment Variables in Python
Simulate reading environment variables from a Kubernetes ConfigMap-mounted directory and test it with mocks.
import os
import tempfile
from unittest.mock import patch
def load_config_from_mount(mount_path):
"""Simulate reading environment variables from a ConfigMap-mounted directory."""
config = {}
for filename in os.listdir(mount_path):
file_path = os.path.join(mount_path, filename)
if os.path.i…Mock Kubernetes HPA CPU Scaling in Python
Python function that simulates CPU utilization and calculates desired replicas using the Kubernetes HPA formula.
import random
import time
def simulate_cpu_utilization(target_utilization=50, samples=10):
"""Simulate CPU utilization readings for HPA mock."""
utilizations = []
for _ in range(samples):
# Simulate fluctuating CPU with random noise around target
current = target_utilization + random.unif…Zero Downtime Migration with Dual Write Pattern in Python
Implement a dual-write pattern that writes user data to both legacy and new systems simultaneously to enable zero-downtime migration.
from datetime import datetime
import json
class UserService:
def __init__(self):
self.legacy_db = {}
self.new_db = {}
self.migration_log = []
def write_user(self, user_id, name, email):
# Write to new system first
user_record = {
"id": user_id,
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