cron-checker/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

A Kubernetes monitoring tool that checks for CronJobs not running according to schedule and sends Slack notifications. It runs as a container inside a K8s cluster, polling all CronJobs every 60 seconds.

Common Commands

# Run tests
go test ./...

# Run tests with race detection and coverage
go test -race -coverprofile=coverage.txt ./...

# Build the binary
CGO_ENABLED=0 go build -o release/cron-checker -ldflags '-w -s'

# Check for vulnerabilities
govulncheck ./...

# Format and vet
go fmt ./...
go vet ./...

# Check for unused modules
go mod tidy

Architecture

This is a single-file Go application (main.go) with comprehensive tests (main_test.go).

Core Components:

• doCheck() - Main loop that polls K8s CronJobs, parses cron schedules, and sends Slack alerts for overdue jobs
• Client / ClientProvider interfaces - Abstractions over K8s client for testability
• ConfigProvider / InClusterProvider - Handles K8s in-cluster authentication

Key Dependencies:

• k8s.io/client-go - Kubernetes API client
• github.com/robfig/cron - Cron schedule parsing
• github.com/multiplay/go-slack - Slack webhook integration
• github.com/alecthomas/kingpin/v2 - CLI flag parsing

Configuration:

• SLACK_URL env var or --slack-url flag (required) - Slack webhook URL for notifications

Building Docker Image

The Dockerfile performs a multi-stage build that runs fmt, vet, and tests before building:

docker build -t cron-checker .

To extract coverage report:

docker build --target export -o . .