40 SRE Scripts

A hands-on library of Python scripts covering real-world Site Reliability Engineering tasks and common interview questions. Every script is self-contained with a deep README that explains the why, the how, and what the interviewer is looking for.

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📋 Script Index

#	Folder	What It Does	Key Concept	Platform
01	disk-usage-check	Checks / filesystem usage, warns if > 80%	shutil.disk_usage()	Linux + macOS
02	memory-usage-check	Parses /proc/meminfo to check available RAM	/proc/meminfo parsing	Linux
03	cpu-usage-check	Two-snapshot delta on /proc/stat for real CPU %	/proc/stat delta method	Linux
04	top-cpu-processes	Ranks top 5 CPU-hungry processes without psutil	/proc/<pid>/stat delta	Linux
05	systemd-service-check	Checks service state; auto-starts if inactive	subprocess + systemctl	Linux (systemd)
06	log-error-counter	Counts ERROR lines; alerts if above threshold	Line-by-line file iteration	All platforms
07	http-health-check	Checks HTTP endpoint — prints UP or DOWN	urllib, timeout, HTTPError vs URLError	All platforms
08	largest-files-finder	Recursively finds top 5 largest files	os.walk(), symlink safety	Linux + macOS
09	tcp-port-checker	Tests if a TCP port is OPEN or CLOSED	Raw socket, 3-way handshake	All platforms
10	stale-log-checker	Warns if a log file hasn't been written to in > 5 min	os.path.getmtime(), Unix timestamps	Linux + macOS
11	suspicious-ip-detector	Flags IPs with > 5 failed login attempts	Dict counting, dict.get() pattern	All platforms
12	http-status-counter	Counts requests per HTTP status code from access logs	Combined Log Format parsing	All platforms
13	mariadb-connection-check	Verifies MariaDB is live by reading the MySQL protocol greeting	MySQL protocol bytes, greeting[4]	All platforms
14	redis-connection-check	Sends RESP PING, verifies PONG, reports RTT latency	RESP protocol, sendall, latency	All platforms
15	port-process-finder	Finds which process owns a TCP port	ss -lptn, subprocess, regex groups	Linux
16	config-file-diff	Compares two config files; reports missing/changed lines	difflib.unified_diff()	All platforms
17	http-retry-health-check	Health check with 3 retries and exponential backoff	Retry loop, 2^attempt backoff	All platforms
18	load-average-check	Warns if 1-min load average exceeds CPU core count	/proc/loadavg, os.cpu_count(), trend	Linux
19	zombie-process-scanner	Scans all processes and reports zombie (Z state) processes	/proc/<pid>/stat, rfind parse, race condition	Linux
20	memory-leak-detector	Detects continuous memory increase across last 3 log readings	split()[-1], values[-3:], chained comparison	All platforms

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🚀 Quick Start

git clone https://github.com/AssassinSaurabh/40-SRE-Scripts.git
cd 40-SRE-Scripts

# System health
python3 01-disk-usage-check/disk_usage_check.py
python3 18-load-average-check/load_average_check.py

# Process management
python3 19-zombie-process-scanner/zombie_process_scanner.py

# Network & ports
python3 09-tcp-port-checker/tcp_port_checker.py google.com 443
python3 15-port-process-finder/port_process_finder.py 8080

# Log analysis
python3 11-suspicious-ip-detector/suspicious_ip_detector.py /var/log/auth.log
python3 12-http-status-counter/http_status_counter.py /var/log/nginx/access.log

# Database checks
python3 13-mariadb-connection-check/mariadb_connection_check.py
python3 14-redis-connection-check/redis_connection_check.py

# Config & files
python3 16-config-file-diff/config_diff.py server1.conf server2.conf
python3 17-http-retry-health-check/http_retry_health_check.py https://myapp.com/health

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📚 What Each README Contains

Every script folder has a README.md with these sections:

1. The Interview Question — exact phrasing as asked in real interviews
2. What This Script Does — numbered list of what the script actually does
3. The Solution — the minimal clean code block
4. How We Achieved This — every line explained from first principles
5. What the Interviewer Is Looking For — table of evaluation criteria
6. How This Convinces the Interviewer — production context + what to say
7. Sample Output — exact terminal output for each scenario
8. Usage — copy-paste commands

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🗺️ Topics Covered

Category	Scripts
System Monitoring	01 Disk, 02 Memory, 03 CPU, 04 Top Processes, 18 Load Average
Process & Service Management	05 Systemd, 15 Port Finder, 19 Zombie Scanner
Log Analysis	06 Error Counter, 10 Stale Log, 11 Suspicious IPs, 12 HTTP Status
Network & Connectivity	07 HTTP Check, 09 TCP Port, 17 Retry Health Check
Database Checks	13 MariaDB, 14 Redis
File & Config	08 Largest Files, 16 Config Diff

Coming soon: DNS lookup, PostgreSQL check, Kubernetes pod status, disk I/O monitor, network bandwidth monitor, deployment verification scripts, cron job utilities.

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🎯 Goal

Build 40 production-grade SRE Python scripts that:

• Use Python built-in modules only (no psutil, no requests, no third-party libs unless the question requires it)
• Demonstrate deep understanding of Linux internals (/proc, ss, systemctl, log formats)
• Show protocol-level knowledge (MySQL greeting packet, RESP PING/PONG, TCP handshake)
• Are ready to copy-paste and run on any Linux server

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Written with deep explanations so that even someone new to SRE can understand not just the what but the why behind every line.