OOMlet — a lightweight, chaos-friendly QA and debugging Spring Boot application designed to help you test, stress, and harden your systems.

🍳 Crack limits. Scramble resources. Cook up resilience.

• Quick Start
• API Endpoints
• Stress Testing Endpoints
• Connectivity & Delay Simulation
• Crash the Application
• Runtime Configuration
• Docker and Kubernetes Support
• Testing and Code Coverage
• Signal Handling
• Architecture Overview

• ✅ Dynamic health check toggling (pass/fail)
• ✅ Simulate arbitrary HTTP response codes
• ✅ Memory and file handle stress testing endpoints
• ✅ CPU load simulation
• ✅ Graceful OS signal handling (SIGINT, SIGTERM, USR1, USR2)
• ✅ Runtime log level adjustment (dynamic)
• ✅ Crash with specific exit codes
• ✅ Outbound connectivity tester (ping a URL)
• ✅ Simulate response latency
• ✅ Full Actuator integration
• ✅ Code coverage enforcement (80% minimum)
• ✅ Built for local development, Docker, and Kubernetes

• Java 17+ (Temurin recommended)
• Maven 3.8+ (no need to install if using the Maven Wrapper)

./mvnw clean package

java -jar target/oomlet-0.0.8.jar

(Optional) Override port:

SERVER_PORT=9090 java -jar target/oomlet-0.0.8.jar

curl 'http://localhost:8080/api/allocate-memory?bytes=104857600'

curl 'http://localhost:8080/api/open-files?count=100'

curl 'http://localhost:8080/api/burn-cpu?millis=5000&threads=4'

curl 'http://localhost:8080/api/ping?url=https://example.com'

curl 'http://localhost:8080/api/latency?delayMillis=1500'

Use this to simulate process failure and container exit.

curl -X POST 'http://localhost:8080/api/crash?code=137'

curl -X POST 'http://localhost:8080/api/logging/spring?level=DEBUG'

curl 'http://localhost:8080/api/logging/spring'

You can limit or expand memory usage for stress tests:

JAVA_OPTS="-Xmx512m -Xms128m" java -jar target/oomlet-0.0.8.jar

docker build -t oomlet:latest .

docker run -p 8080:8080 oomlet:latest

✅ Designed to be liveness- and readiness-probe friendly.
✅ Docker image built for minimal size and startup speed.

Run unit and integration tests:

./mvnw clean verify

Open coverage report:

open target/site/jacoco/index.html

View live coverage:

• GitHub Pages: https://trcjr.github.io/oomlet
• Codecov: https://codecov.io/gh/trcjr/oomlet

✅ Enforced 80%+ line coverage.
✅ Build fails if coverage threshold not met.
✅ CI/CD runs on each push via GitHub Actions.

This project enforces 80% minimum line coverage using JaCoCo.

Fail the build on low coverage by editing pom.xml:

<rule>
  <element>BUNDLE</element>
  <limits>
    <limit>
      <counter>INSTRUCTION</counter>
      <value>COVEREDRATIO</value>
      <minimum>0.80</minimum>
    </limit>
  </limits>
</rule>

Or use .codecov.yml in root:

coverage:
  status:
    project:
      default:
        target: 80%
        threshold: 1%

All GitHub Actions workflows in this project follow strict rules for consistency and reliability. This includes:

• ✅ Git short hashes must be set using git rev-parse --short HEAD and passed via $GITHUB_OUTPUT
• ✅ Helm chart versions must be valid SemVer using the -dev.<short_hash> format
• ✅ CI/CD steps are explicitly structured to avoid flakiness and ensure reproducibility

OOMlet handles:

• SIGINT (Ctrl+C)
• SIGTERM (docker stop, kubectl delete pod)
• SIGHUP, SIGQUIT, SIGUSR1, SIGUSR2

Gracefully shuts down or logs custom signals.

• SIGUSR1 — logs current heap usage and active memory state
• SIGUSR2 — logs thread dump and internal diagnostics

┌────────────────────────────┐
│        Client / User        │
└─────────────┬──────────────┘
              │
        HTTP Requests
              │
┌─────────────▼──────────────┐
│      Spring Boot Server     │
└─────────────┬──────────────┘
              │
    ┌─────────┼──────────┬──────────────┬──────────────┬─────────────┐
    │         │           │              │              │
┌───▼───┐ ┌────▼────┐ ┌────▼────┐ ┌───────▼─────┐ ┌──────▼────┐
│status│ │open-files││allocate │ │ /ulimits    │ │actuator   │
│      │ │          ││memory   │ │ burn-cpu    │ │ health, etc│
└──────┘ └──────────┘└─────────┘ └─────────────┘ └───────────┘
              │
              ▼
    ┌─────────────────────────────┐
    │ SignalHandlerService        │
    └─────────┬───────────────────┘
              ▼
        Graceful Shutdown

MIT — see LICENSE

We welcome PRs and issues. Start with CONTRIBUTING.md
Look for issues labeled good first issue to help out!