"It works on my machine." We've all said it. But does your bash script work when the third-party API takes 15 seconds to respond? Does your backend service gracefully handle a sudden spike of 503 errors from a payment provider? Writing a full mock server just to test a simple retry logic in a script is often overkill. In this tutorial, I'll show you a faster way: Chaos Engineering directly in the terminal. Chaos Engineering directly in the terminal We will use curl and a cloud-based Chaos Proxy to inject failures into real network requests without changing a single line of your application code. curl The Problem: Localhost is Too Perfect When developing locally, network latency is near zero. APIs either work (200 OK) or they don't (Connection Refused). But in production, you face: High Latency: The server is busy.Intermittent Failures: 5% of requests drop.Throttling: You hit the rate limit. High Latency Intermittent Failures Throttling Simulating this in a terminal usually involves complex iptables rules or local tools like tc (Traffic Control). There is an easier way. iptables tc The Solution: Cloud Chaos Proxy Instead of configuring your OS, we will route specific requests through a proxy that "breaks" the traffic according to rules we define. I'll be using chaos-proxy.debuggo.app for this, but the concept applies to any programmable proxy. Video Guide (1:27) Prefer watching? Here is the 90-second workflow: https://www.youtube.com/watch?v=x_S-guPwPEk&embedable=true https://www.youtube.com/watch?v=x_S-guPwPEk&embedable=true Step-by-Step Tutorial Step-by-Step Tutorial 1. Define the Failure First, we need to tell the proxy what to break. Target: httpbin.org (or your API domain). Delay: 7 seconds (Simulate lag). Failure Rate: 1 (100% of requests will fail). Error Code: 503 Service Unavailable. Target: httpbin.org (or your API domain). httpbin.org Delay: 7 seconds (Simulate lag). 7 seconds Failure Rate: 1 (100% of requests will fail). Error Code: 503 Service Unavailable. 2. Trust the Certificate (The "One-Time" Setup) Since we are intercepting HTTPS traffic, we need to trust the proxy's CA certificate. Download the mitmproxy-ca-cert.pem from the dashboard. mitmproxy-ca-cert.pem MacOS: Add it to Keychain Access -> System and set "Always Trust." MacOS: Linux: Copy to /usr/local/share/ca-certificates/ and update. Linux: 3. The Magic Command Now, we use curl with the -x(proxy) flag. curl -x curl -v -x http://user:pass@chaos-proxy.debuggo.app:13979 https://httpbin.org/get curl -v -x http://user:pass@chaos-proxy.debuggo.app:13979 https://httpbin.org/get Understanding the Output When you run this command multiple times: Scenario A (The Chaos): You'll notice the terminal "hangs" for 7 seconds (our delay). Then: < HTTP/1.1 500 Internal Server Error < content-length: 56 < content-type: text/plain ... Debuggo Chaos Injection: 500 Error < HTTP/1.1 500 Internal Server Error < content-length: 56 < content-type: text/plain ... Debuggo Chaos Injection: 500 Error Scenario B (Success): The other 50% of the time, the request passes through to the real server: Scenario B (Success) < HTTP/1.1 200 OK ... { "args": {}, "headers": { ... } } < HTTP/1.1 200 OK ... { "args": {}, "headers": { ... } } Real World Use Cases Real World Use Cases Testing CI Pipelines: Verify that your deployment scripts don't crash if a dependency is slow. Cron Jobs: Ensure your nightly data sync retries correctly on failure. Quick Sanity Checks: Before pushing code, verify how the API client handles a 503 error. Testing CI Pipelines: Verify that your deployment scripts don't crash if a dependency is slow. Testing CI Pipelines Cron Jobs: Ensure your nightly data sync retries correctly on failure. Cron Jobs Quick Sanity Checks: Before pushing code, verify how the API client handles a 503 error. Quick Sanity Checks Conclusion You don't need heavy infrastructure to test network resilience. A simple proxy setup allows you to inject chaos into any HTTP client—be it curl, wget, or your Python/Node.js scripts. curl wget Happy Breaking! 🔨
