DUMMY_BACKEND.md

Dummy / Mock Backends for Local Development

Purpose: Set up local backend servers for testing the proxy without requiring cloud deployments.

TL;DR

• Fastest: cd test/nullserver/Python && python streamserver.py (already in repo)
• Standard Python: python -m http.server 3000 (built-in)
• Full stack example at bottom of this doc

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Included Null Server (Recommended)

Rule: Use the included null server for the fastest mock backend; it requires only Python and no extra dependencies.

The proxy repository includes a lightweight mock server in test/nullserver/Python that responds to all requests with configurable delays.

# Terminal 1 — start the included mock backend
cd test/nullserver/Python
python streamserver.py

# Terminal 2 — start the proxy pointing at it
export Port=8080
export Host1=http://localhost:3000
dotnet run

Note

Host1 must be reachable before the proxy starts or the initial health check will mark it as OPEN.

Tip

Troubleshooting: Run curl http://localhost:3000/ to confirm the mock backend is up before starting the proxy.

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Standard Python HTTP Server

For simple testing, use Python's built-in HTTP server:

# Terminal 1
python -m http.server 3000

# Terminal 2
python -m http.server 5000

# Terminal 3
export Port=8080
export Host1=http://localhost:3000
export Host2=http://localhost:5000
dotnet run

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Testing Scenarios

Rule: Test the proxy with simple requests before running load tests.

# First, verify the backend is serving the file directly (not through proxy)
curl http://localhost:3000/lorem_ipsum.txt

# Then test through the proxy (should return same content)
curl http://localhost:8080/lorem_ipsum.txt

# Simple sequential load test (10 requests, shows status)
for i in {1..10}; do curl -w "Request $i: %{http_code}\n" -o /dev/null http://localhost:8080/lorem_ipsum.txt; done

# Parallel load test with timing (100 requests, 5 concurrent)
time for i in {1..100}; do curl -s http://localhost:8080/lorem_ipsum.txt > /dev/null & [ $((i % 5)) -eq 0 ] && wait; done

Tip

Verify backend first: If curl http://localhost:3000/lorem_ipsum.txt returns empty, the backend isn't serving files. Ensure you're running python -m http.server 3000 from the test/nullserver/Python directory where lorem_ipsum.txt lives.

Warning

Error: A 429 response during load testing means MaxQueueLength was reached — increase it or reduce concurrency.

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Container Development with Mock Backends

Rule: Build the image locally and inject environment variables at docker run time; do not bake secrets into the image.

docker build -t proxy-dev -f Dockerfile .

docker run -p 8080:443 \
  -e Host1=http://host.docker.internal:3000 \
  -e Host2=http://host.docker.internal:5000 \
  -e LogAllRequestHeaders=true \
  -e Workers=5 \
  proxy-dev

Note

Use host.docker.internal to reach mock backends running on the host from inside the container.

Tip

Troubleshooting: If the container exits immediately, check logs with docker logs <container-id> — a missing Host1 value is the most common cause.

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Canonical Example — Full Local Stack

Goal: proxy on port 8080 with two mock backends, header logging enabled, and clear reproduce -> inspect -> verify steps.

Step	Command	Expected result
Start backend 1	python -m http.server 3000	Listening on :3000
Start backend 2	python -m http.server 5000	Listening on :5000
Export config	export Port=8080 Host1=http://localhost:3000 Host2=http://localhost:5000 Workers=10 LogAllRequestHeaders=true	—
Start proxy	dotnet run	Listening on port 8080
Reproduce + inspect	curl -v http://localhost:8080/lorem_ipsum.txt	Lorem ipsum text from backend 1 or 2
Apply fault + verify failover	Stop backend 1; curl http://localhost:8080/	200 OK routed to backend 2

Stopping backend 1 while the proxy is running triggers circuit-breaker logic — subsequent requests route automatically to backend 2.