circuit-breaker fails to get triggered by http error codes

[friedrichtroescher]

Environment info:

• KrakenD version: Version: 2.6.3
• System info: Darwin 23.5.0 arm64
• Hardware specs: Apple M1 Pro, 16GB Ram, Mac OS Sonoma
• Backend technology: Python (Flask)
• Additional environment information:

Describe the bug
If the python backend causes a timeout, the circuit breaker opens as it should. If the backend returns a status code which is not 20x (as described in the official documentation), the circuit breaker is not triggered.

Your configuration file:

To replicate, you can clone the repo https://github.com/friedrichtroescher/testkrakend

krakend.json:

{
  "version": 3,
  "endpoints": [
    {
      "endpoint": "/api",
      "output_encoding": "no-op",
      "input_query_strings": [
        "*"
      ],
      "input_headers": [
        "*"
      ],
      "backend": [
        {
          "encoding": "no-op",
          "host": [
            "localhost:8081"
          ],
          "url_pattern": "/api",
          "extra_config": {
            "qos/circuit-breaker": {
              "interval": 60,
              "timeout": 60,
              "max_errors": 2,
              "name": "version-endpoint",
              "log_status_change": true
            }
          }
        }
      ],
      "extra_config": {
        "qos/ratelimit/router": {
          "max_rate": 1000,
          "capacity": 100,
          "client_max_rate": 200,
          "client_capacity": 100,
          "every": "10m",
          "strategy": "ip"
        }
      }
    }
  ]
}

app.py:

from flask import Flask, request, abort

app = Flask(__name__)
import time


@app.route('/api')
def hello_world():
    # read query parameter "crash"
    crash = request.args.get('crash')
    if crash == "false":
        # raise exception to crash the application
        return 'Hello World!'

    status = int(request.args.get('status'))
    abort(status)


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8081)

requirements.txt:

Flask==2.0.1

Dockerfile:

# Use the official Python image from the Docker Hub
FROM python:3.9-slim

# Set the working directory in the container
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install Flask
RUN pip install flask

# Make port 8081 available to the world outside this container
EXPOSE 8081

# Define environment variable
ENV FLASK_APP=app.py

# Run app.py when the container launches
CMD ["flask", "run", "--host=0.0.0.0", "--port=8081"]

Commands used
How did you start the software?

docker build -t flask-app . && docker run -p 8081:8081 flask-app

krakend run -c krakend.json

curl -v "localhost:8080/api?crash=true&status=500"

Expected behavior
After the third curl within 60 seconds, the circuit breaker should open.

Logs

krakend run -c krakend.json
Parsing configuration file: krakend.json
2024/07/02 15:52:28 KRAKEND INFO: Starting KrakenD v2.6.3
2024/07/02 15:52:28 KRAKEND INFO: Working directory is /Users/friedricht/MaibornWolff/BMW SRPLM Customer Touchpoints/testkrakend
2024/07/02 15:52:28 KRAKEND INFO: Starting the KrakenD instance
2024/07/02 15:52:28 KRAKEND DEBUG: [ENDPOINT: /api] Building the proxy pipe
2024/07/02 15:52:28 KRAKEND DEBUG: [BACKEND: /api] Building the backend pipe
2024/07/02 15:52:28 KRAKEND DEBUG: [BACKEND: /api][CB] Creating the circuit breaker named 'version-endpoint'
2024/07/02 15:52:28 KRAKEND DEBUG: [ENDPOINT: /api] Building the http handler
2024/07/02 15:52:28 KRAKEND DEBUG: [ENDPOINT: /api][JWTSigner] Signer disabled
2024/07/02 15:52:28 KRAKEND DEBUG: [ENDPOINT: /api][Ratelimit] Rate limit enabled. MaxRate: 1.666667, Capacity: 100
2024/07/02 15:52:28 KRAKEND DEBUG: [ENDPOINT: /api][Ratelimit] IP-based rate limit enabled. MaxRate: 0.333333, Capacity: 100
2024/07/02 15:52:28 KRAKEND INFO: [ENDPOINT: /api][JWTValidator] Validator disabled for this endpoint
2024/07/02 15:52:28 KRAKEND INFO: [SERVICE: Gin] Listening on port: 8080
[GIN] 2024/07/02 - 15:52:30 | 500 | 6.345166ms | ::1 | GET "/api?crash=true&status=500"
[GIN] 2024/07/02 - 15:52:31 | 500 | 4.436083ms | ::1 | GET "/api?crash=true&status=500"
[GIN] 2024/07/02 - 15:52:32 | 500 | 3.456792ms | ::1 | GET "/api?crash=true&status=500"
[GIN] 2024/07/02 - 15:52:33 | 500 | 4.512625ms | ::1 | GET "/api?crash=true&status=500"
2024/07/02 15:52:33 KRAKEND DEBUG: [SERVICE: Telemetry] Registering usage stats for Cluster ID bYnAQYy7eLHKdzKDBJOeMCsbB631Syxkmju3Vm4qxpY=

Additional context
It can be validated that the circuit breaker can open by killing the python backend. Oddly, this causes an error which does trigger the circuit breaker.

[kpacha]

please, check this issue: krakend/krakend-circuitbreaker#12

[github-actions]

An issue like this already exists, please follow it in the other thread

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[alombarte]

The documentation has been adjusted for the next release to make it more clear.