The Circuit Breaker Traffic Policy action helps you maintain system reliability by rejecting requests when the error rate and request volume within a rolling window exceed defined thresholds. It pauses traffic temporarily to allow the system to recover and automatically re-evaluates upstream health before resuming.

​
Configuration Reference

The Traffic Policy configuration reference for this action.

​
Supported Phases

on_http_request

​
Type

circuit-breaker

​
Configuration Fields

​
error_threshold
float
default:0.5
Required
Threshold percentage of errors that must be met before requests are rejected.Must be a value between 0.0 and 1.0.
​
volume_threshold
integer
default:10
Number of requests in a rolling window before checking the error threshold.Must be a number between 1 and 2,000,000,000.
​
window_duration
duration
default:10s
Number of seconds in the rolling window that metrics are retained for.Must be a value between 1s and 2m.
​
tripped_duration
duration
default:10s
Number of seconds the system waits after rejecting a request before re-evaluating upstream health.Must be a value between 1s and 2m.
​
num_buckets
integer
Number of buckets that metrics are divided into within the rolling window.Fixed at 10.
​
enforce
boolean
default:true
Determines if the circuit breaker is active.If false, the circuit breaker never trips, and no requests are rejected.

​
Examples

​
Basic Example

This example configuration sets up an endpoint (hotdog.ngrok.app) that allows only 1 request every 60 seconds and trips the circuit breaker for 2 minutes.

​
Example Traffic Policy Document

on_http_request:
  - actions:
    - type: "circuit-breaker"
      config:
        error_threshold: 0
        volume_threshold: 1
        window_duration: "60s"
        tripped_duration: "2m"
        enforce: true

​
Start Endpoint with Traffic Policy

ngrok http 8080 --url hotdog.ngrok.app --traffic-policy-file /path/to/policy.yml

​
Helper script

circuit_breaker.py
import requests
import time


url = "https://hotdog.ngrok.app"

attempt = 1

while True:
    try:
        response = requests.get(url)

        # Log the response
        if response.status_code == 200:
            print(f"Attempt {attempt}: Success ({response.status_code})")
        else:
            print(f"Attempt {attempt}: Failure ({response.status_code})")

        # Stop when circuit breaker trips
        if response.status_code == 503:
            print("\nCircuit breaker tripped!")
            break
    except requests.exceptions.RequestException as e:
        print(f"Attempt {attempt}: Error ({e})")
        break

    attempt += 1
    time.sleep(0.01)  # Reduce delay for faster request rate

➜  ~ python3  circuit_breaker.py
Attempt 1: Success (200)
Attempt 2: Failure (503)

Circuit breaker tripped!

​
Action Result Variables

The following variables are made available for use in subsequent expressions and CEL interpolations after the action has run. Variable values will only apply to the last action execution, results are not concatenated.
This action does not expose any result variables.