circuit-breaker.md

description
This page provides the technical details of the Circuit Breaker policy

Circuit Breaker

Overview

This policy allows switching to another backend or making the call fail with a 503 Service Unavailable in case of errors or latency. It guarantees high availability by making your system resilient if your target is detected as failing.

It is possible to configure errors and latency threshold rates to open the circuit breaker.

Implementation is based on Resilience4j. Refer to their documentation for more information.

Functional and implementation information for the circuit-breaker policy is organized into the following sections:

• Examples
• Configuration
• Compatibility Matrix
• Changelogs

Examples

{% hint style="warning" %} This policy can only be applied to v2 APIs. It cannot be applied to v4 message APIs or v4 proxy APIs. {% endhint %}

{% tabs %} {% tab title="HTTP proxy API example" %} Sample policy configuration:

{
  "name": "Circuit breaker",
  "description": "",
  "enabled": true,
  "policy": "policy-circuit-breaker",
  "configuration": {
    "failureRateThreshold": 1,
    "slowCallRateThreshold": 10,
    "slowCallDurationThreshold": 500,
    "windowSize": 2,
    "waitDurationInOpenState": 50000,
    "redirectToURL": ""
  }
}

{% endtab %} {% endtabs %}

Configuration

Options

You can configure the circuit-breaker policy with the following options:

Property	Required	Description	Type	Default
failureRateThreshold	true	Failure rate threshold before the circuit breaker switches to open state. A failure represents a response’s status code >= 500. The threshold is expressed as a percentage.	integer (min. 0, max.100)	50
slowCallRateThreshold	true	Slow call rate threshold before the circuit breaker switches to open state. A slow call is represented by a response time greater than the configured slowCallDurationThreshold. The threshold is expressed as a percentage.	integer (min. 0, max.100)	50
slowCallDurationThreshold	true	The duration threshold above which a call is considered as slow, increasing slowCallRateThreshold. The duration is expressed in milliseconds.	integer (min. 1)	1000
windowSize	true	The size of the sliding window which is used to record the outcome of calls when the circuit is closed.	integer (min. 0)	100
waitDurationInOpenState	false	The duration in millisecond before switching from open circuit to half-open.	integer (min. 1)	1000
redirectToURL	false	Redirect the call to the given URL instead of returning '503 Service Unavailable' status (supports EL)	string
scope	true	Cached response can be set for a single consumer (application) or for all applications.<br><strong>WARNING:</strong> Please be aware that by using an \"API\" scope, data will be shared between all consumers !	API / APPLICATION	APPLICATION

Phases

The phases checked below are supported by the circuit-breaker policy:

v2 Phases	Compatible?	v4 Phases	Compatible?
onRequest	true	onRequest	false
onResponse	false	onResponse	false
onRequestContent	false	onMessageRequest	false
onResponseContent	false	onMessageResponse	false

Compatibility matrix

The following is the compatibility matrix for APIM and the circuit-breaker policy:

Plugin Version	Supported APIM versions
Up to 1.x	All

Changelogs

{% @github-files/github-code-block url="https://github.com/gravitee-io/gravitee-policy-circuit-breaker/blob/master/CHANGELOG.md" %}