retry.md

description
This page provides the technical details of the Retry policy

Retry

Overview

You can use the retry policy to replay requests when experiencing backend connection issues or if the response meets a given condition.

If the retry takes too long, relative to the timeout value, the request stops and returns status code 502.

{% hint style="info" %} To replay a request with a payload, the Gateway stores it in memory. We recommend you avoid applying it to requests with a large payload. {% endhint %}

Functional and implementation information for the retry policy is organized into the following sections:

• Examples
• Configuration
• Compatibility Matrix
• Errors
• 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:

{
  "retry": {
    "condition": "{#response.status > 500}",
    "maxRetries": 3,
    "timeout": 1000
  }
}

{% endtab %} {% endtabs %}

Configuration

Phases

The phases checked below are supported by the retry policy:

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

Options

The retry policy can be configured with the following options:

Property	Required	Description	Default	Example
condition	true	Condition to test to determine whether or not to retry the request (supports Expression Language)	-	{#response.status > 500}
maxRetries	true	Number of retries before failing (502 - Bad Gateway)	1	-
delay	false	Time between each attempt	0	-
timeout	true	Time after which an operation is considered a failure	1000	-
lastResponse	false	Returns the last attempt response, even if it failed regarding the configured condition. In timeout case, 502 is returned.	false	-

You can enable or disable the policy with policy identifier retry.

Compatibility matrix

The following is the compatibility matrix for APIM and the retry policy:

Plugin version	Supported APIM versions
2.x	All

Errors

HTTP status code	Reason
502	No response satisfies the condition after maxRetries Technical errors when calling the backend (for example, connection refused, timeout)

Changelogs

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