Redirect

Overview

The Redirect policy action enables transforming your URL using regular expressions and redirect through the "location" header.

Example

Traffic Policy for redirecting to a url with a different version and id param.

YAML

# snippet
---
actions:
  - type: "redirect"
    config:
      format: "ngrok"
      from: "/api/v1/users/([0-9]+)"
      to: "/api/v2/users?id=$1"
      status_code: 301
      headers:
        x-custom-header: "custom-value"

JSON

// snippet
{
  "actions": [
    {
      "type": "redirect",
      "config": {
        "format": "ngrok",
        "from": "/api/v1/users/([0-9]+)",
        "to": "/api/v2/users?id=$1",
        "status_code": 301,
        "headers": {
          "x-custom-header": "custom-value"
        }
      }
    }
  ]
}

Request:

curl https://example.ngrok.app/api/v1/users/42

Result:

< HTTP/2 301
< location: https://example.ngrok.app/api/v2/users?id=42
< x-custom-header: custom-value

Behavior

When executed this action will abort the request and replace all matches on the inbound URL with the configured replacements. Before regex replacement, all variables or expressions will be replaced with their corresponding values using cel expressions templating syntax.

Reference

Supported Directions

• Inbound

Configuration

Type
redirect

Parameter		Description
from	string	A regular expression string to match inside of the URL. Supports interpolating the results of cel expressions outside of regular regex.
to	string	A regular expression string to replace the from match with. Supports interpolating the results of cel expressions outside of regular regex.
status_code	int	3xx status code used for redirecting, 302 by default.
headers	Map<string, string>	Headers to be added to the response.
format	string	(default: ngrok) Determines interpolation format in to/from fields.

Templating Syntax

The results of CEL expressions can be interpolated into your policy's config using ngrok's ${} templating syntax. For a complete list of available variables and functions or to see a more detailed explanation, checkout the docs.

More Examples

Using "to" field with templating syntax

YAML

# snippet
---
actions:
  - type: "redirect"
    config:
      format: "ngrok"
      to: "/api/v1/carmen/sandiego/${conn.geo.city}"
      status_code: 301

JSON

// snippet
{
  "actions": [
    {
      "type": "redirect",
      "config": {
        "format": "ngrok",
        "to": "/api/v1/carmen/sandiego/${conn.geo.city}",
        "status_code": 301
      }
    }
  ]
}

Request:

curl https://example.ngrok.app/api/v1

Result:

< HTTP/2 301
< location: https://example.ngrok.app/api/v1/carmen/sandiego/seattle

---

Using cel expressions in headers

YAML

# snippet
---
actions:
  - type: "redirect"
    config:
      format: "ngrok"
      to: "/api/v1/soon?time=${string(conn.ts.start)}"
      status_code: 308
      headers:
        x-custom-header: "custom-value"
        x-template-example: "started at ${conn.ts.start}"

JSON

// snippet
{
  "actions": [
    {
      "type": "redirect",
      "config": {
        "format": "ngrok",
        "to": "/api/v1/soon?time=${string(conn.ts.start)}",
        "status_code": 308,
        "headers": {
          "x-custom-header": "custom-value",
          "x-template-example": "started at ${conn.ts.start}"
        }
      }
    }
  ]
}

Request:

curl https://example.ngrok.app/api/v1/foobar

Result:

< HTTP/2 308
< location: https://example.ngrok.app/api/v1/soon?time=2024-06-24T15:30:00Z
< x-custom-header: 2024-06-24T15:30:00Z
< x-template-example: started at 2024-06-24T15:30:00Z

---

Action Result Variables

The following variables are available following the invocation of this action.

Name	Type	Description
actions.ngrok.redirect.matches	[]string	The list of matched elements.
actions.ngrok.redirect.url	string	The resulting URL sent back for redirect.
actions.ngrok.redirect.error.code	string	Code for an error that occurred during the invocation of an action.
actions.ngrok.redirect.error.message	string	Message for an error that occurred during the invocation of an action.