How to ‘Transform’ Multiple Resources with Regex

Purpose

Veeam Kasten makes use of the 'Transforms' feature to migrate applications between different clusters, between different storage backends, and many other use cases. Transforms enable modifications to Kubernetes resources on restore.

The ability to move an application across clusters is an extremely powerful feature that enables a variety of use cases including Disaster Recovery (DR), Test/Dev with realistic data sets, and performance testing in isolated environments.

Transforms are loosely modeled on JSON patch and support regex to modify resources with a pattern.

The Veeam Kasten for Kubernetes documentation provides a simple example of Transformation. This article provides an example to showcase the use of regex and transforms for modifying ingress/route hostnames.

Solution

Transforming the Routes/Ingresses Hostnames During Restores

'Transformation replace' operations can be used to replace the hostname in the routes/ingresses. However, if multiple ingress/route hostnames follow a particular pattern, regex can be used to match the text and replace them.

Example Scenario

There are 4 ingresses with the hostnames as shown below:

#  kubectl get ingress -n mysql
NAME         CLASS    HOSTS                             ADDRESS   PORTS     AGE
apigateway   <none>   prd-apigateway.apps.example.com             80, 443   4h58m
backend      <none>   cn-backend.apps.example.com                 80        4h57m
frontend     <none>   cn-frontend.apps.example.com                80        4h56m
pgdb         <none>   prd-pgdb.apps.example.com                   80        4h56m

While restoring these ingresses to another cluster, there is a requirement to change the prefixes [prd-] and [cn-] from the ingress hostnames to [dr-]. The restored ingresses/routes are expected to have the following hostnames.

dr-apigateway.apps.example.com
dr-pgdb.apps.example.com
dr-backend.apps.example.com
dr-frontend.apps.example.com

Multiple transformation operations can be used to achieve this, which isn't efficient! Veeam Kasten for Kubernetes has inbuilt support for matching patterns using regex for transformation.

Following regex expression and the JSONpath expression can be used to achieve the desired transformation outcome.

• JSONPath for ingresses: /spec/rules/0/host
• JSONPath for routes: /spec/host
• Regex: (prd|cn)(.*)(\.apps\.example\.com)
• Value: dr${2}${3}

The above expression matches the pattern as shown in the image below

Note: <https://regex101.com/&gt; can be used to test and try out regular expressions.

Adding Transforms Operation From the UI

While performing restore or creating an import policy with restore, in UI, under Optional Restore Settings:

1. Enable Apply transforms to restored resources. 2. SelectAdd new transform to start creating a transformation.

3. In the 'New Transform' form, assign the transform a Display Name.
4. Add a New Operation intended with the transform.
   Operations that are supported include Test, Add, Remove, Copy, Move, and Replace without or with Regex pattern matching.

In this example scenario, Replace with Regex was selected.
(Replace element at path with JSON value. Match the target text with regex and substitute regex capturing groups with value.)

This operation can be tested from the UI by comparing the original and transformed resource.

Adding Transforms Operation From the Policy/RestoreAction API

Transform operations can also be accomplished by editing the Policy CR using 'kubectl edit' to add the transform field, shown below, under restoreParameters while creating an import+restore policy.

This can also be added to a restoreAction (<https://docs.kasten.io/latest/api/actions.html#restoreaction&gt;).

transforms:
- subject:
    resource: ingresses
  name: replace-ingress-host
  json:
  - op: replace
    path: /spec/rules/0/host
    value: dr${2}${3}
    regex: (prd|cn)(.*)(\.apps\.example\.com)

Trigger the import policy and verify the ingress hostnames after the restore.

#  kubectl get ingress -n mysql-clone
NAME         CLASS    HOSTS                            ADDRESS   PORTS     AGE
apigateway   <none>   dr-apigateway.apps.example.com             80, 443   20m
backend      <none>   dr-backend.apps.example.com                80        20m
frontend     <none>   dr-frontend.apps.example.com               80        20m
pgdb         <none>   dr-pgdb.apps.example.com                   80        20m

---

Veeam Kasten for Kubernetes also supports saving these transforms with a resource called Transformsets and these transformsets can be referenced during restore in the restore form.

To submit feedback regarding this article, please click this link: Send Article Feedback
To report a typo on this page, highlight the typo with your mouse and press CTRL + Enter.