How to ‘Transform’ Multiple Resources with Regex
Oops! Something went wrong.
Please, try again later.
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
Adding Transforms Operation From the UI
While performing restore or creating an import policy with restore, in UI, under Optional Restore Settings:
- Enable Apply transforms to restored resources.
- Select Add new transform to start creating a transformation.
- In the ‘New Transform’ form, assign the transform a Display Name.
- 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.)
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).
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
To report a typo on this page, highlight the typo with your mouse and press CTRL + Enter.
Spelling error in text
Thank you!
Your feedback has been received and will be reviewed.
KB Feedback/Suggestion
This form is only for KB Feedback/Suggestions, if you need help with the software open a support case
Thank you!
Your feedback has been received and will be reviewed.
Oops! Something went wrong.
Please, try again later.