Blog Posts

Getting Started With ytt, Part 1

by Varsha Munishwar — Oct 12, 2022

Welcome to the “Getting started with ytt” tutorial series! ¶

Part 1 of this series introduces you to ytt and helps you get started quickly. It is an easy, step-by-step tutorial that you can follow along and see ytt in action on the playground as well as on the CLI.

We will cover the following topics:

Introduction to ytt
What problems is ytt solving?
See ytt in action on interactive playground and CLI

Getting started with ytt - Part 1 ¶

The key moments/timestamps are available if you watch on youtube. Please click on “more” and “view all”.

If you would like to follow along with the video, you can use the YAML code snippets below on the ytt playground.

1) Hello World! ¶

In this example, you will learn how ytt parses input and takes care of spacing and indentation. Jump to this section in the video.

tutorials:
  title: "Hello world, welcome to ytt!"
  #! "Welcome to ytt tutorial series"

2) Sample configuration file ¶

config.yml

apiVersion: v1
kind: Service
metadata:
  name: frontend
  labels:
    app.kubernetes.io/version: 0.1.0
    app.kubernetes.io/name: frontend
spec:
  type: ClusterIP
  ports:
  - port: 80

3) Extract variables ¶

In this example, you will learn how to extract variables. Jump to this section in the video.

config.yml

#@ name = "frontend-service"

apiVersion: v1
kind: Service
metadata:
  name:  #@ name
  labels:
    app.kubernetes.io/version: 0.1.0
    app.kubernetes.io/name: #@ name
spec:
  type: ClusterIP
  ports:
  - port: 80

4) Use functions ¶

In this example, you will learn how to use functions. Jump to this section in the video.

#! Function definition
#@ def name(service_name):
#@   return service_name + "-service"
#@ end

apiVersion: v1
kind: Service
metadata:
  name: #@ name("frontend")
  labels:
    app.kubernetes.io/version: 0.1.0
    app.kubernetes.io/name: #@ name("frontend")
spec:
  type: ClusterIP
  ports:
  - port: 80

5) Load data values ¶

In this example, you will learn how to load data values. Jump to this section in the video.

config.yml

#@ load("@ytt:data","data")

#@ def name(service_name):
#@   return service_name + "-service"
#@ end

apiVersion: v1
kind: Service
metadata:
  name: #@ name(data.values.name)
  labels:
    app.kubernetes.io/version: 0.1.0
    app.kubernetes.io/name: #@ name(data.values.name)
spec:
  type: ClusterIP
  ports:
  - port: 80

values.yml

#@data/values
---
name: frontend

6) Use for loop ¶

In this example, you will learn how to use for loop. Jump to this section in the video.

config.yml

#@ load("@ytt:data","data")

#@ def name(service_name):
#@   return service_name + "-service"
#@ end

#@ for service in data.values.services:
---
apiVersion: v1
kind: Service
metadata:
  name: #@ name(service.name)
  labels:
    app.kubernetes.io/version: #@ data.values.version
    app.kubernetes.io/name: #@ name(service.name)
spec:
  ports:
  - port: 80
#@ end

values.yml

#@data/values
---
version: 0.1.0
services:
- name: frontend
- name: backend

7) Use conditionals if/end ¶

In this example, you will learn how to use if/end. Jump to this section in the video.

config.yml

#@ load("@ytt:data","data")

#@ def name(service_name):
#@   return service_name + "-service"
#@ end

#@ for service in data.values.services:
---
apiVersion: v1
kind: Service
metadata:
  name: #@ name(service.name)
  labels:
    app.kubernetes.io/version: #@ data.values.version
    app.kubernetes.io/name: #@ name(service.name)
spec:
  ports:
  - name: https
    protocol: TCP
    port: 443
    targetPort: 9377
  #@ if service.allowHTTP:
  - name: http
    protocol: TCP
    port: 80
    targetPort: 9376
  #@ end
#@ end

values.yml

#@data/values
---
version: 0.1.0
services:
- name: frontend
  allowHTTP: true
- name: backend
  allowHTTP: false

Steps to run ytt locally: ¶

$ brew tap carvel-dev/carvel
$ brew install ytt
$ git clone https://github.com/carvel-dev/ytt
$ cd carvel-ytt/examples
$ ytt -f playground/basics/example-plain-yaml

What’s next: ¶

Check out the Part 2 of this tutorial series!

Happy Templating :)

Join the Carvel Community ¶

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