Category Archives: two-mins-guide

Kubernetes Tip: How to refer one environment variable in another environment variable declaration?

In Kubernetes, one way to pass configurable data to containers is using environment variable. Below is a pod definition that uses two environment variables.

apiVersion: v1
kind: Pod
metadata:
  name: api
spec:
  containers:
    - image: com.shekhargulati/api
      name: api
      env:
        - name: DATABASE_NAME
          value: "mydb"
        - name: DATASOURCE_URL
          value: jdbc:mysql://mysql:3306/mydb      
      ports:
        - containerPort: 8080

As you can see in the above Pod definition, we are using database name mydb twice. Isn’t it will be awesome if we can use DATABASE_NAME in the DATASOURCE_URL?

Kubernetes supports this use case by providing $(VAR) syntax as shown below.

apiVersion: v1
kind: Pod
metadata:
  name: api
spec:
  containers:
    - image: com.shekhargulati/api
      name: api
      env:
        - name: DATABASE_NAME
          value: "mydb"
        - name: DATASOURCE_URL
          value: "jdbc:mysql://mysql:3306/$(DATABASE_NAME)"
      ports:
        - containerPort: 8080

Enabling Https for local Spring Boot development with mkcert

Today, I discovered mkcert – a tool that generates valid TLS certificate. It works for any hostname or IP, including localhost. In this post, I will show you how to generate a valid PKCS12 format certificate using mkcert. Then, we will use that certificate in a Spring boot application.

We will start by installing mkcert on our local machine. If you are using Mac then we can use brew package manager. For installation instructions specific to your OS you can refer to the documentation.

brew install mkcert

Once mkcert is installed, you can use its CLI to create and install a CA. To do that, run the following command.

mkcert -install

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Dockerizing a Vue.js application

It is common these days to run front-end and back-end services inside Docker containers. The front-end service usually talks using a API with the back-end service.

In this post we will cover following:

  1. Setting up a Docker based development environment with hot reloading
  2. Building a production ready Docker image with API url passed using environment variable

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