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Introduction
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This is a sample guide walks you through the process of deploying Go 
application in a Kubernetes cluster running on minikube using K8S Helm charts.

how to modify the source code for publishing a new application release 
how to perform rolling updates in Kubernetes using the Helm CLI.


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prerequisites
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- Docker environment running.
- Docker Hub account as a registry.
- Minikube installed on your local computer.
- kubectl command line (kubectl CLI) installed.
- Helm v3.x installed.


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Steps
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To create your own application in Go and deploy it on Kubernetes using Helm 
you will typically follow these steps:

Step 1: Obtain the application source code,
Step 2: Build the Docker image,
Step 3: Publish the Docker image into our docker hub,
Step 4: Deploy the application in Kubernetes by using Helm Chart,
Step 5: Update the source code and the Helm chart for publishing a new release.
step 6: perform rolling updates in Kubernetes using the Helm CLI.
step 7: perform rolling back in Kubernetes using the Helm CLI.



Step 1: Obtain the application source code
==========================================

    $ git clone https://github.com/CloudInn/hello-go
    $ cd ./hello-go

Step 2: Build the Docker image
==============================

# note: 
    - My docker hub accout name = omareltamasehy
    - app name : hello-go

# Creating multi stage Dockerfile
    $ touch Dockerfile
    $ touch readme

# build the docker image by executing the below command:
    $ docker build -t omareltamasehy/hello-go:0.1.0 .

# check image existance after building by executing the below command:
    $ docker images omareltamasehy/hello-go




Step 3: Publish the Docker image into our docker hub
=====================================================

# login to docker hub by the below command:
    $ docker login

# push the docker image to the docker hub registry by ececting the below command:
    $ docker push omareltamasehy/hello-go:0.1.0



Step 4: Deploy the application in Kubernetes by using Helm Chart
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# Checking minikube ststus by the below command:
    $ minikube status

# Run the below command if minikube satus is stopped
    minikube start

# we consider that helm version 3 is installed as it is different 
  based on environment

# To create a new chart, you just need run the helm create command, 
  This creates a scaffold with sample files that you can modify 
  to build your custom chart, 
  For this guid, we'll provide you with a ready-made Helm chart.

hello-go
helm-chart
|-- Chart.yaml
|-- values.yaml
|-- requirment.yaml
|-- templates
   |-- NOTES.txt
   |-- _helpers.tpl
   |-- deployment.yaml
   |-- service.yaml



# After creating the chart we need to perform the following steps:
    - check docker hub user name, tag in values.yaml file
    - check templates/deployment.yaml file

# Deploy the Helm chart by executing the following.  
    $ helm install hello-go-first-release ./helm-chart/


# To check the created pods based on our deployment files
  we can run the below command:
    $ kubectl get pods

# To check the result of our deployment and to get the ip address and port 
  to be eble to run our GO app via browser we can run the below command:    
    $ minikube service list
    Example: http://192.168.64.2:32012

Finally, Go application has been successfully deployed on Kubernetes.




step 6: perform rolling updates in Kubernetes using the Helm CLI
===============================================================================

# Rolling updates and rollbacks are important benefits of deploying applications 
  into a Kubernetes cluster. With rolling updates, devops teams can perform 
  zero-downtime application upgrades, which is an important consideration 
  for production environments.

  Helm makes it easy to upgrade the applications with the helm upgrade command,
  as shown below:
    - change replica count value from 3 to 5 as an example 
      $ helm upgrade hello-go-first-release ./helm-chart/
    - to check the changes run the below command:
      $ kubectl get pods


step 7: perform rolling back in Kubernetes using the Helm CLI
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# Kubernetes also supports rollbacks, which enable easy reversal to a previous version
  of an application without a service outage.

Rollbacks are equally simple - just use the helm rollback command 
and specify the revision number to roll back to. 
For example, to roll back to the original version of the application (revision 1),
use the below steps:
    - first we need to know the current revisions for this app by the below command:
        $ helm history hello-go-first-release

    - then we can rollback by the below command after choosing the needed revesion:
        $ helm rollback hello-go-first-release 1


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Thanks for reading
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