Dockerize your application

Install docker to your system -> https://docs.docker.com/engine/install/
Create a file named as "Dockerfile" in your application directory.
Define dependencies in your Dockerfile.

Sample rails application Dockerfile

FROM ruby:2.6.4

RUN apt-get update -o Acquire::CompressionTypes::Order::=gz -qq && apt-get install -y build-essential libpq-dev nodejs

RUN apt-get update --fix-missing

RUN gem install bundler -v 1.17.3

ENV APPLICATION_NAME={{your application name}}

RUN mkdir -p /$APPLICATION_NAME

WORKDIR /$APPLICATION_NAME

ADD Gemfile /$APPLICATION_NAME/Gemfile
ADD Gemfile.lock /$APPLICATION_NAME/Gemfile.lock

ADD . /$APPLICATION_NAME

RUN bundle install

ARG TAG
ENV APP_VERSION=${TAG}
ARG CI_COMMIT_BRANCH
ENV BUILD_BRANCH=${CI_COMMIT_BRANCH}
ARG RAILS_ENV=production
ENV RAILS_ENV="${RAILS_ENV}"
ENV RAILS_SERVE_STATIC_FILES true

RUN RAILS_ENV=${RAILS_ENV} bundle exec rails assets:precompile

EXPOSE 3000
CMD ["bundle", "exec", "rails", "server", "-b", "0.0.0.0", "-p", "3000"]

Once your Dockerfile is ready, run this command to build your application image.

docker image build -t {application_name}:{tag} {Dockerfile path}

On successful image creation, run this command to check your image.

docker image ls #list docker images

After that, run your image to check everything is working as expected.

docker container run -it {REPOSITORY}:{TAG} 
#REPOSITORY & TAG, you will get this from list docker images command

Kubernetes deployment

First, you will get an app 'dev-cluster' from develops team for your kubernetes cluster.
You will need to update this file dev-cluster > cloud > builder-environment.yml as per your need & push the code.

cloudProvider: azure
region: centralindia
environment: dev # dev|stage|prod
deleted: false
machineType: Standard_D2a_v4
nodeCountMin: 2
nodeCountMax: 3
clusterName: studio  # keep it as short as possible, do not inlude domain
logging: loki  # loki|filebeat
gpgKey: B93913AB8235F03C1C60A5368ED7AF1D24303834 # a fingerprint of key used to encrypt variables in platform-automation-tools repo
contactEmail: [email protected]
# Switch between letsencrypt stage (self-signed) or prod SSL certificates
# sslCertificate: stage | prod
dev_tldomain: builder.cafe
masterHighAvailability: false

When ever you need to update your cluster configuration, simply update the above file & push the code.

Next steps

After dev-cluster setup, develops team will provide you some set of files for your application.
You have to add these files in .deploy directory (or create .deploy directory) on your application.
If you have some environment specfic variables, add them in values-{env_name}.yml.

appExtConfig:
  SMTP_ADDRESS: "smtp.develmail.com"
  SMTP_PORT: "587"
  SMTP_USERNAME: "WE4CX23WXDSU33WDOAAEWAK6JU"

And if you have environment specific secret variables, then in that case your have to generate a file named as 'values-{env_name}-secrets.yaml'.

Generation of secrets.yaml file

Download SOPS & install in your system -> https://github.com/mozilla/sops/releases
Import the pgp public key in the app-deploy directory.

cd app-deploy
gpg --import template-app-key-pub.gpg

Create the secrets yaml file in the app-deploy directory, using this command.

sops --pgp 4C80959A5A0DC7D784CEDE1E1B7F34C12F7B86BE values-{env_name}-secrets.yaml

If you don't have the fingerprint id, you can get it with

gpg --list-secret-keys

Edit the contents of the file to look like this

appExtConfig:
    secretStage: hello-world-stage-new

They key name must be appExtConfig.

Save the file and exit.
Verify the contents, it should look like this :

appExtConfig:
    secretStage: ENC[AES256_GCM,data:kfpvQqaezIWs/eb2Q4NAVb5HRW40,iv:x65hdmItrErv6EuAmsWlKdbRVGcYJ1quPF3ECCr7ctU=,tag:0UNrmM9X2WA75DGWenSFbw==,type:str]
sops:
    kms: []
    gcp_kms: []
    azure_kv: []
    lastmodified: '2020-08-25T22:05:10Z'
    mac: ENC[AES256_GCM,data:5db6CLC37zNIzv35OhTkyAr68bIil7+PCNUAyQAh16OqZoVeAxKZLdpe5LHvjmGRImMXPspjs5zyiwWSJhEaCBNSYxrAIJgJrYqpqWyr7jvD2aMxuvKI8VC2t1csnMqKI6Qrp33/5M3EeKnIqJ3vIReXYr8OAzhzmKMDWXmxdkQ=,iv:yX1pMA9XKRjgChckD6fUgkKByOATvpV5Pfy0v66gFpA=,tag:T0mCiZCjc4AqB9RAGDqEAw==,type:str]
    pgp:
    -   created_at: '2020-08-12T17:29:21Z'
        enc: |
            -----BEGIN PGP MESSAGE-----

            hQEMA1gSLZ947okQAQf/bYtv3ObIez55ET8rigjQLoKAdQ8qH4iRnEGs/7pliJ9r
            APuQHq1ggNQthVFkZSJqQmyRjW1r7CwkEOHd2aPiKM3dOGK2vdVBHES4LqWrR4cq
            Oa7VRkUNq1WE/4DZh6NDOSn3vBJnZ8OozDK5hrsl95X1aSNhWH9lKlbFDR8VqxWb
            +zz8h6RK7nEmzduc+l00ONbFGPx6y517QpkPJ0urb/N7XfVDtUN/er/2GGywR9a9
            Wu8KR0lymseyemxf1v9Qw2igbJFfZuQgEp2+83amD4Zc02WGNTGRz8kFJcn9MELV
            Gol91lPJNSzvlglVVwJP47kXPeot9I32FFR3qjwkPdJeAfElVY6zasr75yiOSDgK
            oR787IVYPZMMAr6Z+q7xqMpDrhRX3NEHDOCEATHPxLXVH/HkwRHtEtIfxth87MLg
            ye+HrTuHNSADKGKJRWh3fHuzAY1vfFeGGJFNxQIv7w==
            =B5sa
            -----END PGP MESSAGE-----
        fp: 4C80959A5A0DC7D784CEDE1E1B7F34C12F7B86BE
    unencrypted_suffix: _unencrypted
    version: 3.5.0

Add the file to your git repo, commit & push.

Modify existing secrets

If you have the private key, you can simply edit an existing encrypted file with sops:

sops values-{env_name}-secrets.yaml

If you don't have the private key you must delete the existing file and replace it with the new one you encrypted.

Last step

include .deploy > ci > {file_name}.yml these files in your .gitlab-ci.yml file.

include:
  - /.deploy/ci/.gitlab-ci-unit-tests.yml
  - /.deploy/ci/.gitlab-ci-deploy.yml
  - /.deploy/ci/.gitlab-ci-build.yml
  #include all files which you needed for your pipelines

Be sure your application logger logs to STDERR.
Now commit & push your changes, observe your gitlab pipelines for completion or failure.

manojkumararyan/dockerize-your-application.md