Implementation of CI/CD in Java Application Using Shell and Docker Executor

August 30, 2021

Shell executor is a basic executor that aids in the local development of solutions on the computer where GitLab Runner is installed. Windows Batch has been deprecated in favor of Bash and Windows PowerShell scripts.

You will need to set up GitLab Runner in shell executor mode and configure the paths to get started.

In this situation, the solution will be produced locally using a shell executor on the machine where GitLab Runner is installed. If you’re running GitLab on Linux, then you’ll need to install all the essential software.

.Net applications run on Windows environment.

Prerequisites

To follow through this article, you need to:

  • Have a computer running the windows operating system.
  • Download git into your machine. Click here to download.
  • Download MSBuild or use the visual Studio building tools installed in Visual Studio.
  • Use the same .exe files used to install MSBuild to install VS Web Build. We can achieve this by running the command vs_buildtools.exe — add Microsoft.VisualStudio.Workload.WebBuildTools in the command-line.
  • Download Nuget to reinstall our application’s packages from the official website. Click here to download.

Table of contents

Installation of GitLab Runners

To install and run GitLab Runner on Windows, you’ll need Git and the user password. For more information, see the Git download link in the prerequisites section.

Step-by-step guide:

  1. First create a folder on your computer. For example H:\Runners
  2. To install the GitLab Runner, download the binaries for either Windows 64-bit or 32-bit operating systems and place them in the folder you created. Please note that the following assumes that you’ve changed GitLab-runner.exe to GitLab-runner (optional).

The binary down depends on your computer specifications of the operating system.

  1. Make sure that the GitLab Runner directory and executable have Write rights restricted. Otherwise, regular users can replace the executable and run any code with elevated privileges by substituting their own.
  2. Open a command prompt as an administrator.
  3. Make registration for the runner. This can be achieved by the process of connecting a runner to one or more GitLab instances. Registering multiple runners is as simple as repeating the register command on the same host system.

The following is the process of registering a runner:

  • Run the command ./gitlab-runner.exe register to register a runner.
  • The URL of your GitLab instance must be entered (also known as the GitLab-ci coordinator URL).
  • To register a runner, enter the token you received.
  • Name and describe the runner. This value can be changed later through the GitLab user interface.
  • Separate the tags linked with the runner using commas. This value can be changed later through the GitLab user interface.
  • Provide the executor for the runner. Enter docker for the majority of use cases.
  • For projects that don’t have a default image defined, you’ll be requested to select one. If you selected docker as your executor, use GitLab-ci.yml.
  1. Install GitLab Runner as a service and start it. You can either use the built-in System Account using the command .\gitlab-runner.exe installs to install and .\gitlab-runner.exe start to start the runner (which is preferred). Or a user account to execute the service. Use the commands .\gitlab-runner.exe install --user "Input your user name" --password "Input your password" to install. And, .\gitlab-runner.exe start to start the runners.

Configuring the Runners

GitLab Runner is a build instance that can be used to perform jobs across several machines and send the results to GitLab. It can be installed on different users’ computers, servers, and local devices.

Once the runner has been installed, you can choose to make it shared or specific.

You can use either specific or shared runners to service your jobs.

Shared Runners - These runners are handy for jobs that have similar requirements across many projects. Instead of using several runners for many projects, you may handle them with a single or small number of runners that are easy to maintain and update.

Specific Runners - These runners are important for deploying a specific project when the job has specific criteria or demands. Specific runners organize their data using the FIFO (First In First Out) method, which works on a first-come, first-served basis. An individual runner can be registered with the project registration token; an encrypted version of a certain Runner.

Encryption of a specific runner

You can prevent a specific runner from being used in other projects by encrypting it. To do so, you must first register a runner, as described in the GitLab Runners installation guide above.

Encrypt the runner using the following steps.

  • Go to your project and log in to your GitLab account.
  • By selecting the CI/CD option on the settings page, you may expand the runner’s settings option.
  • The activated runners for the project can be found under the runner’s settings section.
  • Now click on the pencil button.
  • The runner screen will then be opened, and the lock to current projects option will be checked. By clicking on save changes, you’ll be able to keep the changes.

It will successfully update the runner after saving the modifications.

Protect Runners

The runners can be safeguarded to save critical data.

You can protect the runner by following the instructions below:

  • Go through the exact processes (from steps 1 to 4) as in the previous section (encrypting a specific runner).
  • You’ll get the runner screen after tapping the pencil button; select the protected option from there. Unless you click on the save changes button, your alterations will be temporary.

How to create a .gitlab-ci.yml file

The YAML file .gitlab-ci.yml is used to configure particular instructions for GitLab CI/CD.

You define the following in this file:

  • The structure and order in which the runner should do jobs.
  • The choices a runner should make when confronted with various circumstances.

When you commit to a branch other than the default branch, for example, you might want to run a set of tests. You want to run the same suite as before, but additionally, publish your application when you commit to the default branch.

The .gitlab-ci.yml file contains all this information.

To make a .gitlab-ci.yml file, follow the steps below:

  1. Select Project information > Details from the left sidebar.
  2. Select the branch you wish to commit to above the file list, then click the + icon, then New file:
  3. Type .gitlab-ci.yml in the filename field, and paste the following code in the bigger window:
build-job:
  stage: build
  script:
   - echo "Hello, $GITLAB_USER_LOGIN!"

test-job1:
  stage: test
  script:
    - echo "This job puts things to the test."

test-job2:
  stage: test
  script:
    - echo "Unlike test-job1, this job requires more time to complete."
    - echo "Thereafter, it executes the sleep command for 20 seconds."
    - echo "Test-job2 is extended by 20 seconds."
    - sleep 20

deploy-prod:
  stage: deploy
  script:
    - echo "This job uses the $CI_COMMIT_BRANCH branch to deploy something."
  1. Click commit to save your changes.

While creating a GitLab-ci.yml file, one has to arrange the code in stages. Stages are a set of instructions that your code must follow to get to its final destination (production).

You can create any number of stages with any names in GitLab. For this, you need to put them under a certain stage key and specify what sequence you want them to run. Then GitLab will go through each of them one by one. If one of them fails, the others will not run.

These stages include:

  • build stage
  • test stage
  • deploy stage

build stage - This stage will construct the solution confirming that it is constructible. $GITLAB_USER_LOGIN; in this variable, the user who initiated the job is identified by his or her username.

test stage - This stage will run the tests for our solution.

deploy stage - In this stage, we put into practice the solution we built. From the example script above, the CI_COMMIT_BRANCH variable shows the name of the commit branch. These features are available in all branch pipelines, including the default branch pipelines. Merge request and tag pipelines are not supported.

Conclusion

In this article, we have understood what GitLab runners are, their installation, and configuration.

Finally, we looked at the creation of GitLab yml files. I would urge you to dig deeper into this topic and be able to build concrete yml files.


Peer Review Contributions by: Dawe Daniel


About the author

James Bundi

James Bundi is an undergraduate student undertaking Bachelor of Science in Data Science. He is interested in cyber security and ethical stuff. He also loves playing football and table tennis.

This article was contributed by a student member of Section's Engineering Education Program. Please report any errors or innaccuracies to enged@section.io.