Jenkins Shared Library: A Closer Look [2021]

We live in an age of microservices in which contemporary applications are disassembled into components that are deployable individually. We can argue that Jenkins has made its place among the leading original CI / CD tools for deploying microservices. Compared to monolithic applications, there are many pipelines for deploying individual microservices.

You can use the hose as a code to encode the whole process of CI / CD. Treat it like in app development. You can publish your pipeline code and run all test levels before using it to deploy your app.

What is the Jenkins Shared Library?

When we say CI / CD as a symbol, we need modularity and reuse. You have to follow the DRY principle. That is where the shared Library of Jenkinsproves useful.

The Jenkins Shared Library is the idea of ​​including a standard pipe code for version control systems and can be used on any number of pipes by merely referring to it. Multiple teams can use the same directory for their pipeline.

You can compare it with popular programming directories. Programming creates a separate guide that anyone can use when importing code.

For example, if you have ten pipes for micro-services from Java, the old creation procedure is repeated for all ten pipes. Besides, the pipe code is copied and pasted with the addition of new services. If you want to change some parameters in an old construction phase, you need to adjust them manually in all the pipes.

In the same scenario, you will create a shared library for older buildings. For all the pipes, all you have to do is refer to the old building code library. If there are any old changes in the future, all you need to update is the shared library icon.

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Start using shared libraries

A shared directory is a collection of cool files (DSL + Groovy). All cool files must be in the git repository. This example uses Github as a git repository. https://github.com/devopscube/jenkins-shared-library. You can duplicate this repository to get the shared library infrastructure.

The shared library database contains the following volume structures:

The Jenkins Joint Library

| ____ vars

| ____ src

| ____ resources

Vars 

It contains all the WCL code that you can call from the pipeline. It contains all directory files with .groovy extension. .txt files are also supported for documenting the library code that is shared. For instance, if you are having a file with the name maven-build. Groovy, then you will be getting a help file with the name maven-groovy.txt. You can write help documentation to mark the properties of a shared directory in this file. Help files can be viewed from the <your-jenkins-url> / Pipeline Syntax / Global page.

Src

It is a standard Java source directory. Once all the text has been compiled, it will be added to the classpath. Here you can add an incredibly cool code to expand the shared library code. You can also use the Import Manifest to import existing Jenkins categories and extensions.

There are scenarios where cool DSL hardware is not flexible enough to perform certain functions. In this case, you can write custom groove functions in src and read them in the shared library code.

Resources

You can manage all the unnecessary files needed for the hose in this folder. As an example, you may need a general JSON template for making API calls during construction. You can save this JSON template in a resource folder and call it in a shared library through the LibraryResource function.

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Shared Global Library

There are several places where you can set up a shared directory, depending on your usage case. Jenkins Management » System Configuration» Global Pipe Library. You can configure any number of directories as you need.

These libraries are universally available so that every pipeline in your system can use the functions implemented in these libraries.

These libraries are considered “reliable.” You can perform any method in Java, Groovy, Jenkins’ internal API, the Jenkins extension, or a third-party directory. It allows you to precisely identify libraries that fold insecure APIs into high-level envelopes that can be safely used from any pipeline.

Please note that anyone who can pay the commission to this SCM database has unlimited access to Jenkins. You need Total / RunScripts permission to create these directories (this permission is usually given to Jenkins administrators).

Folder-level shared library

All folders created can be linked to shared directories. This mechanism allows you to set a specific directory range for all the pipes within a volume or subfolder.

Folder-based directories are not considered “trusted.” It operates in the groove sandbox, just like a regular pipe.

Automatic shared library

Other plugins may add a way to identify the library on the go. For example, “GitHub Organization Folder”  is a source plugin provided in the GitHub Branch Source. It provides a component that allows scripts to use untrusted libraries such as github.com/orgname/reponame minus any added configuration. In this case, the specified GitHub repository will be loaded from the main branch using anonymous settings.

To check for changes in the library

If you notice a bug in a build with an untrusted directory, click the replay link and edit one or more source files to see if the resulting version works as expected. When you are satisfied with the results, click on the diff link on the Release Status page and apply the difference to your library and your commit pool.

(Even if the library’s requested version is a branch and not a static version like the bookmark, the reactivated version will use the same version as the original version. You cannot pull back the library resources.)

Currently, it doesn’t provide you with the trusted libraries Replay. Changing resource files during Replay is currently not supported.

Also Read: Jenkins Interview Questions & Answers

Conclusion

Here are some of the important things to remember:

  • You will have to use Groovy for writing steps or custom functions.
  • There is a need for writing pipeline steps that you can call from pipelines.
  • You need to create a file in the vars directory of the repository that will be containing the name of your custom step.
  • The def call method should be implemented by the parameters to your step.
  • If there is a need for writing common Groovy code you can add it into src.
  • You can also integrate a shared library in Jenkins through the use of a configure system screen.

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