Jenkinsfile: Pipeline as a Code (Declarative)

Devops Tutorial​​ 25 –​​ Jenkinsfile:​​ Pipeline as a Code​​ (Declarative)

What you will Learn:

  • What is Jenkinsfile

  • Install​​ Pipeline’​​ plugin

  • Create pipeline job

  • Jenkinsfile formats

  • ‘Hello world’ declarative pipeline

  • Pipeline Logs

  • Console output of a run

  • Configure project to add more stages

What is Jenkinsfile?

So far we have been creating freestyle jobs and chaining them to create a pipeline. We can also create a pipeline by scripting inside a Jenkinsfile. That is why Jenkinsfile is also called as ‘Pipeline as a code’. So let us see how to do that.

Install ‘Pipeline’ plugin

First we need to install ‘Pipeline’ plugin

Important note: Restart Jenkins after installing plugin

Create pipeline​​ job

Create a new job, but this time select job type as ‘Pipeline’

Click Ok

You should see 4 tabs:​​ 

General, Build Triggers, Advanced Project Options and Pipeline​​ 

Click ‘Pipeline’ tab. You would see a dropdown, click it. ​​ 

Jenkinsfile formats

Now, Jenkinsfile can be written in 2 formats:​​ 

  • declarative,​​ 

  • scripted

Both these formats use groovy language having a slightly different structure

‘Hello world’ declarative pipeline

Select ‘Hello World’ declarative pipeline from the dropdown​​ shown above. You would see the​​ Jenkinsfile pipeline​​ code​​ snippet​​ shown​​ below

The script starts with ‘pipeline’ keyword followed by ‘agent any’. Latter means that the script can be executed on any agent (or a node or the machine).

We then see the ‘stages’ block that comprises of stage name (here ‘Hello’). The stage name can also be ‘Build’, ‘Deploy’, ‘Test’, Release’.

We then define the​​ steps inside a stage.​​ ​​ 

Apply and Save

Notice above on the right hand side, we see a ‘Stage View’ section that right now has no data because the build has not yet been executed. ​​ 

Click ‘Build Now​​ and wait for the build to get successfully over

We can now​​ see​​ the​​ stage view, see below

You can also see #1, this signifies the pipeline build number.

Pipeline​​ Logs

Hover the mouse over the section seen below

Click ‘Logs’. You would see the log output as seen below

Close the above logs window.

Console output of a run

Click #1​​ link


Click console output

You can see the console output details as seen below

Configure project to add more stages

Click back button (2 times). We would see ‘Configure’

Click ‘Configure’ and focus on below section

Change the stage name to ‘Build’ and edit the echo statement

​​ 

Next, select the lines of the stage block as shown below (lines 5-9)

Copy these lines and paste them after line 9, see below. Change the stage name to ‘Deploy’ and edit echo statement

Similarly add 2 more stages

So our entire Jenkinsfile looks as below

Apply and Save

Click ‘Build Now’​​ 

Wait for the build to get over

 

Notice the Stage view now. We see the 4 stages, see below

So this is how we setup the Jenkinsfile declarative pipeline as a code.​​ 

Thank you for reading!

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