Jenkins scripted pipeline or declarative pipeline

I'm trying to convert my old style project base workflow to a pipeline based on Jenkins. While going through docs I found there are two different syntaxes named scripted and declarative. Such as the Jenkins web declarative syntax release recently (end of 2016). Although there is a new syntax release Jenkins still supports scripted syntax as well.

Now, I'm not sure in which situation each of these two types would be a best match. So will declarative be the future of the Jenkins pipeline?

Anyone who can share some thoughts about these two syntax types.

> When Jenkins Pipeline was first created, Groovy was selected as the foundation. Jenkins has long shipped with an embedded Groovy engine to provide advanced scripting capabilities for admins and users alike. Additionally, the implementors of Jenkins Pipeline found Groovy to be a solid foundation upon which to build what is now referred to as the "Scripted Pipeline" DSL. > > As it is a fully featured programming environment, Scripted Pipeline offers a tremendous amount of flexibility and extensibility to Jenkins users. The Groovy learning-curve isn’t typically desirable for all members of a given team, so Declarative Pipeline was created to offer a simpler and more opinionated syntax for authoring Jenkins Pipeline. > > The two are both fundamentally the same Pipeline sub-system underneath. They are both durable implementations of "Pipeline as code." They are both able to use steps built into Pipeline or provided by plugins. Both are able to utilize Shared Libraries > > Where they differ however is in syntax and flexibility. Declarative limits what is available to the user with a more strict and pre-defined structure, making it an ideal choice for simpler continuous delivery pipelines. Scripted provides very few limits, insofar that the only limits on structure and syntax tend to be defined by Groovy itself, rather than any Pipeline-specific systems, making it an ideal choice for power-users and those with more complex requirements. As the name implies, Declarative Pipeline encourages a declarative programming model. Whereas Scripted Pipelines follow a more imperative programming model.

Copied from Syntax Comparison

Another thing to consider is declarative pipelines have a script() step. This can run any scripted pipeline. So my recommendation would be to use declarative pipelines, and if needed use script() for scripted pipelines. Therefore you get the best of both worlds.

I made the switch to declarative recently from scripted with the kubernetes agent. Up until July '18 declarative pipelines didn't have the full ability to specify kubernetes pods. However with the addition of the yamlFile step you can now read your pod template from a yaml file in your repo.

This then lets you use e.g. vscode's great kubernetes plugin to validate your pod template, then read it into your Jenkinsfile and use the containers in steps as you please.

pipeline {
  agent {
    kubernetes {
      label 'jenkins-pod'
      yamlFile 'jenkinsPodTemplate.yml'
    }
  }
  stages {
    stage('Checkout code and parse Jenkinsfile.json') {
      steps {
        container('jnlp'){
          script{
            inputFile = readFile('Jenkinsfile.json')
            config = new groovy.json.JsonSlurperClassic().parseText(inputFile)
            containerTag = env.BRANCH_NAME + '-' + env.GIT_COMMIT.substring(0, 7)
            println "pipeline config ==> ${config}"
          } // script
        } // container('jnlp')
      } // steps
    } // stage

As mentioned above you can add script blocks. Example pod template with custom jnlp and docker.

apiVersion: v1
kind: Pod
metadata:
  name: jenkins-pod
spec:
  containers:
  - name: jnlp
    image: jenkins/jnlp-slave:3.23-1
    imagePullPolicy: IfNotPresent
    tty: true
  - name: rsync
    image: mrsixw/concourse-rsync-resource
    imagePullPolicy: IfNotPresent
    tty: true
    volumeMounts:
      - name: nfs
        mountPath: /dags
  - name: docker
    image: docker:17.03
    imagePullPolicy: IfNotPresent
    command:
    - cat
    tty: true
    volumeMounts:
      - name: docker
        mountPath: /var/run/docker.sock
  volumes:
  - name: docker
    hostPath:
      path: /var/run/docker.sock
  - name: nfs
    nfs:
      server: 10.154.0.3
      path: /airflow/dags

declarative appears to be the more future-proof option and the one that people recommend. it's the only one the Visual Pipeline Editor can support. it supports validation. and it ends up having most of the power of scripted since you can fall back to scripted in most contexts. occasionally someone comes up with a use case where they can't quite do what they want to do with declarative, but this is generally people who have been using scripted for some time, and these feature gaps are likely to close in time.

more context: https://jenkins.io/blog/2017/02/03/declarative-pipeline-ga/

The Jenkins documentation properly explains and compares both the types.

To quote: "Scripted Pipeline offers a tremendous amount of flexibility and extensibility to Jenkins users. The Groovy learning-curve isn’t typically desirable for all members of a given team, so Declarative Pipeline was created to offer a simpler and more opinionated syntax for authoring Jenkins Pipeline.

The two are both fundamentally the same Pipeline sub-system underneath."

Read more here:https://jenkins.io/doc/book/pipeline/syntax/#compare

1. The declarative pipeline is defined within a block labelled ‘pipeline’ whereas the scripted pipeline is defined within a ‘node’.
2. Syntax - Declarative pipeline has 'Stages' , 'Steps'
3. If the build is failed, declarative one gives you an option to restart the build from that stage again which is not true in scripted option
4. If there is any issue in scripting, the declarative one will notify you as soon as you build the job but in case of scripted , it will pass the stage that is 'Okay' and throw error on the stage which is 'Not ok'

You can also refer this. A very Good read -> https://e.printstacktrace.blog/jenkins-scripted-pipeline-vs-declarative-pipeline-the-4-practical-differences/ @Szymon.Stepniak https://stackoverflow.com/users/2194470/szymon-stepniak?tab=profile

I also have this question, which brought me here. Declarative pipeline certainly seems like the preferred method and I personally find it much more readable, but I'm trying to convert a mid-level complexity Freestyle job to Declarative and I've found at least one plugin, the Build Blocker plugin, that I can't get to run even in the a script block in a step (I've tried putting the corresponding "blockOn" command everywhere with no luck, and the return error is usually "No such DSL method 'blockOn' found among steps".) So I think plugin support is a separate issue even with the script block (someone please correct me if I'm wrong in this.) I've also had to use the script block several times to get what I consider simple behaviors to work such as setting the build display name.

Due to my experience, I'm leaning towards redoing my work as scripted since support for Declarative still isn't up to where we need, but it's unfortunate as I agree this seems the most future proof option, and it is officially supported. Maybe consider how many plugins you intend to use before making a choice.