Last week we released the latest version of Declarative Pipelines, version 1.2.8. With that out, we thought now would be a good time to introduce you to the new features and options that have been added to Declarative since the beginning of 2018. These are all available now in the Update Center, with version 1.2.8.
Declarative Directive Generator
This is something we’re really happy about - if you go to the "Pipeline Syntax"
link from your Pipeline’s page in Jenkins, you’ll see a couple new links on the
left, including "Declarative Directive Generator". The Directive Generator is
much like the Snippet Generator that’s been in Pipeline for a couple years now,
but where the Snippet Generator is just for filling out a form for a step and
generating the Pipeline code that configuration maps to, the Directive
Generator is built to help you write your Declarative Pipeline directives, like
agent, options, stage, and more!
This is the first release to include the Directive Generator, and it’s definitely going to see more polish going forward, but we think it should be quite helpful for you already. We’ll be putting up another blog post looking at the Directive Generator in more detail in the near future.
New when conditions
We’ve added a number of new when conditions, providing you more control over
whether your stages get executed.
-
equals- Compares two values - strings, variables, numbers, booleans - and returns true if they’re equal. I’m honestly not sure how we missed adding this earlier! You can do "not equals" comparisons using thenot { equals … }combination too. -
changeRequest- In its simplest form, this will return true if this Pipeline is building a change request, such as a GitHub pull request. You can also do more detailed checks against the change request, allowing you to ask "is this a change request against the master branch?" and much more. -
buildingTag- A simple condition that just checks if the Pipeline is running against a tag in SCM, rather than a branch or a specific commit reference. -
tag- A more detailed equivalent ofbuildingTag, allowing you to check against the tag name itself.
In addition, we’ve added a new option to when: beforeAgent. This allows you
to specify that the when conditions should be evaluated before entering the
agent for the stage, rather than the normal behavior of evaluating when
conditions after entering the agent. When beforeAgent true is specified,
you will not have access to the agent’s workspace, but you can avoid
unnecessary SCM checkouts and waiting for a valid `agent to be available. This
can speed up your Pipeline’s execution in some cases.
New post conditions
The changed condition has always been a bit confusing, and to be
honest, it wasn’t our best work. changed will fire any time the current run’s
status is different than the previous run’s status - whether the current run is
healthier than the previous one, or the other way around. That’s…not actually
very useful. So now we’ve added two new post conditions that should provide
you with a lot more value than changed has.
-
fixed- This will check to see if the current run is successful, and if the previous run was either failed or unstable. -
regression- This will check to see if the current run’s status is worse than the previous run’s status. So if the previous run was successful, and the current run is unstable, this will fire and its block of steps will execute. It will also run if the previous run was unstable, and the current run is a failure, etc.
New options
The options directive in Declarative can contain a number of different kinds
of configuration: traditional Jenkins job properties, like buildDiscarder,
wrapper steps to execute the entire Pipeline within, like timeout, and
Declarative-specific options that can switch from some default behaviors of
Declarative execution. We’ve added two new Declarative-specific options in the
last few releases.
-
checkoutToSubdirectory- Allows you to override the location that the automatic SCM checkout will use. UsingcheckoutToSubdirectory("foo"), your Pipeline will checkout your repository to"$WORKSPACE/foo", rather than the default of"$WORKSPACE". -
newContainerPerStage- If you’re using a top-leveldockerordockerfileagent, and want to ensure that each of your stages run in a fresh container of the same image, you can use this option. Anystagewithout its ownagentspecified will run in a new container using the image you’ve specified or built, on the same computer and with access to the same workspace.
Stage options
Sometimes, you may only want to disable automatic checkout of your repository,
using the skipDefaultCheckout(true) option, for one specific stage in your
Pipeline. Or perhaps you want to have a timeout that covers an entire
stage, including time spent waiting for a valid agent, post condition
execution, or the new input directive for stages (see further down for more
details on that!). To make those things possible, we’ve added a new options
direction to stage. You can use a subset of the top-level options content
in a stage’s `options - wrapper steps, and Declarative-specific options that
are marked as legal in a stage.
Input
You’ve always been able to run the input step inside a stage’s `steps
block, but we’ve found that approach can lose out on some of the value that the
input step provides.
To help with that, we’ve added a new input directive
to stage, with the same parameters as the input step. When you use the
stage input directive rather than using the step directly, any parameters
you’ve specified for the input will be made available in the stage’s
environment, meaning you can reference parameters from the `input in when
conditions, or in environment variables.
pipeline {
agent any
stages {
stage('Example') {
input {
message "Should we continue?"
ok "Yes, we should."
submitter "alice,bob"
parameters {
string(name: 'PERSON', defaultValue: 'Mr Jenkins', description: 'Who should I say hello to?')
}
}
steps {
echo "Hello, ${PERSON}, nice to meet you."
}
}
}
}Also, the input directive is evaluated before you enter any agent specified
on this stage, so if you are using a top-level agent none and each stage
has its own agent specified, you can avoid consuming an executor while
waiting for the input to be submitted.
Lastly, you can use timeout in the stage options, as
mentioned above, to time-out the input if too much time has passed without a
response.
I hope you find these new features and options for Declarative Pipelines helpful, and I look forward to the rest of 2018 as we continue to invest and improve in Jenkins Pipeline!
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Andrew Bayer
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