How to differentiate build triggers in Jenkins Pipeline - jenkins

I'm hoping to add a conditional stage to my Jenkinsfile that runs depending on how the build was triggered. Currently we are set up such that builds are either triggered by:
changes to our git repo that are picked up on branch indexing
a user manually triggering the build using the 'build now' button in the UI.
Is there any way to run different pipeline steps depending on which of these actions triggered the build?

The following code should works to determine if a user has started the pipeline or a timer/other trigger:
def isStartedByUser = currentBuild.rawBuild.getCause(hudson.model.Cause$UserIdCause) != null

In Jenkins Pipeline without currentBuild.rawBuild access the build causes could be retrieved in the following way:
// started by commit
currentBuild.getBuildCauses('jenkins.branch.BranchEventCause')
// started by timer
currentBuild.getBuildCauses('hudson.triggers.TimerTrigger$TimerTriggerCause')
// started by user
currentBuild.getBuildCauses('hudson.model.Cause$UserIdCause')
You can get a boolean value with:
isTriggeredByTimer = !currentBuild.getBuildCauses('hudson.triggers.TimerTrigger$TimerTriggerCause').isEmpty()
Or, as getBuildCauses() returns an array, the array's size will work correctly with Groovy truthy semantics:
if (currentBuild.getBuildCauses('hudson.triggers.TimerTrigger$TimerTriggerCause')) {

The ability to get causes for a workflow run was released in version 2.22 (2018 Nov 02) to the Pipeline Supporting APIs Plugin. The feature was requested in JENKINS-41272.
A couple methods were added to the currentBuild global variable with that release:
getBuildCauses
Returns a JSON array of build causes for the current build
EXPERIMENTAL - MAY CHANGE getBuildCauses(String causeClass)
Takes a string representing the fully qualified Cause class and returns a JSON array of build causes filtered by that type for the current build, or an empty JSON array if no causes of the specified type apply to the current build
And an example from me submitting:
echo "${currentBuild.buildCauses}" // same as currentBuild.getBuildCauses()
echo "${currentBuild.getBuildCauses('hudson.model.Cause$UserCause')}"
echo "${currentBuild.getBuildCauses('hudson.triggers.TimerTrigger$TimerTriggerCause')}"
And the output:
[Pipeline] echo
[[_class:hudson.model.Cause$UserIdCause, shortDescription:Started by user anonymous, userId:null, userName:anonymous], [_class:org.jenkinsci.plugins.workflow.cps.replay.ReplayCause, shortDescription:Replayed #12]]
[Pipeline] echo
[]
[Pipeline] echo
[]
[Pipeline] End of Pipeline
Finished: SUCCESS
NOTE
There appears to be an issue with the currentBuild.getBuildCauses(type) when the type is a type of Cause contributed by a plugin. For example, currentBuild.getBuildCauses('org.jenkinsci.plugins.workflow.cps.replay.ReplayCause') fails with a java.lang.ClassNotFoundException. This was reported in JENKINS-54673 for the 2.22 version of the Pipeline: Supporting APIs (workflow-support) plugin. It is reportedly fixed in the 2.24 version.

I might be missing something, but you can achieve what you want easily by making use of the when directive:
pipeline {
agent any
stages {
stage('Always') {
steps {
echo "I am always executed"
}
}
stage('ManualTimed') {
steps {
echo "I am only executed when triggered manually or timed"
}
when {
beforeAgent true
anyOf {
triggeredBy 'TimerTrigger'
triggeredBy cause: 'UserIdCause'
}
}
}
stage('GitLabWebHookCause') {
steps {
echo "I am only executed when triggered by SCM push"
}
when {
beforeAgent true
triggeredBy 'GitLabWebHookCause'
}
}
}
}
You will find many similar useful examples for various use cases in the documentation of the when directive.
Edit:
thanks to Jean-Francois Larvoire's answer, I was able to figure out 'my trigger' GitLabWebHookCause I required for my use case.

#vitalii-blagodir:
Your answer works for detecting builds triggered by users and timers, but not by commits.
Instead, I found this to work in my case:
def isTriggeredByIndexing = currentBuild.getBuildCauses('jenkins.branch.BranchIndexingCause').size()
def isTriggeredByCommit = currentBuild.getBuildCauses('com.cloudbees.jenkins.GitHubPushCause').size()
def isTriggeredByUser = currentBuild.getBuildCauses('hudson.model.Cause$UserIdCause').size()
def isTriggeredByTimer = currentBuild.getBuildCauses('hudson.triggers.TimerTrigger$TimerTriggerCause').size()
The .size() suffix returns 0 if the object is missing, or 1 if it's present. This makes the result usable as a boolean.
For finding the object name to use, I found it convenient to display this in the log:
echo "# Build causes"
def buildCauses = currentBuild.buildCauses
def numCause = 0
for (cause in buildCauses) {
echo "${numCause++}: ${cause.shortDescription}" // Display a human-readable index and description
echo "${cause}" // Display the object class name. This allows knowing what names to use in getBuildCauses(name) calls below.
}
Finally, if the goal is to abort a pipeline build in specific cases, then the test must be done before the beginning of the pipeline.
For example, we had a problem with the branch indexing triggering extra useless builds. This was fixed by adding this before the pipeline:
// Avoid useless buils: The branch indexing should only trigger the initial build of a new branch.
def isTriggeredByBranchIndexing = currentBuild.getBuildCauses('jenkins.branch.BranchIndexingCause').size()
if (isTriggeredByBranchIndexing && currentBuild.previousBuild) { // Then it's not the initial build.
echo "# Reindexing a branch already built. It is useless to rebuild it now. Aborting."
currentBuild.result = 'SUCCESS' // Make sure the build is not displayed in red in the Jenkins UI.
return // Abort before the pipeline even starts. (Inside the pipeline, this would only abort one stage.)
}

I think that the answers here are incomplete and do not provide an actual ready to use answer. Here's my code to get it working:
import com.cloudbees.groovy.cps.NonCPS
#NonCPS
def isStartedByTimer() {
def buildCauses = currentBuild.rawBuild.getCauses()
echo buildCauses
boolean isStartedByTimer = false
for (buildCause in buildCauses) {
if ("${buildCause}".contains("hudson.triggers.TimerTrigger\$TimerTriggerCause")) {
isStartedByTimer = true
}
}
echo isStartedByTimer
return isStartedByTimer
}
// [...]
// Other pipeline stuff
script {
isStartedByTimer()
}
When started by user:
00:00:01.353 [hudson.model.Cause$UserIdCause#fa5cb22a]
[Pipeline] echo
00:00:01.358 false
When started by timer:
00:00:01.585 [hudson.triggers.TimerTrigger$TimerTriggerCause#5]
[Pipeline] echo
00:00:01.590 true
Note: the NonCPS decorator is needed because otherwise the next non-script step will throw.

Assuming the two different build causes are "timer" and "push" (to a git repo), you can add the following stage to your Jenkinsfile (in a declarative Jenkins pipeline) to make use of getBuildCauses():
pipeline {
stages {
stage('preparation') {
steps {
script {
// get build cause (time triggered vs. SCM change)
def buildCause = currentBuild.getBuildCauses()[0].shortDescription
echo "Current build was caused by: ${buildCause}\n"
// e.g. "Current build was caused by: Started by GitHub push by mirekphd"
// vs. "Started by timer"
}
}
}
}
}
Then I can decide whether to perform certain stages conditionally (depending on the build cause). For example, pulling a docker base image and inspecting for changes in system libraries (likely security updates) should be done periodically, regardless of whether there was a source code change or not.

We can use "BUILD_CAUSE" variable for getting the information about who initiated the run
for [jenkins-pipeline] you may use
currentBuild.rawBuild.getCauses()
(see github.com/jenkinsci/pipeline-examples/blob/master/… for more details)

There was a similar requirement, where user detail who triggered the build should be there in success / failure notification. The job was already had time based triggered, hence could not use wrap([$class: 'BuildUser']) directly.
I used below step, which print username if the job is triggered manually or timer triggered. So, I used this:
pipeline {
agent any
stages {
stage('Test') {
steps {
script{
env.buildCauses = currentBuild.rawBuild.getCauses()
if (buildCauses.contains("hudson.triggers.TimerTrigger")){
env.builduser = "TimerTrigger"
} else {
wrap([$class: 'BuildUser']) {
env.builduser = "${BUILD_USER}"
}
}
}
echo "Initiated by: ${env.builduser}"
}
}
}
}

Related

How can i stop a remote build in Jenkins if a parameter in the url is not valid?

I run remote builds in Jenkins as follows:
JENKINS_URL/job/JOBNAME/build?token=TOKEN
If i add an extra parameter on the query string as follows:
JENKINS_URL/job/JOBNAME/build?token=TOKEN&User=test#test.com&Key=Wxfder$324
As the first step in the build I want to extract these values ie token, User and Key and do some validation and if not valid , then stop the job.
Is there a Build Step i can use, how can i do this ?
One way to do this is by passing the data you need appending to the build cause. Refer to the following example.
The URL
Note the content assigned to cause= parameter
http://localhost:8080/job/Scripted/build?token=12345678&cause=User:test#test.com,Key:Wxfder$324
The Pipeline
pipeline {
agent any
stages {
stage('Test') {
steps {
script {
def cause = currentBuild.getBuildCauses()[0]
def note = cause.getString("note")
echo "${note}"
}
}
}
}
}
Above will give you the following Output.
[Pipeline] echo
User:test#test.com,Key:Wxfder$324

How do I use `when` condition on a file's last modified time in Jenkins pipeline syntax

I am creating a Jenkins pipeline, I want certain stage to be triggered only when a particular log file's(log file is located in the server node where all the stages are going to run) last modified date is updated after the initiation of pipeline job, I understand we need to use "When" condition but not really sure how to implement it.
Tried referring some of the pipeline related portals but could not able to find an answer
Can some please help me through this?
Thanks in advance!
To get data about file is quite tricky in a Jenkins pipeline when using the Groovy sandbox since you're not allowed to do new File(...).lastModified. However there is the findFiles step, which basically returns a list of wrapped File objects with a getter for last modified time in millis, so we can use findFiles(glob: "...")[0].lastModified.
The returned array may be empty, so we should rather check on that (see full example below).
The current build start time in millis is accessible via currentBuild.currentBuild.startTimeInMillis.
Now that we git both, we can use them in an expression:
pipeline {
agent any
stages {
stage("create file") {
steps {
touch "testfile.log"
}
}
stage("when file") {
when {
expression {
def files = findFiles(glob: "testfile.log")
files && files[0].lastModified < currentBuild.startTimeInMillis
}
}
steps {
echo "i ran"
}
}
}
}

Can a Jenkins pipeline have an optional input step?

Is it possible to create a Jenkins pipeline with an optional input stage?
The below snippet doesn't achieve this goal.
Expected behaviour
The stage (and therefore the input prompt) should only run for specific branches.
Actual behaviour
This stage runs for all branches. The when filter is ignored when an input step is used.
stage('Approve') {
when {
expression { BRANCH_NAME ==~ /^qa[\w-_]*$/ }
}
input {
message "Approve release?"
ok "y"
submitter "admin"
parameters {
string(name: 'IS_APPROVED', defaultValue: 'y', description: 'Deploy to master?')
}
}
steps {
script {
if (IS_APPROVED != 'y') {
currentBuild.result = "ABORTED"
error "User cancelled"
}
}
}
}
The filter is not ignored, it is just evaluated after the input step. In your example, you would always be asked whether to deploy, and in the case that you are not on a QA branch, nothing would happen.
Now you could ask why Jenkins isn't evaluating the 'when' directive first. In that case, you could not use the input parameter in your when condition.
And having multiple when directives would be like scripting within the declarative pipeline.
However, there is an expression that allows you controlling when the 'when' directive is evaluated. This is beforeAgent. It allows you to evaluate the when statement before the agent is allocated. Similar to that, you would need something like beforeInput. You could create a feature request for that.
I stepped away from using the input directive and I use input within a scripting block now, because that provides much more flexibility, e.g. I am sending Slack notifications when somebody has to approve something, which is impossible with the declarative approach. You would need a notify directive for that. And if there was one, is that going to be evaluated before or after the input step?
You see, doing everything declarative is not always the best way. So my recommended approach is the following (disclaimer: this is untested!):
pipeline {
// We want to use agents per stage to avoid blocking our build agents
// while we are waiting for user input.
agent none
...
// The question mark naming convention is helpful to show you which
// approval stage belongs to which work stage.
stage('Release?') {
// Don't allocate an agent because we don't want to block our
// slaves while waiting for user input.
agent none
when {
// You forgot the 'env.' in your example above ;)
expression { env.BRANCH_NAME ==~ /^qa[\w-_]*$/ }
}
options {
// Optionally, let's add a timeout that we don't allow ancient
// builds to be released.
timeout time: 14, unit: 'DAYS'
}
steps {
// Optionally, send some notifications to the approver before
// asking for input. You can't do that with the input directive
// without using an extra stage.
slackSend ...
// The input statement has to go to a script block because we
// want to assign the result to an environment variable. As we
// want to stay as declarative as possible, we put noting but
// this into the script block.
script {
// Assign the 'DO_RELEASE' environment variable that is going
// to be used in the next stage.
env.DO_RELEASE = input ...
}
// In case you approved multiple pipeline runs in parallel, this
// milestone would kill the older runs and prevent deploying
// older releases over newer ones.
milestone 1
}
}
stage('Release') {
// We need a real agent, because we want to do some real work.
agent any
when {
// Evaluate the 'when' directive before allocating the agent.
beforeAgent true
// Only execute the step when the release has been approved.
environment name: 'DO_RELEASE', value: 'yes'
}
steps {
// Make sure that only one release can happen at a time.
lock('release') {
// As using the first milestone only would introduce a race
// condition (assume that the older build would enter the
// milestone first, but the lock second) and Jenkins does
// not support inter-stage locks yet, we need a second
// milestone to make sure that older builds don't overwrite
// newer ones.
milestone 2
// Now do the actual work here.
...
}
}
}
The correct syntax would be more like (completely untested):
stage('Approve') {
when {
expression { BRANCH_NAME ==~ /^qa[\w-_]*$/ }
}
steps {
script {
def IS_APPROVED = input(
message: "Approve release?"
ok: "y"
submitter: "admin"
parameters: [
string(name: 'IS_APPROVED', defaultValue: 'y', description: 'Deploy to master?')
]
)
if (IS_APPROVED != 'y') {
currentBuild.result = "ABORTED"
error "User cancelled"
}
}
}
}
So essentially, you're hitting the limits of declarative pipelines have to fall back to groovy scripting / scripted pipelines.

Jenkins pipeline milestone not cancelling previous ongoing build

I am experimenting with Jenkins pipeline and milestones and cannot figure out why Jenkins is not cancelling the previous build when a new build crosses the milestone.
Example Jenkinsfile
pipeline {
agent any
parameters {
booleanParam(defaultValue: true, description: '', name: 'userFlag')
}
stages {
stage("foo") {
steps {
milestone(ordinal: 1, label: "BUILD_START_MILESTONE")
sh 'sleep 1000'
}
}
}
}
Triggering this pipeline twice does not cancel the 1st job
Try this:
/* This method should be added to your Jenkinsfile and called at the very beginning of the build*/
#NonCPS
def cancelPreviousBuilds() {
def jobName = env.JOB_NAME
def buildNumber = env.BUILD_NUMBER.toInteger()
/* Get job name */
def currentJob = Jenkins.instance.getItemByFullName(jobName)
/* Iterating over the builds for specific job */
for (def build : currentJob.builds) {
/* If there is a build that is currently running and it's not current build */
if (build.isBuilding() && build.number.toInteger() != buildNumber) {
/* Than stopping it */
build.doStop()
}
}
}
I don't think the behavior is "If I'm a newer build that crosses this milestone, then all older build that crossed this milestone will be cancelled"
The actual behavior of the milestone step is that when a more recent pipeline crosses it first, then it prevents older pipeline from crossing that milestone.
I have a simple work around with milestone plugin, according to the document:
Builds pass milestones in order (taking the build number as sorter field).
Older builds will not proceed (they are aborted) if a newer one already passed the milestone.
When a build passes a milestone, any older build that passed the previous milestone but not this one is aborted.
Once a build passes the milestone, it will never be aborted by a newer build that didn't pass the milestone yet.
you can try something like this:
pipeline {
agent any
stages {
stage('Stop Old Build') {
steps {
milestone label: '', ordinal: Integer.parseInt(env.BUILD_ID) - 1
milestone label: '', ordinal: Integer.parseInt(env.BUILD_ID)
}
}
}
}
you can put this at the start of any pipeline.
Assume you just start a new build, #5. The first milestone, will be used to passes #4's second milestone, and the second milestone(of #5) will be used to kill #4's process, if it's currently running.
The disableConcurrentBuilds property has been added to Pipeline. The Pipeline syntax snippet generator offers the following syntax hint:
properties([disableConcurrentBuilds(abortPrevious: true)])
That property is used on ci.jenkins.io to cancel older plugin build jobs when newer plugin build jobs start.
Declarative Pipeline also includes the disableConcurrentBuilds option that is documented in the Pipeline syntax page.
The declarative directive generator suggests the following:
options {
disableConcurrentBuilds abortPrevious: true
}
as per https://jenkins.io/blog/2016/10/16/stage-lock-milestone/, a pair of 'milestone()' works for me to kill the previous jobs while the pipeline kicked off for times,
stage('Build') {
// The first milestone step starts tracking concurrent build order
milestone()
node {
echo "Building"
}}
// The Deploy stage does not limit concurrency but requires manual input
// from a user. Several builds might reach this step waiting for input.
// When a user promotes a specific build all preceding builds are aborted,
// ensuring that the latest code is always deployed.
stage('Deploy') {
timeout(time: 60, unit: 'SECONDS') {input "Deploy?"}
milestone()
node {
echo "Deploying"
}
}
The last milestone helps kill previous builds if reached, say deploy button clicked for the above case. Or the locked resource released for the below case,
// This locked resource contains both Test stages as a single concurrency Unit.
// Only 1 concurrent build is allowed to utilize the test resources at a time.
// Newer builds are pulled off the queue first. When a build reaches the
// milestone at the end of the lock, all jobs started prior to the current
// build that are still waiting for the lock will be aborted
lock(resource: 'myResource', inversePrecedence: true){
node('test') {
stage('Unit Tests') {
echo "Unit Tests"
}
stage('System Tests') {
echo "System Tests"
}
}
milestone()
}
Building on #D.W.'s answer, i found a simple pattern that works. It seems to fit into D.W.'s bullet #3 (which is the official doc): When a build passes a milestone, Jenkins aborts older builds that passed the previous milestone but not this one.
Adding an earlier milestone that everything will pass, and then one after the thing that is going to wait, makes it all work like you think it should. In my case:
steps {
milestone 1
input 'ok'
milestone 2
}
Create two active builds with this, and only approve the second one. You'll see the first one get automatically canceled, because build 2 passed milestone 2 first.
Try taking out milestone 1, and you'll see that build 1 does not get canceled when build 2 passes milestone 2.
Adding the early milestone satisfies the requirement. It seems that a build has to pass any milestone before a future milestone passed by a newer build will cause it to cancel.

How to disable automatic build from scm change in Jenkinsfile

I have a Jenkinsfile that I've set up with a cron for a pipelineTriggers parameter. I can't seem to figure out how to disable the job from building from a merge to the master branch of the repo. Is there a way in the Jenkinsfile to disable the automatic build from an scm change?
If you're using a Multibranch Pipeline, you should be able to do this on the job's Configure page:
Scroll down to "Branch Sources"
Under "Property strategy", choose "Named branches get different properties"
Click "Add exception", enter "master" as the branch name
Click "Add property", choose "Suppress automatic SCM triggering"
Save
That would prevent changes to the master branch from triggering a build of the corresponding job.
For declarative pipelines, use the when directive with a triggeredBy condition, e.g.
when { triggeredBy 'TimerTrigger' }
With the multibranch pipeline, I could not figure out a way to prevent the next build being triggered. As a workaround, I added the following code to my Jenkinsfile (using scripted syntax), to abort the following build if the only changes contain "[ci-skip]" in the commit message:
def abortBuildIfTriggeredBySkippableCommit() {
def changeSetCount = 0;
def ciSkipCount = 0;
if (currentBuild.changeSets != null) {
for (changeSetList in currentBuild.changeSets) {
for (changeSet in changeSetList) {
changeSetCount++;
if (changeSet.msg.contains('[ci-skip]')) {
ciSkipCount++;
}
}
}
}
if (changeSetCount > 0 && changeSetCount == ciSkipCount) {
currentBuild.result = 'NOT_BUILT'
error("Stopping to prevent auto trigger. All commits contained [ci-skip]")
}
}
Note that this code assumes you are using the git plugin, and that the objects in currentBuild.changeSets will be GitChangeSetList.
In a jenkins job you can navigate to advanced source code management
Select behavior Dont trigger build on commit notification
This disables the Started by an SCM change
For people still looking for a solution, go to configuration for the multi branch pipeline, under Property Strategy, choose "Suppress Automatic SCM Triggering".
Note: This is available on cloudbees version of Jenkins. I am not sure, if it matters.
https://support.cloudbees.com/hc/en-us/articles/360026953651-Preventing-builds-from-getting-triggered-when-creating-a-new-multibranch-Pipeline-or-Organization-Folder?page=29
This is what I came up with. I was hoping for something less messy, but this does seem to work:
I have this as the build's properties:
properties([
pipelineTriggers([cron('H H 7 * *')])
])
I then have this function that defines the source of the build:
// check if the job was started by a timer
#NonCPS
def jobStartedByWhat() {
def startedByWhat = ''
try {
def buildCauses = currentBuild.rawBuild.getCauses()
for ( buildCause in buildCauses ) {
if (buildCause != null) {
def causeDescription = buildCause.getShortDescription()
echo "shortDescription: ${causeDescription}"
if (causeDescription.contains("Started by timer")) {
startedByWhat = 'timer'
}
if (causeDescription.contains("Started by user")) {
startedByWhat = 'user'
}
}
}
} catch(theError) {
echo "Error getting build cause: ${theError}"
}
return startedByWhat
}
def startedByWhat = jobStartedByWhat()
I can then evaluate the function at runtime so that if a build gets triggered because of a merge to master, it will not actually run:
node {
try {
checkout scm
if (env.BRANCH_NAME == 'master') {
if (startedByWhat == 'timer' || startedByWhat == 'user') {
..... RUN THE BUILD .....
} else {
.... EXIT WITHOUT RUNNING THE BUILD ....
I stumbled upon this as well. IMO an acceptable solution would be a filter for commit messages when checking out source code - this feature exists for regular Jobs but is missing for multibranch pipelines, see https://issues.jenkins-ci.org/browse/JENKINS-48296.
For those not using the git plugin, this method is a workaround for scripted pipelines (inspired by scarswell's answer):
def abortBuildIfTriggeredBySkippableCommit() {
lastCommitMessage = sh(
script: "${gitBinary} --no-pager log -1 --pretty=%B",
returnStdout: true
)
if (lastCommitMessage != null &&
lastCommitMessage.toString().contains('[maven-release-plugin]')) {
currentBuild.result = 'ABORTED'
error("Stopping build, it was triggered by the maven release plugin")
}
}
For declarative pipelines, there is a much more simple answer now. From the docs:
overrideIndexTriggers
Allows overriding default treatment of branch indexing triggers. If branch indexing triggers are disabled at the multibranch or organization label, options { overrideIndexTriggers(true) } will enable them for this job only. Otherwise, options { overrideIndexTriggers(false) } will disable branch indexing triggers for this job only.
It's a little backwards conceptually, but assuming your jobs are triggering off github webhooks by default, you set overrideIndexTriggers(false) to disable the automatic triggering.
If you are using Pipeline script from SCM then comment out the triggers section(either SCMPoll/BuildPeriodically option ) in Jenkins file as shown below.
//triggers {cron ('H/15 * * * *')}
//pipelineTriggers([pollSCM('H/15 * * * *')])
If you are using Pipeline script then disable the PollSCM/Build periodically(whichever is used) option.
One could disable the scm build trigger by disabling the webhook notification from git.
if (currentBuild.getBuildCauses().toString().contains('BranchIndexingCause') || currentBuild.getBuildCauses().toString().contains('Branch event')) {
print "INFO: Build skipped due to trigger being Branch Indexing"
currentBuild.result = 'ABORTED' // optional, gives a better hint to the user that it's been skipped, rather than the default which shows it's successful
return
}
timestamps{
node
{
stage('Getting Build Parameters')
{
print('build job')
}
}
}
if (currentBuild.getBuildCauses().toString().contains('BranchIndexingCause') || currentBuild.getBuildCauses().toString().contains('Branch event')) {
print "INFO: Build skipped due to trigger being Branch Indexing"
currentBuild.result = 'ABORTED' // optional, gives a better hint to the user that it's been skipped, rather than the default which shows it's successful
return
}
if (currentBuild.getBuildCauses().toString().contains('BranchIndexingCause') || currentBuild.getBuildCauses().toString().contains('Branch event')) {
print "INFO: Build skipped due to trigger being Branch Indexing"
currentBuild.result = 'ABORTED' // optional, gives a better hint to the user that it's been skipped, rather than the default which shows it's successful
return
}

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