gmanfunky / generic-webhook-trigger-plugin

Generic Webhook Trigger Plugin

This is a Jenkins plugin that can:

Receive any HTTP request, JENKINS_URL/generic-webhook-trigger/invoke
Extract values

From POST content with JSONPath or XPath
From the query parameters
From the headers

Contribute those values as variables to the build

There is an optional feature to trigger jobs only if a supplied regular expression matches the extracted variables. Here is an example, let's say the post content looks like this:

{
  "before": "1848f1236ae15769e6b31e9c4477d8150b018453",
  "after": "5cab18338eaa83240ab86c7b775a9b27b51ef11d",
  "ref": "refs/heads/develop"
}

Then you can have a variable, resolved from post content, named reference of type JSONPath and with expression like $.ref .

The optional filter text can be set to $reference and the filter regexp set to ^(refs/heads/develop|refs/heads/feature/.+)$ to trigger builds only for develop and feature-branches.

Use case

This means it can trigger on any webhook, like:

The original use case was to build merge/pull requests. You may use the Git Plugin as described in this blog post to do that. There is also an example of this on the Violation Comments to GitLab Plugin page.

You may want to report back to the invoking system. HTTP Request Plugin is a very convenient plugin for that.

If a node is selected, then all leafs in that node will be contributed. If a leaf is selected, then only that leaf will be contributed.

There are websites to help fiddle with the expressions. You may want to checkout:

This website to fiddle with JSONPath.
This website to fiddle with XPath.
This website to fiddle with regexp.

When using the plugin in several jobs, you will have the same URL trigger all jobs. If you want to trigger only a certain job you can:

Use the token-parameter and have different tokens for different jobs.
Add some request parameter (or header, or post content) and use the regexp filter to trigger only if that parameter has a specific value.

Available in Jenkins here.

Troubleshooting

It's probably easiest to do with curl. Given that you have configured a Jenkins job to trigger on Generic Webhook, here are some examples of how to start the jobs.

curl -vs http://localhost:8080/generic-webhook-trigger/invoke 2>&1

This may start your job, if you have enabled "Allow anonymous read access" in global security config. If it does not, check the Jenkins log. It may say something like this.

INFO: Did not find any jobs to trigger! The user invoking /generic-webhook-trigger/invoke must have read permission to any jobs that should be triggered.

And to authenticate in the request you may try this.

curl -vs http://username:password@localhost:8080/generic-webhook-trigger/invoke 2>&1

There is also a special request parameter named token. When supplied, it is used to authenticate with BuildAuthorizationToken.

The job can then be triggered with that token like this.

curl -vs http://localhost:8080/jenkins/generic-webhook-trigger/invoke?token=abc123 2>&1

Screenshots

If you need the resolved values in pre build steps, like git clone, you need to add a parameter with the same name as the variable.

Job DSL Plugin

This plugin can be used with the Job DSL Plugin. There is also an example int he Violation Comments to GitLab Plugin wiki page.

job('Generic Job Example') {
 parameters {
  stringParam('VARIABLE_FROM_POST', '')
 }

 triggers {
  genericTrigger {
   genericVariables {
    genericVariable {
     key("VARIABLE_FROM_POST")
     value("\$.something")
     expressionType("JSONPath") //Optional, defaults to JSONPath
     regexpFilter("") //Optional, defaults to empty string
     defaultValue("") //Optional, defaults to empty string
    }
   }
   genericRequestVariables {
    genericRequestVariable {
     key("requestParameterName")
     regexpFilter("")
    }
   }
   genericHeaderVariables {
    genericHeaderVariable {
     key("requestHeaderName")
     regexpFilter("")
    }
   }
   printContributedVariables(true)
   printPostContent(true)
   regexpFilterText("\$VARIABLE_FROM_POST")
   regexpFilterExpression("aRegExp")
  }
 }

 steps {
  shell('''
echo $VARIABLE_FROM_POST
echo $requestParameterName
echo $requestHeaderName
  ''')
 }
}

Pipeline Multibranch

This plugin can be used with the Pipeline Multibranch Plugin. Here is an example:

With a Jenkinsfile like this:

node {
 properties([
  pipelineTriggers([
   [$class: 'GenericTrigger',
    genericVariables: [
     [key: 'reference', value: '$.ref'],
     [
      key: 'before',
      value: '$.before',
      expressionType: 'JSONPath', //Optional, defaults to JSONPath
      regexpFilter: '', //Optional, defaults to empty string
      defaultValue: '' //Optional, defaults to empty string
     ]
    ],
    genericRequestVariables: [
     [key: 'requestWithNumber', regexpFilter: '[^0-9]'],
     [key: 'requestWithString', regexpFilter: '']
    ],
    genericHeaderVariables: [
     [key: 'headerWithNumber', regexpFilter: '[^0-9]'],
     [key: 'headerWithString', regexpFilter: '']
    ],
    printContributedVariables: true,
    printPostContent: true,
    regexpFilterText: '',
    regexpFilterExpression: ''
   ]
  ])
 ])

 stage("build") {
  sh '''
  echo Variables from shell:
  echo reference $reference
  echo before $before
  echo requestWithNumber $requestWithNumber
  echo requestWithString $requestWithString
  echo headerWithNumber $headerWithNumber
  echo headerWithString $headerWithString
  '''
 }
}

It can be triggered with something like:

curl -X POST -H "Content-Type: application/json" -H "headerWithNumber: nbr123" -H "headerWithString: a b c" -d '{ "before": "1848f12", "after": "5cab1", "ref": "refs/heads/develop" }' -vs http://admin:admin@localhost:8080/jenkins/generic-webhook-trigger/invoke?requestWithNumber=nbr%20123\&requestWithString=a%20string

And the job will have this in the log:

Contributing variables:

    headerWithString_0 = a b c
    requestWithNumber_0 = 123
    reference = refs/heads/develop
    headerWithNumber = 123
    requestWithNumber = 123
    before = 1848f12
    requestWithString_0 = a string
    headerWithNumber_0 = 123
    headerWithString = a b c
    requestWithString = a string

Plugin development

More details on Jenkins plugin development is available here.

A release is created like this. You need to clone from jenkinsci-repo, with https and have username/password in settings.xml.

mvn release:prepare release:perform