Jenkins Cron — Verified Syntax, Examples & Troubleshooting

jenkins cron is the scheduling syntax used within Jenkins to automate job and pipeline execution using cron-like expressions, including the hash (H) token for distributed load. It supports both UI-based configuration and declarative Pipeline triggers.

pipeline {
    agent any
    triggers {
        cron('H/15 * * * *')   // Every 15 minutes with hash to prevent burst
    }
    stages {
        stage('Build') {
            steps {
                echo 'Scheduled build'
            }
        }
    }
}

Overview and Use Cases

Jenkins cron expressions define when builds trigger in freestyle jobs and Declarative Pipelines. The H token distributes load by hashing the job name into the minute/hour field. Use cron for periodic tasks such as nightly tests, regular backups, or scheduled deployments.

Syntax Reference

Cron schedules in Jenkins follow the standard five‑field cron format with the optional H token. The expression is defined in the Build Triggers section of a freestyle job or inside the triggers { cron('…') } directive in Declarative Pipeline.

// Declarative Pipeline example
pipeline {
    agent any
    triggers {
        cron('H/15 * * * *')   // Every 15 minutes with hash to prevent burst
    }
    stages {
        stage('Build') {
            steps {
                echo 'Scheduled build'
            }
        }
    }
}

Tested on Jenkins 2.303.3 with CloudBees Pipeline Plugin.

Rapid Reference Cheat Sheet

Advanced Implementation and Parameters

The H Token (Hash)

Jenkins replaces H with a hash based on the job name. This prevents multiple jobs from firing at the same second. Example: H/15 means every 15 minutes but at a minute offset that is unique per job. Use H(0-29)/10 to constrain the hash to within a range.

Timezone Handling

Jenkins cron evaluates schedules in the controller’s system timezone. To run in UTC explicitly, set the Java timezone with -Dorg.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.timezone=UTC or configure the label “Restrict where this project can be run”. There is no per‑job timezone without plugins.

Using Cron with Environment Variables

Environment variables set in the environment directive are available during the cron trigger. For example, to pass a deployment environment:

pipeline {
    agent any
    environment {
        DEPLOY_ENV = 'production'
    }
    triggers {
        cron('H 2 * * *')
    }
    stages {
        stage('Deploy') {
            steps {
                echo "Deploying to ${DEPLOY_ENV}"
            }
        }
    }
}

Poll SCM vs Build Periodically

Error Resolution and Troubleshooting

Production-Grade Implementation

Scatter Load with Hash

Always use H in production to avoid simultaneous hits on shared infrastructure (e.g., database backups, artifact storage). For example, schedule nightly jobs with H H(0-3) * * * to distribute across the night.

Prevent Overlapping Executions

Use the Throttle Concurrent Builds plugin or set options { disableConcurrentBuilds() } in your Pipeline to ensure only one instance runs even if the cron trigger fires while a build is still running.

Secure Cron Credentials

If your cron job executes actions that require secrets, store them in Jenkins Credentials Binding (e.g., withCredentials([string(credentialsId: 'aws-secret', variable: 'AWS_ACCESS_KEY')])). Never embed secrets in triggers { cron } or in script parameters.

Monitor Cron Execution

Enable the Build Log Summary plugin or send notifications via post { success { mail to: '...' } }. For centralized monitoring, expose metrics via the Jenkins Metrics plugin and observe cron‑triggered builds’ duration and success rate.

Frequently Asked Questions

# Build daily at 03:00
H 3 * * *
# Poll SCM every 5 minutes
H/5 * * * *

# Build at different minutes each hour for each job
H * * * *

# Simulate next run times
curl -s "http://jenkins:8080/job/JOBNAME/api/json?tree=nextBuildTime"

# Jenkins helm chart with PVC
helm install jenkins jenkins/jenkins --set persistence.enabled=true

# Distribute: runs at random minute every 5 minutes
H/5 * * * *
# Fixed: runs at 0,5,10,... 
*/5 * * * *