Jenkins Configuration as Code (a.k.a. JCasC) Plugin

View the wiki page. See presentation slides from Jenkins World 2018.

Join our Jenkins Configuration as Code office hours meeting scheduled for every second Wednesday. Use the Hangout on Air link from our Gitter chat channel. As an alternative, use the link from the invitation. See previous meeting minutes.

Introduction

Setting up Jenkins is a complex process, as both Jenkins and its plugins require some tuning and configuration, with dozens of parameters to set within the web UI manage section.

Experienced Jenkins users rely on groovy init scripts to customize Jenkins and enforce desired state. Those scripts directly invoke Jenkins API and as such can do everything (at your own risk). But they also require you know Jenkins internals, and are confident in writing groovy scripts on top of Jenkins API.

The Configuration as Code plugin has been designed as an opinionated way to configure Jenkins based on human-readable declarative configuration files. Writing such a file should be feasible without being a Jenkins expert, just translating into code a configuration process one is used to executing in the web UI.

This plugin aims to replace above user interface based configuration with the below text based configuration.

jenkins:
  securityRealm:
    ldap:
      configurations:
        - groupMembershipStrategy:
            fromUserRecord:
              attributeName: "memberOf"
          inhibitInferRootDN: false
          rootDN: "dc=acme,dc=org"
          server: "ldaps://ldap.acme.org:1636"

In addition, we want to have a well documented syntax file, and tooling to assist in writing and testing, so end users have full guidance in using this tool set and do not have to search for examples on the Internet.

Getting Started

First, start a Jenkins instance with the Configuration as Code plugin installed.

• Those running Jenkins as a Docker container (and maybe also pre-installing plugins), do include Configuration as Code plugin.

Second, the plugin looks for the CASC_JENKINS_CONFIG environment variable. The variable can point to any of the following:

• Path to a folder containing a set of config files. For example, /var/jenkins_home/casc_configs.
• A full path to a single file. For example, /var/jenkins_home/casc_configs/jenkins.yaml.
• A URL pointing to a file served on the web. For example, https://acme.org/jenkins.yaml.

If CASC_JENKINS_CONFIG points to a folder, the plugin will recursively traverse the folder to find file (suffix with .yml,.yaml,.YAML,.YML), but doesn't contain hidden files or hidden subdirectories. It doesn't follow symbolic links.

If you do not set the CASC_JENKINS_CONFIG environment variable, the plugin will default to looking for a single config file in $JENKINS_ROOT/jenkins.yaml.

If everything was setup correctly, you should now be able to browse the Configuration as Code page with Manage Jenkins -> Configuration as Code.

Run Locally

Prerequisites: Java, Maven & IntelliJ IDEA

• Ensure Java 8 is available. There are unresolved issues with Java 10/11 as of October 24, 2018.

  /usr/libexec/java_home

  /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
  • If Java 11 is selected by default, check other available Java version below.

  /usr/libexec/java_home --verbose

  Matching Java Virtual Machines (3):
      11.0.1, x86_64: "Java SE 11.0.1"  /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
      10.0.2, x86_64: "Java SE 10.0.2"  /Library/Java/JavaVirtualMachines/jdk-10.0.2.jdk/Contents/Home
      1.8.0_192, x86_64:  "Java SE 8"  /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home
  
  /Library/Java/JavaVirtualMachines/jdk-11.0.1.jdk/Contents/Home
  • Use the alternate Java 8.

  export JAVA_HOME=`/usr/libexec/java_home -v 1.8`
  echo $JAVA_HOME

  /Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home

• Ensure Maven is included in the PATH environment variable.

  export PATH=$PATH:/path/to/apache-maven-x.y.z/bin

IntelliJ IDEA

• Open the root directory of this project in IntelliJ IDEA.
• If you are opening the first time, wait patiently while project dependencies are being downloaded.
• Click Run in the menu. Select Edit Configurations in the menu item.
• Click Add New Configuration (+) in the top left of the shown dialog. Select Maven.
• Under Parameters tab group, Working directory: is /path/to/configuration-as-code-plugin/plugin.
• Under Parameters tab group, Command line: is hpi:run.
• Verify that IntelliJ IDEA is not using bundled maven.
  • Click File -> Preferences... -> Build, Execution, Deployment -> Build Tools -> Maven.
  • Maven home directory: has /path/to/apache-maven-x.y.z value, not Bundled (Maven 3).
• Open http://localhost:8080/jenkins/configuration-as-code/ to test the plugin locally.

CLI

• Go into the plugin child directory under the root directory of this project.
• Use the below commands.

export JAVA_HOME=`/usr/libexec/java_home -v 1.8`
export PATH=$PATH:/path/to/apache-maven-x.y.z/bin
mvn hpi:run

...
INFO: Jenkins is fully up and running

• Open http://localhost:8080/jenkins/configuration-as-code/ to test the plugin locally.

Initial Configuration

When configuring the first Jenkins instance, browse the examples shown in the demos directory of this repository. If you have a plugin that does not have an example, consult the reference help document. Click the Documentation link at the bottom of the Configuration as Code page.

If you want to configure a specific plugin, search the page for the name of the plugin. The page will show you which root element belongs to the configuration. Most installed plugins belong under the unclassified root element.

Examples

This configuration file includes root entries for various components of your primary Jenkins installation. The jenkins one is for the root Jenkins object, and other ones are for various global configuration elements.

jenkins:
  securityRealm:
    ldap:
      configurations:
        - groupMembershipStrategy:
            fromUserRecord:
              attributeName: "memberOf"
          inhibitInferRootDN: false
          rootDN: "dc=acme,dc=org"
          server: "ldaps://ldap.acme.org:1636"

  nodes:
    - permanent:
        name: "static-agent"
        remoteFS: "/home/jenkins"
        launcher:
          jnlp:

  slaveAgentPort: 50000
  agentProtocols:
    - "jnlp2"
tool:
  git:
    installations:
      - name: git
        home: /usr/local/bin/git
unclassified:
  mailer:
    adminAddress: admin@acme.org
    replyToAddress: do-not-reply@acme.org
    # Note that this does not work right now
    #smtpHost: smtp.acme.org
    smtpPort: 4441
credentials:
  system:
    domainCredentials:
      credentials:
        - certificate:
            scope: SYSTEM
            id: ssh_private_key
            keyStoreSource:
              fileOnMaster:
                keyStoreFile: /docker/secret/id_rsa

Also see demos folder with various samples.

Documentation

The configuration file format depends on the version of jenkins-core and installed plugins. Documentation is generated from a live instance, as well as a JSON schema you can use to validate configuration file with your favourite YAML tools.

Handling Secrets

Currently, you can provide initial secrets to JCasC that all rely on <key,value> substitution of strings in the configuration. For example, Jenkins: "${some_var}". Default variable substitution using the :- operator from bash is also available. For example, key: "${VALUE:-defaultvalue}" will evaluate to defaultvalue if $VALUE is unset. To escape a string from secret interpolation, put ^ in front of the value. For example, Jenkins: "^${some_var}" will produce the literal Jenkins: "${some_var}".

We can provide these initial secrets in the following ways:

• Using environment variables.
• Using docker-secrets, where files on path /run/secrets/${KEY} will be replaced by ${KEY} in the configuration. The base folder /run/secrets can be overridden by setting the environment variable SECRETS. So this can be used as a file based secret, and not just docker secrets.
• Using Kubernetes secrets, logic is the same as for docker-secrets. The secret needs to be mounted as a file to /run/secrets/, and then the filename can be used as the KEY. For example:

apiVersion: v1
kind: Secret
metadata:
  name: secret-name
data:
  filename: {{ "encoded string" | b64enc }}

can be used as:

- credentials:
    - string:
      id: "cred-id"
      secret: ${filename}

• Using Vault, see following section.

Vault

Prerequisites:

• The environment variable CASC_VAULT_PW must be present, if token is not used and appRole/Secret is not used. (Vault password.)
• The environment variable CASC_VAULT_USER must be present, if token is not used and appRole/Secret is not used. (Vault username.)
• The environment variable CASC_VAULT_APPROLE must be present, if token is not used and U/P not used. (Vault AppRole ID.)
• The environment variable CASC_VAULT_APPROLE_SECRET must be present, it token is not used and U/P not used. (Vault AppRole Secret ID.)
• The environment variable CASC_VAULT_TOKEN must be present, if U/P is not used. (Vault token.)
• The environment variable CASC_VAULT_PATHS must be present. (Comma separated vault key paths. For example, secret/jenkins,secret/admin.)
• The environment variable CASC_VAULT_URL must be present. (Vault url, including port number.)
• The environment variable CASC_VAULT_MOUNT is optional. (Vault auth mount. For example, ldap or another username & password authentication type, defaults to userpass.)
• The environment variable CASC_VAULT_NAMESPACE is optional. If used, sets the Vault namespace for Enterprise Vaults.
• The environment variable CASC_VAULT_FILE is optional, provides a way for the other variables to be read from a file instead of environment variables.
• The environment variable CASC_VAULT_ENGINE_VERSION is optional. If unset, your vault path is assumed to be using kv version 2. If your vault path uses engine version 1, set this variable to 1.
• The issued token should have read access to vault path auth/token/lookup-self in order to determine its expiration time. JCasC will re-issue a token if its expiration is reached (except for CASC_VAULT_TOKEN).

If the environment variables CASC_VAULT_URL and CASC_VAULT_PATHS are present, JCasC will try to gather initial secrets from Vault. However for it to work properly there is a need for authentication by either the combination of CASC_VAULT_USER and CASC_VAULT_PW, a CASC_VAULT_TOKEN, or the combination of CASC_VAULT_APPROLE and CASC_VAULT_APPROLE_SECRET. The authenticated user must have at least read access.

You can also provide a CASC_VAULT_FILE environment variable where you load the secrets from a file.

File should be in a Java Properties format

CASC_VAULT_PW=PASSWORD
CASC_VAULT_USER=USER
CASC_VAULT_TOKEN=TOKEN
CASC_VAULT_PATHS=secret/jenkins/master,secret/admin
CASC_VAULT_URL=https://vault.dot.com
CASC_VAULT_MOUNT=ldap

A good use for CASC_VAULT_FILE would be together with docker secrets.

version: "3.6"

services:
  jenkins:
    environment:
      CASC_VAULT_FILE: /run/secrets/jcasc_vault
    restart: always
    build: .
    image: jenkins.master:v1.0
    ports:
      - 8080:8080
      - 50000:50000
    volumes:
      - jenkins-home:/var/jenkins_home
    secrets:
      - jcasc_vault

volumes:
  jenkins-home:

secrets:
  jcasc_vault:
    file: ./secrets/jcasc_vault

TODO: Provide a Dockerfile to generate documentation from specified jenkins-core release and plugins.

Installing plugins

We don't support installing plugins with JCasC you need to use something else for this,

Dockers users can use:
https://github.com/jenkinsci/docker/#preinstalling-plugins

Kubernetes users:
https://github.com/helm/charts/tree/master/stable/jenkins

Supported Plugins

Most plugins should be supported out-of-the-box, or maybe require some minimal changes. See this dashboard for known compatibility issues.

Triggering Configuration Reload

You have the following option to trigger a configuration reload:

• via the user interface: Manage Jenkins -> Configuration -> Reload existing configuration

• via http POST to JENKINS_URL/configuration-as-code/reload Note: this needs to include a valid CRUMB and authentication information e.g. username + token of a user with admin permissions. Since Jenkins 2.96 CRUMB is not needed for API tokens.

• via Jenkins CLI

• via http POST to JENKINS_URL/reload-configuration-as-code It's disabled by default and secured via a token configured as system property casc.reload.token. Setting the system property enables this functionality and the requests need to include the token as query parameter named casc-reload-token, i.e. JENKINS_URL/reload-configuration-as-code/?casc-reload-token=32424324rdsadsa.

  curl -X POST "JENKINS_URL:8080/reload-configuration-as-code/?casc-reload-token=32424324rdsadsa"

Jenkins Enhancement Proposal

As configuration as code is demonstrated to be a highly requested topic in Jenkins community, we have published JEP 201 as proposal to make this a standard component of the Jenkins project. The proposal was accepted.