An agent in our implementation of Jenkins is a pre-defined set of Docker images that can be used to perform a build step. The following snippet demonstrates declaring an agent and using the agent in a build step. Note that this is not a full pipeline, just the code that relates to an agent.
...
agent {
node {
label 'docker-builder'
} // end node
} // end agent
...
// run a Docker build
stage ('Docker build') {
steps {
container('docker') {
echo 'docker build'
script {
docker.withRegistry('https://REGISTRY.artifactory.sdodev.leidos.com/', 'CREDENTIAL'){
docker.build('IMAGE:TAG', '.')
} // end docker
} // end script
} //end container
} // end steps
} //end stage
|
Notes:
Line 4: The agent is used to build Docker images. Please see the list of other agents below that have been configured.
Line 11: An agent consists of one or more additional Docker containers. Some commands will only work when issued from within the selected container. This step is selecting the container named 'docker' which contains the the Docker CLI.
Line 14: This line selects the registry from which layers will be pulled when building images. Since we are using private registries, a set of credentials are needed for docker to log into the registry.
Line 15: This will build an image (the first parameter) setting the current directory as the Docker context (the second parameter).
Important: This stage will build the image but not upload the image to a registry. The code snippet below will upload the built image to a registry:
// push image
stage ('Docker push latest') {
steps {
container('docker') {
script{
docker.withRegistry('https://REGISTRY.artifactory.sdodev.leidos.com/', 'CREDENTIAL'){
docker.push('IMAGE:TAG')
} //end docker
} //end script
} // end container
} // end steps
} //end stage |
An alternate way to perform Docker builds is as follows:
pipeline{
agent{
node('docker-builder')
} //end agent
environment {
REGISTRY = "sdo-docker.artifactory.sdo.leidos.com"
IMAGE = "docker-test"
TAG = "1.0"
} // end environment
stages{
stage ('Docker build') {
steps{
container('docker') {
withCredentials([usernamePassword(credentialsId:'docker-test', usernameVariable: 'USER', passwordVariable: 'PASSWORD')]) {
sh '''
docker login -u ${USER} -p ${PASSWORD} ${REGISTRY}
docker build -f docker/Dockerfile -t ${REGISTRY}/${IMAGE}:${TAG} .
docker push ${REGISTRY}/${IMAGE}:${TAG}
''' // end sh
} //end withCredentials
} // end container
} // end steps
} // end stage
} // end stages
} // end pipeline |
Line 16: the credentialsId contains username/password credentials stored in Jenkins that can login/push/pull in the named REGISTRY.
The following additional Agents are configured in Jenkins:
| Name | purpose |
|---|---|
| default | The default agent, provides a JNLP connection back to Jenkins, contains maven and a JDK (1.8) |
| openjdk11 | Contains OpenJDK 11.0.5, container name is openjdk11 |
| docker-builder | Contains an image ('docker') with the Docker CLI for building Docker images (using podman) |
| taurus | Contains a Taurus image ('taurus') for running various test automations. A default JMeter automation framework is available in this image |
| xl-builder | Similar to default but allocates more CPU and memory resources. Some builds may require more resources than the 'default' agent. |
| jenkins-tools-python3 | container name is python3 |
| jenkins-tools-js | container name is js |
| cmake3 | container name is cmake3, contains gcc, g++, make, cmake, cmake3 |
| rpmbuild | container name is rpmbuild, contains rpmdevtools, rpmlint |