Jenkins: Connect to a Docker container from a stage that is run with an agent (another Docker container)

Question

I am in the process of reworking a pipeline to use Declarative Pipelines approach so that I will be able to use Docker images on each stage.

At the moment I have the following working code which performs integration tests connecting to a DB which is run in a Docker container.

node {
    // checkout, build, test stages...
    stage('Integration Tests') {            
        docker.image('mongo:3.4').withRun(' -p 27017:27017') { c ->
        sh "./gradlew integrationTest"
    }
}

Now with Declarative Pipelines the same code would look somehow like this:

pipeline {
    agent none
    stages {
        // checkout, build, test stages...
        stage('Integration Test') {
            agent { docker { image 'openjdk:11.0.4-jdk-stretch' } }
            steps {
                script {
                    docker.image('mongo:3.4').withRun(' -p 27017:27017') { c ->
                        sh "./gradlew integrationTest"
                    }
                }
            }
        }
    }
}

Problem: The stage is now run inside a Docker container and running docker.image() leads to docker: not found error in the stage (it is looking for docker inside the openjdk image which is now used).

Question: How to start a DB container and connect to it from a stage in Declarative Pipelines?

Just some hints, you want to start the db container and the app container that i.e. runs the test. You can start them in a parallel step and stop the db in a post block, however to stop it you need a reference to the db container, seems its possible with a `pipelineContext` variable, check out [this](https://stackoverflow.com/questions/47842241/how-do-i-stop-a-running-container-in-jenkinsfile). — Dominik Gebhart, Sep 14 '19 at 22:41
@Sasha Shpota did you ever find a working solution? I have the exact same issue. — Allen, Dec 31 '19 at 15:34

score 2 · Answer 1 · answered Sep 17 '19 at 04:58

What essentially you are trying is to use is DIND.

You are using a jenkins slave that is essentially created using docker agent { docker { image 'openjdk:11.0.4-jdk-stretch' } }

Once the container is running you are trying to execute a docker command. the error docker: not found is valid as there is no docker cli installed. You need to update the dockerfile/create a custom image having openjdk:11.0.4-jdk-stretch and docker dameon installed.

Once the daemon is installed you need to volume mount the /var/run/docker.sock so that the daemon will talk to the host docker daemon via socket.

The user should be root or a privileged user to avoid permission denied issue.

Seems to be a good solution, may you provide more details with a concrete sample, thanks — Smaillns, Nov 05 '21 at 16:14

score 1 · Answer 2 · answered Sep 13 '19 at 23:48

So if I get this correctly your tests needs two things:

Java Environment
DB Connection

In this case have you tried a different approach like Docker In Docker (DIND) ?

Where you can have custom image that uses docker:dind as a base image and contains your java environment and use it in the agent section then the rest of the pipeline steps will be able to use the docker command as you expected.

GoA Oz · Answer 3 · 2019-09-16T16:52:38.253

In your example you are trying to run a container inside openjdk:11.0.4-jdk-stretch. If this image has not docker daemon installed you will not be able to execute docker, but in this case it will run a docker inside docker that you should not.

So it depends when you want.

Using multiple containers: In this case you can combine multiple docker images, but they are not dependent each others:

pipeline {
agent none
stages {
    stage('Back-end') {
        agent {
            docker { image 'maven:3-alpine' }
        }
        steps {
            sh 'mvn --version'
        }
    }
    stage('Front-end') {
        agent {
            docker { image 'node:7-alpine' }
        }
        steps {
            sh 'node --version'
        }
    }
}

}

Running "sidecar" containers: This example show you to use two containers simultaneously, which will be able to interacts each others:

node {
checkout scm
docker.image('mysql:5').withRun('-e "MYSQL_ROOT_PASSWORD=my-secret-pw"') { c ->
    docker.image('mysql:5').inside("--link ${c.id}:db") {
        /* Wait until mysql service is up */
        sh 'while ! mysqladmin ping -hdb --silent; do sleep 1; done'
    }
    docker.image('centos:7').inside("--link ${c.id}:db") {
        /*
         * Run some tests which require MySQL, and assume that it is
         * available on the host name `db`
         */
        sh 'make check'
    }
}

}

Please refer to the official documentation -> https://jenkins.io/doc/book/pipeline/docker/

I hope it will help you.

Thank you for your answer but have you read the question? In the first example you show how to run two different stages with different agents. How is it related to my problem? In the second example you use scripted pipeline which is what *I am using now* and trying to get rid. — Sasha Shpota, Sep 17 '19 at 09:15

score 0 · Answer 4 · answered Sep 20 '19 at 06:03

I have had a similar problem, where I wanted to be able to use a off-the-shelf Maven Docker image to run my builds in while also being able to build a Docker image containing the application. I accomplished this by first starting the Maven container in which the build is to be run giving it access to the hosts Docker endpoint.
Partial example:

docker run -v /var/run/docker.sock:/var/run/docker.sock maven:3.6.1-jdk-11

Then, inside the build-container, I download the Docker binaries and set the Docker host:

export DOCKER_HOST=unix:///var/run/docker.sock
wget -nv https://download.docker.com/linux/static/stable/x86_64/docker-19.03.2.tgz
tar -xvzf docker-*.tgz
cp docker/docker /usr/local/bin

Now I can run the docker command inside my build-container. As a, for me positive, side-effect any Docker image built inside a container in one step of the build will be available to subsequent steps of the build, also running in containers, since they will be retained in the host.

Jenkins: Connect to a Docker container from a stage that is run with an agent (another Docker container)

4 Answers4