Using testcontainers in a Jenkins Docker Agent: containers fail to start, NoRouteToHostException

Question

I\'m using a Jenkins declarative pipeline with Docker Agents to build and test my software, including running integration tests using testcontainers. I can run my testcontai

Answer 1

After some experimentation, I've discovered the cause of the problem. The crucial action is trying to create a Docker bridge network (using docker network create, or a testcontainers Network object) inside a Docker container that is itself running in a Docker bridge network. If you do this you will not get an error message from Docker, nor will the Docker daemon log file include any useful messages. But attempts to use the network will result in there being "no route to host".

I fixed the problem by giving my outermost Docker containers (the Jenkins Agents) access to the host network, by having Jenkins provide a --network="host" option to its docker run command:

pipeline {
    agent {
        dockerfile {
            filename 'Dockerfile.jenkinsAgent'
            additionalBuildArgs  ...
            args '-v /var/run/docker.sock:/var/run/docker.sock ... --network="host" -u jenkins:docker'
       }
    }
    stages {
...

That is OK because the Jenkins Agents do not need the level of isolation given by a bridge network.