jenkins-agent-entrypoint

#!/bin/bash

set -ex

################################################################################
# Use for testing (not as Jenkins agent):
#  docker run <image/id> <command>
# Use as SSH agent:
#  docker run <image/id> [<public key>]
# Or provide in environment variables :
# * JENKINS_SLAVE_SSH_PUBKEY : SSH public key
#
# Use as regular JNLP agent:
#  docker run <image/id> [options] -url http://jenkins [SECRET] [AGENT_NAME]
# Optional environment variables :
# * JENKINS_TUNNEL : HOST:PORT for a tunnel to route TCP traffic to jenkins host, when jenkins can't be directly accessed over network
# * JENKINS_URL : alternate jenkins URL
# * JENKINS_SECRET : agent secret, if not set as an argument
# * JENKINS_AGENT_NAME : agent name, if not set as an argument
# * JENKINS_AGENT_WORKDIR : agent work directory, if not set by optional parameter -workDir
#
# Use as JNLP agent run in Docker Swarm:
#  docker run <image/id>
# Required environment variables :
# * DOCKER_SWARM_PLUGIN_JENKINS_AGENT_SECRET : jenkins secret if run as swarm agent
# * DOCKER_SWARM_PLUGIN_JENKINS_AGENT_JAR_URL : jenkins url if run as swarm agent
# * DOCKER_SWARM_PLUGIN_JENKINS_AGENT_JNLP_URL : jenkins jnlp url if run as swarm agent

write_key() {
  mkdir -p "${JENKINS_AGENT_HOME}/.ssh"
  echo "$1" > "${JENKINS_AGENT_HOME}/.ssh/authorized_keys"
  chown -Rf jenkins:jenkins "${JENKINS_AGENT_HOME}/.ssh"
  chmod 0700 -R "${JENKINS_AGENT_HOME}/.ssh"
}

################################################################################
# start docker-in-docker
exec "$(which dind)" dockerd \
      --host=unix:///var/run/docker.sock \
      --host=tcp://0.0.0.0:2375 &

################################################################################
# determine which mode to run, default is jnlp
START_MODE=JNLP
if [ -n "$DOCKER_SWARM_PLUGIN_JENKINS_AGENT_JNLP_URL" ]; then
  START_MODE=SWARM
elif [ -n "$JENKINS_SLAVE_SSH_PUBKEY" ]; then
  START_MODE=SSH
elif [ $# -eq 1 ]; then
  if [[ $1 == ssh-* ]]; then
    # only one parameter and it starts with "ssh-", so it's a SSH public key
    START_MODE=SSH
  else
    # if `docker run` only has one arguments, we assume user is running alternate
    # command like `bash` to inspect the image
    START_MODE=COMMAND
  fi
fi

echo ">>>>>> Docker container will be started in $START_MODE mode. <<<<<<"

################################################################################
# start mode: command
#    user run own command like bash
if [ "$START_MODE" = "COMMAND" ]; then
  exec "$@"

################################################################################
# start mode: jnlp
elif [ "$START_MODE" = "JNLP" ]; then
  # if -tunnel is not provided, try env vars
  case "$@" in
    *"-tunnel "*) ;;
    *)
    if [ ! -z "$JENKINS_TUNNEL" ]; then
      TUNNEL="-tunnel $JENKINS_TUNNEL"
    fi ;;
  esac

  # if -workDir is not provided, try env vars
  if [ ! -z "$JENKINS_AGENT_WORKDIR" ]; then
    case "$@" in
      *"-workDir"*) echo "Warning: Work directory is defined twice in command-line arguments and the environment variable" ;;
      *)
      WORKDIR="-workDir $JENKINS_AGENT_WORKDIR" ;;
    esac
  fi

  if [ -n "$JENKINS_URL" ]; then
    URL="-url $JENKINS_URL"
  fi

  if [ -n "$JENKINS_NAME" ]; then
    JENKINS_AGENT_NAME="$JENKINS_NAME"
  fi  

  if [ -z "$JNLP_PROTOCOL_OPTS" ]; then
    echo "Warning: JnlpProtocol3 is disabled by default, use JNLP_PROTOCOL_OPTS to alter the behavior"
    JNLP_PROTOCOL_OPTS="-Dorg.jenkinsci.remoting.engine.JnlpProtocol3.disabled=true"
  fi
  
  # if java home is defined, use it
  JAVA_BIN="java"
  if [ "$JAVA_HOME" ]; then
    JAVA_BIN="$JAVA_HOME/bin/java"
  fi

  # if both required options are defined, do not pass the parameters
  OPT_JENKINS_SECRET=""
  if [ -n "$JENKINS_SECRET" ]; then
    case "$@" in
      *"${JENKINS_SECRET}"*) echo "Warning: SECRET is defined twice in command-line arguments and the environment variable" ;;
      *)
      OPT_JENKINS_SECRET="${JENKINS_SECRET}" ;;
    esac
  fi
  
  OPT_JENKINS_AGENT_NAME=""
  if [ -n "$JENKINS_AGENT_NAME" ]; then
    case "$@" in
      *"${JENKINS_AGENT_NAME}"*) echo "Warning: AGENT_NAME is defined twice in command-line arguments and the environment variable" ;;
      *)
      OPT_JENKINS_AGENT_NAME="${JENKINS_AGENT_NAME}" ;;
    esac
  fi

  #TODO: Handle the case when the command-line and Environment variable contain different values.
  #It is fine it blows up for now since it should lead to an error anyway.

  exec $JAVA_BIN $JAVA_OPTS $JNLP_PROTOCOL_OPTS -cp /usr/share/jenkins/slave.jar hudson.remoting.jnlp.Main -headless $TUNNEL $URL $WORKDIR $OPT_JENKINS_SECRET $OPT_JENKINS_AGENT_NAME "$@"

################################################################################
# start mode: jnlp in swarm
elif [ "$START_MODE" = "SWARM" ]; then
  # this container is started with Jenkins Docker Swarm Plugin, need to start slave
  curl --connect-timeout 20 --max-time 60 -o slave.jar $DOCKER_SWARM_PLUGIN_JENKINS_AGENT_JAR_URL && \
    exec java -jar slave.jar -jnlpUrl $DOCKER_SWARM_PLUGIN_JENKINS_AGENT_JNLP_URL \
      -secret $DOCKER_SWARM_PLUGIN_JENKINS_AGENT_SECRET \
      -noReconnect -workDir $JENKINS_AGENT_HOME

################################################################################
# start mode: ssh
elif [ "$START_MODE" = "SSH" ]; then
  # this container is started with ssh?
  if [[ $JENKINS_SLAVE_SSH_PUBKEY == ssh-* ]]; then
    write_key "${JENKINS_SLAVE_SSH_PUBKEY}"
  fi
  if [[ $# -gt 0 ]]; then
    if [[ $1 == ssh-* ]]; then
      write_key "$1"
      shift 1
    else
      exec "$@"
    fi
  fi

  # ensure variables passed to docker container are also exposed to ssh sessions
  env | grep _ >> /etc/environment

  # start SSHd
  ssh-keygen -A
  exec /usr/sbin/sshd -D -e "${@}"
fi