jenkins-agent

#!/bin/bash -e
#
DOWNLOAD_DIR=/usr/share/jenkins

: ${DOCKER_GROUP:=docker}
: ${DOCKER_SOCKET:=/var/run/docker.sock}

: ${JENKINS_HOME:=/var/jenkins_home}
: ${JENKINS_USER:=jenkins}

: ${JENKINS_AGENT_CONNECTION_MODE:=-http}
: ${JENKINS_AGENT_LABEL:=''}
: ${JENKINS_AGENT_MODE:=NORMAL}
: ${JENKINS_AGENT_NAME:=$HOSTNAME}
: ${JENKINS_AGENT_NUM_EXECUTORS:=1}

JENKINS_AGENT_REMOTE_FS="$JENKINS_HOME"

download_agent_jar() {
    curl -Ssfo "$DOWNLOAD_DIR/agent.jar" $JENKINS_URL/jnlpJars/agent.jar
}

download_cli_jar() {
    curl -Ssfo "$DOWNLOAD_DIR/cli.jar" $JENKINS_URL/jnlpJars/jenkins-cli.jar
}

# a wrapper for jenkins_cli utility
jenkins_cli() {
    java -jar "$DOWNLOAD_DIR/cli.jar" $JENKINS_AGENT_CONNECTION_MODE -s $JENKINS_URL -auth "$JENKINS_AUTH" "$@"
}

# not really used, we use 'jnlpCredentials' instead
# kept for reference
get_node_secret() {
    jenkins_cli groovy = \
        <<< "println jenkins.model.Jenkins.instance.nodesObject.getNode('$JENKINS_AGENT_NAME')?.computer?.jnlpMac"
}

which java &>/dev/null || {
    echo "java is not in the PATH, make sure it's installed"
    exit 1
}

which curl &>/dev/null || {
    echo "curl is not in the PATH, make sure it's installed"
    exit 1
}

[ -z "$JENKINS_URL" -o -z "$JENKINS_AUTH" ] && {
    echo "please set both JENKINS_URL and JENKINS_AUTH env. variables"
    echo "example:"
    echo "  JENKINS_AUTH=user:token"
    echo "  JENKINS_URL=http://localhost:8080"
    exit 1
}

# download required jars
mkdir -p "$DOWNLOAD_DIR"
download_agent_jar
download_cli_jar

# if docker socket provided, then
# allow docker cli to run as jenkins user
[ -S "$DOCKER_SOCKET" ] && {
    DOCKER_GID=$(stat -c '%g' "$DOCKER_SOCKET")
    groupadd -for -g $DOCKER_GID $DOCKER_GROUP
    usermod -aG $DOCKER_GROUP $JENKINS_USER
}

# make sure to delete node on exit
trap 'exit' SIGINT SIGTERM
trap 'jenkins_cli delete-node "$JENKINS_AGENT_NAME" || true' EXIT

# create node, unless it's already exists
jenkins_cli get-node "$JENKINS_AGENT_NAME" &>/dev/null || {
    CONFIG="<slave><label>$JENKINS_AGENT_LABEL</label><launcher class='hudson.slaves.JNLPLauncher' /><mode>$JENKINS_AGENT_MODE</mode><numExecutors>$JENKINS_AGENT_NUM_EXECUTORS</numExecutors><remoteFS>$JENKINS_AGENT_REMOTE_FS</remoteFS></slave>"
    jenkins_cli create-node "$JENKINS_AGENT_NAME" <<< "$CONFIG"
}

# unexport potentially conflicting and sensitive variables
export -n JENKINS_AUTH JENKINS_USER JENKINS_URL

# make sure we don't override variables when running su
truncate -s0 /etc/environment

# run agent
su $JENKINS_USER -c \
    "java $JAVA_OPTS -jar '$DOWNLOAD_DIR/agent.jar' -jnlpCredentials '$JENKINS_AUTH' -jnlpUrl '$JENKINS_URL/computer/$JENKINS_AGENT_NAME/jenkins-agent.jnlp'"

# exit gracefully
exit 0