Introduction
Usually, Jenkins controller and Jenkins agent are located in the same network, therefore it is quite easy to adopt Jenkins agents using SSH. This time we will talk about the situation when Jenkins controller and bunch of other DevOps tools are running in "network A" and Jenkins agents are running in "network B". Quite often connections from A to B are rejected, however, connections from B to A are accepted. There might be various reasons, in general, network B has elevated security expectations. The typical setup is Jenkins controller located in public cloud and Jenkins agent(s) located in a private customer network. Private customer network might be needed in such because some sort of higher data privacy requirements must be matched or some specialised hardware is present in customer premises and it cannot be accessible directly from the public internet.
Solution
The recommended solution is controller/agent setup, when the controller runs in a public environment and agent is running on a server located in a private network. The agent is also called "on-premise executor" (OPE). Jobs are then performing jobs/tasks on such agent in internal/private networks. Jenkins Agent has an active connection from the internal network to internet accessible Jenkins Master via recommended JNLP port tcp/9000 and keeps listening to builds/jobs. Port can be changed, but we will keep talking about 9000. NO direct or NAT network connection is required from the internet to internal network. It is a secure and simple solution.
Requirements:
- Network
- firewall opening for port tcp/9000 from relevant source agent(s) IP(s) in internal network towards internet in general (destination 0.0.0.0)
- network layer (using TDS portal network functionality)
- operating system layer (firewalld if needed)
- firewall opening for port tcp/9000 from relevant source agent(s) IP(s) in internal network towards internet in general (destination 0.0.0.0)
- Jenkins controller running in public
- Decide which port you are going to use as we use fixed setup in our case. We are choosing 9000 in this guide.
- Make sure to have port 9000 opened:
- on network/firewall layer - Firewall
in OS level, for example firewalld:
firewall-cmd --add-port=9000/tcp --permanent firewall-cmd --reload
- Listening on JNLP port tcp/9000
- Go to https://jenkins.xxx.tds.customerx.com/configureSecurity (remember to use correct URL of your Jenkins controller)
- Set "TCP port for inbound agents" to Fixed:9000
- Open "advanced" and choose "Inbound TCP Agent Protocol/4 (TLS encryption)" (deselect others if not relevant)
- node added according to the following steps
- Go to https://jenkins.xxx.tds.customerx.com/computer/new (remember to use correct URL of your Jenkins controller)
- Set "Node name" to relevant name useful for you
- Choose "Permanent"
- Set "Remote root directory" to "/home/jenkins-agent"
- Set "Launch method" to "Launch agent by connecting it to the controller" previously called "Launch agent via Java Web Start"
- Click "Save"
- now go to newly created node and copy secret/token for connecting agent
- Go to https://jenkins.xxx.tds.customerx.com/computer/XXX (remember to use correct URL of your Jenkins controller and replace XXX with the name of your node)
You will see something like:
Run from agent command line: java -jar agent.jar -jnlpUrl https://jenkins.xxx.tds.customerx.com/computer/test/slave-agent.jnlp -secret 8b2911d98400bad5d45635b812b5f2e8e7c1d216bbbae9422a3ba57c691bf762 -workDir "/home/jenkins-agent" Run from agent command line, with the secret stored in a file: echo 8b2911d98400bad5d45635b812b5f2e8e7c1d216bbbae9422a3ba57c691bf762 > secret-file java -jar agent.jar -jnlpUrl https://jenkins.xxx.tds.customerx.com/computer/test/slave-agent.jnlp -secret @secret-file -workDir "/home/jenkins-agent"
Please copy only the secret, which is for example in this case "8b2911d98400bad5d45635b812b5f2e8e7c1d216bbbae9422a3ba57c691bf762"
- running in public
- Jenkins agent node (slave) - or so-called "on-premise executor"
- running on a server in the internal network(s)
- agent service(s) with service auto-start to assure automatic re-connect to Jenkins controller at any time even after server reboot
- Install dependencies
CentOS
yum install java-11-openjdk-devel git -y # you can install also other dependencies that will be required for your jobs
Ubuntu
apt-get update; apt-get install openjdk-11-jdk git -y # you can install also other dependencies that will be required for your jobs
- Installing agent
Prepare a folder for config
mkdir -p /data/configs mkdir -p /opt/jenkins-agent
Create service file /opt/jenkins-agent/jenkins-agent.service
jenkinsope.service[Unit] Description=Jenkins Agent - On Premise Executor Wants=network.target After=network.target [Service] # EnvironmentFile cannnot be used on Debian/Ubuntu anymore - Reference: https://github.com/varnishcache/pkg-varnish-cache/issues/24 # So we are using drop-in config /etc/systemd/system/jenkins-agent.service.d/local.conf ExecStart=/usr/bin/java -Xms${JAVA_MEMORY} -Xmx${JAVA_MEMORY} -jar /opt/jenkins-agent/agent.jar -jnlpUrl ${CONTROLLER_URL}/computer/${NODE_NAME}/jenkins-agent.jnlp -secret ${SECRET} -workDir "${WORK_DIR}" User=jenkins-agent Restart=always RestartSec=10 StartLimitInterval=0 [Install] WantedBy=multi-user.target
Create config file /data/configs/jenkins-agent.conf
JAVA_MEMORY=512m CONTROLLER_URL=https://jenkins.xxx.tds.customerx.com NODE_NAME=XXX SECRET=8b2911d98400bad5d45635b812b5f2e8e7c1d216bbbae9422a3ba57c691bf762 WORK_DIR=/home/jenkins-agent
Create script /opt/jenkins-agent/jenkins-agent-install
#!/bin/bash AGENT_APP_HOME=/opt/jenkins-agent SERVICE_USER=jenkins-agent MAINCONFIG=/data/configs/jenkins-agent.conf OLD_CONF=/data/configs/jenkinsope.conf if [ -f $OLD_CONF ];then mv -f $OLD_CONF $MAINCONFIG;fi source $MAINCONFIG OLD_USER=jenkinsope OLD_HOME=/home/$OLD_USER if [ -d $OLD_HOME ];then sed -i 's#^WORK_DIR.*#WORK_DIR=/home/jenkins-agent#g' $MAINCONFIG sed -i 's#^MASTER_URL#CONTROLLER_URL#g' $MAINCONFIG source $MAINCONFIG # Stopping old service systemctl stop jenkinsope sleep 10 mv $OLD_HOME $WORK_DIR userdel -rf $OLD_USER rm -rf /etc/systemd/system/jenkins-agent.service.d rm -f /usr/lib/systemd/system/jenkinsope.service fi useradd -m -s /bin/bash $SERVICE_USER 2> /dev/null mkdir -p $WORK_DIR/.ssh chmod 700 $WORK_DIR/.ssh touch $WORK_DIR/.ssh/config chmod 600 $WORK_DIR/.ssh/* echo "Changing ownership of home/work folder ($WORK_DIR) and its content (can take long time with many files)..." chown $SERVICE_USER:$SERVICE_USER -R $WORK_DIR curl -s ${CONTROLLER_URL}/jnlpJars/agent.jar -o $AGENT_APP_HOME/agent.jar chmod 644 $AGENT_APP_HOME/agent.jar install -D -m 644 $AGENT_APP_HOME/jenkins-agent.service /usr/lib/systemd/system/jenkins-agent.service mkdir -p /etc/systemd/system/jenkins-agent.service.d echo "[Service]" > /etc/systemd/system/jenkins-agent.service.d/local.conf sed 's#^#Environment=#g' $MAINCONFIG >> /etc/systemd/system/jenkins-agent.service.d/local.conf systemctl daemon-reload systemctl restart jenkins-agent systemctl enable jenkins-agent systemctl status jenkins-agent echo "0 4 * * * root $AGENT_APP_HOME/jenkins-agent-install" > /etc/cron.d/jenkins-agent-update
Run install script
chmod +x /opt/jenkins-agent/jenkins-agent-install /opt/jenkins-agent/jenkins-agent-install
- Uninstalling agent (for cleanup purposes or if you messed up something)
Create script /opt/jenkins-agent/jenkins-agent-uninstall
systemctl disable jenkins-agent systemctl stop jenkins-agent rm -f /usr/lib/systemd/system/jenkins-agent.service rm -rf /etc/systemd/system/jenkins-agent.service.d systemctl daemon-reload userdel -r jenkins-agent rm -rf /home/jenkins-agent
Run install script
chmod +x /opt/jenkins-agent/jenkins-agent-uninstall /opt/jenkins-agent/jenkins-agent-uninstall
- Install dependencies
Inspired by:
- service itself - https://github.com/jenkinsci/systemd-slave-installer-module/blob/master/src/main/resources/org/jenkinsci/modules/systemd_slave_installer/jenkins-slave.service
- service parameters/options - https://gist.github.com/dragolabs/05dfe1c0899221ce51204dbfe7feecbb
- way of service installing - https://gist.github.com/michaelneale/9635744