Bash script to check if a Jenkins slave node is offline and will restart node java process.

jenkins-slave

#!/bin/sh
#
# jenkins-slave:    Launch a Jenkins BuildSlave instance on this node
#
# chkconfig:    - 99 01
# description:  Enable this node to fulfill build jobs
#
 
JENKINS_WORKDIR="/var/jenkins"
JENKINS_USER="jenkins"
JENKINS_URL="http://www.domain.com/"
JENKINS_NODE_LINUX=`hostname -s | cut -d'0' -f1`
JENKINS_NODE_NR=`hostname -s | cut -d'0' -f2`
JENKINS_NODENAME="${JENKINS_NODE_LINUX}_slave_node_${JENKINS_NODE_NR}"
 
[ -x /usr/bin/java ] || exit 0
 
download_jar()
{
    cd $JENKINS_WORKDIR
    curl -s -o slave.jar $JENKINS_URL/jnlpJars/slave.jar || exit 0
}
 
start()
{
    cd $JENKINS_WORKDIR
    [ -f slave.jar ] || download_jar
 
        echo -n "Starting Jenkins BuildSlave ($JENKINS_NODENAME): "
        sh -c "\
      java -jar $JENKINS_WORKDIR/slave.jar \
             -jnlpUrl $JENKINS_URL/computer/$JENKINS_NODENAME/slave-agent.jnlp \
             >$JENKINS_WORKDIR/slave.log 2>&1 &"
 
        echo Done.
}
 
stop()
{
    echo -n "Shutting down Jenkins BuildSlave ($JENKINS_NODENAME): "
    killall -9 java
    killall -9 java
    echo  "deleting java client file "
    cd $JENKINS_WORKDIR
    rm -f slave.jar
    echo Done.
}
 
# See how we were called.
case "$1" in
  start)
    start
        ;;
  stop)
    stop
        ;;
  restart|reload)
    stop
    start
    ;;
  status)
    status java
    ;;
  *)
        echo $"Usage: $0 {start|stop|restart|reload}"
        exit 1
esac
 
exit 0

jenkinsRestart.sh

#!/bin/bash
#
# Checking Jenkins offline and restart if offline
#
JENKINS_URL="http://www.domain.com/"
JENKINS_NODE_LINUX=`hostname -s | cut -d'0' -f1`
JENKINS_NODE_NR=`hostname -s | cut -d'0' -f2`
JENKINS_NODENAME="${JENKINS_NODE_LINUX}_slave_node_${JENKINS_NODE_NR}"
CHECKED=`curl --silent $JENKINS_URL/computer/$JENKINS_NODENAME/api/json | grep -Po '"offline":true' | cut -d':' -f2`
if [[ "$CHECKED" == "true" ]]; then
        service jenkins-slave restart
        echo "INFO: $JENKINS_NODENAME was offline and are now restarted"
        exit 0
fi
echo "INFO: $JENKINS_NODENAME is online, no need to restart."
exit 0

If you experience issues with constantly connecting & disconnecting node, this is due to java version. Check which java your jenkins use - the node has to use the same version of java for running slave.jar.

Hi,
How can get the jenkins api as mentioned in curl url.

I matched the java version, problem of slave.jar disconnection still exists. happens a log in packer build