Restart Jenkins from the build of Jenkins

build.sh

#!/bin/sh -e

CWD=$WORKSPACE/..

echo "cd $CWD"
cd $CWD

if [ `ruby queue_count.rb` -gt 0 ]; then
 echo "Too busy..."
 exit 1
fi

echo "Restarting jenkins..."
# refs: https://wiki.jenkins-ci.org/display/JENKINS/Spawning+processes+from+build
daemonize -E BUILD_ID=${BUILD_ID} $CWD/restart-jenkins
echo "SUCCESS!"

Makefile

suid: restart_jenkins
	sudo chown root restart_jenkins
	sudo chmod u+s restart_jenkins

restart_jenkins: restart_jenkins.c
	cc restart_jenkins.c -o restart_jenkins

queue_count.rb

#!/usr/bin/env ruby

require 'open-uri'
require 'json'

json = open('http://localhost/queue/api/json').read
hash = JSON.parse(json)

puts hash['items'].count

restart_jenkins.c

#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

int main() {
   if (setuid(0) == -1) {
     printf("setuid: %s\n", strerror(errno));
     return 1;
   }
   return system("service jenkins restart");
}