Why does my RightScript not finish when attempting to launch a background process?
Background Information
Upon running a RightScript that attempts to start a background task, you may notice that the script/recipe never finishes and execution hangs, stalling the boot process. This is due to the way that our Chef/Rightscript provider handles detaching from a subprocess and applies to v5 RightImages.
Note: This is for v5 Rightimages ONLY! If you are still using a v4 RightImage (now deprecated) this technique is not needed.
Answer
Daemonize wrapper
Instead of running your script as such:
#!/bin/bash /path/to/your/process &
Try using this 'daemonize' script that will properly launch a task in the background, as such:
cat <<"EOF" >/usr/bin/daemonize #!/bin/sh cd / ( exec "$@" <&- >&- 2>&- )& EOF chmod +x /usr/local/bin/daemonize daemonize <your_process>
Be sure to replace the last <your_process> with your process/task name that you'd like to start in the background. This will properly launch the service in the background in a method that is friendly to our RightScript provider.
RightScript: Run attachment in background
This is useful when a RightScript attachment is intended to run backgrounded (detached from RightLink) and its output logged to a local file.
Import Run attachment in background from the MultiCloud Marketplace for use as a RightScript in your ServerTemplate or as an Any Script/Operational Script.
Dealing with packages that launch a daemon
In RightScripts where a package is installed and the package installation (e.g. via postinst or %post) launches a daemon, you can use the following example RightScript. The script also caters for the situation where a configuration is changed and the service needs to be restarted (Chef handles this with notifications, which is a better practice).
Example: Install Jenkins CI Server w/ config change
#!/bin/bash -e
# for verification on the instance, use:
# tail -f /var/log/messages /var/log/jenkins-install.log
log_file="/var/log/jenkins-install.log"
# log function, accepts stdin
# redirects direct to the log can pipe to this function, but PIPESTATUS needs to be checked for exit code
log () {
echo "$*"
printf "%s %s\n" "$(date)" "$*" >> "$log_file"
logger -t RightScale-debug "$*"
}
touch "$log_file"
:> "$log_file"
# Set up the apt repo
wget -q -O - http://pkg.jenkins-ci.org/debian/jenkins-ci.org.key | apt-key add -
echo "deb http://pkg.jenkins-ci.org/debian binary/" > /etc/apt/sources.list.d/jenkins.list
if dpkg -l jenkins >> "$log_file" 2>&1; then
if /etc/init.d/jenkins status | grep 'is running'; then
log 'Stopping the jenkins service.'
exec $(/etc/init.d/jenkins stop <&- >&- 2>&- )&
fi
fi
# Install the packages
apt-get -y update
# detach and background sub-process
exec $($(apt-get -y install --reinstall jenkins >> "$log_file" 2>&1) <&- >&- 2>&- )&
# race condition here due to backgrounding
# this will loop forever if the package install failed and the service didn't start
log 'Waiting for jenkins service...'
while [ 1 ]; do
if file /etc/init.d/jenkins >> "$log_file" 2>&1 && /etc/init.d/jenkins status | grep 'is running'; then
break;
else
echo '.'
fi
sleep 1
done
log 'Setting up /etc/default/jenkins.'
# Config jenkins to listen on the ip
echo 'JAVA_ARGS="-Djava.net.preferIPv4Stack=true" # make jenkins listen on IPv4 address' >> /etc/default/jenkins
# restart the daemon
log 'Restarting the jenkins service.'
exec $(/etc/init.d/jenkins restart <&- >&- 2>&- )&
# optional service check after a sleep (to allow the detached restart to complete)
sleep 5
/etc/init.d/jenkins status
log "== Install log ($log_file) =="
cat "$log_file"
log "===="
- © Copyright 2015 RightScale Technical Support