Leveraging Upstart for User Jobs

2 minute read

Ubuntu and Upstart

A while back Ubuntu switched from the classic bash script disaster know as SysV to upstart. I won’t even get started on how terrible SysV was, but it was pretty bad as it was all shell scripts, no dependencies, no events, no parallelization, no integrated process monitoring, cgroups, etc.

I’ve used systemd before both in Fedora and embedded systems based around openembedded and loved it. It seems more natural and powerful then upstart. Upstart is what I have in Ubuntu (at least until I switch back to Fedora). So that’s what I’ll use today.

Bottom line is upstart is better then most init/process managers, with the exception of systemd. Specifically I’m talking about the ghetto shell or scripted process manager you wrote because you didn’t know any better… Ahem, I mean what I wrote.

Additionally upstart will respawn daemons that die and manages logging stdout and stderr to some place useful (~/.cache/upstart for user session), manage stdout/stderr for logging, support for asynchronous events, etc.

Fixing My Mess

A while back I wrote a blog post about imapfilter. In that post I complained that imapfilter’s daemon mode is useless as it terminates and exits when it encounters IMAP server errors. After that my email is no longer filtered and I’m upset. I then wrote a simple and quick python wrapper to babysit imapfilter. Everything worked pretty well, but it all still felt wrong.

Today I got annoyed with the wrapper and autostart stuff so I removed it and re-implemented it upstart. Now upstart handles starting imapfilter in the first place and respawning it when it dies. Two birds, one stone.

Enabling Upstart User Sessions

First we need to enable upstart user sessions so that upstart fires up for my user when I login to the desktop. I found a blog post about Ubuntu user sessions that was very helpful. In a nutshell you need to do the following and then re-login to Ubuntu:

sudo sed -i 's/^#ubuntu/ubuntu/' /etc/upstart-xsessions

Setting up imapfilter

Place the following in ~/.config/upstart/imapfilter.conf:

description "imapfilter"
author "Kyle Manna <kyle@kylemanna.com>"

# Start after keyring registers on dbus
start on started dbus 
#stop on desktop-end

# Automatically restart process if crashed
respawn

# Log this job's stdout to ~/.cache/upstart/<name>.log
# default is console log
#console log

# Start in foreground mode so it can be properly managed
exec imapfilter -v

Now upstart will take of the rest. It will setup the DBUS_SESSION_BUS_ADDRESS environment variable that the imapfilter python and lua scripts need set for accessing the user’s key chain. All magic, to start that magic run the following:

start imapfilter

Imapfilter is now stated and all it’s output will be in ~/.cache/upstart/imapfilter.log. An easy way to monitor it for debugging is tail -f ~/.cache/upstart/imapfilter.log. Double check that upstart thinks imapfilter is running with:

$ initctl status imapfilter
imapfilter start/running, process 3459

And since the start on started dbus is in the job config file, the imapfilter task will be auto started every time the user logs in to the Ubuntu desktop session. Logging in to the desktop session. Set it and forget it.

Doing More

Upstart user session jobs:

$ initctl list
xsession-init stop/waiting
imapfilter start/running, process 3459
dbus start/running, process 3458
gnome-session start/running, process 3482
ssh-agent start/running
logrotate stop/waiting
im-config start/running
upstart-file-bridge start/running, process 3468
gnome-settings-daemon start/running, process 3481
re-exec stop/waiting
upstart-event-bridge start/running, process 3463

Upstart user session global environment:

$ initctl list-env
DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-vGmn0j3MRp
GNOME_DESKTOP_SESSION_ID=this-is-deprecated
INSTANCE=
JOB=dbus
PATH=/home/nitro/bin:/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
SESSIONTYPE=gnome-session
SESSION=ubuntu
SSH_AGENT_PID=3460
SSH_AUTH_SOCK=/tmp/ssh-ZlMOWJzORL00/agent.3457
UPSTART_EVENTS=started xsession

Documentation

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