[lxc-devel] [PATCH 2/2] daemon: remove pidfile when daemon container is stopped

[Stéphane Graber]

On Mon, Jan 20, 2014 at 03:22:31PM +0800, Qiang Huang wrote:
> On 2014/1/19 8:57, Stéphane Graber wrote:
> > On Sat, Jan 18, 2014 at 03:00:00PM +0800, Qiang Huang wrote:
> >> This is for bug: https://github.com/lxc/lxc/issues/89
> >>
> >> When start container with daemon model, the daemon process's
> >> father will return back to main in start time, and pidfile
> >> is removed then, that's not right.
> >> So we store pidfile to lxc_container, and remove it when
> >> lxc_container_free.
> > 
> > That one looks wrong to me, removing the pid file on lxc_container_free
> > is wrong. We want the pidfile removed when the background lxc-start
> > exits, not whenever a random API client flushes the container from
> > memory.
> > 
> > With your patch, doing something like:
> >  - lxc-start -n p1 -d -p /tmp/pid
> >  - python3
> >      import lxc
> >      p1 = lxc.Container("p1")
> >      p1 = None
> 
> I'm sorry I'm not family with python, can you explain how this would
> happen in real world? Thanks.

In the real world, anything using the API to control an already running
backgrounded container with a PID file and that does lxc_container_put
once it's done dealing with the container object will cause the PID file
to be removed.

Actually, even calling lxc-list should cause the PID file to be removed
as lxc-list calls list_containers which calls list_defined_containers
which in turns iterate through all containers, get their struct and then
lxc_container_put them.

> 
> > 
> > Or the equivalent with any binding, or directly in C, will destroy the
> > pid file even though the container is clearly still running.
> 
> I thought when the backgroud lxc-start exits, it's time for container
> to free, because there are no other place to do lxc_contaier_get to
> hold the container from freeing.
> 
> I must missed something :( , so waiting for your more details.
> 
> 

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 836 bytes
Desc: Digital signature
URL: <http://lists.linuxcontainers.org/pipermail/lxc-devel/attachments/20140120/6d4b6039/attachment.pgp>