[lxc-devel] Container autostart proposal V2

Tue May 28 21:04:45 UTC 2013

On 05/28/2013 04:37 PM, Michael H. Warfield wrote:
> On Tue, 2013-05-28 at 15:58 -0400, Stéphane Graber wrote: 
>> Hey everyone,
> 
>> Thanks for the feedback on my previous autostart proposal.
> 
>> Here's a detailed bullet-point list of what should be done to implement
>> autostarting containers in upstream LXC.
> 
> Yes.  I concur with virtually (excuse the pun) all of this...
> 
>> Changes to the container config:
>>  - ADD: lxc.start.auto (integer, 0 = disabled, 1 = enabled, default: 0)
> 
> This default could be conditional.  That's how I would incorporate the
> Ubuntu paradigm.  Anything in /etc/lxc/auto should be default: 1.
> 
>>  - ADD: lxc.start.delay (integer, time in second, default: 0)
>>  - ADD: lxc.start.order (integer, boot order, default: 0)
>>  - ADD: lxc.group (string, multi-value, default: empty)
> 
> I would also like to see an "lxc.start.disabled" flag, ala OpenVZ.  It
> has been surprisingly helpful at times at preventing accidents when
> working on large systems.  If disabled is set to 1 you prohibit starting
> unless some sort of override is issued (force parameter or edit the
> config).  It may not seem like a major thing and there are ways around
> it but it has been handy back in my OpenVZ days.  Just a suggestion.  If
> it's too complicated, it's no big thing.

Sure, that's easy enough to add and if that helps people migrate from
OpenVZ that's fine.
I personally never used the disabled property back when I was still
using OpenVZ but I guess on a system shared with multiple sysadmins it
may make sense.

>>  - NOTE: lxc.start.auto is an integer as there are plans to implement a
>> third value 2 = last-state.
> 
> YES!
> 
> I'm attaching some bash pseudo code that implements
> scanning /etc/lxc/auto (autoboot default on) and
> then /var/lib/lxc/*/config (autoboot default off) and then sorting the
> boot order off all enabled containers into a list and emitting that list
> on stdout.
> 
> The "last state" is conditionalized based on the existence of a
> file /var/lib/lxc/{CONTAINER}/state file and that file containing the
> line "running".  Just a thought.
> 
> I did not implement group filtering or boot order filtering (both good
> ideas).  The issue of the "delay" parameter is up to the actual startup
> code itself.
> 
> This issue of the container name vs the container config is a royal
> PITA.  You can't really deterministically say what the container name
> name should be based on the contents of the container config but it
> relates to the LXC /var/lib/lxc subdirectory (but then the Ubuntu
> autoboot paradigm breaks that) but there's nothing in the content of the
> config file that directly relates back to the putative container name
> (NO it's NOT the utsname).  Maybe that's something else we should
> address.
> 
> It's strictly proof of concept code but it parses my config files and
> does basically the right thing.  It's a strawman to show that this isn't
> really all that difficult to implement.  Use as you see fit.  I've tried
> to comment it with the gotcha's and ideas I see.  Code is attached way
> below the jump.
> 
> Let me repeat this one last time and make it very clear.  This is proof
> of concept code entirely.  It is NOT READY FOR PRIME TIME.  It is not
> intended to go into the repositories and it has a lot of loose ends
> (which I tried to document in the comments - spaces in path names WILL
> break it!).  It's not intended as a patch but just an idea of how "I
> would do it."  Your mileage may vary.
> 
> Let the rock throwing commence.
> 
>> Changes to the system config:
>>  - ADD: lxc.autostart.enabled (boolean, default: false)
>>  - ADD: lxc.autostart.group (string, multi-value, default: empty)
> 
>> Changes to the commands:
>>  - lxc-config
>>    * Add a "-n <container>" option to query the container config instead
>> of the system config
>>
>>  - lxc-list
>>    * Allow filtering by group
>>    * Allow showing the groups in the fancy view
>>
>>  - lxc-start
>>    * Add a "-a" option which will match any container that has
>> lxc.start.auto set to 1
>>    * Add a "-g <groups>" option which will match any container that has
>> one of the groups in lxc.group matching one of the groups in <groups>
>> (comma separated).
>>    * Both options imply -n.
>>    * NOTE: When starting containers, sort them by start order
>> (lxc.start.order) and wait until the delay is passed before starting the
>> next one (lxc.start.delay).
>>
>>  - lxc-stop
>>    * Add a "-a" option which will match any container that has
>> lxc.start.auto set to 1
>>    * Add a "-g <groups>" option which will match any container that has
>> one of the groups in lxc.group matching one of the groups in <groups>
>> (comma separated).
>>    * Both options imply -n.
>>
>> Examples:
>>  - lxc-start -a => Starts all auto-started containers that are in one of
>> the groups listed in lxc.autostart.group (system config). If the system
>> config entry isn't set, start all containers that DO NOT have
>> lxc.start.group set (container config).
>>  - lxc-start -g django => Starts all the containers that have django in
>> their lxc.start.group regardless of the autostart flag.
>>  - lxc-start -g django -a => Starts all autostarted containers that have
>> django in their lxc.start.group.
>>  - lxc-start -g django,graphite -a => Starts all autostarted containers
>> that have either django or graphite in their lxc.start.group
>>  - lxc-start -g any => Starts all defined containers regardless of
>> autostart flag or group.
>>
>>  - lxc-stop behaves in the exact same way as lxc-start but
>> stopping/shutting down/rebooting the container instead.
>>
>>  - lxc-config -n p1 lxc.utsname => returns p1
>>  - lxc.config lxc.autostart.enabled => returns true
> 
> 
> Regards,
> Mike
> 

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com

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