On 28. 11. 18 18:29, Bogdan Dobrelya wrote:
On 11/28/18 6:02 PM, Jiří Stránský wrote:

Reiterating again on previous points:

-I'd be fine removing systemd. But lets do it properly and not via 'rpm
-ev --nodeps'.
-Puppet and Ruby *are* required for configuration. We can certainly put
them in a separate container outside of the runtime service containers
but doing so would actually cost you much more space/bandwidth for each
service container. As both of these have to get downloaded to each node
anyway in order to generate config files with our current mechanisms
I'm not sure this buys you anything.

+1. I was actually under the impression that we concluded yesterday on
IRC that this is the only thing that makes sense to seriously consider.
But even then it's not a win-win -- we'd gain some security by leaner
production images, but pay for it with space+bandwidth by duplicating
image content (IOW we can help achieve one of the goals we had in mind
by worsening the situation w/r/t the other goal we had in mind.)

Personally i'm not sold yet but it's something that i'd consider if we
got measurements of how much more space/bandwidth usage this would
consume, and if we got some further details/examples about how serious
are the security concerns if we leave config mgmt tools in runtime images.

IIRC the other options (that were brought forward so far) were already
dismissed in yesterday's IRC discussion and on the reviews. Bin/lib bind
mounting being too hacky and fragile, and nsenter not really solving the
problem (because it allows us to switch to having different bins/libs
available, but it does not allow merging the availability of bins/libs
from two containers into a single context).

We are going in circles here I think....

+1. I think too much of the discussion focuses on "why it's bad to have
config tools in runtime images", but IMO we all sorta agree that it
would be better not to have them there, if it came at no cost.

I think to move forward, it would be interesting to know: if we do this
(i'll borrow Dan's drawing):

|base container| --> |service container| --> |service container w/
Puppet installed|

How much more space and bandwidth would this consume per node (e.g.
separately per controller, per compute). This could help with decision

As I've already evaluated in the related bug, that is:

puppet-* modules and manifests ~ 16MB
puppet with dependencies ~61MB
dependencies of the seemingly largest a dependency, systemd ~190MB

that would be an extra layer size for each of the container images to be
downloaded/fetched into registries.

Thanks, i tried to do the math of the reduction vs. inflation in sizes as follows. I think the crucial point here is the layering. If we do this image layering:

|base| --> |+ service| --> |+ Puppet|

we'd drop ~267 MB from base image, but we'd be installing that to the topmost level, per-component, right?

In my basic deployment, undercloud seems to have 17 "components" (49 containers), overcloud controller 15 components (48 containers), and overcloud compute 4 components (7 containers). Accounting for overlaps, the total number of "components" used seems to be 19. (By "components" here i mean whatever uses a different ConfigImage than other services. I just eyeballed it but i think i'm not too far off the correct number.)

So we'd subtract 267 MB from base image and add that to 19 leaf images used in this deployment. That means difference of +4.8 GB to the current image sizes. My /var/lib/registry dir on undercloud with all the images currently has 5.1 GB. We'd almost double that to 9.9 GB.

Going from 5.1 to 9.9 GB seems like a lot of extra traffic for the CDNs (both external and e.g. internal within OpenStack Infra CI clouds).

And for internal traffic between local registry and overcloud nodes, it gives +3.7 GB per controller and +800 MB per compute. That may not be so critical but still feels like a considerable downside.

Another gut feeling is that this way of image layering would take longer time to build and to run the modify-image Ansible role which we use in CI, so that could endanger how our CI jobs fit into the time limit. We could also probably measure this but i'm not sure if it's worth spending the time.

All in all i'd argue we should be looking at different options still.

Given that we should decouple systemd from all/some of the dependencies
(an example topic for RDO [0]), that could save a 190MB. But it seems we
cannot break the love of puppet and systemd as it heavily relies on the
latter and changing packaging like that would higly likely affect
baremetal deployments with puppet and systemd co-operating.

Ack :/

Long story short, we cannot shoot both rabbits with a single shot, not
with puppet :) May be we could with ansible replacing puppet fully...
So splitting config and runtime images is the only choice yet to address
the raised security concerns. And let's forget about edge cases for now.
Tossing around a pair of extra bytes over 40,000 WAN-distributed
computes ain't gonna be our the biggest problem for sure.

[0] https://review.rdoproject.org/r/#/q/topic:base-container-reduction




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