Re: Relationship between snaps and containers, if any

[Gustavo Niemeyer]

It seems that the most common way to deploy Docker is by mapping ports out
of the private IP addresses into the local host's public IP, which means
it's completely analogous to multiple processes in the same host. Even when
assigning the docker container to an external IP, a commonly recommended
practice is to use -p ::, which
means the public IP is sitting on the external host. E.g.:

http://stackoverflow.com/questions/26539727/giving-a-
docker-container-a-routable-ip-address

That also maps exactly to just asking the process bind to the particular IP.



On Thu, Jan 26, 2017 at 11:12 AM, Mark Shuttleworth  wrote:

>
> Well, from an *external* point of view, all the docker mysql processes
> are the same, on the same port, just with different IP addresses. That's
> the very nice property of docker for "hyper-elastic" workloads. I don't
> think snaps will be useful in that context, unless snaps find a way to
> live inside docker containers, but that's OK since snaps are useful in
> other contexts.
>
> Mark
>
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Re: Relationship between snaps and containers, if any

[Luther Goh Lu Feng]

Thanks Mark, your explanation is clear. But I am also thinking along similar 
lines to Gustavo's suggestion of running a snap multiple times, and wondering 
if that is the same as having multiple docker processes.


-- Luther 

On Wednesday, January 25, 2017 10:13 PM, Gustavo Niemeyer 
 wrote:




Interesting.. I actually don't see that line between snaps and Docker.  Just 
like you can run "docker run mysql" several times, one may run "mysnap.mysql" 
several times. In both cases the daemon will be visible to the external world 
via a separate port of the local host's public IP address. In both cases mysql 
will be isolated from the local environment by confinement.

It's even a bit more convenient to do that using a snap. Easier to manage the 
process on a systemd unit, for example, since the mysql process will indeed be 
a child of systemd/etc instead of a child of the docker daemon.



On Wed, Jan 25, 2017 at 11:51 AM, Mark Shuttleworth  wrote:


>The best way to think of this is to know that snaps are GREAT when you
>have a precise 1:1 relationship between "machines" and "running
>instances". And Docker is GREAT when you want an elastic relationship.
>So for example, if you want a MySQL "appliance" on a device, there will
>only ever be 1 MySQL instance on that device, you want a snap. If you
>want a cluster where there may be 1-many instances of MySQl on each
>actual machine or VM, then you want Docker.
>
>The reason for this is that Docker gives each running process its own IP
>address. That's perfect for the hyper-elastic case - each extra MySQSL
>is just another IP address to talk to. But if you have a machine where
>you already have an IP address and all you want is a MySQL there then a
>snap will be easier.
>
>This is why a snap of the Docker daemon makes such sense - in your
>cluster, you want exactly one copy of Docker itself running on each
>machine, and that is best pulled in as  a snap. That docker process then
>manages an arbitrary number of docker processes on each machine.
>
>Make sense?
>Mark
>
>
>
>
>
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Re: Relationship between snaps and containers, if any

[Gustavo Niemeyer]

Interesting.. I actually don't see that line between snaps and Docker.
Just like you can run "docker run mysql" several times, one may run
"mysnap.mysql" several times. In both cases the daemon will be visible to
the external world via a separate port of the local host's public IP
address. In both cases mysql will be isolated from the local environment by
confinement.

It's even a bit more convenient to do that using a snap. Easier to manage
the process on a systemd unit, for example, since the mysql process will
indeed be a child of systemd/etc instead of a child of the docker daemon.


On Wed, Jan 25, 2017 at 11:51 AM, Mark Shuttleworth  wrote:

>
> The best way to think of this is to know that snaps are GREAT when you
> have a precise 1:1 relationship between "machines" and "running
> instances". And Docker is GREAT when you want an elastic relationship.
> So for example, if you want a MySQL "appliance" on a device, there will
> only ever be 1 MySQL instance on that device, you want a snap. If you
> want a cluster where there may be 1-many instances of MySQl on each
> actual machine or VM, then you want Docker.
>
> The reason for this is that Docker gives each running process its own IP
> address. That's perfect for the hyper-elastic case - each extra MySQSL
> is just another IP address to talk to. But if you have a machine where
> you already have an IP address and all you want is a MySQL there then a
> snap will be easier.
>
> This is why a snap of the Docker daemon makes such sense - in your
> cluster, you want exactly one copy of Docker itself running on each
> machine, and that is best pulled in as  a snap. That docker process then
> manages an arbitrary number of docker processes on each machine.
>
> Make sense?
> Mark
>
>
>
>
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> Snapcraft mailing list
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> an/listinfo/snapcraft
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Re: Relationship between snaps and containers, if any

[Mark Shuttleworth]

The best way to think of this is to know that snaps are GREAT when you
have a precise 1:1 relationship between "machines" and "running
instances". And Docker is GREAT when you want an elastic relationship.
So for example, if you want a MySQL "appliance" on a device, there will
only ever be 1 MySQL instance on that device, you want a snap. If you
want a cluster where there may be 1-many instances of MySQl on each
actual machine or VM, then you want Docker.

The reason for this is that Docker gives each running process its own IP
address. That's perfect for the hyper-elastic case - each extra MySQSL
is just another IP address to talk to. But if you have a machine where
you already have an IP address and all you want is a MySQL there then a
snap will be easier.

This is why a snap of the Docker daemon makes such sense - in your
cluster, you want exactly one copy of Docker itself running on each
machine, and that is best pulled in as  a snap. That docker process then
manages an arbitrary number of docker processes on each machine.

Make sense?
Mark




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Re: Relationship between snaps and containers, if any

[Loïc Minier]

Hi Luther!

Docker containers and snaps are different but sometimes overlap in solving
certain classes of technical problems. For instance, "software
distribution" as a broad problem is addressed by both snaps and Docker
containers, but with very different implementations.

First of all, yes you can run Docker on top of an all-snaps system such as
Ubuntu Core, and the Docker snap will also give you a Docker engine runtime
on Ubuntu classic.

Docker containers and snaps are built on different goals. Snaps will
typically look and feel like system or user apps running directly on your
regular system: you see them in the process list, they see each other if
the sandboxing allows it, they may interact with the screen/USB
devices/whatever if permissions allow it etc.. Docker containers feel more
like very efficient virtual machines that you connect to, they allow for
sandboxing as well – where the whole container is sandboxed – and for
resource quotas.

On your question of snapping a docker container: yes, you would be able to
wrap a Docker image inside a snap which would be a client of the Docker
snap.

On the top of my head, I can personally think of two main cases where you
would want to run containers on top of an all snap system: when your
workload is already packaged as a container, or when you want to use the
resource limits featured in Docker or LXD (e.g. limit network usage, CPU
usage etc.).

Cheers,
- Loïc Minier

On Wed, Jan 25, 2017 at 12:53 AM, Luther Goh Lu Feng 
wrote:

> I seek clarity in understanding how docker containers are different from
> snaps. The question originated as I pondered if docker containers are the
> equivalent of snaps. Is there a blog post or FAQ somewhere that already
> addresses this?
>
>
> I also read this article[1], though dated, mentions docker support in
> Snappy, which makes me wonder:
>
> - the scenarios that I would want to deploy docker containers alongside
> snaps
> - snapping a docker container.
>
> Appreciate if someone can enlighten me. Thanks.
>
>
> -- Luther
> [1] http://thenewstack.io/snappy-ubuntu-a-new-cloud-os-with-
> support-for-docker-in-a-post-shellshock-era/
>
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Relationship between snaps and containers, if any

[Luther Goh Lu Feng]

I seek clarity in understanding how docker containers are different from snaps. 
The question originated as I pondered if docker containers are the equivalent 
of snaps. Is there a blog post or FAQ somewhere that already addresses this?


I also read this article[1], though dated, mentions docker support in Snappy, 
which makes me wonder:

- the scenarios that I would want to deploy docker containers alongside snaps
- snapping a docker container.

Appreciate if someone can enlighten me. Thanks.


-- Luther
[1] 
http://thenewstack.io/snappy-ubuntu-a-new-cloud-os-with-support-for-docker-in-a-post-shellshock-era/

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