Relationship between snaps and containers, if any
Luther Goh Lu Feng
elfgoh at yahoo.com
Thu Jan 26 06:44:49 UTC 2017
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.
On Wednesday, January 25, 2017 10:13 PM, Gustavo Niemeyer <gustavo.niemeyer at canonical.com> 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 <mark at ubuntu.com> 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.
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gustavo @ http://niemeyer.net
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