Dne 16.9.2014 v 17:08 Miloslav Trmač napsal(a):
----- Original Message -----
Well, what we would need is:
1. Ability to keep multiple versions (both ABI-compatible and
ABI-incompatible) of a single application or library or service installed
and running at the same time.
Other distributions allow to install multiple version of same libraries
AFAIK only when the ABI (soname) is different. We also need to allow for the case when the ABI stays the same but the internal implementation changes (e.g. changing a format of a resource file that is used by the library, making old processes incompatible with the newly installed resource).
That's what I mean - when something changes in the library - soname should
change. It's quite broken to release same version of library with the same
name when there is different internal implementation. It's something library
package maintainer should take care of...
There is also support for versioned symbols.
2. Ability to detect which processes depend on which versions of which
components.
We already managed to brought in systemd....
I can’t see how systemd helps. See the other discussions about Python/Ruby modules that leave no obvious trace of their dependency after being loaded into memory.
It has similar complexity and maybe packages could be described just like
services - so similar thing could be possibly reused here ?
Anyway - I've not been thinking too deeply about this...
3. Ability to automatically restart such processes without loosing state
(either completely transparently or with some user notification for GUIs).
I'm not quite sure why we would need restart - simply delayed lazy release of
unused packages would do the trick here - doing here state-full design is much
more complex thing....
Because otherwise you end up with an old version of Firefox running for 60 days (or however long a laptop can run with suspends and no restarts; most people about never quit their browser), and that version of Firefox keeping an old version of a system-wide daemon running for 60 days as well..
Sure if user is able to run Firefox for 60 days (though my usually goes out
of RAM in just a week or so, if it's not crashing earlier...) - then he is
happy user.
I guess something may show to user some nice gui dialog warning like - 'Hey
there is a new version installed - so 'restart' your browser to get new cool
feature' (FF normally already detects upgrades and suggest restart)
I don't see nothing wrong with this case - it's per user and doesn't require
upgrade - and if I've something important is running in my browser I could
delay restart to the moment I don't care.
And surprisingly even Systemd guru realized there is something broken with
current filesystem layout - except solving it with Btrfs is not really a
fix...
The sad thing is that adding more workarounds like namespaces and the like really might be easier than agreeing on making a real change and getting it done :( But we will live with the costs forever.
Look at NixOS - there are no namespace or btrfs requirements....
Zdenek
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