Re: Smooth upgrades for socket activated services

[Mike Hearn <mike@hydraulic.software>]

Sorry, by "apps" I meant anything not supplied by OS developers. In
this context, servers e.g. custom web app servers. I do currently run
some of those with DynamicUser=1 and similar.

> As long as the tool updating the disk image creates the new one under
> a temporary name, and then replaces the old one with it via renaming,
> upgrading portable services is as easy as restarting them

Great.

> > > But of course such an approach requires that services are written in a
> > > way this is possible
> >
> > Right. I think that'd be quite hard to do especially with servers
> > written in portable languages that don't expose stuff unavailable on
> > Windows e.g. the JVM.
>
> Why would that be? portable services are just regular services that
> happen to come with their own disk images, that's all.

Sorry I meant the serialization and transmission of FDs to the fd
store to support user-transparent restart. For example the Java API
has no way to send fds over a UNIX domain socket because Windows
doesn't support that, so you need third party libraries. And then it
would appear to turn into a general problem of serializing the entire
state of the app which is quite hard. Easier to assume that one
connection should stick with one server version for the lifetime of
that connection and then just phase in new servers as new connections
roll in.