Re: graceful restart under runit

["Dražen Kačar" <dave@fly.srk.fer.hr>]

Alex Efros wrote:
> On Wed, Nov 15, 2006 at 12:47:54PM +0100, Dra?en Ka?ar wrote:
> > Say I have a TCP server which listens on incoming connections on some TCP
> > port. Occasionaly I'd like to install and run a new version of the server
> > executable. Server source is under my control, for all intents and
> > purposes.
> [...] 
> > Is there a way to get around this?
> 
> Probably you can just fork() after receiving SIGUSR1 and exit from parent
> leaving child to process existing connection.

Servers which use process per connection do something like that already
(the parent process signals the children, exits and leaves them to finish
sessions and then they exit too).

However, there are multithreaded monsters which can't do that. fork()
replicates just the calling thread[1], so it's not an option and exit()
will terminate all threads (ie. all sessions).

[1] It's possible to replicate all threads on Solaris, but that's too
    unportable for my purposes. Besides, calling fork() from an MT process
    usually uncovers bugs in various libraries which aren't prepared to
    deal with that.

-- 
 .-.   .-.    Yes, I am an agent of Satan, but my duties are largely
(_  \ /  _)   ceremonial.
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     |        dave@fly.srk.fer.hr