Re: OT: /package and /service

[prj@po.cwru.edu (Paul Jarc)]

Payal Rathod <payal-supervision@scriptkitchen.com> wrote:
> 1. Why is /package made with sticky bit set?

To simplify code that looks for package directories.  Category
directories (which may contain packages or subcategories) are sticky,
and package directories are not sticky.  /package contains categories,
so its consistent to make it sticky.  Otherwise, code would have to
treat /package itself specially instead of just checkign for the
sticky bit to decide whether to descend into subdirectories.

> 2. In /service/<process>/supervise/ there are 4 files,
> 2 fifos - control and ok
> 2 normal files - lock and status
> Why are fifos used here? Which document explains this?

It's not documented.  supervise/ok is used by svok and svc to detect
whether supervise is running.  A regular file wouldn't work for this,
because the file could be in the same state even if supervise died.

supervise/control is used by svc to send commands to supervise.  There
are ways to use regular files instead, but the pipe is simpler.

> But what about svscan itself? What if it dies? Who restarts it?

I run svscan as process 1, so I don't have to worry about it.

With svscanboot, I believe the intent is that init (on SysV systems,
anyway) would restart svscan if it dies.  But it won't actually be
restarted until readproctitle exits too, and that won't normally
happen until all supervises exit.

> Also is there any documentation which says why are there so many dots in 
> that script and what do they signify?

<URL:http://cr.yp.to/daemontools/readproctitle.html>
Those dots are replaced by the data read by readproctitle.  The number
of dots determines how much of that log you'll be able to see at one
time.


paul