Re: testing the current bootstrap context?
Re: testing the current bootstrap context?
- Subject: Re: testing the current bootstrap context?
- From: Bill Janssen <email@hidden>
- Date: Tue, 14 Apr 2009 12:51:59 PDT
- Comments: In-reply-to Terry Lambert <email@hidden> message dated "Fri, 10 Apr 2009 12:17:36 -0700."
Terry Lambert <email@hidden> wrote:
> On Apr 10, 2009, at 11:55 AM, Bill Janssen <email@hidden> wrote:
> > Terry Lambert <email@hidden> wrote:
> >
> >> On Apr 10, 2009, at 9:31 AM, Bill Janssen <email@hidden> wrote:
> >>> Michael Smith <email@hidden> wrote:
> >>>> On Apr 9, 2009, at 9:30 AM, Bill Janssen wrote:
> >>>>> Michael Smith <email@hidden> wrote:
> >>>>>> It's usually straightforward for the daemon to vend the
> >>>>>> appropriate
> >>>>>> self-manipulation functionality; frequently you want to gate this
> >>>>>> with
> >>>>>> application-specific logic anyway.
> >>>>>
> >>>>> Well, the daemon does a lot of things, but what I'm concerned with
> >>>>> is
> >>>>> stop, start, and restart.
> >>>>
> >>>> Why do you need 'stop'? Why can't you just ask the daemon to
> >>>> enter a
> >>>> state where it refuses requests?
> >>>
> >>> Because I want to fix it with new code.
> >>
> >> So just fix it and tell it to exit.
> >>
> >> When a process exits and launchd restarts it, launchd doesn't know if
> >> it's running old code or new code when it's relaunched, it just knows
> >> its path.
> >
> > Sure, but the old code does bad things on exit (like saving state in
> > an
> > invalid format). I'm pretty sure I need, in the general case, to be
> > able to stop it, fix things, and restart it.
>
> Support a command to exit without saving state before your first
> deployment.
>
> Robust systems self-heal rather than requiring an external agency. Why
> do you need it stopped while you fix things externally, rather than
> having a check to see if things need to be fixed be the first thing
> you do when you restart, and self-heal?
>
> If nothing else, instead of installing the binary for your process,
> install the binary for the fix process instead, and have the last
> thing it does as it fixes things is replace its binary and exit.
>
> We intentionally erected a protection domain barrier here, where
> processes that do what your process wants to do have to ask permission
> to perform privileged operations, or at least politely request those
> privileged operations be performed on their behalf.
>
> Your code needs to either ask politely like everyone else, or run as root.
Just to finish this off, here's what I did. My daemon is now a
/Library/LaunchDaemon/foo.plist daemon, RunAtLoad and KeepAlive, with
UserName set to the user it belongs to. So it gets run (and restarted)
in the startup context. I've added prologue code (not Prolog code :-)
to the daemon's initialization routine which checks for a blocking file
in a certain place, and if it's there, just loops and waits for it to go
away, which when it does the daemon process exits. This check happens
before the daemon does any initialization.
So "stop" is basically, "touch" the blocking file and "kill -TERM" the
daemon; "start" just removes the blocking file; and "restart" is "kill
-TERM" the daemon. Actions the user can perform without admin
privileges. Still seems convoluted.
Bill
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