Damien Sorresso <mailto:[email protected]>
July 22, 2015 at 6:19 PM
James,
Some replies inline...
On 22 Jul, 2015, at 17:46, James Bucanek <[email protected]
<mailto:[email protected]>> wrote:
Damien,
Thanks for the suggestion, and apologies for the tardy reply; I just
got buried under twenty other to-do items that were higher on the list.
I tried removing the LimitLoadToSessionType entry from my agent's
plist, but it doesn't make any difference. When trying to install it
as a system-wide agent, the process still doesn't start.
In launchd's lexicon, "system-wide agent" is a conflict of
terminology. System-wide things are, by definition, daemons. Agents
are things which run on a per-user basis (cf. launchd(8)). So the real
question is about the desired lifecycle of your job. Do you want it to
run when a user logs in and to go away when the user logs out? Or do
you want it to be available regardless of any user being logged in?
That's the problem; I don't know what to call them. It's an agent, but
it's an agent for all users (/Library/LaunchAgents) to distinguish it
for exclusively for an individual user (~/Library/LaunchAgents). And it
should run in the context of the user's bootstrap, not just within the
GUI login.
My reading of LimitLoadToSessionType would lead me to believe that
it's applicable to my service, which *is* an agent. It runs as a
regular user, and the docs would indicate that this property is just
a hint to the load balancer on how to constrain its use of
CPU/memory/IO. It doesn't make sense that it would keep the process
from starting in the first place.
Wow, no that's not at all what that key is for. Please file a bug
explaining how the documentation misled you into that impression so we
can make it clearer!
I think I got this confused with ProcessType. Both have a "Background" type.
I'll file a bug report on the docs, but one problem that I run into is
that terms are often never defined. For example, the
LimitLoadToSessionType section in man 5 launchd.plist describes it thusly:
"LimitLoadToSessionType <string or array or strings>
This configuration file only applies to sessions of the type(s)
specified."
But the descriptions of what "type(s)" can be is never defined or
explained in the man pages for launchd.plist, launchctl, or launchd. I'm
sure the description of what LimitLoadToSessionType does is accurate,
but I still left wondering what values are valid or what they mean. :)
Session types are basically collections of certain kinds of jobs. The
"Aqua" session is all the jobs associated with a graphical login on
the console. By default, if your job is an agent, it is loaded into
the Aqua session. (That is, if no LimitLoadToSessionType key is present.)
The Background session is a collection of jobs that can run on behalf
of a user even if that user is not logged in at the graphical console.
They might be doing things like performing Spotlight indexing on that
user's home directory even when that user isn't logged in for example.
What I want, and I think that's what I've configured in the .plist, is a
per-user Agent running in the Background session, for all users. The
.plist is placed in /Library/LaunchAgents and the LimitLoadToSessionType
is set to Background. (See my earlier message. It has all the details.)
So if you have a vanilla Terminal prompt and do a `launchctl load`,
your plist will attempt to load in the Aqua session. If that service
has LimitLoadToSessionType set to "Background", then that load will
fail because it's attempting to load in the Aqua session and your
service has expressed that it should only load in the Background session.
In my case, the 'launchctl load ...' command is being executed via
NSTask launched from a helper running as root, itself launched from a
privileged helper service installed via SMJobBless. I don't know if this
puts launchctl in the context of Background session of the user or in
the root System session.
James
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