Multiple instances of a daemon

[Christopher Cowart]

On Wed, Nov 07, 2007 at 08:48:03AM -0500, Bill Moran wrote:
>In response to Christopher Cowart <ccowart at rescomp.berkeley.edu>:
>> Hello,
>> 
>> I want to be able to use the same rc script to start several instances
>> of a daemon. When I've encountered this desire before, I've cp'd the
>> script, given it a unique name, and carried on with my business. This is
>> a but kludgy and makes updating scripts a manual task.
>> 
>> Today, I realized the arpd port didn't provide an rc script, so I set
>> out to write one. I also knew that I was going to be launching several
>> different arpd's, so I wanted to figure out a better way to deal with
>> this problem.
>> 
>> I thought I'd be clever and use symlinks:
>> rc.d $ ls -l arpd*
>> -r-xr-xr-x 1 root wheel 486 Nov  7 00:01 arpd
>> lrwxr-xr-x 1 root wheel   4 Nov  6 23:32 arpd_vlan665 -> arpd
>> lrwxr-xr-x 1 root wheel   4 Nov  6 23:32 arpd_vlan679 -> arpd
>> 
>> Then I wrote my rc script with `name=${0##*/}'. Everything was fantastic
>> doing manual starts and stops. Then I tried rebooting...
>> 
>> After a few boots, some debugging, and a lot of tracing through /etc/rc
>> and /etc/rc.subr, I found the problem (or is it a feature?).
>> run_rc_script() sources the script. All the talk about not sourcing the
>> "current shell" anymore, and I foolishly assumed that meant something
>> more like calling the script and less like sourcing it in a subshell.
>> 
>> I would really find it convenient to use the symlink trick shown above,
>> because it means a symlink-compatible rc-script can be updated by the
>> port or mergemaster, and all the "copies" will "just work." I'd be
>> willing to take the time to implement something, but I don't pretend 
>> to know all the use cases or the motivation behind this design. 
>> 
>> One approach could be that run_rc_script() throws the rc script name
>> into a variable visible to the sourced script, say _rc_script_name. 
>> Then name could be something like `${_rc_script_name:-${0##*/}}' or a
>> less terse if/then.
>> 
>> Is this a feature other people would like to see, or is it just me?
>
>The canonical way of doing this has been a "profiles"-enabled rc
>script.  See the Apache or Slony rc scripts for examples.
>
>Not sure if your approach might be better.

The jail rc script takes a smilar approach. It seems like when somebody
wants to "profile" their script, they have to write the logic from
scratch (or copy, paste, and tweak). Would a better solution be to 
provide some default notion of profiling in the rc.subr library so rc 
scripts can take advantage of it by default? 

-- 
Chris Cowart
Lead Systems Administrator
Network & Infrastructure Services, RSSP-IT
UC Berkeley
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 825 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/freebsd-rc/attachments/20071107/01f551d5/attachment.pgp