[OCF]Resource Agent Environment variables

[Lars Marowsky-Bree]

On 2003-07-18T17:14:10,
   Alan Robertson <alanr@unix.sh> said:

> So, one could make this script usable as both a resource agent, and an init 
> script, one could change that first line so that it looked more like this:
> 	test "X$OCF_RA_VERSION_MAJ" = X && . /etc/syconfig/syslog

Indeed.

> And then this script could be called either as an OCF resource script, or 
> as an init script with very minimal changes.  However, there is one rub, 
> which I'd like to make go away...

I sort of agree, but not with the solution ;-)

> In Section 3.5.1, the spec says:
> >3.5.1. Syntax for instance parameters
> >
> >They are directly converted to environment variables; the name is prefixed
> >with "OCF_RESKEY_".
> >
> >The instance parameter "force" with the value "yes" thus becomes:
> >	OCF_RESKEY_force=yes
> >in the environment.
> >
> >See section 4. for a more formal explanation of instance parameters
> 
> This make it incompatible with common usage in current init scripts.  And, 
> given the advantages that we *almost* have, I'd like to drop the prefix 
> from environment variables.  This would make it more palatable, I think, 
> and easier to treat an only-slightly-hacked init script directly as an init 
> script.  A proposed new Section 3.5.1:
> 
> -------------------------------------------------------------------------
> 3.5.1. Syntax for instance parameters
> 
> They are directly converted to environment variables.  There is no prefix 
> added to the environment variables.
> 
> The instance parameter "force" with the value "yes" thus becomes:
> 	force=yes
> in the environment.

Imagine an instance parameter called "HOME", no_proxy etc. Whoa, clash!

That the sysconfig files tend to clutter the environment isn't all that
great and not exactly an example to be followed to the dot ;-) They
should, I think, indeed use a prefix or at least on parsing should be
prefixed with SYSCONFIG_${FILENAME}_...., because it's a royal pain in
the butt (in theory) to load two sysconfig files with overlapping
variable names, but that's an LSB discussion and doesn't belong here.

Also there may be differences between the exact interpretation of
instance variables vs global ones. At least there may be more of them
for an instance, global ones may have different defaults, and even
though you are an instance, you may still want to know the 'global'
configuration to interact with.

So we don't want to create an implicit overlap which is hard to break.

I'd suggest using glue code like

. /etc/sysconfig/script
if [ -n "$OCF_RA_MAJOR" ]; then
	SCRIPT_FOO="${OCF_RESKEY_force}"
	SCRIPT_BAR=$(grep ${OCF_RESKEY_mount} /etc/fstab)
	if [ -z "$SOME_VARIABLE_FROM_SYSCONFIG" ]; then
		# option not set, need to handle reskey differently
		...
	fi
	...
fi

to translate. The surgery required is still pretty minor and allows us
to preserve the best of both worlds.

Would that be acceptable?


Sincerely,
    Lars Marowsky-Brée <lmb@suse.de>

-- 
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