Dear All,
I wanted to have a bit more control over the vars I use in my domain config
files so that I could achieve more with a single file and just change the var
values passed on the command line. A couple of examples:
(*)combining a vm ''type'' (e.g. www, cvs) and an
''id'', checking to see if a disk image for such exists and
cloning it from a ''type'' master if not.
(*)getting a known offset for certain octets in mac addresses dependant on the
''type'' so that dhcp allocates predictable results.
The first of these was possible using a temp file to hold state, created using
inner functions within the check() function for each var. The second appears to
be impossible.
The attached (and inline) patch creates two new functions that can be called
from the config file to register ''postcheck'' functions and
subsequently call them with the full dictionary of defined vars. Changes made
to the vars'' values in the postchecks are maintained across calls and
are carried into the config proper.
My python skills aren''t great so any suggestions more than welcome,
especially regards to ''hiding'' the vars_{ex|im}port functions.
I appreciate there are more pressing areas of work but this makes my life easier
and may do others'' too. If there are sanctioned ways of getting a
similar level of functionality please let me know.
# HG changeset patch
# User dkendall <dan.kendall@centri.net>
# Date 1161957184 -3600
# Node ID 6c528a82d57b5fc32c517ebaab5b7c985f2b338c
# Parent 4a320d26fc24bc49ae24f31dec2bf006a9ddc7a8
Create postcheck() that calls postcheck routines registered using the new
xm_vars.reg_postcheck(). Each of these receives dictionary of the vars
and changes made to var values are permanent. Kinda like an all in one
check() that knows about all defined vars. Allows for more generic config
files.
Signed-off-by: dan kendall <dan.kendall@centri.net>
diff -r 4a320d26fc24 -r 6c528a82d57b tools/python/xen/xm/help.py
--- a/tools/python/xen/xm/help.py Thu Oct 26 16:56:16 2006 +0100
+++ b/tools/python/xen/xm/help.py Fri Oct 27 14:53:04 2006 +0100
@@ -35,6 +35,7 @@ class Vars:
self.help = help
self.env = env
self.vars = []
+ self.postchecks = []
def var(self, name, use=None, check=None):
"""Define a configuration variable.
@@ -58,6 +59,34 @@ class Vars:
else:
for v in self.vars:
v.doCheck(self.env)
+
+ def reg_postcheck(self, pcheck):
+ """Register routine to run after check
+ """
+ self.postchecks.append(pcheck)
+
+ def vars_export_dict(self):
+ """Export the var list to a dictionary
+ """
+ d = {}
+ for v in self.vars:
+ d[v.name] = self.env[v.name]
+ return d
+
+ def vars_import_dict(self,d):
+ """Import var list from dictionary
+ Note we only import already declared vars
+ """
+ for v in self.vars:
+ self.env[v.name] = d[v.name]
+
+ def postcheck(self):
+ """Perform any register post check routines
+ """
+ for c in self.postchecks:
+ d = self.vars_export_dict()
+ c(d)
+ self.vars_import_dict(d)
def doHelp(self, out=sys.stderr):
"""Print help for the variables.
@@ -86,7 +115,12 @@ class Var:
def doCheck(self, env):
"""Execute the check and set the variable to the new
value.
"""
- if not self.check: return
+ #ensure variable gets back to config variable ''space''
even
+ #if no check registered
+ #if not self.check: return
+ if not self.check:
+ env[self.name] = ''''
+ return
try:
env[self.name] = self.check(self.name, env.get(self.name))
except StandardError, ex:
****************************************************************
This email and any files transmitted with it are confidential
and intended solely for the use of the individual or entity to
whom they are addressed. If you are not the intended recipient
of this email and have received it in error you should delete
it and notify Centrinet Ltd immediately at email@centri.net
This email has been scanned for viruses, but no responsibility
is accepted by Centrinet for any loss or damage arising in any
way from its receipt or use thereof.
The views expressed in this email may not necessarily reflect
the views of Centrinet Ltd or any associated company.
****************************************************************
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xensource.com
http://lists.xensource.com/xen-devel