[augeas-devel] Some ideas about how to use Augeas with IPA

[Dmitri Pal]

Hi,

I have been evaluating the Augeas library for potential use with IPA 
(especially for the centralized policy management) and found that though 
it is a pretty powerful tool there are certain features that would make 
it much more attractive for the IPA project.
I will list the requirements with the explanation of the use case .

1) When setting the value validate the provided data against the regular 
expression.
Let us say that we have a file that reads several comma separated values 
per rule.
Then the lenses will contain a definition of the "word" as any character 
that is not a space or a comma. The defined "word" will be used in the 
parsing rule. If then when use set command to update the values in the 
entry we provide value that contains comma the set command should fail 
since the data when saved will violate the lenses grammar and library 
will fail to parse it back.
2) The match command matches the exact value of the label. It would be 
very useful to be able to do the regular expression searches. This would 
help if you have to combine two files and want to extract a subset of 
the entries that matches the regular expression. I also means that there 
should be a way to iterate through the result set.
3) Currently the library is bound to the physical file. There should be 
an option to save/read the data to/from the buffer so that the caller 
can take advantage of the fact that data can come from different 
sources. This can be used when parts of the file are stored in the 
external facility other than the file - for example in the DB or LDAP. 
Let us imagine that there is an XML data stored in the ldap field. The 
application can connect to LDAP, request the attribute, feed it to 
Augeas library specifying a read lenses and then save the Augeas tree in 
a file using a different lenses. It creates a very powerful mechanism.
4) Managing the order of the entries. Currently I do not see a way of 
inserting the entries in the middle of the file. Some configuration 
files have rules that are applied in order so capability of inserting a 
new entry in the middle is very important.
5) To be able to effectively merge the configuration data from different 
sources and apply changes to the file it might be very beneficial to be 
able to sort the entries in the node tree by a specific criteria. This 
capability will allow a much simpler implementation logic when 2 
different trees need to be compared and merged.
6) Create a copy of the node tree. If I have a tree that I read from the 
file and I want to start playing with it in therms of sorting or merging 
it would be nice to be able create a copy of the tree before starting 
the procedure so that the original tree can be preserved and would not 
require re-red from the disk of merge comes to an unresolvable error.

Thank you,             

-- 
Dmitri Pal
Engineering Manager
Red Hat Inc.