On 06/02/2014 09:37 AM, Nikolai Kondrashov wrote:
On 05/31/2014 04:45 AM, Dmitri Pal wrote:
> I reworked the design based on the feedback provided.
> It is a completely rewritten version.
> Please take a look.
I'm likely awfully under-informed (I haven't seen any prior discussion or
requirements, never used the library), but I'd like to give my opinion
if only as an exercise.
I wouldn't like to steal much of anyone's time so please ignore me if I'm
entirely missing the point. I've likely missed some requirements and
needs details figured out, but I think this general approach would be
for both end-users and developers.
First of all, the proposal sounds terribly complicated.
Hm. I think it is significantly simplified in comparison to the previous
The function is not SSSD specific. It is a part of the generic library,
it is up to application developer to use different aspects of it.
I would rather implement a complex function and have a simplified use of
it than have a simplified function and then several month later realize
that we need to have more flexibility and a break ABI or have function
augment2, augment3 etc - ugly.
Both in merging logic
and in permission requirements. What's worse, this complexity is
system administrators (users) in the code. It means that all the
passed to "ini_config_augment" will need to be documented somewhere.
The function is for developers not for admins. It is a tool. It is up to
the developer to use it in such a way that admin can understand.
As in: "you can put these and these sections in these files and the
need to have these and these permissions and be owned by such and such
and group, etc.".
This is an application choice. SSSD might not required to use it (at
first) up until it realizes that overwriting some sections is not a good
This will be needed for every application using this feature
and it will need to be updated with the code. And all hell will break
when someone decides to adjust ini_config_augment arguments based on
previously read keys/sections. Just because it can be done, you know.
I do not think it is a valid concern. You can shoot yourself into the
head in so many different ways.
Assigning special treatment to "augmenting" configuration, and adding
to ignore erros there specifically, also doesn't seem right. Given the
overwriting feature is provided, the *whole* of the actual
be placed there, and thus it seems better to give equal treatment both
"main" and to the "augmented" configuration. I.e. either provide a
ignore/enforce errors in both or in none.
I disagree. Overwriting is much more dangerous than augmenting.
From my, once again, entirely uninformed view as a potential user and an
administrator I would have liked to see the following instead.
Allow both sections and keys appear more than once in a configuration
Ini library support this but it is application's choice to allow it or not.
SSSD does not allow it while GSS proxy does.
Repeated keys would overwrite previous value. New keys in repeated
would add keys. Missing keys in repeated sections wouldn't change
I assume this is the way it works currently, as some QA tests use it.
You are not testing the library itself. SSSD reads the config with a
special flag indicating what you described but there are all sorts of
different modes that can be specified that would treat duplicates as
errors or preserve the original value.
Again library provides flexibility, application decides on the best
option to use.
Adjust the configuration language to add syntax to remove sections and
NO. No language. That adds much more complexity then needed.
Something which can be understood with little or no documentation.
key_a = 1
key_b = 2
key_c = 3
; Add "key_d" to "section_b"
key_d = 4
; Remove "section_a"
; Start "section_a" anew
key_d = 42
; Remove "key_c" from "section_b" and overwrite
key_c = 2
Add configuration language syntax to include files/directories of files,
optionally specifying file permission requirements and section
permissions. With this amount of features the need for documentation
them would be inevitable, but we can at least try:
key_a = 1
key_b = 2
key_c = 3
; Include an application configuration file, only allowed to add some
<application.conf add section_c_*,
; Include a subdirectory of configuration files, allowed to add any
; and modify/remove some sections
<service.d add *,
; Include another configuration file keeping the permissions intact
I am strongly apposed any kind of the include directives.
Having include directives means someone needs to insert them.
The use case we are trying to solve is to be able to augment config
files without changing the main config file.
Included files would be processed as if read at the spot of the directive
without any other requirements.
This is a significant rewrite of the parser because of the language of
the INI file change. Now any config file is a config file. As soon as
you introduce language you have a "proper" ini file and one that needs
to be merged and processed. It is just way more complex than suggested.
I.e. they can continue existing or start new
sections. The usual ordering of files in directories would apply. Nested
includes should be possible allowing applications to sub-delegate some of
their configuration. Includes should not be allowed to relax section
addition/modification permissions, only to make them stricter. File
requirements should probably be changeable, though.
The ideas is to avoid the includes and have any config file be a valid
The support for the extended syntax may be configurable via the API.
This way there might be no need to add another function, although a
for merging many files from the code would be useful.
There is already a way to merge snippets in the library. The function is
proposed to have a one tool instead of implementing the same
functionality in different places.
This way everything is visible to and controllable by the
doesn't need application-specific documentation, only the configuration
language documentation, which may be borrowed from the library and would
rarely change. More complicated include statements would need some
but at least those would be close to the actual logic.
If someone want to implement it be my guest. Having spent some time in
the area I would say it is power of magnitude more complex than the
original "more complex" design that was proposed (you can read it in the
Sr. Engineering Manager IdM portfolio
Red Hat, Inc.