[Freeipa-devel] [Freeipa-users] Auto membership plugin

Mon Apr 11 18:32:30 UTC 2011

On 04/11/2011 10:58 AM, Nathan Kinder wrote:
> On 04/11/2011 10:25 AM, Dmitri Pal wrote:
>> On 04/11/2011 11:27 AM, Nathan Kinder wrote:
>>> On 04/08/2011 09:07 AM, Dmitri Pal wrote:
>>>> On 04/08/2011 11:49 AM, JR Aquino wrote:
>>>>> Is there any way to capture a description associated with the regex
>>>>> ->   group mapping?
>>>>>
>>>>> I was thinking that after time, it would be important to look back
>>>>> on rules and know why they were put there.
>>>>>
>>>>> Particularly in the case of regex, since it may not be completely
>>>>> obvious by looking back at alphabet soup.
>>>>>
>>>>> _______________________________________________
>>>>> Freeipa-users mailing list
>>>>> Freeipa-users at redhat.com
>>>>> https://www.redhat.com/mailman/listinfo/freeipa-users
>>>>>
>>>>>
>>>> The more I think about current design the more I want to normalize
>>>> things.
>>>> I would rather instead of:
>>>>
>>>> dn: cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
>>>> objectclass: autoMemberDefinition
>>>> autoMemberScope: dc=example,dc=com
>>>> autoMemberFilter: objectclass=ipaHost
>>>> autoMemberExclusiveRegex:
>>>> cn=webservers,cn=hostgroups,dc=example,dc=com:fqdn=^www5\.example\.com
>>>> autoMemberInclusiveRegex:
>>>> cn=webservers,cn=hostgroups,dc=example,dc=com:fqdn=^www[1-9]+\.example\.com 
>>>>
>>>> autoMemberInclusiveRegex:
>>>> cn=webservers,cn=hostgroups,dc=example,dc=com:fqdn=^web[1-9]+\.example\.com 
>>>>
>>>> autoMemberInclusiveRegex:
>>>> cn=mailservers,cn=hostgroups,dc=example,dc=com:fqdn=^mail[1-9]+\.example\.com 
>>>>
>>>> autoMemberDefaultGroup: cn=orphans,cn=hostgroups,dc=example,dc=com
>>>> autoMemberGroupingAttr: member:dn
>>>>
>>>>
>>>> Have something like:
>>>>
>>>> dn: cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
>>>> objectclass: autoMemberDefinition
>>>> objectclass: cnContainer
>>>> autoMemberScope: dc=example,dc=com
>>>> autoMemberFilter: objectclass=ipaHost
>>>> autoMemberRegexRule: cn=Webserver Inclusion
>>>> Rule,cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
>>>> autoMemberRegexRule: cn=Mailserver Inclusion
>>>> Rule,cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
>>>> autoMemberRegexRule: cn=Desktop exclusion Rule,cn=Hostgroups,cn=Auto
>>>> Membership Plugin,cn=plugins,cn=config
>>>> autoMemberDefaultGroup: cn=orphans,cn=hostgroups,dc=example,dc=com
>>>> autoMemberGroupingAttr: member:dn
>>>>
>>>>
>>>> dn: cn=Webserver Inclusion Rule,cn=Hostgroups,cn=Auto Membership
>>>> Plugin,cn=plugins,cn=config
>>>> objectclass: autoMemberDefinitionRegexRule
>>>> cn: Webserver Inclusion Rule
>>>> description: Rule contains regular expression to include webserver
>>>> hosts into the webserver group.
>>>> include: yes<- include or exclude
>>>> memberGroup: cn=webservers,cn=hostgroups,dc=example,dc=com
>>>> arrtibuteToMath: fgdn
>>>> expressionToMatch: ^www[1-9]+\.example\.com
>>>>
>>>>
>>>> Or something along those lines...
>>> It's a nice logical layout, but it would be hard for an administrator
>>> to figure out what exactly would happen if they were to add a host
>>> with a specific hostname.  Since the config is spread over so many
>>> entries, one would have to look at the top level config entry to find
>>> each rule DN, fetch each rule DN to look at the regexes.  All of the
>>> information is so spread out that you can't just look in one place to
>>> see the rules that will be used.  This could make things difficult
>>> from a troubleshooting perspective.
>> This should not be viewed in raw. THe UI and CLi should come to the 
>> rescue.
>> I am not sure that this is a right approach to mix readability and
>> normalization.
>> To follow this logic no-one would ever normalize data in any DB due to
>> the claim that it would be hard to join tables.
> The feature is implemented outside of the UI, and I would like to be 
> able to troubleshoot it without the UI without a ton of hassle.  
> Ultimately, it is a DS plug-in, and we should be able to troubleshoot 
> it easily as a single component instead of requiring the UI to 
> understand what it is doing.  We have run into this same issue with 
> things like access control since ACI attributes can live anywhere in 
> the database.  It is for this reason that we have things like the get 
> effective rights control for evaluating settings.
>
> If one adds an inclusion rule, but doesn't realize that an exclusion 
> rule is overriding it, they could easily get confused.  I understand 
> that we want the UI to be able to notice this and present it to the 
> user, but there is plenty of room for error in the UI as we add more 
> and more logic into it.
>
> I am not totally opposed to this approach, but I want to point out 
> some of the downsides in going in this direction.  I usually like to 
> make the internal representation of plug-in configuration closely 
> mirror the layout of the configuration entries/attributes themselves.  
> In this case, it would be highly inefficient to do so.  Internally to 
> the plug-in, we will be representing the config for a specific object 
> type as a single struct with a list of all inclusive and exclusive 
> rules.  I can convert multiple config entries into this same internal 
> format, but it is something I generally like to avoid.
>
> I will look into this approach further.  I have the current approach 
> from the design document implemented and working at this point, so 
> some surgery will be required to go back to a different configuration 
> layout.  Parsing and loading the configuration when it is split across 
> so many dependent entries is not going to be trivial.  I can see 
> plenty of corner cases in configuration validation cropping up.  
> Dynamic config changes will also be more difficult to handle, as we 
> will have to back track to find what config entries reference a 
> modified rule.
>>> The description issue is a tough one to deal with if we have the
>>> config in the form that is currently described in the design doc.
>>> Since we want a description per regex rule, we should need to make the
>>> description be a part of the regex rule value instead of a separate
>>> description attribute.  I don't necessarily like this approach, as the
>>> readability of the config will not be nice.
>>>
>> I think this tips the scale towards the approach I proposed.
> Yes, it does.
I started writing up some notes to map out how we would represent the 
configuration with this split out approach.  We would have one top level 
config entry per filter/scope.  Child entries would be 
inclusive/exclusive rule entries.  We sould load all child entries as 
regex rules, so we don't need pointers to each regex entry in the 
top-level entry.  Here is an example:

-------------------------------------------------------------------------------------------------
dn: cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
objectclass: autoMemberDefinition
autoMemberScope: dc=example,dc=com
autoMemberFilter: objectclass=ipaHost
autoMemberGroupingAttr: member:dn
autoMemberDefaultGroup: cn=orphans,cn=hostgroups,dc=example,dc=com

dn: cn=www 5,cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
objectclass: autoMemberRegexRule
description: exclude www5 from being added to webservers
autoMemberRegexType: exclusive
autoMemberRegexAttr: fqdn
autoMemberTargetGroup: cn=webservers,cn=hostgroups,dc=example,dc=com
autoMemberRegex: ^www5\.example\.com

dn: cn=www hosts,cn=Hostgroups,cn=Auto Membership 
Plugin,cn=plugins,cn=config
objectclass: autoMemberRegexRule
description: include www hosts in webservers
autoMemberRegexType: inclusive
autoMemberRegexAttr: fqdn
autoMemberTargetGroup: cn=webservers,cn=hostgroups,dc=example,dc=com
autoMemberRegex: ^www[1-9]+\.example\.com

dn: cn=web hosts,cn=Hostgroups,cn=Auto Membership 
Plugin,cn=plugins,cn=config
objectclass: autoMemberRegexRule
description: include web hosts in webservers
autoMemberRegexType: inclusive
autoMemberRegexAttr: fqdn
autoMemberTargetGroup: cn=webservers,cn=hostgroups,dc=example,dc=com
autoMemberRegex: ^web[1-9]+\.example\.com

dn: cn=mail hosts,cn=Hostgroups,cn=Auto Membership 
Plugin,cn=plugins,cn=config
objectclass: autoMemberRegexRule
description: include mail hosts in mailservers
autoMemberRegexType: inclusive
autoMemberRegexAttr: fqdn
autoMemberTargetGroup: cn=mailservers,cn=hostgroups,dc=example,dc=com
autoMemberRegex: ^mail[1-9]+\.example\.com
-------------------------------------------------------------------------------------------------

What I don't like about this approach is that the first 3 regex rules 
really belong together, as they all have to do with webservers.  It 
makes sense to split out the mail hosts regex since it is logically 
different.  If you have the case where your hosts have hostnames that 
don't follow any sort of format, you may end up having many inclusive 
rule entries for all of your different webservers.  I see that as being 
a headache in many cases.  Keep in mind that the above is a very simple 
example.  You would likely have many more entries in an actual deployment.

To alleviate this problem, we could make the autoMemberRegex attribute 
multi-valued, but you would only have one description per regex rule 
entry, not per regex.  This is more flexible, as administrators could 
choose when to group regexes together vs. having them separate.  The 
only real advantage is to add a description to a group of regex rules 
though.

This is all equivalent to the following config with the method described 
in the design doc (without the ability to have descriptions):

-------------------------------------------------------------------------------------------------
dn: cn=Hostgroups,cn=Auto Membership Plugin,cn=plugins,cn=config
objectclass: autoMemberDefinition
autoMemberScope: dc=example,dc=com
autoMemberFilter: objectclass=ipaHost
autoMemberExclusiveRegex: 
cn=webservers,cn=hostgroups,dc=example,dc=com:fqdn=^www5\.example\.com
autoMemberInclusiveRegex: 
cn=webservers,cn=hostgroups,dc=example,dc=com:fqdn=^www[1-9]+\.example\.com
autoMemberInclusiveRegex: 
cn=webservers,cn=hostgroups,dc=example,dc=com:fqdn=^web[1-9]+\.example\.com
autoMemberInclusiveRegex: 
cn=mailservers,cn=hostgroups,dc=example,dc=com:fqdn=^mail[1-9]+\.example\.com
autoMemberDefaultGroup: cn=orphans,cn=hostgroups,dc=example,dc=com
autoMemberGroupingAttr: member:dn
-------------------------------------------------------------------------------------------------

-NGK
>>> _______________________________________________
>>> Freeipa-users mailing list
>>> Freeipa-users at redhat.com
>>> https://www.redhat.com/mailman/listinfo/freeipa-users
>>>
>>>
>>
>
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