[Freeipa-devel] server_del (re)implementation in domain level 1 topology management

[Petr Vobornik]

On 03/17/2016 04:10 PM, Martin Babinsky wrote:
> On 03/17/2016 03:37 PM, Petr Vobornik wrote:
>> On 03/17/2016 03:17 PM, Martin Babinsky wrote:
>>> On 03/17/2016 02:55 PM, Petr Vobornik wrote:
>>>> On 03/17/2016 02:39 PM, Martin Babinsky wrote:
>>>>> Hi list,
>>>>>
>>>>> I would like to discuss the merge of `del_master_managed()` function
>>>>> from `ipa-replica-manage` command into the server_del API call that
>>>>> is a
>>>>> part of the managed replication topology design update[1] (see also
>>>>> the
>>>>> corresponding upstream ticket [2]).
>>>>>
>>>>> Before I head down into coding I want to be sure that everyone is one
>>>>> the same page regarding the expected use-cases which govern the API
>>>>> design.
>>>>>
>>>>> IIUC, there are two main uses of the new functionality according to
>>>>> design document:
>>>>>
>>>>> 1.) run 'server_del' when 'ipa-replica-manage del' is run in
>>>>> domain-level 1
>>>>
>>>> Right, this is for backwards compatibility(BC).
>>>>
>>>>>
>>>>> 2.) during 'ipa-server-install --uninstall', 'server_del' should be
>>>>> called on one of remote masters to remove the uninstalled server from
>>>>> the managed topology
>>>>>
>>>>> What I didn't get from the design document is whether the method
>>>>> should
>>>>> have some kind of 'force' option which should bypass all topology
>>>>> connectivity checks. Currently both `ipa-replica-manage del` and
>>>>> server
>>>>> uninstaller have options which will force the removal even if it
>>>>> disconnects the topology ('--force' in the former,
>>>>> '--ignore-disconnected-topology' in the latter).
>>>>
>>>> I would say that uninstaller should do checks in validate method
>>>> therefore the subsequent `server-del` doesn't need to do it again
>>>> but it
>>>> shouldn't harm. I.e. it should follow what the user specified. If user
>>>> wants to skip (--ignore-d..-t..) then skip. If not then it will fail in
>>>> validate method.
>>>>
>>>> Only issue might be error state where servers have different picture of
>>>> the topology.
>>>>
>>> If the view of the topology is not self-consistent then you have plenty
>>> of other issues to take care of and that may include some forced removal
>>> and recreation of nodes.
>>>
>>>>>
>>>>> I guess the 'server_del' method should inherit this flag so that we
>>>>> retain the original functionality (for better or worse). I propose to
>>>>> name this option 'ignore_topology_disconnect' because it is more
>>>>> descriptive than plain 'force'.
>>>>
>>>> +1
>>>>
>>>> And in BC case, `ipa-replica-manage --force` would call `server-del
>>>> --ig..-d..-t...`
>>>>
>>> Yes.
>>>>>
>>>>> I would also like to ask whether 'server_del' (which is currently
>>>>> NO_CLI) should be usable also from command line.
>>>>
>>>> IMO yes, it should mostly as a couterpart of `ipa-replica-manage
>>>> --force
>>>> --clean`
>>>>
>>>> Which bring us to --clean option and what it should do...
>>>>
>>> According to the design, '--clean' should be used as a cleanup of
>>> leftovers after deleted servers. How I image it from the implementation
>>> point of view is that when '--clean' is specified and the server was
>>> already deleted, the NotFound error raised from the framework should be
>>> ignored and the code should continue in clean up. (I assume that
>>> segment/service/dns cleanup will be done in post_callback portion and
>>> the topology connectivity/sanity checks in the pre_callback).
>>
>> When thinking about it, clean could be a separate command which would be
>> called internally in post callback of server-del. It would reduce the
>> number of ifs in server-del and simplify it in general. It would work
>> only if server entry doesn't exists.
>>
> That was my original idea. I also thought that 'check_last_link_managed'
> could be a separate command, but it is probably not a very good idea to
> add the overhead of calling two separate commands to a single API call.
> OTOH it would improve the code organization IMHO.

Not sure if check_last_link_managed should be an API command. It is 
already a separate function. What would be the use case for it as a command?

Maybe the function should be moved from ipaserver/install/replication to 
a more suitable place given that it's used from API - it's up to you.

>
>>> That means that '--clean' has no additional effect when the server
>>> exists.
>>
>> Right
>>
>>>>>
>>>>>
>>>>> [1] http://www.freeipa.org/page/V4/Manage_replication_topology_4_4
>>>>> [2] https://fedorahosted.org/freeipa/ticket/5588
>>>>>
>
>
-- 
Petr Vobornik