Re: (ITS#6365) Bad slapcat output when slapd running

[masarati@aero.polimi.it]

> Howard Chu wrote:
>> Peter Mogensen wrote:
>>> This is mirrormode.
>>> There's no "provider" as such. However, there's one server which is
>>> used
>>> for application access and to minimize disk load on that server, the
>>> plan was to take most backups from the other.
>>> I can't see any difference between what you call "initializing" and
>>> normal running state, except that the difference between server-1 and
>>> server-2 is (somewhat) larger.
>>
>> If the problem is as Ando suggests, then it's because in the syncrepl
>> Refresh
>> phase it's receiving entries out-of-order from the provider. Ando is
>> suggesting that the problem is caused when a child entry is replicated
>> before
>> its parent. Once the Refresh phase ends and it transitions to the
>> Persist
>> phase, all entries' parents will exist and so this particular condition
>> will
>> no longer occur.
>>
>> Of course, no one is saying for certain that this is the explanation,
>> yet.
>
> It sounds reasonable to me :)
> But unless you are not in any way allowed to - ever - make writes to
> more than one server in a mirromode setup, this could (as I hear it)
> potentially happen at any time.
> The only reason I have to only make writes to one server is that I
> currently (this will change) have an application which is dependant on
> making writes and immediately reading back the entry.
>
> As I hear what you're saying is that any write to a server in a
> mirrormode setup could invalidate a slapcat running on the other.
> This would mean that you can never write to more that one server at all
> and that's the only server you can slapcat while running.
> That takes a lot of the "mirror" out of "mirrormode". Doesn't it?

Based on my *very incomplete and possibly wrong* analysis, the problem
would be automatically cured by using back-bdb.  Also, fixing back-hdb *if
it's broken at all* should be possible.

p.