[SSSD] How to tune the failover mecanism ?

Dmitri Pal dpal at redhat.com
Mon Dec 3 21:54:31 UTC 2012


On 12/03/2012 04:27 PM, Simo Sorce wrote:
> On Mon, 2012-12-03 at 16:16 -0500, Dmitri Pal wrote:
>> On 12/03/2012 03:21 PM, Simo Sorce wrote:
>>> On Mon, 2012-12-03 at 21:12 +0100, Olivier wrote:
>>>> I may be wrong but that is not exactly the way I read the man page :
>>>> http://linux.die.net/man/5/sssd-ldap
>>>>
>>>> On failover section :
>>>>
>>>> --> Further connection attempts are made to machines or services
>>>> marked as offline after a --> specified period of time; this is
>>>> currently hard coded to 30 seconds.
>>>>
>>>> As I understand it, once a machine or service has been stamped "offline",
>>>> then it won't be queried before 30 second has passed.
>>>>
>>>> The delay I would like to know (and to tune if possible) is the time after which
>>>> sssd query the next ldap server in ldap_uri list if the current one is
>>>> not reachable
>>>> (IMHO, 5 second would be more than enough and I think would even tune less
>>>>  if I could).
>>> Ah I think you've been mislead by the timeout section.
>>>
>>> That doesn't apply to a specific server but to a general attempt to go
>>> online.
>>>
>>> If I remember correctly, when SSSD tries to go online it will try the
>>> first server, and if it fails it will immediately try the next and so on
>>> until it finds one that works or goes back offline because none work.
>>>
>>> If it goes back offline it will wait at least 30 sec. before going
>>> online but will go online only if there is an event that requires data
>>> after the 30 sec. has gone by.
>>>
>>> HTH,
>>> Simo.
>>>
>> I think the question is for how long SSSD waits to detect that the
>> server is offline and whether this is configurable.
> It is not, SSSD will find out the first time it needs to resolve
> something and will try to fetch data from the offline server.
>
> At that point it will determine the server is offline.
>
> What we may do is to retry immediately once, I do not recall if we do
> that.
>
> Simo.
>
Let me try again...

SSSD sends a request to the central server because something triggered a
lookup.
How long SSSD waits to declare that server is not reachable before
trying another server?
What is the length of this timeout and is it configurable and how?

Does the question makes sense now?


-- 
Thank you,
Dmitri Pal

Sr. Engineering Manager for IdM portfolio
Red Hat Inc.


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