Dne čtvrtek 19 července 2012 16:10:08, Stephen Gallagher napsal(a):
> On Tue, 2012-07-17 at 11:21 +0200, Jan Zelený wrote:
>> Dne středa 11 července 2012 13:34:33, Stephen Gallagher napsal(a):
>>> On Thu, 2012-06-21 at 12:15 +0200, Jan Zelený wrote:
>>>>> On Fri, 2012-06-08 at 12:56 +0200, Jan Zelený wrote:
>>>>>> Hi everybody,
>>>>>> I'm sending some patches which implement the primary server
>>>>>> support as
>>>>>> I
>>>>>> see it. It it based on comment #6 in the related ticket
>>>>>>
https://fedorahosted.org/sssd/ticket/1128
>>>>>>
>>>>>>
>>>>>> Patch #0001 basically adds the necessary support in failover
code
>>>>>> Patches #0002 - #0004 extend this support in each provider
>>>>>> Patch #0005 documents the new concept in failover section in man
>>>>>> pages
>>>>>> Patches #0006 - #0008 add new options for each provider which
>>>>>> utilize
>>>>>> this
>>>>>> concept.
>>>>>>
>>>>>>
>>>>>> Just briefly about the approach. When adding a new server to the
>>>>>> list
>>>>>> of
>>>>>> servers related to a service, each server can be marked either
as
>>>>>> primary
>>>>>> or secondary.
>>>>>>
>>>>>> When selecting new server from failover list, the algorithm
>>>>>> iterates
>>>>>> over
>>>>>> the list twice - first it tries to look for primary server and
if
>>>>>> none
>>>>>> is
>>>>>> found, it tries also secondary server.
>>>>>>
>>>>>> If a server is returned from failover, and it is not primary
>>>>>> server, a
>>>>>> timeout is set (currently hard-coded for 30 seconds) for primary
>>>>>> server
>>>>>> lookup. This timeout is rescheduled until a primary server is
>>>>>> found.
>>>>>> If a
>>>>>> primary server (either working or neutral) is found after this
>>>>>> timeout,
>>>>>> status of the backend is reset, i.e. first all offline and then
>>>>>> all
>>>>>> online callbacks are called. This is done to interrupt
connection
>>>>>> to
>>>>>> the
>>>>>> secondary server in favor of new connection to a primary server.
>>>>>
>>>>> I think this is dangerous. I don't want us to force offline
>>>>> operation
>>>>> even momentarily.
>>>>
>>>> I changed the concept to re-connection, which is done instantly,
>>>> without
>>>> scheduling any events. Combined with the possibility to mark LDAP
>>>> connections as "disconnecting", it is addressing the original
issue of
>>>> going offline and back online.
>>>>
>>>>>> I have just couple concerns about things which I have yet to
>>>>>> inspect.
>>>>>> First of all when connection to the old server is interrupted,
>>>>>> what if
>>>>>> an
>>>>>> operation is currently in progress on this connection? I know
>>>>>> ticket
>>>>>> #1027 induces similar scenario. Maybe to kill two birds with one
>>>>>> stone
>>>>>> I
>>>>>> could design an extension to immediately invoke callbacks of all
>>>>>> operations running on existing connection. What do you think
about
>>>>>> that?
>>>>>
>>>>> Better behavior would be to allow existing communications to
>>>>> complete,
>>>>> and only direct new requests to the primary server. I think
>>>>> interrupting
>>>>> in-progress requests would be dangerous and unpredictable.
>>>>
>>>> Done, see the proposed concept of reconnection.
>>>>
>>>>>> My second concern is about port status timeout. After some time
a
>>>>>> port
>>>>>> is
>>>>>> marked as neutral if originally marked as not-working. That
>>>>>> effectively
>>>>>> leads to second attempt to primary server reconnection being
>>>>>> successful
>>>>>> even though the server is still not running. As a result, an
>>>>>> unnecessary
>>>>>> reconnection to secondary server is performed once some data are
>>>>>> needed
>>>>>> from the server.
>>>>>
>>>>> This is intentional behavior. It's done so that if we eventually
>>>>> lose
>>>>> connection to the current server, we'll be able to retry that
one
>>>>> again
>>>>> while looping through the failover code. I'd suggest just
resetting
>>>>> the
>>>>> port-neutralizer timeout when you make the primary reconnection
>>>>> attempt
>>>>> and it fails.
>>>>
>>>> I left it as it was. It is impossible for failover code to check if
>>>> the
>>>> port is online. Therefore this solution is probably the best we can
>>>> do.>
>>>>
>>>>>> Thank you very much for your opinions on this
>>>>>> Jan
>>>>>
>>>>> General comment: I don't think I like the term
"secondary" here. I
>>>>> think
>>>>> we might want to use something more descriptive. Perhaps
"backup"?
>>>>> I'm
>>>>> soliciting suggestions :)
>>>>
>>>> Backup seems as good as any. Should I rename all those config options
>>>> or
>>>> do you have any other ideas?
>>>>
>>>>> Patch 0001: Nack
>>>>> See above concerns.
>>>>
>>>> Hopefully addressed.
>>>>
>>>>> Patch 0002: Nack
>>>>>
>>>>> Please add a comment explaining why secondary_urls gets promoted to
>>>>> primary.
>>>>
>>>> Added DEBUG message, that's more useful I guess
>>>>
>>>>> Patch 0003: Ack
>>>>>
>>>>>
>>>>>
>>>>> Patch 0004: Nack
>>>>>
>>>>> Please add a comment explaining why secondary_urls gets promoted to
>>>>> primary.
>>>>
>>>> Added DEBUG message, that's more useful I guess
>>>>
>>>>> Patch 0005: Nack
>>>>>
>>>>> Typos in manpage:
>>>>> "For each failover-enabled config option two variants
exists:"
>>>>> should be
>>>>> "For each failover-enabled config option, two variants
exist:"
>>>>> and
>>>>> "it will replace current" should be "it will replace
the current"
>>>>
>>>> Fixed
>>>>
>>>>> Patch 0006: Nack
>>>>>
>>>>> Typo in the manpage:
>>>>> "If neither options is specified," should be "If
neither option is
>>>>> specified,"
>>>>>
>>>>> You removed the warning about missing ldap_uri. You should put it
>>>>> back
>>>>> in if both urls and secondary_urls are NULL.
>>>>>
>>>>> Please add the same config debug information that you used in the
>>>>> IPA
>>>>> provider (about promoting secondary servers to primary)
>>>>
>>>> Done
>>>>
>>>>> Patch 0007: Nack
>>>>>
>>>>> Same comment about the warning when the servers are unspecified.
>>>>
>>>> Done
>>>
>>> These patches look good by inspection, but due to divergence in the
>>> codebase, they no longer apply atop the master. Please rebase them so I
>>> can run some tests.
>>>
>>> Also, the AD provider probably needs modification as well to take
>>> advantage of this new feature (sorry, it landed first).
>>
>> Rebased on top of current master. Those AD provider changes are included
>> as
>> well, I didn't have a chance to test them though.
>
> These patches don't apply cleanly. Patch 0010 fails with missing blobs.
> Please submit rebased patches (or identify which other patches are
> required).
Here it is, rebased on top of current master (strange that many times rebase
works while applying the patch doesn't). No additional patches required.
Thanks
Jan
Nack.
IPA and LDAP works. I didn't test AD because I don't have any AD server
available.
Kerberos backup servers don't seem to work. I think it is because you
are loading wrong option in krb5_init.c:103.
Manpage failover section:
- says that the primary server timeout is 60 seconds but you use 30
seconds in the code.
- "After this timeout SSSD will periodically try to reconnect to one of
*the* primary servers."?
data_provider_fo.c:452 You have two subsequent spaces in the debug message.
data_provider_fo.c:477 Can you put the DEBUG statement just on two lines
please? I found this little confusing.
data_provider_fo.c:538 You should check if new_subreq is not null. I
know it is not possible in the current code flow, but what if.
fail_over.c:836 The commentary says: "Also cancel the primary server
reactivation event until the lookup is complete". Are you cancelling the
timer somewhere?
sdap_service_init(), ad_servers_init(): You're allocating tmp_ctx on
mem_ctx instead of NULL.
krb5_common.c:623 Invalid debug message. At this point backup servers
aren't present.