[389-users] replication failure - clock skew

[Rich Megginson]

On 02/09/2012 12:52 PM, Greg Kuchyt wrote:
> On 02/09/2012 02:38 PM, Rich Megginson wrote:
>> On 02/09/2012 12:23 PM, Greg Kuchyt wrote:
>>> Yesterday afternoon, one of my consumers randomly crashed/rebooted.
>>> Upon rebooting, its replication agreement with its master failed with
>>> the following error:
>>>
>>> Unable to acquire replica: Excessive clock skew between the supplier
>>> and the consumer. Replication is aborting
>>>
>>> I did a little bit of Google searching and found some list traffic
>>> from a few years ago. From that I derived that this replica was hosed
>>> and I would need to re-initialize it. No problem. A re-initialization
>>> didn't do anything, same error. Starting from scratch from a
>>> completely new/fresh replica produces the same result. That's when I
>>> noticed the following errors in the logs on the master.
>>>
>>> csngen_new_csn - Warning: too much time skew (-115319 secs). Current
>>> seqnum=1
>>>
>>> I downloaded the readNsState.py script attached to the following
>>> ticket (https://bugzilla.redhat.com/show_bug.cgi?id=233642). Running
>>> this on the master produced the following output
>>>
>>> For replica cn=replica,cn=o\3Dpotsdam.edu,cn=mapping tree,cn=config
>>> len of nsstate is 40
>>> CSN generator state:
>>> Replica ID : 6560
>>> Sampled Time : 1328928777
>>> Time in hex : 0x4f35d809
>>> Time as str : Fri Feb 10 21:52:57 2012
>>> Local Offset : 0
>>> Remote Offset : 261
>>> Seq. num : 1
>>> System time : Thu Feb 9 14:00:01 2012
>>> Diff in sec. : -114776
>>>
>>> This leads me to believe that the clock skew problem is on the master.
>>>
>>> I am not really sure how the clock skew happened. All of these systems
>>> synchronize their clocks via a centralized time server and all the
>>> times on their clocks are correct. There are 3 or 4 other replicas
>>> that are still receiving incremental updates fine, but any attempt to
>>> add a new replica results in a failed replication agreement due to
>>> excessive clock skew.
>>>
>>> I am writing to get a better understanding of the situation and see if
>>> there is anything to be done to resolve this. At the moment it seems
>>> as if I am caught in an unfortunate situation that will require
>>> re-initialization of my master from a back-up.
>>>
>>> Thanks for any help that can be provided.
>> What is your 389-ds-base version and platform?
>>> -- 
>>> 389 users mailing list
>>> 389-users at lists.fedoraproject.org
>>> https://admin.fedoraproject.org/mailman/listinfo/389-users
>>
>
> Rich,
>
> The master and a few replicas are running on Scientific Linux 6.1 
> x86_64. Here, we're using the stock packages along with the modified 
> 389-ds-base packages in your fedorapoeople.org repo. So that puts it 
> at 1.2.9.9-1 for 389-ds-base I believe.
>
> Two replicas (including the one that rebooted/failed) are on Fedora 12 
> x86_64 and their 389-ds-base is 1.2.5-1.
There was a known problem with clock skew calculation and handling in 
1.2.5 - please try upgrading everything to 1.2.9.9.  I realize fedora 12 
is no longer supported.
>
> Let me know what other info you need. Thanks.
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