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From Udo Kohlmeyer <...@apache.org>
Subject Re: [DISCUSS] TTL setting on WAN
Date Wed, 20 Mar 2019 18:10:44 GMT
If all that the customer is concerned about is that the receiving side 
gets the "latest" data, conflation is definitely the best bet. How do we 
classify old? The only classification that I have of old (in this 
context) is that there is a newer version of a data entry. This 
classification is not time based, as a TTL approach would require, but 
state.

What is the use of WAN replication if we are proposing to only replicate 
*some* of the data. How would the clusters ever know if they are 
in-sync? I believe we are just opening a door that we will never be able 
to close again and will cause us endless issues.

--Udo

On 3/20/19 10:56, Bruce Schuchardt wrote:
> Udo, in the cases I've looked at the user is okay with inconsistency 
> because they don't really care about the old data. They're most 
> interested in getting the newest data and keeping the sending site 
> from going down.  I guess the docs for TTL should make it very clear 
> that it will cause inconsistencies.
>
> Conflation does seem like an appropriate thing to try if the same keys 
> are being updated - I'll do some investigation and see why it wasn't 
> appropriate.
>
>
> On 3/20/19 10:51 AM, Udo Kohlmeyer wrote:
>> -1, I don't believe this is a feature that we should support. IF a 
>> client is experiencing slow WAN replication and users only care about 
>> the "latest" data, then maybe the user should use "conflation".
>>
>> With a TTL model, we are messing with our consistency tenet. I'm am 
>> NOT in support of a setting that can cause inconsistency.
>>
>> Dead-letter queues is another area that WILL cause data/site 
>> inconsistency. I think we really have to take a step back, think 
>> about WHAT tenets are important to GEODE and then act accordingly.
>>
>> --Udo
>>
>> On 3/20/19 10:46, Bruce Schuchardt wrote:
>>> IDK Anil, we'll figure that out in the implementation.  I was 
>>> thinking it would be in the dispatch threads, so if distribution is 
>>> need that will happen as it does now.  I'm hopeful that this won't 
>>> perturb the code too much.
>>>
>>> One thing that was brought up to me in person was the Dead Letter 
>>> Queue 
>>> <https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=80452478>

>>> initiative that seems to have stalled.  That seems like a very 
>>> similar idea though it's reacting to errors coming from the 
>>> receiving side and not a local condition.  I like the callback, 
>>> stats, gfsh and cluster config integration in that write-up & think 
>>> they might be useful here.  There is also relevant discussion in 
>>> that page about things like PDX registrations.  Is that initiative 
>>> going to move forward at some point or is it off the boards?
>>>
>>> On 3/20/19 10:25 AM, Anilkumar Gingade wrote:
>>>> +1. Will the expiration (destroy) be applied on local queues or the
>>>> expiration will be replicated (for both serial and parallel)?
>>>>
>>>> -Anil.
>>>>
>>>>
>>>> On Wed, Mar 20, 2019 at 8:59 AM Bruce Schuchardt 
>>>> <bschuchardt@pivotal.io>
>>>> wrote:
>>>>
>>>>> We've seen situations where the receiving side of a WAN gateway is 
>>>>> slow
>>>>> to accept data or is not accepting any data.  This can cause 
>>>>> queues to
>>>>> fill up on the sending side.  If disk-overflow is being used this can
>>>>> even lead to an outage.  Some users are concerned more with the 
>>>>> latest
>>>>> data and don't really care if old data is thrown away in this
>>>>> situation.  They may have set a TTL on their Regions and would 
>>>>> like to
>>>>> be able to do the same thing with their GatewaySenders.
>>>>>
>>>>> With that in mind I'd like to add this method to 
>>>>> GatewaySenderFactory:
>>>>>
>>>>> /** * Sets the timeToLive expiration attribute for queue entries 
>>>>> for the
>>>>> next * {@code GatewaySender} created. * * @param timeToLive the
>>>>> timeToLive ExpirationAttributes for entries in this region * 
>>>>> @return a
>>>>> reference to this GatewaySenderFactory object * @throws
>>>>> IllegalArgumentException if timeToLive is null * @see
>>>>> RegionFactory#setEntryTimeToLive */ public GatewaySenderFactory
>>>>> setEntryTimeToLive(ExpirationAttributes timeToLive);
>>>>>
>>>>> The exact implementation may not be the same as for Regions since we
>>>>> probably want to expire the oldest entries first and make sure we 
>>>>> do so
>>>>> in their order in the queue.
>>>>>
>>>>>
>>>

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