[infinispan-dev] Distributed Counter Discussion

[Dan Berindei]

On Mon, Mar 21, 2016 at 1:43 PM, Bela Ban <bban at redhat.com> wrote:
>
>
> On 21/03/16 11:12, Pedro Ruivo wrote:
>> Hi all,
>>
>> @Eric, thanks for the requirements.
>>
>> @Bela, does JGroups counter supports that semantics (AP)?
>
> No. You'd have to catch the MergeView and do this manually.

I should also mention that you don't get a "cluster split" event. With
when a cluster ABC splits into A and BC and merges back, you could get
quite a view sequence like this:

A, B, C: A|3 [A, B, C]
A: A|4 [A, B]
A: A|5 [A] (could be missing)
B, C: B|4 [B, C]
A, B, C: B|6 [B, C, A] (merge view)

So it's not that easy to keep track of counter additions "since the split".

>
>> Infinispan does not have eventually consistency (yet) neither an update log. So, it
>> can't reconcile the counter and you will lose one of the partition updates.
>
> Same for the JGroups counter service. The jgroups-raft CounterService
> provides strong consistency, but at the expense of availability.
>
>> On 03/18/2016 02:19 PM, Eric Wittmann wrote:
>>> Agreed. :)
>>>
>>> On 3/18/2016 9:31 AM, Bela Ban wrote:
>>>> So actually you don't care if you have multiple counters in case of a
>>>> network split, but you do care that the numbers of different counters
>>>> get reconciled when a network partition heals.
>>>>
>>>> Example
>>>> - C1: 1000
>>>> - Network split: C1: 1000, C2: 1000
>>>> - Different clients update counters on both sides of the partition: C1:
>>>> 1500 C2: 1600
>>>> - Network split disappears, reconciling C1 to 2100: 1000 +500 +600. This
>>>> means the 500 added to C1 should have been added to C2 as well, and the
>>>> 600 to C2 should have been added to C1
>>>>
>>>> If such a behavior would be acceptable, then we could do without CP and
>>>> live with AP
>>>>
>>>> On 18/03/16 14:19, Eric Wittmann wrote:
>>>>> Yes, precisely.  The API Gateway itself is clustered.  It services a
>>>>> large volume of inbound traffic which it reverse-proxies to appropriate
>>>>> back-end APIs after applying policies such as security, rate limiting,
>>>>> caching, etc.
>>>>>
>>>>> -Eric
>>>>>
>>>>> On 3/18/2016 2:32 AM, Bela Ban wrote:
>>>>>> Stupid question: whay do you need a distributed counter for this? Is the
>>>>>> service you're monitoring replicated in a cluster?
>>>>>>
>>>>>> On 17/03/16 18:06, Eric Wittmann wrote:
>>>>>>> Greetings.  Apologies for coming in a bit late on this conversation.
>>>>>>> Tristan pointed me to it a couple of days ago and unfortunately I'm just
>>>>>>> now getting time to reply.
>>>>>>>
>>>>>>> I can try to quickly give an overview of apiman's (JBoss API Management
>>>>>>> Gateway) requirements.
>>>>>>>
>>>>>>> What we're trying to do is implement support for Limiting policies:
>>>>>>>
>>>>>>> * Rate Limiting/Throttling (e.g. limit of 100 requests per second)
>>>>>>> * Quotas (e.g. limit of 100,000,000 requests per month)
>>>>>>> * Transfer Quotas (e.g. limit of 2.5GB of data downloaded per day)
>>>>>>>
>>>>>>> We will need to support multiple backing implementations of the Rate
>>>>>>> Limiter, and we're trying to get Infinispan to be one of those
>>>>>>> implementations.
>>>>>>>
>>>>>>> In no particular order, we would need the following characteristics:
>>>>>>>
>>>>>>> - Can be "squishy" for quotas and transfer quotas:  If you
>>>>>>>          get 100,001,017 requests that's OK
>>>>>>> - Strict would be cool as an option:  Hard-fail when the
>>>>>>>          counter reaches the limit - no chance it will go over.
>>>>>>> - Lots of individual counters:  users may publish 100s of
>>>>>>>          APIs to the Gateway, and each API may be consumed by
>>>>>>>          100s or 1000s of users/client.  Depending on configuration
>>>>>>>          of the policy, *each* user/client has a separate limit.
>>>>>>> - Counters need to be created dynamically:  users can
>>>>>>>          add APIs via the Management UI, configure them to add
>>>>>>>          policies (e.g. a Quota policy) and then publish them to
>>>>>>>          a running Gateway, at which point end users can invoke
>>>>>>>          the API through the Gateway, which will use a counter
>>>>>>>          to enforce the Quota.
>>>>>>> - Counter values reset at the end of a time boundary:  for
>>>>>>>          example, at the end of the month the counter value for
>>>>>>>          the example quota above would reset to 0.
>>>>>>> - Don't care (right now) what the counter value is: at the
>>>>>>>          moment we simply need to know if some counter max value
>>>>>>>          has been reached.  In the future we would like to know
>>>>>>>          when a max value is being "approached" (e.g. to notify a
>>>>>>>          user)
>>>>>>> - Should be persistent: it would not be ideal for e.g. per-
>>>>>>>          month quota values to be lost on server restart.
>>>>>>>
>>>>>>> That's all the high level requirements I can think of off the top of my
>>>>>>> head, and after reading all of the current messages in this thread. :)
>>>>>>>
>>>>>>> -Eric
>>>>>>> _______________________________________________
>>>>>>> infinispan-dev mailing list
>>>>>>> infinispan-dev at lists.jboss.org
>>>>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>>>>>>
>>>>>>
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>>>>
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>
> --
> Bela Ban, JGroups lead (http://www.jgroups.org)
>
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