[infinispan-dev] Distributed Counter Discussion

[Bela Ban]

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.

> 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
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>>>>>>
>>>>>
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-- 
Bela Ban, JGroups lead (http://www.jgroups.org)