Re: [akka-user] Re: Performant SequenceID Generation

2016-08-02 Thread Patrik Nordwall 
You're welcome

tis 2 aug. 2016 kl. 19:40 skrev Dagny T :

>
> Thank you, Jim and Patrik for your responses!
>
> Looking into the VersionVector.scala.
> Always amazed at what a good source of learning it is to see
> well-structured, code-reviewed Open Source(!)
>
> THANKS again!
> D
>
> On Thursday, July 28, 2016 at 11:23:46 AM UTC-7, Dagny T wrote:
>>
>>
>> So, in the context of async messaging systems where you can't predict the
>> sequencing of incoming messages.
>>
>> Typically, you have in the message (or event) payload:
>> - an Originating Entity Unique ID
>> - then a Version or Sequence ID for each incremental state-change event
>> on that originating entity
>>
>> So, if I need to initialize EntityID Generation, as well as its sub
>> VersionID Generation across a distributed cluster;
>>
>> Does AKKA provide an out-of-box configurable Sequence ID Generator
>> service cluster?
>> Otherwise, how is this typically handled in AKKA, and where can I get
>> sample code which demonstrates this?
>>
>> THANKS!
>> D
>>
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-- 
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[akka-user] Re: Performant SequenceID Generation

2016-08-02 Thread Dagny T 

Thank you, Jim and Patrik for your responses!

Looking into the VersionVector.scala.  
Always amazed at what a good source of learning it is to see 
well-structured, code-reviewed Open Source(!)

THANKS again!
D

On Thursday, July 28, 2016 at 11:23:46 AM UTC-7, Dagny T wrote:
>
>
> So, in the context of async messaging systems where you can't predict the 
> sequencing of incoming messages.
>
> Typically, you have in the message (or event) payload:
> - an Originating Entity Unique ID
> - then a Version or Sequence ID for each incremental state-change event on 
> that originating entity
>
> So, if I need to initialize EntityID Generation, as well as its sub 
> VersionID Generation across a distributed cluster; 
>
> Does AKKA provide an out-of-box configurable Sequence ID Generator service 
> cluster?
> Otherwise, how is this typically handled in AKKA, and where can I get 
> sample code which demonstrates this?
>
> THANKS!
> D
>

-- 
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>>  Check the FAQ: 
>> http://doc.akka.io/docs/akka/current/additional/faq.html
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Re: [akka-user] Re: Performant SequenceID Generation

2016-08-02 Thread Patrik Nordwall 
There is a public version vector implementation in akka-distributed-data,
if that is what you are looking for.
https://github.com/akka/akka/blob/master/akka-distributed-data/src/main/scala/akka/cluster/ddata/VersionVector.scala

/Patrik
fre 29 juli 2016 kl. 05:08 skrev Jim Hazen :

> I think what you're looking for here is called a vector clock.  Akka uses
> them internally within its clustering implementation, however the
> implementation isn't public.
>
> There are some open source scala/java implementations you might want to
> evaluate (Google).  I don't have experience with any of them.
>
> The problem is more annoying than it sounds.  You need a causal sequence
> of events (ie, this mutation happened from observation of state x), not
> just an increasing ID.  Vclocks help with that.  But then your app needs to
> deal with merge conflicts and resolution.  Plus your clients need to be
> vclock aware since you pass the current vclock along with your update.
> There are additional issues with vector clocks as well, but you're asking
> to solve a very complex distributed problem.
>
> The Basho guys (developers of the distributed Riak DB) have some good
> material on vclocks.  They've also apparently moved from vclocks to Dotted
> Version Vectors.
>
> If you want to start down the rabbit hole start here:
>
> http://docs.basho.com/riak/kv/2.1.4/learn/concepts/causal-context/#dotted-version-vectors
>
> If you want to take a look at an implementation (and detailed description
> of how it works) start here (the code is in Erlang, but the conceptual
> diagrams of the algorithm are portable to any lang):
> https://github.com/ricardobcl/Dotted-Version-Vectors
>
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