And for a more complex example, here are the events for the "Spaces" in my
app
<https://github.com/jducoeur/Querki/blob/master/querki/scalajvm/app/querki/spaces/SpaceMessagePersistence.scala>
-- basically CRUD-like operations on a roughly object-oriented database.
(Note that these events are specifically designed to be serialized using
the Kryo library, but that's an unusual choice.)
On Sun, Mar 12, 2017 at 3:27 PM, Guido Medina <oxyg...@gmail.com> wrote:
> A concrete example:
>
> Imagining you are doing some accounting and your events are a Json
> representing any particular operation:
>
> 1. {"op":"set", "value":0}
> 2. {"op":"add", "value":20}
> 3. {"op":"substract", "value":20}
>
> Then when you reply the events your account total should be zero.
>
> That's the simplest example I could come up with, basically you store each
> Json event and your actor "knows" what to do with such information when it
> is activated.
>
> HTH,
>
> Guido.
>
> On Sunday, March 12, 2017 at 6:03:31 PM UTC, Justin du coeur wrote:
>>
>> Generally not -- you define the "event" as a serializable data structure
>> that *describes* the transformation to execute, and that gets stored in the
>> event stream. When you reload the Actor, you "replay" those events, and
>> your recovery logic interprets the events to actually change the data. You
>> generally have a function that takes the stream of events and the starting
>> state, and does this interpretation.
>>
>> In principle, I suppose you *could* save the functions themselves as
>> bytecode, but I don't think I've ever heard of anyone doing so, and it
>> seems quite dangerous -- it could fail to load because dependencies had
>> changed, and other such problems. (And it would likely be very bulky and
>> redundant.)
>>
>> On Sun, Mar 12, 2017 at 9:59 AM, kant kodali <kant...@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> What does it mean when someone says we store the event itself rather
>>> than storing the state/data? such that the events can be replayed to store
>>> the state/data. Does it mean storing the functions/transformation itself
>>> (simply put the JVM byte code for the function itself) ?
>>>
>>> Thanks!
>>> kant
>>>
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