[rules-users] Drools and event based decisions, i.e. streaming market quotes

[Mark Proctor]

Henry Canterburry wrote:
> Mark,
>
> Thanks for the reply. My timeframe matches the one you mentioned 
> although I would naturally be looking for working and production ready 
> functionality. In the meantime, did any of the approaches I mentioned 
> make any sense or would you say that drools is not the right tool at 
> this point? I do have helper classes and other intermediary data 
> caching approaches at this time that permit me to query past data and 
> an entire streaming architecture to feed data.
>
> Thanks
> HC
>
>
> Mark Proctor wrote:
>> What's your time scale for this? We are currently implementing CEP 
>> extendions to the language and engine which will do all of this for 
>> you, we'll have a milestone release out in february when you can 
>> first play with this and aiming to get a full release end of Q1 start 
>> of Q2.
>>
>> Mark
>> Henry Canterburry wrote:
>>> What would be the best approach using drools to handle event driven 
>>> decisions based on streaming data? In my case I am looking for a 
>>> typical stock market scenario. Ticker quotes usually come in at 
>>> second increments and depending on how many ticker symbols you 
>>> subscribe to at any one time, there can be a lot of data coming and 
>>> and changing every second. However, there probably isn't a need to 
>>> keep large quantities of historic data in memory...maybe the last 
>>> 200-500 ticks. The outputs are if a stock should be sold or bought, 
>>> at what quantity and what price. Once the decision has been made, we 
>>> need to make sure it does not persist past the point of being valid 
>>> given the state of that data.
>>>
>>> If I have rules that are meant to derive/calculate info and 
>>> decisions from the streaming data, what is the best integration 
>>> architecture for the rule engine with the rest of the application?
>>>
>>> Stateful session which constantly updates the ticks in working 
>>> memory and queries the memory for results on an ongoing basis? In 
>>> this case, the session would be kept alive for as long as the data 
>>> stream is going (i.e. hours)? This approach would require very 
>>> rigorous working memory management and all the objects in it.
>>>
>>> Or...loop constantly over a stateless session for each tick? This 
>>> would reduce the need to manage the number of objects in working 
>>> memory since only the amount needed would be inserted in the first 
>>> place and read back the results? Sounds inefficient and with lots of 
>>> overhead.
really don't know. Try the stateful approach first and see how that pans 
out.
>>>
>>> Also, what about multi-threaded environments? Any potential for 
>>> conflicts between concurrent session instances?
events are normally stateless, so you should have no problem there. 
Mutable objects in different threads being updated is of course a 
problem, shadow proxies can help a little there - but you still need to 
be careful.
>>>
>>> Thanks
>>> HC
>>>
>>>
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>>>
>>
>>
>
>