Use only latest values

[Maria Musterfrau <da...@gmx.at>]

Hi,
 
I would like to cache values and to use only the latest "valid" values to build a sum.
In more detail, I receive values from devices periodically. I would like to add up all the valid values each minute. But not every device sends a new value every minute. And as long as there is no new value the old one should be used for the sum. As soon as I receive a new value from a device I would like to overwrite the old value and to use the new one for the sum. Would that be possible with the combination of Storm and Redis?

My idea was to use the following:

- Kafka Spout
- Storm Bolt for storing the tuples in Redis and for overwriting the values as soon as a new one is delivered
- Storm Bolt for reading the latest tuples from Redis
- Storm Bolt for grouping (I would like to group the devices per region)
- Storm Bolt for aggregation
- Storm Bolt for storing the results again in Redis

Thank you in advance.

Regards,
Daniela