Hi all,

I'm currently working on a Flink Application where I match events against a set of rules. At the beginning I wanted to dynamically create streams following the category of events (Event are JSON formatted and I've a field like "category":"foo" in each event) but I'm stuck by the impossibility to create streams at runtime.

So, one of the solution for me is to create a single Kafka topic and then use the "KeyBy" operator to match events with "category":"foo" against rules also containing "category":"foo" in rule specification. 

Now I have some cases where events and rules have one category and one subcategory. At this point I'm not sure about the "KeyBy" operator behavior.

Example :
  • Events have : "category":"foo" AND "subcategory":"bar"
  • Rule1 specification has : "category":"foo" AND "subcategory":"bar"   
  • Rule2 specification has : "category':"foo"
  • Rule3 specification has : "category":"bar"
In this case, my events need to be match against Rule1, Rule2 and Rule3. 

If I'm right, if I apply a multiple key "KeyBy()" with "category" and "subcategory" fields and then apply two single key "KeyBy()" with "category" field, my events will be consumed by the first "KeyBy()" operator and no events will be streamed in the operators after ? 

Is there any way to process the same stream one time for multi key KeyBy() and another time for single key KeyBy() ? 

Thanks !
Sébastien.