In my previous company we developed a rules engine/CEP based on Hadoop. I don't remember the reasons why but we discarded Drool (the other existing software in the market did not match our need neither). Hive was definitely not an option because it had too much latencies (take care about those last 2 sentences: those design decisions were made 3 years ago, lot of things have changed since and you might reconsider those choices). The 1st implementation of the CEP was done using MapReduce and HBase (to maintain the states). The rules where loaded from a MySQL database and applied by the MapReduce job. Since we still had some latencies (due to MR), we started to move the code to Spark (streaming), still keeping HBase as a backend. Using HBase coprocessors was also an idea. Can't say much because I left the company before seeing that change in production. The front-end was web-graphical-drag&drop, so it allowed the user to quickly implement the business logic without our help. I'm not sure my answer is exactly what you were looking for. If you find some good opensource CEP projects that suit you, please let me know. I still feel curious about it.
... View more
