Bolt-B accumulates tuples that Bolt A sends and needs to know when Spout finished emitting. Only then can Bolt-B start writing to SQL.
- From Bolt-A to Bolt-B, it is a FieldsGrouping.
- Spout emits only a few tuples and then stops emitting.
- Bolt A takes those tuples and generates millions of tuples.
1. How can all Bolts B be notified that it is time to write to SQL?
2. After all Bolts B have written to SQL, how to know that all Bolts B have completed writing?
3. How to stop the topology? I know of localCluster.killTopology("HelloStorm"), but shouldn't there be a way to do it from the Bolt?