description about topology:
spout continuously sends tuple to read bolt.
read bolt processes and send the result to next bolt and so on.
situation:
1 spout sends tuple 1 to read bolt
2 read bolt gives tuple 1 to write bolt
3 write bolt gives tuple 1 to R bolt
4 R bolt processes tuple 1
when tuple 2 sends from spout?
after processing tuple 1 in R bolt or after readbolt sends tuple1 to write bolt?
