Storm Management and Maintenance - Real-time Analytics with Storm and Cassandra - page 192

Scenario 1
This following figure illustrates a simple topology with three moving components: one
spout and two bolts. Here, all the components are executing on separate nodes in the
cluster, thus every tuple has to do two network hops to complete its execution.
Let's say we are not satisfied with the throughput and decide to increase the parallelism.
The moment we try to move into this technique, the question that arises is where to in-
crease it and by how much. That could be computed based on the capacity of the bolt,
which should be visible from the Storm UI. The following screenshot illustrates this:
Here, the circled value is the capacity of the second bolt, which is around 0.9 and it's
already in red, which means this bolt is over-worked and increasing parallelism here should
help. Any topology would actually break and stop acking when the bolt capacity crosses 1 .
To fix this, let's see the next scenario, which provides a solution for this issue.