Storm in a Clustered Mode - Real-time Analytics with Storm and Cassandra - page 79

• Topology Name : This is specified when submitting the topology. You can refer to
the WordCountTopology.java file, which we created earlier. The following
snippet, word-count , is the name of that topology:
cluster.submitTopology ("word-count", conf,
builder.createTopology());
In our preceding sample screenshot, AAA-topology-1407803669812 is the name
of the topology.
• ID : This is the Storm-generated unique ID that is a combination of the topology
name, timestamp, and ID, which is used by Storm to identify and differentiate the
topology.
• Status : This denotes the state of the topology, which could be active for a live to-
pology, killed when a topology is killed using the UI or CLI, inactive for a deac-
tivated topology, and rebalancing for a topology where the rebalance command is
executed wherein the number of workers allocated to the topology is increased or
decreased.
• Uptime : As the name suggests, this mentions the duration for which the topology
has been running. For example, our sample topology has been running for 8 days
15 hours 6 months 16 seconds.
• Num workers : This specifies how many workers are allocated to the topology.
Again, if we refer to WordCountTopology.java , we will see this snippet
where it is declared as 3 :
conf.setNumWorkers( 3 );
• Num executors : This specifies the sum total of the number of executors in the to-
pology. This is connected to the parallelism hint that is specified during the over-
all integration of the topology in the topology builder as follows:
builder.setSpout("spout", new RandomSentenceSpout(),
5 );
Here, in our WordCount topology, we have specified the parallelism of the
spout as 5 , so five instances of the spout will be spawned in the topology.
• Num tasks : This gains the sum total of another parameter that is specified at the
time of overall integration in the topology, as shown:
builder.setSpout("spout", new RandomSentenceSpout(),
5). setNumTasks(10) ;