Time for action – the third run

Let's validate that assumption by running the algorithm for the third time.

1. Execute the MapReduce job:

   $ hadoop jar graph.jarGraphPathgraphout2graphout3
   

2. Examine the output file:

   $ hadoop fs -cat /user/hadoop/graphout3/part-r-00000
   12,3,40D
   21,41D
   31,5,61D
   41,21D
   53,62D
   63,52D
   76-1P
   

What just happened?

We now see nodes 1 through 6 are complete. But node 7 is still pending and no nodes are currently being processed, as shown in the following figure:

The reason for this state is that though node 7 has a link to node 6, there is no edge in the reverse direction. Node 7 is therefore effectively unreachable from node 1. If we run the algorithm one final time, we should expect to see the graph unchanged.