Resolution: Not A Problem
macOS Mojave and High Sierra
MacBook Pro (Retina, 13-inch, Mid 2014)
Oracle Java 1.8.0_144-b01 and previous versions
Inside org.apache.nutch.indexer.IndexerMapReduce.IndexerReducer, the setup() function should read the value of "indexer.delete" from nutch-site.xml, and assign the value to the variable of "delete". See the following line of code.
(line 201) delete = conf.getBoolean(INDEXER_DELETE, false);
However, the value of "indexer.delete" set in nutch-site.xml and nutch-default.xml is not assigned to the variable, "delete". I put the following setting in one of nutch-site.xml and nutch-default.xml, or in both of them. The variable of "delete" remains false.
<description>Whether the indexer will delete documents GONE or REDIRECTS by indexing filters
I also changed the line of code to
delete = conf.getBoolean(INDEXER_DELETE, true);
Whatever value of "indexer.delete" is set in nutch-site.xml or nutch-default.xml, the value of "delete" remains false.