Thanks, Masatake Iwasaki.
2332 A comma separated list of the fully-qualified class name of classes
2333 implementing SpanReceiver. The tracing system works by collecting
2334 information in structs called 'Spans'. It is up to you to choose
2335 how you want to receive this information by implementing the
2336 SpanReceiver interface.
I think this description should be something more like "The HTrace SpanReceiver to use for the NameNode, DataNode, and JournalNode." We shouldn't try to explain what spans are... let's just link to the HTrace documentation rather than repeating it here.
2344 A comma separated list of the fully-qualified class name of classes
2345 implementing SpanReceiver. This property is used by DFSClient
2346 for tracing started internally.
I think this description should be something more like "The HTrace SpanReceiver for the HDFS client. You do not need to enable this if your client has been modified to use HTrace." Again, just provide a reference to the HTrace docs.
213 ### Starting tracing spans by configuration for HDFS client
215 You can start tracing spans by setting configuration for HDFS client.
216 This is useful for tracing programs where you don't have access to the source code.
How about, "The DFSClient can enable tracing internally. This allows you to use HTrace with your client without modifying the client source code."