RegionServers do reportForDuty on startup to tell Master they are available. If Master is initializing, and especially on a big cluster when it can take a while particularly if something is amiss, the log every three seconds is annoying and doesn't do anything of use. We should spew less those logs. Here is example:
For example, I am looking at a large cluster now that had a backlog of procedure WALs. It is taking a couple of hours recreating the procedure-state because there are millions of procedures outstanding. Meantime, the Master log is just full of the above message – every three seconds...