As the data keeps growing, the HBase cluster may become unbalanced due to poorly designed table schema or row keys, or for some other reasons. Many requests may go to a small part of the regions of a table. This is usually called the hot spot region issue.
There are two types of hot spot region issues—hot write and hot read issues. Hot write is generally more important for us, because hot read would benefit greatly from the HBase internal cache mechanism. A solution for the hot write region issue is to find out the hot regions, split them manually, and then distribute the split regions to other region servers.
An HBase edit will firstly be written to the region server's Write-ahead-Log (WAL) . The actual update to the table data occurs once the WAL is successfully appended. This architecture makes it possible to get an approximate write diagnosis easily.
We will create a WriteDiagnosis.java Java source to get write diagnostic information from WAL, in this...
