HBase fixing region missing Region //regionname// on HDFS but not listed in .META or deployed on any server

If you see this error on HBase

Region //regionname// on HDFS but not listed in .META or deployed on any server

then use the add_regions.rb script to have this fixed. 

Normally hbase errors can be fixed by hbase hbck -fix
But this approach works mostly in cases where the region is listed in .META but not assigned etc.

In such cases, the script add_regions.rb comes to our rescue. It can be used as follows:

hbase org.jruby.Main add_regions.rb //full-path-region-on-HDFS/.regioninfo

This will add the region to the .META. table. Next assign the region to a region-server. To do this , launch hbase shell and issue the command

assign 'full-region-name'

on the hbase shell.

The full region-name includes the standard format tablename.startrowkey.timestamp.md5sum.

The dot at the end is important and should be included while passing to the assign command.

Now run hbase hbck again and look at status 'simple' on the shell. Your region numbers should have increased according to the regions you have added now. The errors related to not listed in .META should be gone now.

Moving Hbase heap dump locations

Occasionally HBase can generate heap dumps on OOM and put it in the bin folder (which is default). This can cause quite a lot of issues, if the system partitioning is not prepared for huge gigabyte files in the bin folder for hbase. To move the dump cores to another folder ,

Do this in the file  hbase-ver-conf/hbase-env.sh, add  -XX:HeapDumpPath=/path/to/dump to the line

>> export HBASE_OPTS="$HBASE_OPTS -XX:+HeapDumpOnOutOfMemoryError $HBASE_GC"

Restart HBase.

Now you can sleep well without fears of heap dumps filling up the hbase binary partitions :)