question Re: How do Zookeeper save HBase Column and Column Family metadata in Znode? in Archives of Support Questions (Read Only)

How do Zookeeper save HBase Column and Column Family metadata in Znode?

xiaqinglinv5 — Wed, 30 Nov 2016 18:19:31 GMT

I am trying to write a zookeeper watcher to monitor hbase column family and hbase column modification.

I know Hbase table is saved as a znode under the /table znode, but I did not get much info about how do zookeeper save the metadata of hbase column family and hbase column, so How can I get notified when there is any modification in hbase column family or hbase columns ?

Re: How do Zookeeper save HBase Column and Column Family metadata in Znode?

asinghal — Wed, 30 Nov 2016 18:28:24 GMT

Table metadata is stored as table descriptor in the corresponding table directory and is read and altered there itself. I don't think that we have any znode where we keep the information of columnfamily during alter or create table.

Re: How do Zookeeper save HBase Column and Column Family metadata in Znode?

xiaqinglinv5 — Wed, 30 Nov 2016 18:58:32 GMT

Where is that table directory? Is it also in Zookeeper？

Re: How do Zookeeper save HBase Column and Column Family metadata in Znode?

asinghal — Wed, 30 Nov 2016 19:05:16 GMT

it is in hdfs and if you are using HDP then it may be under /apps/hbase/data/data/<namespace>/<tableName>/.tabledesc/

Re: How do Zookeeper save HBase Column and Column Family metadata in Znode?

Enis — Thu, 01 Dec 2016 03:38:12 GMT

The best way to observe and run custom logic when a table is modified would be to write a master coprocessor. Your MasterObserver will be called before and after any table is modified (see https://hbase.apache.org/book.html#cp).

However, unlike column families, columns in HBase are not predefined. So you cannot observe column changes since there is no fixed "schema". Please read up on the HBase data model.

Re: How do Zookeeper save HBase Column and Column Family metadata in Znode?

xiaqinglinv5 — Thu, 01 Dec 2016 16:18:53 GMT

Thanks I think that solves my problem, I used to use the Zookeeper watcher but it can only get the hbase table modification.