Cassandra
--------------------------
.. include:: includes/intro.rst
This section only covers the bare minimum, for more information, see the `cassandra
documentation `__
How to see cluster health
~~~~~~~~~~~~~~~~~~~~~~~~~~
You want to see ``UN`` (``Up`` & ``Normal``) everywhere:
.. code:: sh
nodetool status
How to inspect tables and data manually
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.. code:: sh
cqlsh
# from the cqlsh shell
describe keyspaces
use ;
describe tables;
select * from WHERE = LIMIT 10;
How to rolling-restart a cassandra cluster
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For maintenance you may need to restart the cluster.
On each server one by one:
1. check your cluster is healthy: ``nodetool status``
2. ``nodetool drain && systemctl stop cassandra`` (to stop accepting writes and flush data to disk; then stop the process)
3. do any operation you need, if any
4. Start the cassandra daemon process: ``systemctl start cassandra``
5. Wait for your cluster to be healthy again.
6. Do the same on the next server.