Clickhouse tables frequently goes into read-only mode

[Csingh Singh]

Hi all

Following is my Clickhouse details

clickhouse-server: 20.12.4 revision 54442 

Number of replicas: 2

Number of shards : 2

I am facing a problem in which Clickhouse frequently turns into read-only mode. It happens for both the instances of Clickhouse

Following workaround does not work:

 1. sudo -u clickhouse touch /var/lib/clickhouse/flags/force_restore_data

 2. Restart the server

system.replicas table shows "is_readonly" flag true.

How I can remove the is_readonly = 1 to 0 , so that insertion in table can work as usual.

Or if there is any way to make the tables writable.

Thanks

[tatiana....@lifestreet.com]

Replicated tables go readonly when ClickHouse loses its connection to ZooKeeper.

They recover automatically when the connection is restored.

You need to improve connectivity with ZooKeeper.

[francesco pinta]

Hi all,

I have the same problem and there is no connectivity problem to zookeeper (is on the same server).

I have two nodes, and, when one of these crashes and come back up, the replication stop working and I don't find a way to re-establishing replication.

It appens every reboot of the node, and I haven't find a procedure to solve the issues (apart to rebuild the cluster!)

Finally, I think clickhouse is not fault tolerant!

Regards.

Francesco

[Derek Chia]

Very likely this is due to connectivity issues with ZooKeeper. Also, 20.12.4 is long deprecated, please update to a recent version.