Replica Re-initialization

Performing a re-initialization of a Replica

Re-initialization of a Replica have to be performed when Postgres is not able to catch-up with the primary database and Patroni is not capable of recovering it automatically. The re-initialization of a Replica allows you to copy its data from scratch directly from the primary and recover it completely.

To perform this we will use the patronictl reinit command:

As we can see in the cluster status shown before the primary node is the one called stackgres-0 with the leader role and we going to reinit the node called stackgres-1 so we run:

bash-4.4$ patronictl switchover stackgres

Then this show us the current status and we will be asked for the replica node (note that the command already give us the replica node name):

+ Cluster: stackgres -------------+---------+---------+----+-----------+
| Member       | Host             | Role    | State   | TL | Lag in MB |
+--------------+------------------+---------+---------+----+-----------+
| stackgres-0  | 10.244.0.23:7433 | Leader  | running |  2 |           |
| stackgres-1  | 10.244.0.22:7433 | Replica | running |  2 |         0 |
+--------------+------------------+---------+---------+----+-----------+
Which member do you want to reinitialize [stackgres-1]? []:

And as a final question and warning asks if we want to proceed with the change:

Are you sure you want to reinitialize members stackgres-1? [y/N]:

After accept the change Patroni will output the operation status:

Success: reinitialize for member stackgres-1

The old replica node stackgres-1 will be stopped and then re-joined to the cluster.

bash-4.4$ patronictl list
+ Cluster: stackgres -------------+---------+---------+----+-----------+
| Member       | Host             | Role    | State   | TL | Lag in MB |
+--------------+------------------+---------+---------+----+-----------+
| stackgres-0  | 10.244.0.23:7433 | Leader  | running |  2 |           |
| stackgres-1  | 10.244.0.22:7433 | Replica | running |  2 |         0 |
+--------------+------------------+---------+---------+----+-----------+

IMPORTANT NOTE: We strongly recommend to not manipulate the cluster with any other patronictl to avoid data lost or damage the entire configuration. Use the command explained above only if you know what are you doing.