How do you promote a replica in Postgres?

To promote a replica in PostgreSQL, you need to perform the following steps:

  1. On the standby server, shut down the PostgreSQL service using the appropriate command for your operating system. For example, on Linux you can use the systemctl command like this:
sudo systemctl stop postgresql
  1. Move or rename the recovery.conf file on the standby server. This file contains the configuration for the standby server, and it needs to be removed or renamed to prevent the standby server from trying to reconnect to the master server when it is restarted.
  2. Start the PostgreSQL service on the standby server. This will start the standby server as a standalone server, without the replication configuration.
  3. Connect to the standby server using a PostgreSQL client, such as psql, and run the following query to promote the standby server to a master server:
SELECT pg_promote();

This will perform the necessary actions to promote the standby server to a master server, such as updating the internal state of the server and removing the replication-related files and settings.

  1. Once the promotion is successful, you can reconfigure the other replicas to connect to the new master server and start replicating from it.

Note that these are the basic steps for promoting a replica in PostgreSQL. There are many other factors to consider and configure, such as security, performance, and monitoring, to ensure that your replication setup is reliable and efficient. It is recommended to consult the PostgreSQL documentation and other resources to learn more about the details and best practices for promoting a replica in PostgreSQL.

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