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postgresqlpatroni

Postgres Patroni and etcd on the Same Machine

Assuming I have 2 postgres servers (1 master and 1 slave) and I'm using Patroni for high availability

1) I intend to have three-machine etcd cluster. Is it OK to use the 2 postgres machines also for etcd + another server, or it is preferable to use machines that are not used by Postgres?

2) What are my options of directing the read request to the slave and the write requests to the master without using pgpool?

Thanks!

Solution

    1. yes, it is the best practice to run etcd on the two PostgreSQL machines.

    2. the only safe way to do that is in your application. The application has to be taught to read from one database connection and write to another.

      There is no safe way to distinguish a writing query from a non-writing one; consider

      SELECT delete_some_rows();

      The application also has to be aware that changes will not be visible immediately on the replica.

      Streaming replication is of limited use when it comes to scaling...