added initial setup of replicas

files/postgres/replica/replica_config.conf

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+# If the instance is lower capacity than r5.xlarge, then set it to a lower number.
+# Also tune the "MaxOpenConns" setting under the "SqlSettings" of the Mattermost app accordingly.
+# Note that "MaxOpenConns" on Mattermost is per data source name.
+max_connections = 1024
+
+# Set it to 1.1, unless the DB is using spinning disks.
+random_page_cost = 1.1
+
+# This should be 32MB if using read replicas, or 16MB if using a single PostgreSQL instance.
+# If the instance is of a lower capacity than r5.xlarge, then set it to a lower number.
+work_mem = 16MB
+
+# Set both of the below settings to 65% of total memory. For a 32 GB instance, it should be 21 GB.
+# If on a smaller server, set this to 20% or less total RAM.
+# ex: 512MB would work for a 4GB RAM server
+shared_buffers = 512MB
+effective_cache_size = 512MB
+
+# If you are using pgbouncer, or any similar connection pooling proxy,
+# in front of your DB, then apply the keepalive settings to the proxy instead,
+# and revert the keepalive settings for the DB back to defaults.
+tcp_keepalives_idle = 5
+tcp_keepalives_interval = 1
+tcp_keepalives_count = 5
+
+# 1GB (reduce this to 512MB if your server has less than 32GB of RAM)
+maintenance_work_mem = 512MB
+
+autovacuum_max_workers = 4
+autovacuum_vacuum_cost_limit = 500
+
+## Intentionally disabled here because running in docker this may cause performance problems.
+
+# If you have more than 32 CPUs on your database server, please set the following options to utilize more CPU for your server:
+# max_worker_processes = 12
+# max_parallel_workers_per_gather = 4
+# max_parallel_workers = 12
+# max_parallel_maintenance_workers = 4
+
+
+# If the instance is lower capacity than r5.xlarge, then set it to a lower number.
+# Also tune the "MaxOpenConns" setting under the "SqlSettings" of the Mattermost app accordingly.
+# Note that "MaxOpenConns" on Mattermost is per data source name.
+max_connections = 1024
+
+# This setting should be 16MB on read nodes, and 32MB on writer nodes
+work_mem = 16MB
+
+# The below settings allow the reader to return query results even when the primary has a write process running, a query conflict.
+# This is set to on because of the high volume of write traffic that can prevent the reader from returning query results within the timeout.
+# https://www.postgresql.org/docs/current/hot-standby.html#HOT-STANDBY-CONFLICT
+hot_standby = on
+hot_standby_feedback = on
+
+# connection string to sending server
+# This was created when you added a replication role to the primary database.
+# username - replace "test" with the role you made
+# password - replace "testpassword" with the role password
+# host - replace "x.x.x.x" with your IP or URL string.
+primary_conninfo = 'host=cs-repro-postgres port=5432 user=replicauser password=replicauser_password'
+
+log_connections = on
+log_disconnections = on
+log_replication_commands = on