The following sections provide steps to configure your AlloyDB Omni primary server for replication, configure the replica server, and verify replication status on the primary server.
For details, see Install AlloyDB Omni on Kubernetes .
Configure your primary server for replication
-
Update the network or firewall settings of your primary server's host so that it allows ingress traffic from the replica server's host through the primary server's Postgres port .
-
Create a replication user:
Docker
docker exec CONTAINER_NAME psql -h localhost -U postgres -c "create user REPLICA_USER with replication password ' PASSWORD '"Replace the following:
-
REPLICA_USER: the name of the replica user. -
PASSWORD: the password for the replica user. -
CONTAINER_NAME: the name that you assigned to the AlloyDB Omni container when you installed it.
Podman
podman exec CONTAINER_NAME psql -h localhost -U postgres -c "create user REPLICA_USER with replication password ' PASSWORD '"Replace the following:
-
REPLICA_USER: the name of the replica user. -
PASSWORD: the password for the replica user. -
CONTAINER_NAME: the name that you assigned to the AlloyDB Omni container when you installed it.
-
-
Add the following lines in the
/ DATA_DIR /pg_hba.conffile of the primary server beforehost all all all scram-sha-256that exists in the file:host alloydbmetadata alloydbmetadata IP_RANGE trust host replication REPLICA_USER IP_RANGE scram-sha-256Replace the following:
-
IP_RANGE: the IP range, in CIDR notation, of the subnet where your replica machine is located. For example,203.0.113.0/24. -
DATA_DIR: the data directory path of the primary server.
-
-
Restart your primary server:
Docker
docker restart CONTAINER_NAMEPodman
podman restart CONTAINER_NAME
Create and configure the replica server
To create and configure an AlloyDB Omni replica server, complete the following steps:
-
Ensure the replica has network connectivity to the primary server:
ping SOURCE_IPReplace
SOURCE_IPwith the IP address of the primary AlloyDB Omni instance to replicate from. -
Ensure the replica can connect to the primary server:
Docker
docker run -it --rm google/alloydbomni psql "host= SOURCE_IP user= REPLICA_USER replication=1" -c "IDENTIFY_SYSTEM;"Podman
podman run -it --rm google/alloydbomni psql "host= SOURCE_IP user= REPLICA_USER replication=1" -c "IDENTIFY_SYSTEM;"The output should look similar to the following:
systemid | timeline | xlogpos | dbname ---------------------+----------+-----------+-------- 7376500460465963036 | 1 | 0/454B670 | (1 row) -
The replica must have a persistent storage location on disk:
Docker
mkdir alloydb && docker run --rm -it \ -e PGDATA = /var/lib/postgresql/data/pgdata \ -v " $PWD /alloydb" :/var/lib/postgresql/data \ -p 5432 :5432 \ --user $( id -u ) : $( id -g ) \ google/alloydbomni \ /usr/lib/postgresql/15/bin/pg_basebackup \ --pgdata = /var/lib/postgresql/data/pgdata \ --checkpoint = fast \ --host = " SOURCE_IP " \ --port = " SOURCE_PORT " \ --username = REPLICA_USER \ --create-slot \ --write-recovery-conf \ --slot = " SLOT_NAME "Replace the following:
-
SOURCE_PORT: the TCP port of the primary AlloyDB Omni instance to replicate from. If you don't provide this value, then AlloyDB Omni applies a default value of5432. -
SLOT_NAME: the label for the name of the replication slot.
Podman
mkdir alloydb && podman run --rm -it \ -e PGDATA = /var/lib/postgresql/data/pgdata \ -v " $PWD /alloydb" :/var/lib/postgresql/data \ -p 5432 :5432 \ --user $( id -u ) : $( id -g ) \ google/alloydbomni \ /usr/lib/postgresql/15/bin/pg_basebackup \ --pgdata = /var/lib/postgresql/data/pgdata \ --checkpoint = fast \ --host = " SOURCE_IP " \ --port = " SOURCE_PORT " \ --username = REPLICA_USER \ --create-slot \ --write-recovery-conf \ --slot = " SLOT_NAME "Replace the following:
-
SOURCE_PORT: the TCP port of the primary AlloyDB Omni instance to replicate from. If you don't provide this value, then AlloyDB Omni applies a default value of5432. -
SLOT_NAME: the label for the name of the replication slot.
-
-
Start your replica instance:
Docker
docker run --detach \ --name pg-service \ -e POSTGRES_PASSWORD = a \ -e PGDATA = /var/lib/postgresql/data/pgdata \ -v " $PWD /alloydb" :/var/lib/postgresql/data \ -v /dev/shm:/dev/shm \ -p 5432 :5432 \ --user $( id -u ) : $( id -g ) \ google/alloydbomniPodman
podman run --detach \ --name pg-service \ -e POSTGRES_PASSWORD = a \ -e PGDATA = /var/lib/postgresql/data/pgdata \ -v " $PWD /alloydb" :/var/lib/postgresql/data \ -v /dev/shm:/dev/shm \ -p 5432 :5432 \ --user $( id -u ) : $( id -g ) \ google/alloydbomni
Verify replication status on the primary server
To verify replication is configured properly, run the following command on the primary server's host:
Docker
docker
exec
-it
CONTAINER_NAME
psql
-h
localhost
-U
postgres
-c
"select * from pg_stat_replication"
Podman
podman
exec
-it
CONTAINER_NAME
psql
-h
localhost
-U
postgres
-c
"select * from pg_stat_replication"
The output table contains one row for every replica connected to your primary database server.
After you set up replication, all inserts, updates, and deletions to rows in your primary database server become readable on your replica within seconds.
