The replication.mode sync-all option allow to create or convert all cluster members as synchronous replicas. As indicated in the CRD reference the synchronous replicas are not tightly coupled to the leader since Patroni will turn off synchronous replication if no more replicas are avaible.
Setting up such an option is quite simple as all the provided options. Look that the number of syncIntances is set to 1 intentionally to demonstrate that sync-all overrides the syncIntances variable.
cat << EOF | kubectl apply -f -
apiVersion: stackgres.io/v1
kind: SGCluster
metadata:
namespace: failover
name: sync-cluster
spec:
postgres:
version: '16.1'
instances: 4
sgInstanceProfile: 'size-s'
pods:
persistentVolume:
size: '10Gi'
configurations:
sgPostgresConfig: 'pgconfig1'
sgPoolingConfig: 'poolconfig1'
prometheusAutobind: true
nonProductionOptions:
disableClusterPodAntiAffinity: true
replication:
mode: sync-all
role: ha-read
syncInstances: 1
EOF
$ kubectl -n failover exec -it sync-cluster-0 -c patroni -- patronictl list
+ Cluster: sync-cluster (7373750354182599290) -----+-----------+----+-----------+
| Member | Host | Role | State | TL | Lag in MB |
+----------------+------------------+--------------+-----------+----+-----------+
| sync-cluster-0 | 10.244.0.11:7433 | Leader | running | 2 | |
| sync-cluster-1 | 10.244.0.10:7433 | Sync Standby | streaming | 2 | 0 |
| sync-cluster-2 | 10.244.0.4:7433 | Sync Standby | streaming | 2 | 0 |
| sync-cluster-3 | 10.244.0.8:7433 | Sync Standby | streaming | 2 | 0 |
+----------------+------------------+--------------+-----------+----+-----------+
``