PostgreSQL cluster fault tolerance for 1C
By default, a PostgreSQL cloud database cluster for 1C consists of a single master-node. To provide cluster fault tolerance, you need to add replicas to the cluster.
Master node
By default, a cluster consists of one master node, the master. When connected to the master node, all operations are available: read (SELECT) and write (INSERT, UPDATE, DELETE and others).
All data changes on the master node are duplicated on the replicas. The replication process does not affect the operation of replicas and the master node.
Replicas
Replicas are full copies of the master node. They are available only for reading data (SELECT).
The presence of replicas in the cluster ensures its fault tolerance — if the master node stops working, its role will be taken over by one of the replicas and the cluster will continue to operate normally. When the master node is restored, it will take over the role of the replica. The address of the master node will change.
If there are no replicas in the cluster, the cluster will be unavailable until the master node is restored. No data will be lost in the process.
We recommend create fault-tolerant clusters with replicas or add replicas to existing clusters.
Change the number of replicas
You can increase or decrease the number of replicas. When you change the number of replicas, the cluster continues to run.
- In Control Panel, go to Cloud Platform → Databases.
- Open the cluster page → Settings tab.
- Click Scale Cluster.
- Specify the new number of replicas. If there are no free addresses on the subnet to which the cluster is connected, a replica cannot be added — each new replica occupies a new address on the subnet.
- Click Save.