Creating a PostgreSQL cluster

PostgreSQL cluster is one or more database hosts that can have replication configured between them. Replication is enabled by default in any cluster consisting of more than one host: the master host accepts write requests, synchronously duplicates changes in the primary replica, and does it asynchronously in all the others.

The number of hosts that can be created together with a PostgreSQL cluster depends on the storage option selected:

  • When using network drives, you can request any number of hosts (from one to the limits of the current quota).
  • When using SSDs, you can create at least three replicas along with the cluster (a minimum of three replicas is required to ensure fault tolerance). If the available folder resources are still sufficient after creating a cluster, you can add extra replicas.

By default, Managed Service for PostgreSQL sets the maximum limit on the number of connections to each PostgreSQL cluster host This maximum is calculated as follows: 200 × <number of vCPUs per host>. For example, for a cluster of the s1.micro class the max_connections default parameter value is 400 and it cannot be increased.

Important

The total number of connections reserved for users must not exceed the value of the parameter max_connections. Keep in mind that Managed Service for PostgreSQL reserves 15 connections for service users per user PostgreSQL host. For example, if the cluster has the setting "max_connections": 100 you can reserve a maximum of 85 connections for cluster users.

How to create a PostgreSQL {#create-cluster} cluster

  1. In the management console, select the folder where you want to create a DB cluster.

  2. Click on Managed Service for PostgreSQL.

  3. Click Create cluster and select the necessary DBMS. Once a cluster is created, you cannot change the DBMS.

  4. Enter the cluster name in the Cluster name field. The cluster name must be unique within the Cloud.

  5. Select the environment where you want to create the cluster (you cannot change the environment after cluster creation):

    • production — for stable versions of your apps.
    • prestable — to perform testing, including that of the Managed Service for PostgreSQL service itself. The prestable environment is updated more often, which means that known problems are fixed sooner in it, but this may cause backward incompatible changes.
  6. Select the DBMS version.

  7. Select the host class that will define the technical specifications of the VMs where the DB hosts will be deployed. For the list of available classes, see the section Host classes. When you change the host class for the cluster, the characteristics of all existing hosts change, too.

  8. In the Storage size section:

    • Select the type of storage, either a more flexible network type (network-hdd or network-nvme) or faster local SSD storage (local-nvme). The size of the local storage can only be changed in increments of 100 GB.
    • Select the size to be used for data and backups. For more information about how backups take up storage space, see Backups.
  9. In the Database section, specify DB attributes:

    • Database name. The DB name must be unique within the folder and contain only Latin letters, numbers, and underscores.
    • The name of the user who is the DB owner. The username may only contain Latin letters, numbers, and underscores. By default, the new user is assigned 50 connections to each host in the cluster.
    • User's password (from 8 to 128 characters).
  10. In the Hosts section, select parameters for database hosts created with the cluster (keep in mind that if you use SSDs when creating PostgreSQL clusters, you can set at least three hosts). If you open the Advanced settings section, you can choose specific subnets for each host. By default, each host is created in a separate subnet.

  11. Click Create cluster.

If you don't have Yandex.Cloud CLI, install it.

The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id flag.

To create a cluster:

  1. See the description of the CLI's create cluster command:

    $ yc managed-postgresql cluster create --help
    
  2. Check whether the folder has any subnets for the cluster hosts:

    $ yc vpc subnet list
    

    If there are no subnets in the folder, create the necessary subnets in the VPC service.

  3. Specify the cluster parameters in the create command (the example shows only mandatory flags):

    $ yc managed-postgresql cluster create \
       --name <cluster name> \
       --environment <prestable or production> \
       --network-name <network name> \
       --host zone-id=<availability zone>,subnet-id=<subnet ID> \
       --resource-preset <host class> \
       --user name=<username>,password=<user password> \
       --database name=<database name>,owner=<database owner name> \
       --disk-type <network-hdd | network-nvme | local-nvme> \
       --disk-size <storage size in GB>
    

    The subnet ID subnet-id should be specified if the selected availability zone contains two or more subnets.

Examples

Creating a single-host cluster

To create a cluster with a single host, you should pass a single parameter, --host.

Let's say we need to create a PostgreSQL cluster with the following characteristics:

  • Named mypg.
  • In the production environment.
  • In the default network.
  • With a single host of the s1.nano class in the b0rcctk2rvtr8efcch64 subnet and the ru-central1-c availability zone.
  • With SSD network storage of 20 GB.
  • With one user (user1) and the password user1user1.
  • With one db1 database owned by the user user1.

Run the command:

$ yc managed-postgresql cluster create \
     --name mypg \
     --environment production \
     --network-name default \
     --resource-preset s1.nano \
     --host zone-id=ru-central1-c,subnet-id=b0rcctk2rvtr8efcch64 \
     --user name=user1,password=user1user1 \
     --database name=db1,owner=user1 \
     --disk-type network-nvme \
     --disk-size 20