Configure PostgreSQL¶

Specify the version¶

Set the version in the server’s Pillar file:

postgres:
  version: 15

Enable public access¶

By default, PostgreSQL only allows local connections (see the template for the pg_bha.conf configuration file).

To enable public access, update the server’s Pillar file:

postgres:
  version: 15
  public_access: True

Add users, groups, databases and schemas¶

To configure the database for an application:

Add a user for the application, in a private Pillar file, replacing PASSWORD with a strong password (uncheck Symbols) and USERNAME with a recognizable username:
```
postgres:
  users:
    USERNAME:
      password: "PASSWORD"
```
Create the database for the application, revoke all schema privileges from the public role, and grant all schema privileges to the new user. Replace DATABASE and USERNAME:
```
postgres:
  users:
    USERNAME:
      password: "PASSWORD"
  databases:
    DATABASE:
      user: USERNAME
```

Create a schema, if needed by the application. Replace SCHEMA and OWNER, and change TYPE to user or group:

postgres:
  users:
    USERNAME:
      password: "PASSWORD"
  databases:
    DATABASE:
      user: USERNAME
      schemas:
        SCHEMA:
          name: OWNER
          type: TYPE

Note

If the owner needs to be a group, create the group, replacing NAME:

postgres:
  groups:
    - NAME

If another application needs read-only access to the database, create a group and its privileges, replacing APPLICATION and SCHEMA:

postgres:
  groups:
    - APPLICATION_read
  users:
    USERNAME:
      password: "PASSWORD"
  databases:
    DATABASE:
      user: USERNAME
      privileges:
        SCHEMA:
          APPLICATION_read:

Note

In most cases, the SCHEMA is public, and the DATABASE, APPLICATION and USERNAME are all the same.

Add the private Pillar file to the top file entry for the application.

Note

To delete a PostgreSQL user, follow these instructions.

Configure PostgreSQL¶

Note

Even if you don’t need to configure PostgreSQL, you must still set the following, in order for its SLS file to be automatically included:

postgres:
  configuration: False

Put your configuration template in the salt/postgres/files/conf directory. In most cases, you should use the shared configuration template.
Set postgres.configuration in the server’s Pillar file:
```
postgres:
  configuration:
    name: kingfisher-main1
    source: shared
    context:
      mykey: myvalue
```
The keys of the context mapping are made available as variables in the configuration template.
If you use the shared configuration template, under the context mapping:
- If you need more connections, set max_connections (100, default).
- Set storage to either ssd (solid-state drive, default) or hdd (hard disk drive).
- Set type to either oltp (online transaction processing, default) or dw (data warehouse).
- Set content to add content to the configuration file.
```
postgres:
  configuration:
    name: registry
    source: shared
    context:
      max_connections: 300
      storage: hdd
      type: oltp
      content: |
        max_wal_size = 10GB
```
Set vm.nr_hugepages in the server’s Pillar file, following PostgreSQL’s instructions:
```
vm:
  nr_hugepages: 1234
```
Deploy the service

The configuration file will be in the /etc/postgresql/11/main/conf.d/ directory on the server (for PostgreSQL version 11).

Use CA certificates¶

Note

Only do this if a third-party service requires CA certificates.

Set the hostname for PostgreSQL:

postgres:
  ssl:
    servername: postgres.kingfisher.open-contracting.org

Configure the mod_md Apache module to copy the SSL certificates to PostgreSQL’s directory:

apache:
  public_access: True
  modules:
    mod_md:
      MDMessageCmd: /opt/postgresql-certificates.sh

Acquire the SSL certificates.

Set up backups¶

See also

Restore from backup

pgBackRest is used to create and manage offsite backups.

Create an S3 bucket
Create an IAM user with API keys

See also

pgBackRest sample Amazon S3 policy
Create a *.conf configuration file in the salt/postgres/files/pgbackrest/ directory

Install and configure pgBackRest. Add to your service’s Pillar file, for example:

postgres:
  backup:
    configuration: kingfisher-main1
    # The rest are specific to your configuration file.
    stanza: kingfisher
    retention_full: 4
    repo_path=/kingfisher
    process_max: 4
    cron: |
        MAILTO=root
        # Daily incremental backup
        15 05 * * 0-2,4-6 postgres pgbackrest backup --stanza=kingfisher-2023
        # Weekly full backup
        15 05 * * 3 postgres pgbackrest backup --stanza=kingfisher-2023 --type=full 2>&1 | grep -v "unable to remove file.*We encountered an internal error\. Please try again\.\|expire command encountered 1 error.s., check the log file for details"

See also

Add, in a private Pillar file:

postgres:
  backup:
    s3_bucket: ocp-db-backup
    s3_region: eu-central-1
    s3_endpoint: s3.eu-west-1.amazonaws.com
    s3_key: ...
    s3_key_secret: ...

See also

Amazon S3 regular endpoints

Create the stanza, if it doesn’t exist yet:
```
su -u postgres pgbackrest stanza-create --stanza=example
```
See also

Create the Stanza

Additional steps for replica servers¶

When pgbackrest runs it will try backing up PostgreSQL data from a replica/standby server if any are configured. This is great because it gives us a backup of production while also reducing load during the backup.

Note

You can find the recovery steps here.

SSH into the main server as the postgres user.
Generate an SSH key pair, if one doesn’t already exist:
```
ssh-keygen -t rsa -b 4096
```
Add the public SSH key to the ssh.postgres list in the replica server’s Pillar file:
```
ssh:
  postgres:
    - ssh-rsa AAAB3N...
```
Set postgres.ssh_key in the main server’s private Pillar file to the private SSH key:
```
postgres:
  ssh_key: |
    -----BEGIN RSA PRIVATE KEY-----
    ...
```
Deploy the main server and replica server

Set up replication¶

To configure a main server and a replica server:

Create configuration files for each server, as above. For reference, see the files for kingfisher-main1 and kingfisher-replica1.

Add the replica’s IP addresses to the main server’s Pillar file:

postgres:
  replica_ipv4:
    - 148.251.183.230
  replica_ipv6:
    - 2a01:4f8:211:de::2

Add the replica user to the main server’s private Pillar file:
```
postgres:
  users:
    replica:
      password: example_password
      replication: True
```
You will also need to pass this user to the replica server. This is used to populate the postgresql.conf file via pgbackrest.
```
postgres:
  replication:
    username: replica
    password: example_password
    primary_slot_name: replica1
```
Note

If the replica user’s password is changed, you must manually update the /var/lib/postgresql/11/main/postgresql.conf file on the replica server (for PostgreSQL version 11).
Deploy both servers
Connect to the main server as the root user, and create a replication slot, replacing SLOT with the value of postgres:replication:primary_slot_name.
```
su - postgres
psql -c "SELECT * FROM pg_create_physical_replication_slot('SLOT');"
```
Transfer data and start replication.
1. Connect to the replica server as the root user.
2. Stop the PostgreSQL service and delete the main cluster’s data.
```
systemctl stop postgresql
rm -rf /var/lib/postgresql/11/main
```
3. Switch to the postgres user and transfer PostgreSQL data.
```
su - postgres
mkdir /var/lib/postgresql/11/main
pgbackrest --stanza=example --type=standby restore
```
4. Switch to the root user and start the PostgreSQL service.
```
exit
systemctl start postgresql
```
5. Double-check that the service started:
```
pg_lsclusters
```