setup_coldfront_db

The setup_coldfront_db role creates the role, database and extensions ColdFront needs on a pgEdge Distributed Postgres node, where coldfront_enabled is set. It runs after Postgres is configured and before setup_pgedge, so that in mesh mode the extensions exist before the database joins Spock.

The role performs the following tasks on inventory hosts:

• Ask Postgres whether this node is a standby and which libraries it has loaded, retrying while a replica is still coming up.
• Check that Postgres has loaded pg_duckdb and coldfront, and stop with the reason if it has not.
• Create coldfront_duckdb_role, the NOLOGIN role pg_duckdb gates DuckDB execution on.
• Create coldfront_db, the database ColdFront's tiered storage lives in.
• Create the pg_duckdb and coldfront extensions in coldfront_db, with dblink as well in mesh mode.

Role Dependencies

This role requires the following roles for normal operation:

• role_config provides shared configuration variables to the role.
• install_coldfront installs the ColdFront packages.
• setup_postgres, or setup_patroni on an HA cluster, writes ColdFront's libraries and settings into the Postgres configuration and restarts Postgres to load them.

When to Use

Execute this role on the pgedge group where coldfront_enabled is set, after setup_postgres on a simple cluster or setup_patroni on an HA cluster, and before setup_pgedge.

In the following example, the playbook creates ColdFront's objects on a simple cluster:

- hosts: pgedge
  collections:
    - pgedge.platform
  roles:
    - install_pgedge
    - role: install_coldfront
      when: coldfront_enabled | bool
    - setup_postgres
    - role: setup_coldfront_db
      when: coldfront_enabled | bool
    - setup_pgedge
    - role: setup_coldfront
      when: coldfront_enabled | bool

Configuration

This role uses the following parameters from the inventory file:

See the ColdFront Configuration reference for descriptions and defaults.

How It Works

Loaded libraries

Creating ColdFront's extensions needs its libraries loaded, and Postgres loads them only when it starts. setup_postgres and setup_patroni restart Postgres to load them only where pg_allow_restart allows. Where a restart was held back, the role stops before CREATE EXTENSION and says so; restart Postgres, then run the role again.

Mesh mode

In mesh mode coldfront_db is one of db_names, which setup_pgedge puts into Spock. Spock replicates a CREATE EXTENSION issued once a database has a Spock node to the other nodes, which create the extension themselves, so the role creates every extension before setup_pgedge runs, as upstream's mesh setup does.

Under HA

The role runs on each zone's leader only, and the replicas receive its results through physical replication. After a failover the leader need not be first_node_in_zone, so each node asks its own Postgres whether it is a standby.

Idempotency

This role is idempotent and safe to re-run on inventory hosts. The role, database and extensions are created only where they do not exist, and the role writes no configuration and restarts nothing.