install_etcd

The install_etcd role installs etcd, a distributed key-value store that Patroni uses for consensus and leader election in high availability Postgres clusters.

The role performs the following tasks on inventory hosts:

Install the etcd package from the pgEdge repository.
Create the etcd system user and data directory.
Register the etcd systemd service without starting it.

The etcd service is not started by this role. The setup_etcd role handles cluster configuration and service startup.

Role Dependencies

This role requires the following role for normal operation:

role_config provides shared configuration variables to the role.

When to Use

Execute this role on pgedge hosts in high availability configurations before configuring Patroni. Only high availability deployments need this role; set is_ha_cluster to true to enable HA mode.

In the following example, the playbook installs etcd as part of a high availability cluster deployment:

- hosts: pgedge
  collections:
    - pgedge.platform
  roles:
    - install_etcd
    - install_patroni

Configuration

This role uses the following parameters from the inventory file:

Parameter	Use Case
`etcd_user`	Specify the system user that runs etcd.
`etcd_group`	Specify the system group for etcd.
`etcd_data_dir`	Set the directory for etcd database storage.
`etcd_config_dir`	Set the directory for etcd configuration files.

See the Configuration Reference for defaults.

How It Works

The role installs etcd from the pgEdge package repository and prepares the service for later configuration.

Install the etcd package from the pgEdge repository using the system package manager (APT or DNF).
Create the etcd_user system account and the data directory.
Register the etcd systemd service unit without starting it.

Usage Examples

In the following example, the playbook installs etcd using default settings:

- hosts: pgedge
  collections:
    - pgedge.platform
  roles:
    - install_etcd

In the following example, the playbook specifies custom paths for etcd:

- hosts: pgedge
  collections:
    - pgedge.platform
  vars:
    etcd_data_dir: /data/etcd
    etcd_config_dir: /opt/etcd/config
  roles:
    - install_etcd

Artifacts

This role creates the following files on inventory hosts:

File	New / Modified	Explanation
`/etc/systemd/system/etcd.service`	New	Systemd service unit for etcd.
`{{ etcd_config_dir }}/`	New	Configuration directory for etcd settings.
`{{ etcd_data_dir }}/`	New	Data directory for etcd database storage.

Platform-Specific Behavior

On Debian-based systems, the role uses APT to install the etcd package. On RHEL-based systems, the role uses DNF. The etcd binaries are installed to system paths in both cases.

Idempotency

This role is idempotent and safe to re-run on inventory hosts. The role skips user creation and package installation when the targets already exist.