Parameters

Etcd is a distributed, reliable key-value store used to store the most critical config/consensus data in the system.

Etcd is used as the DCS used by the HA agent Patroni, which is very important for the high availability of PostgreSQL in Pigsty.

Pigsty use the hard-coded group etcd for etcd cluster, which can be an external etcd cluster, r a new etcd cluster created by Pigsty using the etcd.yml playbook.

Parameters

There are 10 parameters about the ETCD module.

Defaults

The default parameters of Etcd is defined in roles/etcd/defaults/main.yml

#-----------------------------------------------------------------
# etcd
#-----------------------------------------------------------------
#etcd_seq: 1                      # etcd instance identifier, explicitly required
etcd_cluster: etcd                # etcd cluster & group name, etcd by default
etcd_safeguard: false             # prevent purging running etcd instance?
etcd_clean: true                  # purging existing etcd during initialization?
etcd_data: /data/etcd             # etcd data directory, /data/etcd by default
etcd_port: 2379                   # etcd client port, 2379 by default
etcd_peer_port: 2380              # etcd peer port, 2380 by default
etcd_init: new                    # etcd initial cluster state, new or existing
etcd_election_timeout: 1000       # etcd election timeout, 1000ms by default
etcd_heartbeat_interval: 100      # etcd heartbeat interval, 100ms by default

etcd_seq

name: etcd_seq, type: int, level: I

etcd instance identifier, REQUIRED

no default value, you have to specify it explicitly. Here is a 3-node etcd cluster example:

etcd: # dcs service for postgres/patroni ha consensus
  hosts:  # 1 node for testing, 3 or 5 for production
    10.10.10.10: { etcd_seq: 1 }  # etcd_seq required
    10.10.10.11: { etcd_seq: 2 }  # assign from 1 ~ n
    10.10.10.12: { etcd_seq: 3 }  # odd number please
  vars: # cluster level parameter override roles/etcd
    etcd_cluster: etcd  # mark etcd cluster name etcd
    etcd_safeguard: false # safeguard against purging
    etcd_clean: true # purge etcd during init process

etcd_cluster

name: etcd_cluster, type: string, level: C

etcd cluster & group name, etcd by default

default values: etcd, which is a fixed group name, can be useful when you want to use deployed some extra etcd clusters

etcd_safeguard

name: etcd_safeguard, type: bool, level: G/C/A

prevent purging running etcd instance? default value is false

If enabled, running etcd instance will not be purged by etcd.yml playbook.

etcd_clean

name: etcd_clean, type: bool, level: G/C/A

purging existing etcd during initialization? default value is true

If enabled, running etcd instance will be purged by etcd.yml playbook, which makes the playbook fully idempotent.

But if etcd_safeguard is enabled, it will still abort on any running etcd instance.

etcd_data

name: etcd_data, type: path, level: C

etcd data directory, /data/etcd by default

etcd_port

name: etcd_port, type: port, level: C

etcd client port, 2379 by default

etcd_peer_port

name: etcd_peer_port, type: port, level: C

etcd peer port, 2380 by default

etcd_init

name: etcd_init, type: enum, level: C

etcd initial cluster state, new or existing

default values: new, which will create a standalone new etcd cluster.

The value existing is used when trying to add new member to existing etcd cluster.

etcd_election_timeout

name: etcd_election_timeout, type: int, level: C

etcd election timeout, 1000 (ms) by default

etcd_heartbeat_interval

name: etcd_heartbeat_interval, type: int, level: C

etcd heartbeat interval, 100 (ms) by default