Listar réplicas / nós do cluster

Oracle

-- Standby destinations:
SELECT dest_id, destination, status, target
FROM v$archive_dest
WHERE status <> 'INACTIVE';
-- RAC instances: SELECT inst_id, instance_name, status FROM gv$instance;

A configuração do Data Guard também pode ser vista com DGMGRL> SHOW CONFIGURATION.

PostgreSQL

SELECT application_name, client_addr, state, sync_state
FROM pg_stat_replication;

Lista as réplicas conectadas apenas no PRIMARY; cada linha é um standby.

MySQL

SHOW REPLICAS;
-- Before 8.0.22: SHOW SLAVE HOSTS;

Execute no servidor de origem; mostra as réplicas que têm report-host definido. SHOW SLAVE HOSTS é um alias no 8.0.22–8.3 e foi removido no 8.4.

SQL Server

SELECT ar.replica_server_name, ars.role_desc,
       ars.connected_state_desc, ars.synchronization_health_desc
FROM sys.dm_hadr_availability_replica_states ars
JOIN sys.availability_replicas ar ON ars.replica_id = ar.replica_id;

role_desc distingue PRIMARY/SECONDARY; synchronization_health_desc fornece a saúde geral.

MongoDB

rs.status().members.map(m => ({ name: m.name, state: m.stateStr, health: m.health }))

stateStr retorna PRIMARY/SECONDARY/ARBITER; health 1 significa saudável.

Redis

INFO replication
# If Sentinel is used:
# SENTINEL replicas <master-name>

As linhas slave0, slave1... fornecem ip/port/offset de cada réplica.