[pgpool-general: 8511] PgPool showing node as down but it's up

[shacky]

Hi,
I have a 3-nodes PgPool 4.2.10 cluster connected to a 3-nodes PostgreSQL
12.13 cluster.
I am in streaming replication mode, the streaming replication is actually
working well without any errors.

Suddenly PgPool began to recognise the node_id 2 as down, but it is up and
running and reachable from the PgPool node itself:
=================================================================
bash-4.4$ psql -h 127.0.0.1 -p 5432 -U pgpool -c "show pool_nodes;" postgres
 node_id |       hostname        | port | status | lb_weight |  role   |
select_cnt | load_balance_node | replication_delay | replication_state |
repl
ication_sync_state | last_status_change
---------+-----------------------+------+--------+-----------+---------+------------+-------------------+-------------------+-------------------+-----
-------------------+---------------------
 0       | postgres1.my.domain.com | 5432 | up     | 0.333333  | primary |
2801705    | true              | 0                 |                   |

                   | 2022-12-06 20:28:45
 1       | postgres2.my.domain.com | 5432 | up     | 0.333333  | standby |
0          | false             | 0                 |                   |

                   | 2022-12-06 20:28:45
 2       | postgres3.my.domain.com | 5432 | down   | 0.333333  | standby |
0          | false             | 0                 |                   |

                   | 2022-12-06 20:26:32
(3 rows)
=================================================================

The PostgreSQL node is up and running and reachable from the PgPool node
itself:
=================================================================
bash-4.4$ psql -hpostgres3.my.domain.com -Upgpool -W -dpostgres -c'SELECT
pg_is_in_recovery();'
Password for user pgpool:
 pg_is_in_recovery
-------------------
 t
(1 row)
=================================================================

I tried to attach it using pcp_attach_node, but nothing happens (no errors
and no logs into the PgPool log file even if it is configured as debug1):
=================================================================
bash-4.4$ pcp_attach_node 2 -h localhost -p 9898 -w -v
pcp_attach_node -- Command Successful
=================================================================

Could you help me to understand what's wrong, please?

Thank you very much!
Bye
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