PgPool-II can't find the servers where the databases live (even though the PgPool is on a db server)

PgPool-II 4.3.3 Postgresql 13.9 RHEL 8.6 Postgresql is installed on FOOBARa and FOOBARb, and data is successfully being stream replicated from a to b. Then I installed PgPool-II on a, and configured the two backend_host configuration variables to point to the two db servers. However, pgpool throws getaddrinfo() failed with error "Name or service not known" on **both** it's own node and the remote node, even though the two hostname commands (and ssh) work perfectly. What am I misunderstanding? $ grep backend_hostname pgpool.conf backend_hostname0 = 'FOOBARa' backend_hostname1 = 'FOOBARb' $ hostname FOOBARa $ ssh -q FOOBARb hostname FOOBARb 2023-01-25 12:07:45.156: child pid 786204: DEBUG: initializing backend status 2023-01-25 12:07:45.157: main pid 786138: WARNING: failed to connect to PostgreSQL server, getaddrinfo() failed with error "Name or service not known" 2023-01-25 12:07:45.157: main pid 786138: LOG: find_primary_node: make_persistent_db_connection_noerror failed on node 0 2023-01-25 12:07:45.165: main pid 786138: DEBUG: authenticate kind = 10 2023-01-25 12:07:45.172: main pid 786138: LOG: find_primary_node: make_persistent_db_connection_noerror failed on node 1 2023-01-25 12:07:45.172: main pid 786138: DEBUG: pool_acquire_follow_primary_lock: lock was not held by anyone 2023-01-25 12:07:45.172: main pid 786138: DEBUG: pool_acquire_follow_primary_lock: succeeded in acquiring lock 2023-01-25 12:07:45.172: main pid 786138: DEBUG: verify_backend_node_status: there's no primary node 2023-01-25 12:07:45.172: main pid 786138: DEBUG: pool_release_follow_primary_lock called