How to connect to Pgpool that requires mTLS

[erhhung]

I'm aware that there's an outstanding PR (#34) that seeks to support HTTPS for the pgpool2_exporter metrics endpoint itself (by default on port 9719).

However, how would pgpool2_exporter connect to the Pgpool service endpoint if Pgpool has been configured to require client certs? I'm currently deploying pgpool2_exporter as a sidecar container in the Pgpool pod (as part of Bitnami's postgresql-ha Helm chart), but I'm having trouble getting it to connect to Pgpool:

Error from pgpool2_exporter:

error connecting to Pgpool-II: pq: CERT authentication failed

Error from Pgpool:

ERROR:  CERT authentication failed
DETAIL:  no valid certificate presented