[Metricbeat][Elasticsearch module] "basepath" configuration field is not working properly. Bug ?

Elastic Stack Beats
,
1

Hello,

Scenario :

I try to retrieve metrics from an Elasticsearch service through an Nginx reverse proxy. Elasticsearch endpoint is https :// FQDN:443 /elasticsearch. Metricbeat version is 8.15.2

This is the reason why I need to use the "basepath" field, documented here : (...)

Config file :

- module: elasticsearch
  enabled: true
  metricsets:
    - node
    - node_stats
    - index
    - index_recovery
    - index_summary
    - ingest_pipeline
    - shard
  period: 10s
  hosts: ["https://FQDN:443"]
  basepath: "/elasticsearch"
  scope: cluster

Test module config (in failure, excepted shard metrics, run : metricbeat test modules -v)

elasticsearch...
  node...
    error... ERROR failed to get info from Elasticsearch: invalid character '<' looking for beginning of value
  node_stats...
    error... ERROR invalid character '<' looking for beginning of value
  index...
    error... ERROR failed to get info from Elasticsearch: invalid character '<' looking for beginning of value
  index_recovery...
    error... ERROR invalid character '<' looking for beginning of value
  index_summary...
    error... ERROR failed to get info from Elasticsearch: invalid character '<' looking for beginning of value
  ingest_pipeline...
    error... ERROR failed to get info from Elasticsearch: invalid character '<' looking for beginning of value
  shard...OK

On my Elasticseach in output, we saw issues in most of these URL, with basepath config missing. Consequence : metricbeat request a wrong service, retrieve an HTML page with "<" character

screenshot_bug_metricbeat-2
screenshot_bug_metricbeat-21485×762 269 KB

I tried to play with multiple configs, with no success. Is it a bug in metricbeat code ? I'm not a Go developer/expert, but you seems to have different parsing methods in metricsets files (please refer to Github Beats code)
Thanks in advance for your help,