Beginner question about importing metric from FROST-Server and json-exporter

Exporters and Metrics
1

Hi,

i’m currently trying to import weather data from a FROST-Server into my prometheus instance. I’m trying to use the JSON-Exporter for that purpose. The FROST-Server has a REST-API, that returns JSON data objects.

I have the following config.yml for my json-exporter:

---
modules:
  default:
    metrics:
    - name: frost_observations
      type: object
      valuetype:  
      path: '{.value[*]}'
      epochTimestamp: '{.value[@.resultTime]}'
      help: frost server observations
      honor_labels: false
      labels:
        datastream: '{ .Datastream.name }'
      values:
        result: '{.result}'

    http_client_config:
      basic_auth:
        username: ****
        password_file: /config/frost-password.txt

this is my prometheus.yml

global:
  scrape_interval:     1m # By default, scrape targets every 15 seconds.
scrape_configs:
  - job_name: 'frost'
    scrape_interval: 15s
    static_configs:
      - targets:
          - "https://url-to-my-server/FROST-Server/v1.1/Observations?$expand=Datastream"
    metrics_path: /probe
    scheme: http
    relabel_configs:
    - source_labels: [__address__]
      target_label: __param_target
    - source_labels: [__param_target]
      target_label: instance
    - target_label: __address__
      ## Location of the json exporter's real <hostname>:<port>
      replacement: json-exporter:7979 # equivalent to "localhost:7979"

When running the json-exporter i’m getting a lot of errors like this

* collected metric "frost_observations_result" { label:<name:"datastream" value:"" > untyped:<value:11 > } was collected before with the same name and label values

I can solve this issue, by adding the label id: { .id }. But this will create a timeseries for every record of the FROST-Server, which IMHO makes no sense. I want to have a time series for each Datastream.name.
I don’t understand, why i’m getting this error message, and how a possible fix could be.

The returned data (from this url https://url-to-my-server/FROST-Server/v1.1/Observations?$expand=Datastream) represents multiple timeseries (Observations) from different sensors. The parameter $expand=Datastream returns the linked Datastream. The name of the Datastream is somethink like this:

Sensor-1 temperature
Sensor-1 humidity
Sensor-2 temperature
Sensor-2 humidity

which is why i want to use it as a label, to create a timeseries for each sensor-property combination.

It seems, that i still lack some basic understanding of what a metric is. Does a metric represent a timeseries, or a single value?

Can anyone help me?