How to see the hostname of the instance that has generated the data for Pushgateway

I have prometheus server that is using self discovery for Azure VMs which are running WMI exporter. In Grafana I am using dashboard variables for filtering (see screenshot).

On the VMs I have created a custom exporter that outputs the metric with the value of 1 for each server and each server is sending the values to a single Pushgateway that is configured in etc/prometheus/prometheus.yaml

- job_name: 'push-gateway'
  static_configs:
  - targets: ['localhost:9091']

When I look at scraped metrics I always see the instance: localhost:9091 and job: push-gateway regardless of the server the metric came from. If I add those labels manually I see the "exported" prefix (see screenshot).

What I am confused about is, how can I ensure that the "job" and "instance" for the custom created metric have the same "job" and "instance" values that match the server that has generated the metrics so I can use dashboard variables to extract the correct data for the selected server?

You can use metric_relabel_configs to rewrite labels after scraping. An example:

- job_name: pushgateway
  # This is necessary if metrics in pushgateway have "job" or "instance" labels.
  # With "honor_labels: true" Prometheus will save those as "exported_job" and "exported_instance" respectively.
  honor_labels: true
  static_configs:
  - targets:
    - my-pushgateway.com:9091
  metric_relabel_configs:
  # copy pushgateway address from "instance" to "source" label
  - source_labels: [instance]
    target_label: source

  # replace "instance" label value with one from "exported_instance" label
  - source_labels: [exported_instance]
    target_label: instance

  # remove "exported_instance" label
  - source_labels: [exported_instance]
    action: labeldrop

If you previously had metrics like this:

my_metric{job="pushgateway", instance="my-pushgateway.com:9091", exported_instance="example.com"}

then with the configuration from the example above they will look like this:

my_metric{job="pushgateway", instance="example.com", source="my-pushgateway.com:9091"}