promtail static_configs targets can have any value

[Mario-Hofstaetter]

Describe the bug
Documentation https://github.com/grafana/loki/blob/v1.3.0/docs/clients/promtail/configuration.md#static_config
states that in static_config:

# Configures the discovery to look on the current machine. Must be either
# localhost or the hostname of the current computer.
targets:
  - localhost

However, this is not enforced, and has no effect?

To Reproduce
Run promtail with a scrape_configs containing:

    static_configs:
      - targets:
          - "foobar"

on a machine not named foobar 😄
Service Discovery shows __address__="foobar",
but logs are pushed to loki correctly. __address__ label is not visible inside grafana.

Expected behavior
??? Is this an unused config value when running static?
Does this have any effect?

Environment:

• Promtail bare-metal on Windows 10, 1909

[adityacs]

@Mario-Hofstaetter The labels with __ is dropped here https://github.com/grafana/loki/blob/master/pkg/promtail/targets/filetargetmanager.go#L249

If you want to add host label, You can add an extra label under labels

labels:
      job: varlogs
      __path__: /var/log/*log
      hostname: systemhostname

[cyriltovena]

__address__ and __host__ are not available those are labels used only during scrapping. You could still add them via relabelling or pipeline stage or even like @adityacs suggested.

And yes:

# Configures the discovery to look on the current machine. Must be either
# localhost or the hostname of the current computer.
targets:
  - localhost

is not used in Loki and doesn't have side effects.

Feel free to send a PR to update the documentation.

[stale]

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