Config parser does not complain about overriden parts of configuration

[RichiH]

While I readily agree that autogenerated config files should not have this problem, and that YAML works that way, especially in the trial phase, this can confuse users. Warning or, preferably, erroring out would be appreciated.

If you run with a configuration like:

scrape_configs:
  - job_name: 'prometheus_system'
    target_groups:
    - targets: ['localhost:9100']

scrape_configs:
  - job_name: 'foo_system'
    target_groups:
    - targets: ['foot:9100']

the former scrape_configs is silently discarded. While that's the obvious case, constructs like

scrape_configs:
  - job_name: 'prometheus_system'
    target_groups:
    - targets: ['localhost:9100']

rule_files:
  - 'prometheus.rules'

scrape_configs:
  - job_name: 'foo_system'
    target_groups:
    - targets: ['foo:9100']

are silently discarded as well.

So to summarize: Yes, I fat-fingered, but principle of least surprise would be to error out instead of silently carrying on.

[fabxc]

Unfortunately, that is an issue of the YAML parser package. Detecting this in a clean way in Prometheus is not really an option.

If no error is thrown, the YAML spec would actually require any subsequent occurrences to be discarded rather then the previous ones (http://yaml.org/spec/1.1/#id932806).

I agree that it's annoying and an error message would be nice to have. But it's not enough of a problem to introduce silly hacks to the Prometheus code base to work around a bug in an upstream package (for which there's not alternative).

[RichiH]

Closing as per IRC.

Created go-yaml/yaml#154 instead.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.