How can you find out why Prometheus cannot scrape a certain target?

You can't find this out, as Prometheus does not show this information anywhere. The /targets page only shows whether a target is up or down, but not why.

Prometheus logs all target scrape failures and the exact failure reason.

The /targets page shows the last scrape error for all targets that currently cannot be scraped.

None of the above.

Which kinds of relabeling problems can the /service-discovery page help debug?

If the /service-discovery page shows incorrect "Target labels" for a target although the "Discovered Labels" are as expected, this may point to an issue with your relabeling rules.

If the /service-discovery page shows that a discovered target is unexpectedly dropped, this might point to an issue with your relabeling rules.

If the /service-discovery page shows that a discovered target is unexpectedly kept, this might point to an issue with your relabeling rules.

All of the above.

Which kinds of information does the /tsdb-status page show you about the TSDB?

The total number of time series in the entire TSDB.

The total number of time series in the TSDB's current head block.

The top 10 metric names with the largest number of series in the current head block.

All of the above.

Knowledge Check