`monitoring.md`: Add input Tail plugin metrics to monitoring page

[c-neto]

The input tail plugin exports several metrics that are not currently documented.

These metrics are defined in: https://github.com/fluent/fluent-bit/blob/master/plugins/in_tail/tail_config.c#L472-L524

It is necessary to add a new section to the Fluent Bit Monitoring documentation detailing all available input Tail plugin metrics.

• Page Link:
  • https://docs.fluentbit.io/manual/administration/monitoring
  • https://docs.fluentbit.io/manual/data-pipeline/inputs/tail
• Related Issue: in_tail: Expose Metrics to Track Skipped Long Lines fluent-bit#11457

[eschabell]

Hi @c-neto,

Thanks for the fixes you are suggesting here. I have unfortunately just before you sent these submitted a rather comprehensive update to the Monitoring doc page. The changes you propose I have pulled into that PR and tagged it as fixing this issue, so once it merges, it should close this out for you.

I will be marking the doc PR #2380 as duplicate, to save us both time as the location you wanted to add them is I believe incorrect. I have added them into the existing table in this PR #2378 while giving you named credit for the help in the commit.

I hope this works for you?

I will cross-post this to the PR.

[c-neto]

Hi @eschabell,

Okay, that seems good to me!