'tail' input attempts to seek in pipes

[fetzerch]

Relevant telegraf.conf

[[inputs.tail]]
  files = ["/dev/ttyUSB.ARDUINO.ONEWIRE"]
  pipe = true

Logs from Telegraf

Mar 14 13:04:37 beaver telegraf[743589]: 2025-03-14T12:04:37Z E! [inputs.tail] Stopping tail on "/dev/ttyUSB.ARDUINO.ONEWIRE": Seek error on /dev/ttyUSB.ARDUINO.ONEWIRE: seek /dev/ttyUSB.ARDUINO.ONEWIRE: illegal seek

System info

Telegraf 1.34.0

Docker

No response

Steps to reproduce

1. Use tail input with pipes after 1.34.0

Expected behavior

Input plugin should not attempt to seek when pipe = true is configured.

Actual behavior

Input plugin ignores pipe = true and attempts to seek. Leading to illegal seek.

Additional info

I'm using the tail input plugin to read logs from an Arduino (connected over USB). Starting with Telegraf 1.34.0, this is no longer possible because tail always attempts to seek the file, even if pipe=true is configured.

The issue got introduced in #16342 which accidentally removes the check for the pipe option and the plugin now unconditionally seeks. See my comment: #16342 (review)

For reference: The pipe=true option got introduced in #2090.

[jochym]

I can confirm. This got propagated to debian stable package and broke my system. I had to pin the package at 1.33.

[srebhan]

@fetzerch and @jochym please test the binary in PR #16674, available as soon as CI finished the tests, and let me know if this fixes the issue!

[fetzerch]

@srebhan thanks, I tried it and can confirm that it's working again!