Tailing files stopped working since v1.15

[Tenzer]

I've upgraded from Telegraf v1.14 to v1.15.1 in our systems today and found that it broke one of our use cases.

We are tailing some log-like files from a service, the service outputs lines in InfluxDB format which is then read by Telegraf and passed on to our metrics system. I made a minimal example of this:

telegraf.conf

[[inputs.tail]]
  files = ["clock.log"]
  data_format = "influx"

[[processors.printer]]

[[outputs.discard]]

I've then run this loop in bash in order to write to clock.log:

while :; do
    echo "clock now=$(date +%s)"
    sleep 1
done >> clock.log

Using that example I was able to use Git bisect which pointed at this stopping working when #7792 was merged.

I've tried to set character_encoding in the config file to both an empty string and "utf-8" but it doesn't seem to make any difference, so I think the problem might more deeply rooted.

[9point6]

We've also had a similar issue with inputs.tail. Validated that locking to < 1.15.0 has mitigated the issue for us

[danielnelson]

Can everyone affected try out one of these builds with the proposed fix and let us know if it resolves the issue?

[Tenzer]

@danielnelson Thanks, I can confirm it fixes the problem for me.

[philipptrenz]

I can also confirm that this fixes the issue, thanks! 👌🏼