Telegraf won't start on empty (zero-length) statefile

[burkart]

Relevant telegraf.conf

[agent]
  statefile = "/var/lib/telegraf/statefile"

# Dedup uses the statefile
[[processors.dedup]]
  dedup_interval = "60s"

Logs from Telegraf

E! [telegraf] Error running agent: unmarshalling states failed: unexpected end of JSON input

System info

Telegraf 1.29.2, Debian 12.4, Docker 24.0.7

Docker

No response

Steps to reproduce

1. Enable statefile in telegraf.conf
2. Make sure statefile is empty (0 bytes)
3. Start Telegraf

Expected behavior

Telegraf starts and fills statefile on exit.

Actual behavior

Telegraf fails to start.

Additional info

Telegraf comes with a zero-length statefile /var/lib/telegraf/statefile that's generated by scripts/{deb,rpm}/post-install.sh.

Telegraf starts successfully if the file contents are "{}" (without the quotes).

[shengbinxu]

Yes, I also encountered this issue. The version I am using is 1.29.1, and the issue can be resolved by writing the following content in the file.

{}

[srebhan]

@shengbinxu this should be fixed in v1.30.0+...