Graylog output plugin: non-standard fields should be prefixed

[alespour]

Relevant telegraf.conf:

[[outputs.graylog]]
  ## UDP endpoint for your graylog instances.
  servers = ["127.0.0.1:12201"]

Expected behavior:

Input plugin name field (e.g. "name":"log_tail") should be sent with _ prefix. Regarding Gelf specification (https://docs.graylog.org/en/4.1/pages/gelf.html#gelf-payload-specification), all non standard fields should always be prefexed with _.

Actual behavior:

Input plugin name field (e.g. "name":"log_tail") are not sent with "_" prefix.

Additional info:

Mentioned in #9644 (as "not so important issue").

[popey]

Thanks for reporting the issue. Is that really all that's needed configuration-wise to reproduce this issue? Are there any other plugins or options which need configuring to get this problem occurring?

[alespour]

Sorry, I have updated the config section. Based on customer comment #9644 (comment), it's really just the graylog plugin, nothing else needs to be configured.