fix: update the precision parameter default value

[powersj]

In #10803, precision parsing was made more strict so that incorrect
values would be caught. The default precision value however is not
correct as an empty string.

fixes: #10813

[reimda]

I would guess that most telegraf users made their config files by running telegraf config or copying/editing /etc/telegraf/telegraf.conf that came in the deb/rpm. For all releases before this change, all those config files have precision = "", so it's a safe guess that a large portion, maybe almost all telegraf users have precision = "" in their telegraf.conf.

Making duration parsing more strict seems like a good thing, but it looks like that will mean requiring all those config files to be updated manually. I don't think that's practical.

I think we're going to need to add a special case in UnmarshalTOML to accept "" and treat it like telegraf did previously. Otherwise we're going to inconvenience too many people.

The original intent of the changes to UnmarshalTOML was to stop accepting a unit with no value (like "ns") because it's confusing/misleading. I think we can do that while still accepting "" for backward compatibility.

[powersj]

I would guess that most telegraf users made their config files by running telegraf config or copying/editing /etc/telegraf/telegraf.conf that came in the deb/rpm. For all releases before this change, all those config files have precision = "", so it's a safe guess that a large portion, maybe almost all telegraf users have precision = "" in their telegraf.conf.

Right, good catch

I think we're going to need to add a special case in UnmarshalTOML to accept "" and treat it like telegraf did previously. Otherwise we're going to inconvenience too many people.

Done - I am still updating the default value to align with the comment but checking for the empty string now.

[telegraf-tiger]

Download PR build artifacts for linux_amd64.tar.gz, darwin_amd64.tar.gz, and windows_amd64.zip.
Downloads for additional architectures and packages are available below.

👍 This pull request doesn't change the Telegraf binary size

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Artifact URLs

DEB	RPM	TAR GZ	ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_i386.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz
		static_linux_amd64.tar.gz

[pichlermarc]

Looks great, thanks! 🙂
Thanks also for looking out for the existing config files generated with telegraf config. 👍