feat(agent): add ignore_error_inputs option for inputs

[observeralone]

Required for all PRs:

• Updated associated README.md.
• Wrote appropriate unit tests.
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resolves #11289, resolves #10694, resolves #3167

revival of #11304

Summary

Add two options: agent.ignore_error_inputs and plugin.IgnoreInitError
If (plugin.ignore_init_error || ignore_error_inputs) is true, discard the input plugins that produce the error during initialization. Otherwise, the program will exit when an input plugin has an error occurred during the initialization.

[Hipska]

For me same remark as in #11304 (review): This ignore errors check should happen against the result of Start() instead of Init(). We really want telegraf to halt when the plugin has wrong configuration or it could not be correctly initialised.

[observeralone]

For me same remark as in #11304 (review): This ignore errors check should happen against the result of Start() instead of Init(). We really want telegraf to halt when the plugin has wrong configuration or it could not be correctly initialised.

The major purpose is let the telegraf can be normally run even if some of the plugins have problem whatever it’s failed in Init or start.
If we think one of plugin failed in Init(), then the whole telegraf should be exited, I respect it, but can we give an option to let the user select what behavior they like?
This requirement is reasonable, and the code changes has no risk. but it really help us a lot - we cannot go through all of plugins to correct the init behavior! So, many thanks if we can accept this PR as soon as possible !

[telegraf-tiger]

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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

[observeralone]

@Hipska
Sorry about the slow reply.
The problem with spaces you mentioned has been rolled back.
This PR is to fix the init error, we hope to deal with this problem, not directly crash.
If we want to do it on the start side, it will be implemented through another PR after.

[srebhan]

@observeralone after discussing this matter with the team, we came to the conclusion that a global option to ignore all errors is not the way we want to go. There have been similar proposals (#10111) and requests (#3723, #9778) for the output side.

However, we think it's better to fix the individual plugins to avoid connecting to services in Init but use Start (or maybe Connect in the future) instead. Furthermore, we do see the demand for a more dynamic configuration of telegraf and other features such as life-cycle and connection management. We will start a discussion on how to integrate such features in future versions of telegraf.

For now, I'm closing this PR as a correct implementation requires a rework of Telegraf internals which is out-of-scope for now.

[default-student]

While I can completely understand that the general ignoring of errors is not the way to go, I have to say that it would be a great hotfix until the error handling is actually implemented in the various plugins.

In my case weve got a large production floor with many machines serving data via opcua, but not all of them are running all the time.
Telegraf cannot be used in this case as it just exits if it cant reach a server.