fix (inputs/mongodb): Add direct connection to mongod plugin

[denispershin]

Required for all PRs:

• Updated associated README.md.
• Wrote appropriate unit tests.
• Pull request title or commits are in conventional commit format

Since 1.19.2 version, telegraf collect statistics from primary node, even if secondary node was specified. It can be fixed with connection=direct with connection string in config file, but I think this MR better way to fix this problem, no any action from users required.

resolves #9555

[telegraf-tiger]

☺️ This pull request doesn't significantly change the Telegraf binary size (less than 1% increase)

📦 Looks like new artifacts were built from this PR.

Expand this list to get them here ! 🐯

Artifact URLs

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

[srebhan]

To be honest I would prefer documenting the option to set connection=direct to the connection string instead of adding (redundant) code. @reimda any preference?

[denispershin]

To be honest I would prefer documenting the option to set connection=direct to the connection string instead of adding (redundant) code. @reimda any preference?

it could, but i guess, that many developers just update telegraf and can't realize that they receive wrong data, after they understand it, tried figure out what the problem and after many hours they may be remember about documentation, find what changed and fix it.
In this fix, no any action needed from user side.

[srebhan]

@denispershin I understand your point, but changing the behavior of telegraf will fix the problem for you , but it might break the setup of other people that rely on the current behavior. So changing the behavior by default cannot be done anyway as telegraf "guarantees" that your existing config will exhibit the same behavior for minor-version updates.

This being said, the difference is either setting the connection=direct option in the server string OR setting an explicit option direct_connection = true in the config. The later is more explicit but comes with all the burden of redundancy. What if direct_connection is set to true but the server string contains directConnection=false etc.
Another point is that the first (specifying options via the server string) is extensively documented and does provide a ton of other options. We really don't want to duplicate those.

So my suggestion would be to add a big warning to the config option, that you need to set directConnection=true on secondaries if you want to get data from there...

Let's see what the Influx people think about it...

[srebhan]

@denispershin after having talked to the Influx people, we agreed on that having that option in the connection string is good enough. However, we also agreed on that the documentation could be improved maybe spending an extra section or a heads-up on this fact. Are you willing to enhance the documentation of the current behavior and the use of connection=direct?

[telegraf-tiger]

Hello! I am closing this issue due to inactivity. I hope you were able to resolve your problem, if not please try posting this question in our Community Slack or Community Page. Thank you!