feat: Migrate to urfave/cli

[sspaink]

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

related to: #11316

There is a goal to clean up the flags and commands of Telegraf (#11316), to help that effort I've migrated the project from using the standard library flag package to using urfave/cli. The urfave/cli package offers a clean and straightforward way to implement flags and commands. I believe this will help provide and easy foundation to begin updating and maintaining the flags/commands.

The goal of this pull request is to just begin using "urfave/cli" package, with no breaking changes, so everything should work as it does now. Then in future pull requests, we can begin deprecating and introducing new flags/commands. I've also added test coverage around the flag/commands which didn't exist before. To add the test coverage I moved the main business logic to a separate function called runApp where the actual agent, pprof, and config get passed in. These are mocked out in the new tests.

The flags --sample-config and --version have already been marked as deprecated because there are duplicate commands that already exists telegraf config and telegraf version. I also marked --plugin-directory as deprecated as this is a feature that was quickly disabled after introduction and would require a special build of Telegraf to get working that is not being released officially.

[powersj]

Huge thank you for this. It will make things much more consistent and more easily make changes down the road. Some initial questions for our chat today after quickly scanning this PR:

1. Windows only flags now show up in linux output, is there a way to filter these? I don't find this as a blocker
2. Tested on mac and windows? What can I do to help?
3. Why were the internal version variables made public?
4. What prompted the pprof changes?

[sspaink]

1. Windows only flags now show up in linux output, is there a way to filter these? I don't find this as a blocker
Good catch, this is fixable
2. Tested on mac and windows? What can I do to help?
Windows services and Mac needs to be tested
3. Why were the internal version variables made public?
For testing, https://github.com/influxdata/telegraf/blob/cliv2/cmd/telegraf/telegraf_test.go#L314-L357 using it to set the version to something predictable.
4. What prompted the pprof changes?
For testing and err channel was added to avoid calling panic if the pprof fails

Action items from discussion:

1. Test windows
2. Test mac
3. Test error conditions (bad config ,etc)
4. Test version
5. Test sample config with diff
6. Add tests for all flags
7. Consider different name for "AgentManager"

[powersj]

Test sample config with diff

This looks good no diff between the file generated and the file from master

Test version

Once I added your Makefile changes locally, I think the only difference is the lack of a newline.

# telegraf from your branch
❯ ./telegraf version | od -c
0000000   T   e   l   e   g   r   a   f       1   .   2   4   .   0   -
0000020   a   a   b   9   5   4   a   8       (   g   i   t   :       c
0000040   l   i   v   2   @   a   a   b   9   5   4   a   8   )
0000056
# this is telegraf built from master
❯ /tmp/telegraf version | od -c
0000000   T   e   l   e   g   r   a   f       1   .   2   4   .   0   -
0000020   9   e   a   2   d   e   a   c       (   g   i   t   :       m
0000040   a   s   t   e   r   @   9   e   a   2   d   e   a   c   )  \n
0000060

[sspaink]

@powersj I've added the missing newline, nice find!

[sspaink]

I've tested windows service by running the following commands:

telegraf.exe --service install	Install telegraf as a service
telegraf.exe --service uninstall	Remove the telegraf service
telegraf.exe --service start	Start the telegraf service
telegraf.exe --service stop	Stop the telegraf service

With a simple config:

[[inputs.cpu]]

[[outputs.file]]
    files = ["H:\\Sandbox\\test.txt"]

There was an issue I resolved in the latest commit, were I had added an error channel that was blocking the service from starting. I replaced it with just printing an error message.

The struct AgentManager has also been renamed to Telegraf to prevent overloading the word Agent which already has a meaning in this project.

[powersj]

I completed my testing on macOS, went through each of the options, and ensured they worked as I understood them.

On Linux, I tried several invalid configs and options to ensure we still error as expected.

I have put a few comments below, primarily nits and clean-up.

[powersj]

+1

Looks great, and makes it much easier for us to maintain the CLI going forward, as well as extend it with additional subcommand and flags.

My only concern was re: internal variables, but we can chat as a team about that and make changes before v1.24.0 if needed.

[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 significantly change the Telegraf binary size (less than 1%)

📦 Click here to get additional PR build artifacts

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