feat: add OpenTSDB data format parser (mark two)

[nick-kentik]

Required for all PRs

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

resolves #8559

Added a parser for OpenTSDB's Telnet style put API format.
For more detail of the format, see

http://opentsdb.net/docs/build/html/api_telnet/put.html
http://opentsdb.net/docs/build/html/user_guide/writing/index.html#data-specification

This is heavily based on the effort by @envzhu in #9690 - I merged that branch against latest master, then made the (minimal) changes necessary to get it working, and the existing tests passing.

A quick end-to-end test also looked good. Here's the telegraf.conf I used:

[[outputs.file]]
files = ["stdout"]
data_format = "prometheus"

[[inputs.socket_listener]]
service_address = "tcp://127.0.0.1:4242"
data_format = "opentsdb"

A telnet session as input:

telnet localhost 4242
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
version
put sys.if.bytes.out 1479496100 1.3E3 host=web01 interface=eth0
^]
telnet> quit
Connection closed.

And the telegraf process output:

./telegraf --config telegraf.conf 
2023-05-05T09:49:26Z I! Loading config: telegraf.conf
2023-05-05T09:49:26Z I! Starting Telegraf 1.27.0-e36d3a8c
2023-05-05T09:49:26Z I! Available plugins: 235 inputs, 9 aggregators, 28 processors, 23 parsers, 57 outputs, 3 secret-stores
2023-05-05T09:49:26Z I! Loaded inputs: socket_listener
2023-05-05T09:49:26Z I! Loaded aggregators: 
2023-05-05T09:49:26Z I! Loaded processors: 
2023-05-05T09:49:26Z I! Loaded secretstores: 
2023-05-05T09:49:26Z I! Loaded outputs: file
2023-05-05T09:49:26Z I! Tags enabled: host=starbook
2023-05-05T09:49:26Z I! [agent] Config: Interval:10s, Quiet:false, Hostname:"starbook", Flush Interval:10s
2023-05-05T09:49:26Z I! [inputs.socket_listener] Listening on tcp://127.0.0.1:4242
2023-05-05T09:49:38Z E! [parsers.opentsdb::socket_listener] Error parsing "version" as opentsdb: doesn't have required fields
# HELP sys_if_bytes_out_value Telegraf collected metric
# TYPE sys_if_bytes_out_value untyped
sys_if_bytes_out_value{host="web01",interface="eth0"} 1300

[telegraf-tiger]

Thanks so much for the pull request!
🤝 ✒️ Just a reminder that the CLA has not yet been signed, and we'll need it before merging. Please sign the CLA when you get a chance, then post a comment here saying !signed-cla

[nick-kentik]

I'll need to get advice on the CLA; I'll leave this as draft until then.

[nick-kentik]

!signed-cla

[nick-kentik]

OK, I think this is ready for review now.

cc @powersj @Hipska @srebhan - and thanks again to @envzhu for doing the hard work on mk1 ^^

Any problems, just let me know; I'm motivated to get this merged.

[srebhan]

Thanks for the nice addition @nick-kentik and sorry for the long response time! I have some minor comments...

[nick-kentik]

Thanks for the review @srebhan ! I've addressed your comments, with a few tweaks in places; I've resolved the comments where I've applied your suggestion unchanged.

There's just the discussion about what to do when some lines in the input are invalid; I've not made any changes there yet.

[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 decreases the Telegraf binary size by -3.60 % for linux amd64 (new size: 168.8 MB, nightly size 175.1 MB)

📦 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_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
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

[srebhan]

Looks good to me. Thanks for your nice contribution @nick-kentik!

[powersj]

Thank you!

[nick-kentik]

Great, thanks for the merge!