feat(inputs.gnmi): set max gRPC message size

[powersj]

Adds an option to let a user set the max gRPC message size. By default, this is set to 4MB and allows a user to receive larger messages if required by the end device.

fixes: #12463

[srebhan]

Looks good but I really want the size to be config.Size in order to make it more human-readable.

[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_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
		static_linux_amd64.tar.gz

[srebhan]

LGTM. Thanks @powersj!

[mohsin106]

I downloaded the Alpine Docker image version 1.25.1 and currently getting this error:

Mon, Feb 6 2023 4:24:04 pm | 2023-02-06T21:24:04Z I! Using config file: /etc/telegraf/telegraf.conf
Mon, Feb 6 2023 4:24:04 pm | 2023-02-06T21:24:04Z E! error loading config file /etc/telegraf/telegraf.conf: plugin inputs.gnmi: line 12: configuration specified the fields ["max_msg_size"], but they weren't used

Is this because the network device that I'm connecting to doesn't recognize the "max_msg_size" parameter?

My gNMI config looks like this:

[[inputs.gnmi]]
  addresses = ["10.30.45.50:10161"]
  username = "$user"
  password = "$password"
  redial = "10s"
  enable_tls = true
  insecure_skip_verify = true
  max_msg_size = "10MB"
  [[inputs.gnmi.subscription]]
    name = "test"
    path = "/components"
    subscription_mode = "sample"
    origin = "openconfig-platform"
    sample_interval = "10s"

[powersj]

I downloaded the Alpine Docker image version 1.25.1 and currently getting this error:

As this is a feature it will go into 1.26 next month, not 1.25.1. You can also grab a nightly docker image and give it a try there as well.