Author Archives: bullgare

MGTS(GPON)+Keenetic and external access to Synology

Adding a comment to an article about using Keenetic router behind an MGTS(gpon) receiver to make Synology services like DS Audio/Video/Photo and so on to be available via Quickconnect feature by Synology. First of all, enable KeenDNS like shown below And then enable it on Synology Control Panel like this: And now on any device …

Useful links for proto generator development

https://rotemtam.com/2021/03/22/creating-a-protoc-plugin-to-gen-go-code/ https://medium.com/@tim.r.coulson/writing-a-protoc-plugin-with-google-golang-org-protobuf-cd5aa75f5777 https://github.com/nametake/protoc-gen-gohttp https://github.com/drekle/protoc-gen-goexample/blob/c60883c9711f3cfbd5191fd697651dbd067e6fdd/main.go#L135 https://github.com/grpc-ecosystem/grpc-gateway/blob/24434e22fb9734f1a62c81c4ea246125d7844645/examples/internal/proto/examplepb/echo_service_grpc.pb.go https://pkg.go.dev/google.golang.org/protobuf/compiler/protogen#Options.Run https://github.com/lyft/protoc-gen-star https://go.dev/blog/protobuf-apiv2 https://docs.buf.build/build/usage/#configuration https://github.com/grpc-ecosystem/grpc-gateway https://github.com/googleapis/googleapis/tree/master/google/api https://github.com/bufbuild/buf https://stackoverflow.com/questions/36540427/cannot-find-package-google-protobuf https://pkg.go.dev/google.golang.org/protobuf https://developers.google.com/protocol-buffers/docs/reference/go-generated#package https://stackoverflow.com/questions/61666805/correct-format-of-protoc-go-package https://grpc.io/docs/languages/go/quickstart/ https://github.com/protocolbuffers/protobuf/tree/master/src/google/protobuf https://github.com/gogo/protobuf/blob/b03c65ea87cdc3521ede29f62fe3ce239267c1bc/protobuf/google/protobuf/descriptor.proto

Go study

A list of resources for learning golang https://github.com/ardanlabs/gotraining/tree/master/reading

Set github actions for you repo

If you want to run tests/linters against you golang project, place something like the example below in .github/workflows/somename.yml to your project:

name: ci-cd

on:
  push:
    branches:
      - '**'

env:
  GONOSUMDB: "github.com/<your-organization>"
  GOPRIVATE: "github.com/<your-organization>"
jobs:
  ci-cd:
    strategy:
      matrix:
        go-version: [ 1.16.x ]
    runs-on: ubuntu-latest
    steps:
      - name: Install Go
        uses: actions/setup-go@v2
        with:
          go-version: ${{ matrix.go-version }}
      - name: Write .netrc for private go modules
        env:
          NETRC_USER: ${{ secrets.NETRC_USER }}
          NETRC_PASS: ${{ secrets.NETRC_PASS }}
        run: echo "machine github.com login ${{ secrets.NETRC_USER }} password ${{ secrets.NETRC_PASS }}" > $HOME/.netrc
      - name: Checkout the code
        uses: actions/checkout@master
        with:
          fetch-depth: 1
      - name: Run Makefile::ci-cd-check
        run: make ci-cd-check

name: ci-cd

on:

push:

branches:

- '**'

env:

GONOSUMDB: "github.com/<your-organization>"

GOPRIVATE: "github.com/<your-organization>"

jobs:

ci-cd:

strategy:

matrix:

go-version: [ 1.16.x ]

runs-on: ubuntu-latest

steps:

- name: Install Go

uses: actions/setup-go@v2

with:

go-version: ${{ matrix.go-version }}

- name: Write .netrc for private go modules

env:

NETRC_USER: ${{ secrets.NETRC_USER }}

NETRC_PASS: ${{ secrets.NETRC_PASS }}

run: echo "machine github.com login ${{ secrets.NETRC_USER }} password ${{ secrets.NETRC_PASS }}" > $HOME/.netrc

- name: Checkout the code

uses: actions/checkout@master

with:

fetch-depth: 1

- name: Run Makefile::ci-cd-check

run: make ci-cd-check

Good article on that — https://github.com/mvdan/github-actions-golang

Postgresql exercises

Basic querying — https://pgexercises.com/questions/basic/. Joins — https://pgexercises.com/questions/joins/. Data modification — https://pgexercises.com/questions/updates/. Aggregations — https://pgexercises.com/questions/aggregates/. That could be useful to refresh your memory. Not really up-to-date, but still pretty useful.

Mac OS — decrease pdf size via Preview app

To decrease the size of the .pdf filled with images, in Preview you can go to Export and set Quartz Filter→Reduce File Size before saving. If the images are too blurry for you, you can add your own profile. 1. Create a directory — /Library/Filters. 2. Add new filter file with unique filter — i.e. …

Parental control for Linux Mint

Time limiter with UI — Timekpr (https://www.linuxuprising.com/2019/11/timekpr-next-is-linux-parental-control.html) Domain blocker — Mintnanny (https://www.reallinuxuser.com/how-to-setup-parental-control-in-linux-mint/), too simple.

Shell: repeat a task multiple time

All shells (bash/zsh):

watch -n 3 "curl --location --request GET 'http://...'"

1	watch -n 3 "curl --location --request GET 'http://...'"

will run curl every 3 seconds until you break it. zsh specific:

repeat 5 { curl --location --request GET 'http://...' }

1	repeat 5 { curl --location --request GET 'http://...' }

will repeat it 5 times without any delay

Nullable fields in json generated from protobuf file

Native support With grpc v2 for go, protofile’s optional option is supported, so you don’t need to import proto extensions anymore and use things like google.protobuf.StringValue. my.proto

message FeeView {
    optional string name = 1 [json_name = "name"];
}

message FeeView {

optional string name = 1 [json_name = "name"];

}

go mapper

var name *string
if fee.Name != nil {
	name = &fee.Name
}

fee := &desc.FeeView{
	Name: name,
}

var name *string

if fee.Name != nil {

name = &fee.Name

}

fee := &desc.FeeView{

Name: name,

}

Legacy way with extensions Null for nil value my.proto

import "google/protobuf/wrappers.proto";

message FeeView {
    google.protobuf.StringValue name = 1 [json_name = "name"];
}

import "google/protobuf/wrappers.proto";

message FeeView {

google.protobuf.StringValue name = 1 [json_name = "name"];

}

go mapper

import "github.com/gogo/protobuf/types"

var name *types.StringValue
if fee.Name != nil {
	name = &types.StringValue{
		Value: *fee.Name,
	}
}

fee := &desc.FeeView{
	Name: name,
}

import "github.com/gogo/protobuf/types"

var name *types.StringValue

if fee.Name != nil {

name = &types.StringValue{

Value: *fee.Name,

}

fee := &desc.FeeView{

Name: name,

}

Which will lead to this json response

{"translation_key":"a fee","name":null,"value":5,"style":"body","text_color":"grey","tag":null}

1	{"translation_key":"a fee","name":null,"value":5,"style":"body","text_color":"grey","tag":null}

Omit a field …

Using tcpdump for k8s pods

You need wireshark to be installed on your local machine — download (more on this below). If you don’t have tcpdump installed inside the pod, you can install it with

# get pod name
kubectl get po -Lversion,cfg,infra-cfg -lapp=<pod-tag>
kubectl exec -it <pod-name> sh
# inside the pod, alpine
apk add tcpdump

# get pod name

kubectl get po -Lversion,cfg,infra-cfg -lapp=<pod-tag>

kubectl exec -it <pod-name> sh

# inside the pod, alpine

apk add tcpdump

Then, on your local machine:

kubectl exec <pod-name> -- tcpdump -i eth0 -w - | wireshark -k -i -

1	kubectl exec <pod-name> -- tcpdump -i eth0 -w - \| wireshark -k -i -

If you want to see packets in grpc/http2, you can add a rule in Wireshark. For this, click …