Author Archives: bullgare

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 …

Talk about pros and cons of GraphQL

Pros: Very flexible — clients decide which fields of which entities they need. Documentation and test UI are available by default. Cons: Code looks ugly. N+1 selects problem is hard to solve (most probably — with some ad-hoc). It’s harder to test as you don’t know all the use cases. Not a binary protocol — …

DOCKER_CONTENT_TRUST=1 docker run --rm --name dd-agent -p 8126:8126 -v /var/run/docker.sock:/var/run/docker.sock:ro -v /proc/:/host/proc/:ro -v /sys/fs/cgroup/:/host/sys/fs/cgroup:ro -e DD_API_KEY=REPLACE_WITH_NEW_KEY -e DD_SITE=datadoghq.eu datadog/agent

1	DOCKER_CONTENT_TRUST=1 docker run --rm --name dd-agent -p 8126:8126 -v /var/run/docker.sock:/var/run/docker.sock:ro -v /proc/:/host/proc/:ro -v /sys/fs/cgroup/:/host/sys/fs/cgroup:ro -e DD_API_KEY=REPLACE_WITH_NEW_KEY -e DD_SITE=datadoghq.eu datadog/agent

Run virtual machine Ubuntu/Windows on m1 macos

There is a program called UTM based on QEMU and developed for m1 MacBook virtualization. At least Ubuntu Server is working fine for me. https://mac.getutm.app/guide/. More info on this — https://eshop.macsales.com/blog/72081-utm-virtual-machine-on-m1-mac/

Debugging go app in Jetbrains Goland on m1

First download a proper version of GoLand here — select .dmg (MacOS Apple Silicon) here (direct link — https://www.jetbrains.com/go/download/download-thanks.html?type=eap&platform=macM1&build=211.6556.11&code=GO). Then make sure you are using arm version of go (go version go1.16.2 darwin/arm64). If not, download and install arm version of golang (like «go1.16.2.darwin-arm64.pkg») from the list here — https://golang.org/dl/. Now it should work. With …

Example of using embed in go

Nice article on using go templates with embed introduced in go1.16: https://philipptanlak.com/web-frontends-in-go/. That’s the code:

Run Steam on MacBook with m1 chip (apple silicon)

You need to install Crossover. Then you need to install Steam there. Good video explaining the process of installing Steam on Apple Silicon chips: https://www.youtube.com/watch?v=3TdCV7fn2CA Here is the list of supported games — https://applesilicongames.com/