Category Archives: golang

Forward multiple kubernetes pods for local development

kubefwd is a great tool that can forward a lot of pods at once to your local machine. The only downside for me is that it touches your local /etc/hosts. That’s how I use it:

sudo KUBECONFIG=<path to your k8s config> kubefwd svc -l "app in (first-api, second-api, third-service)"

1	sudo KUBECONFIG=<path to your k8s config> kubefwd svc -l "app in (first-api, second-api, third-service)"

It does not have huge documentation, but it is written in golang, and you can check how the source …

Force ipv4 for golang http client

Sometimes you want to prevent your http client from using ipv6/tcp6. That’s how you do it.

dialer := &net.Dialer{
	Timeout:   dialTimeout,
	KeepAlive: keepAliveTimeout,
}

transport := &http.Transport{
	Proxy:             http.ProxyFromEnvironment,
	ForceAttemptHTTP2: false,
	DialContext: func(ctx context.Context, network string, addr string) (net.Conn, error) {
		ipv4, err := resolveIPv4(addr)
		if err != nil {
			return nil, err
		}

		return dialer.DialContext(ctx, network, ipv4)
	},
}

httpClient := &http.Client{
	Transport: transport,
	Timeout:   args.HTTPTimeout,
}

// resolveIPv4 resolves an address to IPv4 address.
func resolveIPv4(addr string) (string, error) {
	url := strings.Split(addr, ":")

	m := new(dns.Msg)
	m.SetQuestion(dns.Fqdn(url[0]), dns.TypeA)
	m.RecursionDesired = true

	config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
	c := new(dns.Client)
	r, _, err := c.Exchange(m, net.JoinHostPort(config.Servers[0], config.Port))
	if err != nil {
		return "", err
	}
	for _, ans := range r.Answer {
		if a, ok := ans.(*dns.A); ok {
			url[0] = a.A.String()
		}
	}

	return strings.Join(url, ":"), nil
}

dialer := &net.Dialer{

Timeout: dialTimeout,

KeepAlive: keepAliveTimeout,

}

transport := &http.Transport{

Proxy: http.ProxyFromEnvironment,

ForceAttemptHTTP2: false,

DialContext: func(ctx context.Context, network string, addr string) (net.Conn, error) {

ipv4, err := resolveIPv4(addr)

if err != nil {

return nil, err

}

return dialer.DialContext(ctx, network, ipv4)

}

httpClient := &http.Client{

Transport: transport,

Timeout: args.HTTPTimeout,

}

// resolveIPv4 resolves an address to IPv4 address.

func resolveIPv4(addr string) (string, error) {

url := strings.Split(addr, ":")

m := new(dns.Msg)

m.SetQuestion(dns.Fqdn(url[0]), dns.TypeA)

m.RecursionDesired = true

config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")

c := new(dns.Client)

r, _, err := c.Exchange(m, net.JoinHostPort(config.Servers[0], config.Port))

if err != nil {

return "", err

}

for _, ans := range r.Answer {

if a, ok := ans.(*dns.A); ok {

url[0] = a.A.String()

}

return strings.Join(url, ":"), nil

}

Install go2 beta on MacOS

A quick guide on installing golang v2 development revision. It works for my MacOS Big Sur (with an Intel processor).

Using DataDog on your CentOs

DD_AGENT_MAJOR_VERSION=7 DD_API_KEY=<your-key> DD_SITE="datadoghq.eu" bash -c "$(curl -L https://s3.amazonaws.com/dd-agent/scripts/install_script.sh)"

sudo nano /etc/datadog-agent/datadog.yaml
# uncomment logs_enabled: true
sudo systemctl restart datadog-agent
sudo mkdir /etc/datadog-agent/conf.d/go.d
sudo nano /etc/datadog-agent/conf.d/go.d/conf.yaml
# and add contents from the url below

DD_AGENT_MAJOR_VERSION=7 DD_API_KEY=<your-key> DD_SITE="datadoghq.eu" bash -c "$(curl -L https://s3.amazonaws.com/dd-agent/scripts/install_script.sh)"

sudo nano /etc/datadog-agent/datadog.yaml

# uncomment logs_enabled: true

sudo systemctl restart datadog-agent

sudo mkdir /etc/datadog-agent/conf.d/go.d

sudo nano /etc/datadog-agent/conf.d/go.d/conf.yaml

# and add contents from the url below

https://app.datadoghq.eu/logs/onboarding/server https://docs.datadoghq.com/agent/faq/error-restarting-agent-already-listening-on-a-configured-port/ Or, if you want a dockerized version of DataDog agent, and you want to listen to docker logs, you can do this:

docker run -d --name datadog-agent \
           -e DD_API_KEY=<DATADOG_API_KEY> \
           -e DD_LOGS_ENABLED=true \
           -e DD_LOGS_CONFIG_CONTAINER_COLLECT_ALL=true \
           -e DD_CONTAINER_EXCLUDE_LOGS="name:datadog-agent" \
           -e DD_SITE="datadoghq.eu"  \
           -v /var/run/docker.sock:/var/run/docker.sock:ro \
           -v /proc/:/host/proc/:ro \
           -v /opt/datadog-agent/run:/opt/datadog-agent/run:rw \
           -v /sys/fs/cgroup/:/host/sys/fs/cgroup:ro \
           datadog/agent:latest

docker run -d --name datadog-agent \

-e DD_API_KEY=<DATADOG_API_KEY> \

-e DD_LOGS_ENABLED=true \

-e DD_LOGS_CONFIG_CONTAINER_COLLECT_ALL=true \

-e DD_CONTAINER_EXCLUDE_LOGS="name:datadog-agent" \

-e DD_SITE="datadoghq.eu" \

-v /var/run/docker.sock:/var/run/docker.sock:ro \

-v /proc/:/host/proc/:ro \

-v /opt/datadog-agent/run:/opt/datadog-agent/run:rw \

-v /sys/fs/cgroup/:/host/sys/fs/cgroup:ro \

datadog/agent:latest

More info here — https://docs.datadoghq.com/agent/docker/log/?tab=containerinstallation Then you will see your logs here — https://app.datadoghq.eu/logs

Install go with gvm on MacOS Big Sur

I used to use gvm for this — https://github.com/moovweb/gvm. But initial installation of go from scratch does not work for Big Sur as 1.4 does not have a binary for this OS (this command fails — gvm install go1.4 -B). To use gvm, you can do this: 0. Install gvm — bash <

Complete list of swagger options to protobuf file

Here is an example with many options that help generate proper swagger out of protofile. Original URL — https://raw.githubusercontent.com/grpc-ecosystem/grpc-gateway/master/examples/internal/proto/examplepb/a_bit_of_everything.proto.

Refactor your code and know it’s completely backward compatible

The idea is to run 2 versions of code on production: 1 (control group) — is your old implementation which will be returned to the end user 2 (the experiment) — is a new implementation which results will be checked against the control group and logged It will be run asynchronously and only for a …

GRPC fallback to Rest API with custom field names

When you generate JSON for Rest API from proto-file, protoc-gen-gofast generates field names for JSON in lowerCamelCase format while most of the Rest APIs use snake_case for that. And if you want to replace some legacy API with your new implementation without breaking backward compatibility, you need to fix it. There could be different ways …

«Awesome go» resources

A list of good resources for each go specific part — https://github.com/avelino/awesome-go. A list of good tools for go performance or just fast libs — https://github.com/cristaloleg/awesome-go-perf

Go library for creating slack bots

You can use it like that:

package main

import (
	"context"
	"github.com/shomali11/slacker"
	"log"
)

func main() {
	bot := slacker.NewClient("<YOUR SLACK BOT TOKEN>")

	definition := &slacker.CommandDefinition{
		Handler: func(request slacker.Request, response slacker.ResponseWriter) {
			response.Reply("pong")
		},
	}

	bot.Command("ping", definition)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	err := bot.Listen(ctx)
	if err != nil {
		log.Fatal(err)
	}
}

package main

import (

"context"

"github.com/shomali11/slacker"

"log"

)

func main() {

bot := slacker.NewClient("<YOUR SLACK BOT TOKEN>")

definition := &slacker.CommandDefinition{

Handler: func(request slacker.Request, response slacker.ResponseWriter) {

response.Reply("pong")

}

bot.Command("ping", definition)

ctx, cancel := context.WithCancel(context.Background())

defer cancel()

err := bot.Listen(ctx)

if err != nil {

log.Fatal(err)

}

https://github.com/shomali11/slacker