Author Archives: bullgare

How to split disk pool on synology nas

I have a Synology NAS DS 218+. When I bought it, I decided to make a RAID1 pool from two disks. But after time passed, I realized that I don’t have enough space to store all files. And I decided to make two separate disks instead of one RAID1. RAID0 is worse for me comparing …

Another cool article on using PostgreSQL+pgBouncer with go

Extremely interesting and very practical talk about problems occurring with go+pgBouncer (in Russian, sorry). https://habr.com/ru/company/oleg-bunin/blog/461935/ And a video on that: https://www.youtube.com/watch?v=Uojy57I-xP0

Remove auto-restarting process on mac

I got problems with a process which descrbibed itself on my mac as /Library/PrivilegedHelperTools/com.alibaba.security.aliedr. It was launched with root privileges and was started by the system after sudo pkill -f com.alibaba.security.aliedr. Renaming a file in the dir and rebooting did not help. What did help is this article — https://www.macworld.com/article/2047747/take-control-of-startup-and-login-items.html. I’ve found it and renamed …

env-file parser for Goland

You can use env-file parser for running and debugging your app in Jetbrains’ products like Goland. It’s pretty simple and works. https://github.com/Ashald/EnvFile

How golang garbage collection works

It is a Mark-and-Sweep GC. Phases Mark Stop-the-World: Set write barrier (to know how much was allocated during maark phase) Concurrent: Mark all memory which is still in use by the app Stop-the-World: Remove write barrier Concurrent: Sweep (it actually happens on new allocations) Details/Algorithm It’s a tri-color process: grey for objects to check, black …

Linux. History of system usage

There is a way to monitor your system usage and log to a file easily — with atop command. On my Ubuntu it can be installed with

sudo apt-get install atop

1	sudo apt-get install atop

It can be started as a top command — it’s output almost the same. But the most interesting feature is that it starts a daemon that logs …

Style guide for golang project file structure

Highly recommended. It has a couple of odds like not explaining about /test dir (I assume, they wanted to say to put there only e2e and other integrational tests, not unit-test as the latter should be kept together with the code itself in files like …_test.go). But it’s awesome in general. https://github.com/golang-standards/project-layout

Golang patterns. Worker pool

func worker(id int, jobs <-chan int, results chan<- int) {
    for j := range jobs {
        fmt.Println("worker", id, "started  job", j)
        time.Sleep(time.Second)
        fmt.Println("worker", id, "finished job", j)
        results <- j * 2
    }
}

func main() {

    // In order to use our pool of workers we need to send
    // them work and collect their results. We make 2
    // channels for this.
    jobs := make(chan int, 100)
    results := make(chan int, 100)

    // This starts up 3 workers, initially blocked
    // because there are no jobs yet.
    for w := 1; w <= 3; w++ {
        go worker(w, jobs, results)
    }

    // Here we send 5 `jobs` and then `close` that
    // channel to indicate that's all the work we have.
    for j := 1; j <= 5; j++ {
        jobs <- j
    }
    close(jobs)

    for a := 1; a <= 5; a++ {
        <-results
    }
}

func worker(id int, jobs <-chan int, results chan<- int) {

for j := range jobs {

fmt.Println("worker", id, "started job", j)

time.Sleep(time.Second)

fmt.Println("worker", id, "finished job", j)

results <- j * 2

}

func main() {

// In order to use our pool of workers we need to send

// them work and collect their results. We make 2

// channels for this.

jobs := make(chan int, 100)

results := make(chan int, 100)

// This starts up 3 workers, initially blocked

// because there are no jobs yet.

for w := 1; w <= 3; w++ {

go worker(w, jobs, results)

}

// Here we send 5 `jobs` and then `close` that

// channel to indicate that's all the work we have.

for j := 1; j <= 5; j++ {

jobs <- j

}

close(jobs)

for a := 1; a <= 5; a++ {

<-results

}

Further reading: https://gobyexample.com/worker-pools

PgBouncer and prepared statements

In our system, we use connection pooler called PgBouncer as a proxy to PostgreSQL server. PgBouncer has two main modes Session pooling mode This mode is less performant (it’s a default mode). When a client connects, a server connection will be assigned to it for the whole duration it stays connected. So it does not …

Golang: testing http and grpc servers

HTTP server is quite easy to test — here is a nice video about it: