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First of all I have to admit that I am a beginner concerning concurrency in general, but reading a lot about it recently. Because I heard that Golang is strong on that area. I wanted to ask how (concurrent) servers are written in this language.

I mean, there are different ways in how to write a server that can handle multiple requests/connections concurrently. You can use threads, asynchronous programming (async/asyncio in Python for example), and in Golang there are goroutines, which is more or less a lightweight thread.

However, when using Python and async/asyncio you can have one single process and one thread and it's able to handle concurrency. However, the code is complicated (at least for me without any background).

My question: What is the way to go to write a concurrent server in Golang? Just a new goroutine for every connection or are there any asynchronous ways? What's the "best practice"?

I mean is it not expensive to have LOTS of goroutines on a highly used server? How to do a well-written server in Golang?

stevenferrer
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Aliquis
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  • Goroutines are lightweight and very cheap (compared to threads). The go runtime is capable of handling even hundreds of thousands of goroutines efficiently. – icza Sep 21 '17 at 09:39
  • Also see this possible duplicate: [Process Management for the Go Webserver](https://stackoverflow.com/questions/37529511/process-management-for-the-go-webserver/37531953#37531953). – icza Sep 21 '17 at 09:57

3 Answers3

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For beginner the best way to start is just use https://golang.org/pkg/net/http/ and just write http handlers. You don't need to initialize Go routines - the http.Server will do it for you.

The code will be straight forward with blocking calls. You don't need to think about concurrency at this stage as Go will do it for you. For example when you do a call like

record, err := someDb.GetRecordByID(123)

actually it's an asynchronous call that blocks current flow but release thread to other Go routines. It will continue flow once data returned and a thread (may be different from previous) becomes available.

If you will need to do concurrent calls within 1 HTTP request you can start Go routines. But leave it for later stage and do the Go lang tour on concurrency first.

If you really need a high load solution for HTTP requests consider using https://github.com/valyala/fasthttp instead of standard http package.

Alexander Trakhimenok
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For HTTP @icza's comments & Alexander's answer give a fair idea. Just to add Goroutines are not expensive because they are lighter than normal threads. They can have variable sized stack (probably start as low as 2k) & hence can scale up very well with less operating overhead.

Also on http, there are third party libraries like Gorilla mux which can make life better as also other frameworks like Buffalo which you can explore. While I haven't used the latter, I have heard it makes life easier.

Now if you are going to be writing your own custom server (something different from http) then again Go is a great choice for it. The program can start as simple as https://golang.org/pkg/net/#example_Listener (To try running this program, you can use netcat like this from another terminal)

$ nc localhost 2000
Hellow
Hellow

And finally channels in Go make sharing data & communication much easier and safer across routines taking care of the synchronization aspects. Hope this helps.

Ravi R
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My question: What is the way to go to write a concurrent server in Golang? Just a new goroutine for every connection or are there any asynchronous ways? What's "best practice"?

Golang http package will do requests concurrency handling for you and I really like that code looks like synchronous and you don't need to add any async/await keywords. Here is how you start

func helloHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello")
}

http.HandleFunc("/hello", helloHandler)
log.Fatal(http.ListenAndServe(":8080", nil))
Andzej Maciusovic
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