Containers Aren't Linux Processes

There are many ways to create containers, especially on Linux and alike. Besides the super widespread Docker implementation, you may have heard about LXC, systemd-nspawn, or maybe even OpenVZ.

The general concept of the container is quite vague. What's true and what's not often depends on the context, but the context itself isn't always given explicitly. For instance, there is a common saying that containers are Linux processes or that containers aren't Virtual Machines. However, the first statement is just an oversimplified attempt to explain Linux containers. And the second statement simply isn't always true.

In this article, I'm not trying to review all possible ways of creating containers. Instead, the article is an analysis of the OCI Runtime Specification. The spec turned out to be an insightful read! For instance, it gives a definition of the standard container (and no, it's not a process) and sheds some light on when Virtual Machines can be considered containers.

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Exploring Go net/http Package - On How Not To Set Socket Options

Go standard library makes it super easy to start an HTTP server:

package main

import "net/http"

func main() {
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        w.Write([]byte("Hello there!\n"))
    })

    http.ListenAndServe(":8080", nil)
}

...or send an HTTP request:

package main

import "net/http"

func main() {
    resp, err := http.Get("http://example.com/")
    body, err := io.ReadAll(resp.Body)
}

In just ~10 lines of code, I can get a server up and running or fetch a real web page! In contrast, creating a basic HTTP server in C would take hundreds of lines, and anything beyond basics would require third-party libraries.

The Go snippets from above are so short because they rely on powerful high-level abstractions of the net and net/http packages. Go pragmatically chooses to optimize for frequently used scenarios, and its standard library hides many internal socket details behind these abstractions, making lots of default choices on the way. And that's very handy, but...

What if I need to fine-tune net/http sockets before initiating the communication? For instance, how can I set some socket options like SO_REUSEPORT or TCP_QUICKACK?

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