Category Archives: Programming

Golang’s sync.Map internals

Great article on the topic — https://victoriametrics.com/blog/go-sync-map/index.html. The whole series of articles is solid, so please take a look if you are interested. Let me share the most important insights. How it works Internal structure is:

type Map struct {
	mu Mutex
	read atomic.Pointer[readOnly]
	dirty map[any]*entry
	misses int
}

type Map struct {

mu Mutex

read atomic.Pointer[readOnly]

dirty map[any]*entry

misses int

}

MVC, MVP, MVVM, MVVM-C, and VIPER architecture patterns comparison

Great diagram comparing MVC, MVP, MVVM, MVVM-C, and VIPER architecture patterns from ByteByteGo: They also provide the following description: — MVC, the oldest pattern, dates back almost 50 years — Every pattern has a «view» (V) responsible for displaying content and receiving user input — Most patterns include a «model» (M) to manage business data …

Cleanlinter — my first golang linter

I’ve implemented my first go linter, called cleanlinter — https://github.com/bullgare/cleanlinter. It’s a simplistic linter to check golang project internal imports according to Clean Architecture pattern. Installation

go install github.com/bullgare/cleanlinter/cmd/cleanlinter@latest

1	go install github.com/bullgare/cleanlinter/cmd/cleanlinter@latest

Usage

cleanlinter \
-cleanlinter_path_to_domain=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/domain \
-cleanlinter_path_to_usecase=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/usecase \
-cleanlinter_path_to_adapter=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/adapter \
-cleanlinter_path_to_infra=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/infra \
./...

cleanlinter \

-cleanlinter_path_to_domain=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/domain \

-cleanlinter_path_to_usecase=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/usecase \

-cleanlinter_path_to_adapter=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/adapter \

-cleanlinter_path_to_infra=github.com/bullgare/cleanlinter/test/testdata/src/project_correct/internal/infra \

./...

To be honest, writing proper integration tests made much more time than just writing the linter. Articles, discussions, examples that helped me: https://developer20.com/custom-go-linter/ https://stackoverflow.com/questions/72933175/go-get-filepath-from-ast-file https://github.com/bkielbasa/cyclop/blob/master/pkg/analyzer/analyzer.go https://github.com/alingse/asasalint/blob/main/asasalint_test.go

DDD/Clean Architecture go linters

Origin (in Russian) Tech talk (paid access only, unfortunately): https://conf.ontico.ru/online/hl2023/details/5206668 Presentation: https://docs.google.com/presentation/d/1n5jCie-9tBw3QEEF6NsNco4mS9xYkg52/edit#slide=id.g29c6e2d30cb_0_169 Linters Dependencies between layers: https://github.com/OpenPeeDeeP/depguard https://github.com/fe3dback/go-arch-lint/ You can also check mine (very simplistic) — https://blog.bullgare.com/2024/06/cleanlinter-my-first-golang-linter/ Others: https://github.com/nishanths/exhaustive — to check using all microtypes in enums/switches. https://github.com/go-simpler/musttag + https://github.com/maranqz/golangconf2023/blob/main/tags/rules.go — to prevent using struct tags in Domain models (Value Objects). https://github.com/maranqz/gopublicfield — to prevent …

Protobuf: safer usage for buf

A drop-in replacement for buf issued by Ozon. Repository: https://github.com/easyp-tech/server Presentation (for subscribers only, unfortunately): https://conf.ontico.ru/online/hl2023/details/5206585

Maps internals in Go

Idea Map is passed as a value, but it consists of a pointer to hmap which has all the details on map implementation. So, if you change/add to map, it will be reflected everywhere. And that’s why you cannot assign to an uninitialized map (no memory allocated, no hash seed generated yet). runtime/map.go

type hmap struct {
	count     int // # live cells == size of map.  Must be first (used by len() builtin)
	B         uint8  // log_2 of # of buckets (can hold up to loadFactor * 2^B items)
	hash0     uint32 // hash seed

	buckets    unsafe.Pointer // array of 2^B Buckets. may be nil if count==0.
	oldbuckets unsafe.Pointer // previous bucket array of half the size, non-nil only when growing
	nevacuate  uintptr        // progress counter for evacuation (buckets less than this have been evacuated)
}

type hmap struct {

count int // # live cells == size of map. Must be first (used by len() builtin)

B uint8 // log_2 of # of buckets (can hold up to loadFactor * 2^B items)

hash0 uint32 // hash seed

buckets unsafe.Pointer // array of 2^B Buckets. may be nil if count==0.

oldbuckets unsafe.Pointer // previous bucket array of half the size, non-nil only when growing

nevacuate uintptr // progress counter for evacuation (buckets less than this have been evacuated)

}

Buckets …

Docker and Kubernetes basics for developers

Docker Docker containers are much more lightweight compared to classic VMs as they leverage host OS instead of starting their own OS. Containers are using 2 features of Linux-based OS: Namespaces and Cgroups (Control Groups). Namespace Lets you allocate resources in an isolated environment (like a sandbox). On a container start, docker daemon generates a …

Go’s Concurrency and Channel Internals

Go is implementing CSP (Communicating Sequential Processing): processes are communicating through channels, they can block each other while waiting for read/writes to channels. Actor model makes inter-process communications more explicit and non-blocking. CSP vs Actor explained — https://dev.to/karanpratapsingh/csp-vs-actor-model-for-concurrency-1cpg. Channels requirements goroutine-safe store and pass data across goroutines FIFO can block/unblock goroutines

Protobuf: add header parameters

They finally added it to the grpc-gateway: https://github.com/grpc-ecosystem/grpc-gateway/pull/3010/files#diff-c255ac405628aada46c25a2c9765605e9f823bc523d3739fd3fa71d4bcbf5c99. So, to use it you can just update to the version 2.14.0 or above — https://github.com/grpc-ecosystem/grpc-gateway/releases/tag/v2.14.0, and add something like this to your protofile:

        option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {
            summary: "Create a new foo.";
            parameters: {
                headers: {
                    name: "My-Custom-Header";
                    description: "Some custom header description";
                    required: true;
                };
            };
        };

option (grpc.gateway.protoc_gen_openapiv2.options.openapiv2_operation) = {

summary: "Create a new foo.";

parameters: {

headers: {

name: "My-Custom-Header";

description: "Some custom header description";

required: true;

};

Go scheduler details

Scheduler was implemented by Dmitry Vyukov in go 1.1 and lives in runtime/proc.go. Good resources https://www.youtube.com/watch?v=-K11rY57K7k — video by Dmitry Vyukov (slides as pdf) https://www.ardanlabs.com/blog/2018/08/scheduling-in-go-part2.html — nice article by Bill Kennedy in 3 parts. Most of the images below are taken from this article. Main ideas Goroutines are very light weight (~2KB+) and very cheap …