Initial commit.

.drone.yml

@@ -0,0 +1,59 @@
+---
+kind: pipeline
+type: docker
+name: "Tests and linting"
+
+trigger:
+  event:
+    exclude:
+      - pull_request
+
+steps:
+  - name: Linting
+    image: code.pztrn.name/containers/go-toolbox:v4
+    pull: if-not-exists
+    commands:
+      - task lint
+
+  - name: Tests
+    image: code.pztrn.name/containers/go-toolbox:v4
+    pull: if-not-exists
+    commands:
+      - task test
+
+---
+kind: pipeline
+type: docker
+name: "Build Release"
+
+depends_on:
+  - "Tests and linting"
+
+trigger:
+  event:
+    - tag
+
+steps:
+  - name: Build Docker image for Featurer
+    image: code.pztrn.name/containers/mirror/plugins/buildx:1.1.11
+    settings:
+      registry: code.pztrn.name
+      username: drone
+      password:
+        from_secret: drone_secret
+      repo: code.pztrn.name/pztrn/notificator
+      dockerfile: server/Dockerfile.featurer
+      auto_tag: true
+      force_tag: true
+
+  - name: Build Docker image for CMS
+    image: code.pztrn.name/containers/mirror/plugins/buildx:1.1.11
+    settings:
+      registry: code.pztrn.name
+      username: drone
+      password:
+        from_secret: drone_secret
+      repo: code.pztrn.name/pztrn/notificator
+      dockerfile: server/Dockerfile.CMS
+      auto_tag: true
+      force_tag: true

.gitignore

@@ -0,0 +1,2 @@
+*DS_Store*
+_build

.golangci.yml

@@ -0,0 +1,71 @@
+---
+run:
+  timeout: 5m
+
+linters:
+  enable-all: true
+  disable:
+    # deprecated
+    - varnamelen
+    - testpackage
+    - containedctx # very strange linter
+    - gomnd
+    - execinquery
+    # meaningfully disabled
+    - gochecknoglobals
+    - exhaustruct
+    - depguard # wtf is this linter
+    - tparallel # duplicates paralleltest
+    - unused # not very clever lint for generics
+    - ireturn # not very clever lint for generics
+    - interfacebloat # love big interfaces :)
+    - gci # whines about imports too much.
+
+linters-settings:
+  cyclop:
+    skip-tests: true
+    max-complexity: 20
+    package-average: 10
+  forbidigo:
+    forbid:
+      - '^(fmt\.Print(|f|ln)|print|println)$'
+      - '^time\.Now\(\)($|\.F|\.A|\.B|\.L|\.UTC\(\)\.I|,|\))(# Calls of time\.Now() without \.UTC() is prohibited\.)?'
+  funlen:
+    ignore-comments: true
+    lines: 200
+    statements: 60
+  gocyclo:
+    min-complexity: 20
+  gofumpt:
+    extra-rules: true
+  govet:
+    enable-all: true
+  lll:
+    line-length: 120
+  nestif:
+    min-complexity: 20
+  tagliatelle:
+    case:
+      use-field-name: true
+      rules:
+        json: snake
+        yaml: camel
+
+issues:
+  exclude-use-default: false
+  exclude:
+    - ST1000 # package comment
+    - package-comments
+  exclude-rules:
+    - path: .+_test\.go
+      linters:
+        - gosec
+    - linters:
+        - godox
+      text: "TODO"
+    # Default error checking pattern "if err := ... ;err != nil {}" multiple times makes go vet to whine.
+    - linters:
+        - govet
+      text: 'declaration of "err" shadows'
+  max-issues-per-linter: 0
+  max-same-issues: 0

.markdownlint.json

@@ -0,0 +1,4 @@
+{
+    "line-length": false,
+    "first-line-h1": false
+}

.yamllint

@@ -0,0 +1,9 @@
+---
+extends: default
+
+rules:
+  line-length: disable
+  braces:
+    min-spaces-inside: 1
+    max-spaces-inside: 1
+

README.md

@@ -0,0 +1,3 @@
+# Featurer
+
+Features toggling server.

Taskfile.yml

@@ -0,0 +1,58 @@
+---
+version: "3"
+
+vars:
+  BRANCH:
+    sh: ./scripts/version-data-generator.sh branch
+  BUILD_DATE:
+    sh: date '+%Y-%m-%d %H:%M:%S %z'
+  BUILD_NUMBER:
+    sh: ./scripts/version-data-generator.sh build_number
+  COMMIT:
+    sh: ./scripts/version-data-generator.sh commit
+  VERSION:
+    sh: ./scripts/version-data-generator.sh version
+  BASIC_LDFLAGS: "-X 'go.dev.pztrn.name/featurer/server/internal/application.Version={{ .VERSION }}' -X 'go.dev.pztrn.name/featurer/server/internal/application.Branch={{ .BRANCH }}' -X 'go.dev.pztrn.name/featurer/server/internal/application.Commit={{ .COMMIT }}' -X 'go.dev.pztrn.name/featurer/server/internal/application.Build={{ .BUILD_NUMBER }}' -X 'go.dev.pztrn.name/featurer/server/internal/application.BuildDate={{ .BUILD_DATE }}'"
+  LDFLAGS: "{{ .BASIC_LDFLAGS }}"
+
+includes:
+  server: ./server
+
+tasks:
+  cleanup:
+    desc: "Cleanup _build directory."
+    cmds:
+      - task: server:cmd:cms:cleanup
+      - task: server:cmd:featurer:cleanup
+
+  default:
+    desc: "Default help."
+    cmds:
+      - echo "Run \"task -l\" for list of available tasks."
+
+  lint:
+    desc: "Runs linters."
+    cmds:
+      - golangci-lint run ./...
+      - go vet ./...
+
+  pre-commit:
+    desc: "Runs some tasks before comitting."
+    cmds:
+      - task: lint
+      - task: test
+
+  test:
+    desc: "Run tests."
+    cmds:
+      - go test ./...
+
+  vars:
+    desc: "Show vars which will be used for building or running."
+    silent: true
+    cmds:
+      - echo "BRANCH={{ .BRANCH }}"
+      - echo "BUILD_DATE={{ .BUILD_DATE }}"
+      - echo "BUILD_NUMBER={{ .BUILD_NUMBER }}"
+      - echo "COMMIT={{ .COMMIT }}"
+      - echo "VERSION={{ .VERSION }}"

client/go/client.go

@@ -0,0 +1,4 @@
+package client
+
+// Client is a Featurer client for Golang application.
+type Client struct{}

go.mod

@@ -0,0 +1,3 @@
+module go.dev.pztrn.name/featurer
+
+go 1.23

scripts/version-data-generator.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+
+VERSION_PREFIX="v"
+
+# shellcheck disable=SC1083
+BUILD_NUMBER=$(git rev-list --count --all)
+BRANCH_NAME=$(git branch --show-current)
+COMMIT=$(git rev-parse HEAD)
+VERSION=$(git tag | sort | grep "${VERSION_PREFIX}" | tail -n 1 | cut -c$((${#VERSION_PREFIX} + 1))-)
+
+if [ "${VERSION}" == "" ]; then
+    VERSION="0.1.0-dev"
+fi
+
+function show_help() {
+    echo "$0 [param]"
+    echo ""
+    echo "Parameters:"
+    echo ""
+    echo "  branch          Show branch."
+    echo "  build_number    Show build number (commits count)."
+    echo "  commit          Show commit hash."
+    echo "  version         Show version (real or '0.1.0-dev' if no version tags present)."
+}
+
+case $1 in
+branch)
+    echo "${BRANCH_NAME}"
+    ;;
+build_number)
+    echo "${BUILD_NUMBER}"
+    ;;
+commit)
+    echo "${COMMIT}"
+    ;;
+version)
+    echo "${VERSION}"
+    ;;
+*)
+    show_help
+    ;;
+esac

server/Dockerfile.CMS

@@ -0,0 +1,18 @@
+FROM code.pztrn.name/containers/go-toolbox:v4 AS build
+
+WORKDIR /featurer
+COPY . /featurer
+RUN --mount=type=cache,target="$GOCACHE" task server:cmd:cms:build
+
+FROM debian:12.6-slim
+
+RUN apt-get update && \
+    apt-get install -y ca-certificates iputils-ping && \
+    rm -rf /var/lib/apt/* /var/cache/apt/*
+
+COPY --from=build /featurer/_build/featurer-cms /featurer-cms
+COPY --from=build /usr/local/bin/dlv /dlv
+
+COPY server/entrypoint-cms.sh /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]

server/Dockerfile.featurer

@@ -0,0 +1,18 @@
+FROM code.pztrn.name/containers/go-toolbox:v4 AS build
+
+WORKDIR /featurer
+COPY . /featurer
+RUN --mount=type=cache,target="$GOCACHE" task server:cmd:featurer:build
+
+FROM debian:12.6-slim
+
+RUN apt-get update && \
+    apt-get install -y ca-certificates iputils-ping && \
+    rm -rf /var/lib/apt/* /var/cache/apt/*
+
+COPY --from=build /featurer/_build/featurer /featurer
+COPY --from=build /usr/local/bin/dlv /dlv
+
+COPY server/entrypoint-featurer.sh /entrypoint.sh
+
+ENTRYPOINT ["/entrypoint.sh"]

server/Taskfile.yml

@@ -0,0 +1,6 @@
+---
+version: "3"
+
+includes:
+  cmd: ./cmd
+  localdev: ./localdev

server/cmd/Taskfile.yml

@@ -0,0 +1,6 @@
+---
+version: "3"
+
+includes:
+  cms: ./cms
+  featurer: ./featurer

server/cmd/cms/Taskfile.yml

@@ -0,0 +1,21 @@
+---
+version: "3"
+
+tasks:
+  build:
+    desc: "Builds Featurer's CMS binary."
+    cmds:
+      - task: cleanup
+      - go build -ldflags="{{ .LDFLAGS }}" -tags netgo -o _build/featurer-cms{{exeExt}} ./server/cmd/cms/main.go
+    sources:
+      - ./**/*.go
+      - ./Taskfile.yml
+      - ./go.mod
+    generates:
+      - ./_build/featurer-cms{{exeExt}}
+    method: none
+
+  cleanup:
+    desc: "Deletes Featurer's CMS binary from local build cache."
+    cmds:
+      - rm -f _build/featurer-cms{{exeExt}}

server/cmd/cms/main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"log/slog"
+
+	"go.dev.pztrn.name/featurer/server/internal/application"
+	"go.dev.pztrn.name/featurer/server/internal/services/core/datastore"
+)
+
+func main() {
+	_ = slog.SetLogLoggerLevel(slog.LevelDebug)
+
+	app := application.New()
+
+	slog.Info(
+		"Launching Featurer's CMS...",
+		"version", application.Version,
+		"build", application.Build,
+		"branch", application.Branch,
+		"commit", application.Commit,
+		"build date", application.BuildDate,
+	)
+
+	// Initializing core services first.
+	checkError(datastore.Initialize(app))
+
+	// Then - features services.
+
+	// Start application.
+	checkError(app.Start())
+
+	<-app.GetShutdownDoneChannel()
+	slog.Info("Featurer's CMS.")
+}
+
+func checkError(err error) {
+	if err == nil {
+		return
+	}
+
+	panic(err)
+}

server/cmd/featurer/Taskfile.yml

@@ -0,0 +1,21 @@
+---
+version: "3"
+
+tasks:
+  build:
+    desc: "Builds Featurer main binary."
+    cmds:
+      - task: cleanup
+      - go build -ldflags="{{ .LDFLAGS }}" -tags netgo -o _build/featurer{{exeExt}} ./server/cmd/featurer/main.go
+    sources:
+      - ./**/*.go
+      - ./Taskfile.yml
+      - ./go.mod
+    generates:
+      - ./_build/featurer{{exeExt}}
+    method: none
+
+  cleanup:
+    desc: "Deletes Featurer main binary from local build cache."
+    cmds:
+      - rm -f _build/featurer{{exeExt}}

server/cmd/featurer/main.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"log/slog"
+
+	"go.dev.pztrn.name/featurer/server/internal/application"
+	"go.dev.pztrn.name/featurer/server/internal/services/core/datastore"
+)
+
+func main() {
+	_ = slog.SetLogLoggerLevel(slog.LevelDebug)
+
+	app := application.New()
+
+	slog.Info(
+		"Launching Featurer server...",
+		"version", application.Version,
+		"build", application.Build,
+		"branch", application.Branch,
+		"commit", application.Commit,
+		"build date", application.BuildDate,
+	)
+
+	// Initializing core services first.
+	checkError(datastore.Initialize(app))
+
+	// Then - features services.
+
+	// Start application.
+	checkError(app.Start())
+
+	<-app.GetShutdownDoneChannel()
+	slog.Info("Featurer stopped.")
+}
+
+func checkError(err error) {
+	if err == nil {
+		return
+	}
+
+	panic(err)
+}

server/entrypoint-cms.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+echo "* Starting Featurer's CMS..."
+if [ -n "${FEATURER_DEBUG}" ]; then
+    exec /dlv --listen=:4000 --headless=true --log=true --accept-multiclient --api-version=2 exec /featurer-cms --continue
+else
+    exec /featurer-cms
+fi

server/entrypoint-featurer.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+
+echo "* Starting Featurer..."
+if [ -n "${FEATURER_DEBUG}" ]; then
+    exec /dlv --listen=:4000 --headless=true --log=true --accept-multiclient --api-version=2 exec /featurer --continue
+else
+    exec /featurer
+fi

server/internal/application/application.go

@@ -0,0 +1,114 @@
+package application
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"os"
+	"os/signal"
+	"sync"
+	"syscall"
+)
+
+var (
+	// ErrApplication indicates that error appeared somewhere in application's lifecycle controller.
+	ErrApplication = errors.New("application")
+
+	// Version is application's version.
+	Version string
+	// Branch is a branch name from which application was built.
+	Branch string
+	// Commit is a commit hash from which application was built.
+	Commit string
+	// Build is a build number.
+	Build string
+	// BuildDate is a date on which application was built.
+	BuildDate string
+)
+
+// Application is an application's lifecycle controlling structure.
+type Application struct {
+	ctx           context.Context
+	shutdownDone  chan struct{}
+	cancelFunc    context.CancelFunc
+	services      map[string]Service
+	dataPath      string
+	servicesMutex sync.RWMutex
+}
+
+// New creates new application's lifecycle controlling structure.
+func New() *Application {
+	appl := &Application{}
+	appl.initialize()
+
+	return appl
+}
+
+// GetContext returns application's global context.
+func (a *Application) GetContext() context.Context {
+	return a.ctx
+}
+
+// GetShutdownDoneChannel returns channel on which lifecycle controller will tell about shutdown completion.
+// Should be used only in main()!
+func (a *Application) GetShutdownDoneChannel() chan struct{} {
+	slog.Debug("Returning shutdown completion channel.")
+
+	return a.shutdownDone
+}
+
+func (a *Application) initialize() {
+	a.ctx, a.cancelFunc = context.WithCancel(context.Background())
+	a.ctx, a.cancelFunc = signal.NotifyContext(a.ctx, os.Interrupt, syscall.SIGTERM)
+
+	a.services = make(map[string]Service)
+
+	a.shutdownDone = make(chan struct{}, 1)
+}
+
+// Shutdown stops application and all registered services.
+func (a *Application) Shutdown() error {
+	a.cancelFunc()
+
+	a.servicesMutex.RLock()
+	defer a.servicesMutex.RUnlock()
+
+	for _, service := range a.services {
+		if err := service.Shutdown(); err != nil {
+			slog.Error("Error appeared when trying to shut down service", "service", service.GetName(), "error", err.Error())
+		}
+	}
+
+	a.shutdownDone <- struct{}{}
+
+	return nil
+}
+
+// Start starts application and all registered services.
+func (a *Application) Start() error {
+	go a.signalsListener()
+
+	a.servicesMutex.RLock()
+	defer a.servicesMutex.RUnlock()
+
+	// First pass - connecting dependencies.
+	for _, service := range a.services {
+		if err := service.ConnectDependencies(); err != nil {
+			return fmt.Errorf("%w: connecting dependencies for service '%s': %w", ErrApplication, service.GetName(), err)
+		}
+	}
+
+	// Second pass - launching startup tasks.
+	for name, service := range a.services {
+		slog.Debug("Launching startup tasks for service", "service", name)
+
+		if err := service.LaunchStartupTasks(); err != nil {
+			return fmt.Errorf("%w: launching startup tasks for '%s': %w", ErrApplication, service.GetName(), err)
+		}
+	}
+
+	slog.Debug("Application started.")
+
+	return nil
+}

server/internal/application/service.go

@@ -0,0 +1,54 @@
+package application
+
+import (
+	"errors"
+	"fmt"
+)
+
+var (
+	// ErrServiceAlreadyRegistered appears when trying to register a service with already taken name.
+	ErrServiceAlreadyRegistered = errors.New("service already registered")
+	// ErrServiceNotRegistered appears when trying to get a registered service with unknown name.
+	ErrServiceNotRegistered = errors.New("unknown service")
+)
+
+// Service это интерфейс, которому должны соответствовать все сервисы, используемые в приложении.
+type Service interface {
+	ConnectDependencies() error
+	GetName() string
+	Initialize() error
+	LaunchStartupTasks() error
+	Shutdown() error
+}
+
+// GetService возвращает сервис по имени, или же ошибку, если сервис не был зарегистрирован ранее.
+func (a *Application) GetService(name string) (Service, error) {
+	a.servicesMutex.RLock()
+	service, found := a.services[name]
+	a.servicesMutex.RUnlock()
+
+	if !found {
+		return nil, fmt.Errorf("%w: get service '%s': %w", ErrApplication, name, ErrServiceNotRegistered)
+	}
+
+	return service, nil
+}
+
+// RegisterService регистрирует сервис, или возвращает ошибку, если сервис с таким именем уже был
+// зарегистрирован ранее.
+func (a *Application) RegisterService(service Service) error {
+	_, found := a.services[service.GetName()]
+	if found {
+		return fmt.Errorf("%w: register service '%s': %w", ErrApplication, service.GetName(), ErrServiceAlreadyRegistered)
+	}
+
+	if err := service.Initialize(); err != nil {
+		return fmt.Errorf("%w: initializing service '%s': %w", ErrApplication, service.GetName(), err)
+	}
+
+	a.servicesMutex.Lock()
+	a.services[service.GetName()] = service
+	a.servicesMutex.Unlock()
+
+	return nil
+}

server/internal/application/signals.go

@@ -0,0 +1,24 @@
+package application
+
+import (
+	"log/slog"
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+func (a *Application) signalsListener() {
+	slog.Info("Starting listening for SIGTERM signal...")
+
+	listener := make(chan os.Signal, 1)
+
+	signal.Notify(listener, syscall.SIGTERM, os.Interrupt)
+
+	<-listener
+	slog.Info("Got SIGTERM, stopping Featurer...")
+
+	if err := a.Shutdown(); err != nil {
+		slog.Error("Something went wrong when trying to shutdown application", "error", err.Error())
+		slog.Error("!!! APPLICATION CANNOT BE STOPPED NORMALLY, KILL IT MANUALLY !!!")
+	}
+}

server/internal/services/core/datastore.go

@@ -0,0 +1,16 @@
+package core
+
+import "errors"
+
+// ServiceNameDatastore is a service name for data storage implementation.
+const ServiceNameDatastore = "datastore"
+
+var (
+	// ErrDatastore indicates that error appeared somewhere in data storage service.
+	ErrDatastore = errors.New("datastore")
+	// ErrDatastoreServiceIsInvalid appears when data storage implementation isn't conforming to interface.
+	ErrDatastoreServiceIsInvalid = errors.New("invalid datastore implementation")
+)
+
+// DataStore is an interface for data storage implementations.
+type DataStore interface{}

server/internal/services/core/datastore/datastore.go

@@ -0,0 +1,48 @@
+package datastore
+
+import (
+	"fmt"
+	"log/slog"
+
+	"go.dev.pztrn.name/featurer/server/internal/application"
+	"go.dev.pztrn.name/featurer/server/internal/services/core"
+)
+
+type datastore struct {
+	app *application.Application
+}
+
+// Initialize initializes service.
+func Initialize(app *application.Application) error {
+	plan := &datastore{
+		app: app,
+	}
+
+	if err := app.RegisterService(plan); err != nil {
+		return fmt.Errorf("%w: %w", core.ErrDatastore, err)
+	}
+
+	return nil
+}
+
+func (p *datastore) ConnectDependencies() error {
+	return nil
+}
+
+func (p *datastore) GetName() string {
+	return core.ServiceNameDatastore
+}
+
+func (p *datastore) Initialize() error {
+	slog.Info("Initializing data storage...")
+
+	return nil
+}
+
+func (p *datastore) LaunchStartupTasks() error {
+	return nil
+}
+
+func (p *datastore) Shutdown() error {
+	return nil
+}

server/localdev/Taskfile.yml

@@ -0,0 +1,19 @@
+---
+version: 3
+
+includes:
+  common: ./common
+  featurer: ./featurer
+
+tasks:
+  down:
+    desc: "Removes development environment."
+    cmds:
+      - task: featurer:down
+      - task: common:network-down
+
+  up:
+    desc: "Creates development environment."
+    cmds:
+      - task: common:network-up
+      - task: featurer:up

server/localdev/common/Taskfile.yml

@@ -0,0 +1,15 @@
+---
+version: "3"
+
+tasks:
+  network-down:
+    desc: "Deletes Docker network for development."
+    dir: "./server/localdev/common"
+    cmds:
+      - docker compose -p featurer-network -f network.yaml down
+
+  network-up:
+    desc: "Creates Docker network for development"
+    dir: "./server/localdev/common"
+    cmds:
+      - docker compose -p featurer-network  -f network.yaml up -d

server/localdev/common/network.yaml

@@ -0,0 +1,18 @@
+---
+services:
+  dummy:
+    image: busybox
+    container_name: featurer-dummy
+    hostname: dummy
+    networks:
+      featurer:
+        ipv4_address: 248.248.0.254
+
+networks:
+  featurer:
+    driver: bridge
+    name: "featurer"
+    ipam:
+      config:
+        - subnet: 248.248.0.0/24
+          gateway: 248.248.0.1

server/localdev/featurer/Taskfile.yml

@@ -0,0 +1,47 @@
+---
+version: "3"
+
+tasks:
+  build:
+    desc: "Builds Featurer's container."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - docker compose -p featurer -f docker-compose.yaml build
+
+  down:
+    desc: "Deletes all Featurer's data (down)."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - docker compose -p featurer -f docker-compose.yaml down --volumes
+
+  logs:
+    desc: "Show Featurer logs."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - docker compose -p featurer -f docker-compose.yaml logs -f
+
+  restart:
+    desc: "Restart Featurer."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - docker compose -p featurer -f docker-compose.yaml restart
+
+  start:
+    desc: "Start Featurer."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - docker compose -p featurer -f docker-compose.yaml start
+
+  stop:
+    desc: "Stop Featurer without deleting it's data."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - docker compose -p featurer -f docker-compose.yaml stop
+
+  up:
+    desc: "Start Featurer (up -d)."
+    dir: "./server/localdev/featurer"
+    cmds:
+      - task: :common:network-up
+      - task: build
+      - docker compose -p featurer -f docker-compose.yaml up -d

server/localdev/featurer/docker-compose.yaml

@@ -0,0 +1,16 @@
+---
+services:
+  featurer:
+    container_name: "featurer"
+    build:
+      context: ../../../
+      dockerfile: server/Dockerfile.featurer
+    networks:
+      featurer:
+        ipv4_address: 248.248.0.2
+    cap_add:
+      - SYS_PTRACE
+
+networks:
+  featurer:
+    external: true