implemented it to the point where it's functional for now.

detailed error handling, preparation of thorough test code, and tidying up the formatting will be addressed later.

.github/dependabot.yml

@@ -0,0 +1,27 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+      time: "09:00"
+      timezone: "Asia/Tokyo"
+    reviewers:
+      - "tukaelu"
+    open-pull-requests-limit: 5
+    labels:
+      - "dependencies"
+  - package-ecosystem: gomod
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+      time: "09:00"
+      timezone: "Asia/Tokyo"
+    open-pull-requests-limit: 5

.github/workflow/ci.yml

@@ -0,0 +1,35 @@
+---
+name: test
+on:
+  pull_request: {}
+  push:
+    branches: [main]
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+"
+env:
+  DEBIAN_FRONTEND: noninteractive
+  TZ: 'Asia/Tokyo'
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: golangci/golangci-lint-action@v3
+  test:
+    strategy:
+      matrix:
+        os: ['ubuntu-latest', 'macOS-latest', 'windows-latest']
+        go: ["1.21.x", "1.20.x"]
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/setup-go@v4
+      with:
+        go-version: ${{ matrix.go }}
+    - uses: actions/checkout@v4
+    - uses: actions/cache@v3
+      with:
+        path: ~/go/pkg/mod
+        key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+        restore-keys: |
+          ${{ runner.os }}-go-
+    - run: go test -v ./...

.gitignore

@@ -0,0 +1,2 @@
+dist/
+*.yml

Makefile

@@ -0,0 +1,29 @@
+PROG_NAME ?= ikesu
+VERSION ?= $(shell git describe --tags --abbrev=0)
+REVISION := $(shell git rev-parse --short HEAD)
+
+OUTPUT_DIR ?= dist
+
+OS := $(shell go env GOOS)
+ARCH := $(shell go env GOARCH)
+BUILD_LDFLAGS := "-X main.version=$(VERSION) -X main.revision=$(REVISION)"
+
+SOURCES = $(shell find . -type f -name '*.go')
+
+.PHONY: test
+test:
+	go clean -testcache
+	go test -v ./...
+
+lint:
+	golangci-lint run
+
+build: $(OUTPUT_DIR) $(SOURCES)
+	go mod tidy
+	GOOS=$(OS) GOARCH=$(ARCH) CGO_ENABLED=0 go build -ldflags=$(BUILD_LDFLAGS) -o $(OUTPUT_DIR)/$(PROG_NAME) ./cmd/$(PROG_NAME)/
+
+clean:
+	rm -r $(OUTPUT_DIR)/*
+
+$(OUTPUT_DIR):
+	mkdir -p $(OUTPUT_DIR)

cmd/ikesu/loaders.go

@@ -0,0 +1,6 @@
+package main
+
+// Register as loader.
+import (
+	_ "github.com/tukaelu/ikesu/internal/config/loader/file"
+)

cmd/ikesu/main.go

@@ -0,0 +1,131 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+	"strings"
+	"syscall"
+
+	"github.com/aws/aws-lambda-go/lambda"
+	"github.com/mackerelio/mackerel-client-go"
+	"github.com/urfave/cli/v2"
+
+	"github.com/tukaelu/ikesu/cmd/ikesu/subcommand"
+	"github.com/tukaelu/ikesu/internal/config"
+	"github.com/tukaelu/ikesu/internal/constants"
+	"github.com/tukaelu/ikesu/internal/logger"
+)
+
+var version string
+var revision string
+
+func main() {
+	cli := &cli.App{
+		Name:  "ikesu",
+		Usage: "We monitor the health of the fish in the \"Ikesu\".",
+		Flags: []cli.Flag{
+			&cli.StringFlag{
+				Name:        "mackerel-apikey",
+				DefaultText: "**********",
+				EnvVars:     []string{"MACKEREL_APIKEY", "IKESU_MACKEREL_APIKEY"},
+				Required:    true,
+			},
+		},
+		Commands: []*cli.Command{
+			{
+				Name:      "checker",
+				Usage:     "Detects disruptions in posted metrics and notifies the host as a CRITICAL alert.",
+				UsageText: "ikesu checker -config <config file> [-dry-run]",
+				Action: func(ctx *cli.Context) error {
+
+					// Show the provider name and metric name, then terminate.
+					if ctx.Bool("show-providers") {
+						showProvidersInspectionMetricMap()
+						return nil
+					}
+
+					var l *logger.Logger
+					var err error
+					if l, err = logger.NewDefaultLogger("info", ctx.Bool("dry-run")); err != nil {
+						return err
+					}
+
+					config, err := config.NewCheckerConfig(ctx.Context, ctx.String("config"))
+					if err != nil {
+						return err
+					}
+					if err := config.Validate(); err != nil {
+						return err
+					}
+					checker := &subcommand.Checker{
+						Config: config,
+						Client: mackerel.NewClient(ctx.String("mackerel-apikey")),
+						DryRun: ctx.Bool("dry-run"),
+						Logger: l,
+					}
+
+					// wrap function
+					handler := func(ctx context.Context) error {
+						return checker.Run(ctx)
+					}
+					l.Log.Info("Run command", "version", ctx.App.Version)
+					l.Log.V(1).Info(fmt.Sprintf("config: %+v", config))
+
+					if isLambda() {
+						lambda.StartWithOptions(handler, lambda.WithContext(ctx.Context))
+						return nil
+					}
+					return handler(ctx.Context)
+				},
+				Flags: []cli.Flag{
+					&cli.StringFlag{
+						Name:    "config",
+						Usage:   "Specify the path to the configuration file.",
+						Aliases: []string{"c"},
+						EnvVars: []string{"IKESU_CHECKER_CONFIG"},
+					},
+					&cli.BoolFlag{
+						Name:  "show-providers",
+						Usage: "List the inspection metric names corresponding to the provider for each integration.",
+					},
+					&cli.BoolFlag{
+						Name:  "dry-run",
+						Usage: "Only a simplified display of the check results is performed, and no alerts are issued.",
+					},
+				},
+			},
+		},
+	}
+
+	cli.Version = fmt.Sprintf("%s (rev.%s)", version, revision)
+
+	ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGTERM, syscall.SIGINT, syscall.SIGHUP)
+	defer cancel()
+
+	if err := cli.RunContext(ctx, os.Args); err != nil {
+		fmt.Println(err.Error())
+		os.Exit(1)
+	}
+}
+
+func isLambda() bool {
+	return os.Getenv("AWS_EXECUTION_ENV") != "" || os.Getenv("AWS_LAMBDA_RUNTIME_API") != ""
+}
+
+func showProvidersInspectionMetricMap() {
+	integrations := constants.GetIntegrations()
+	providers := constants.GetProviders()
+	immap := constants.GetProvidersInspectionMetricMap()
+	for i := 0; i < len(integrations); i++ {
+		fmt.Printf("Integration: %s\n", integrations[i])
+		fmt.Println(strings.Repeat("-", 30))
+		for _, key := range providers {
+			if metric, ok := immap[integrations[i]][key]; ok {
+				fmt.Printf("provider: %-20s, metric: %s\n", key, metric)
+			}
+		}
+		fmt.Println("")
+	}
+}