webhooker/cmd/webhooker/main.go

// Package main is the entry point for the webhooker application.
package main

import (
	"fmt"
	"io"
	"os"
	"time"

	"go.uber.org/fx"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/database"
	"sneak.berlin/go/webhooker/internal/datadir"
	"sneak.berlin/go/webhooker/internal/delivery"
	"sneak.berlin/go/webhooker/internal/globals"
	"sneak.berlin/go/webhooker/internal/handlers"
	"sneak.berlin/go/webhooker/internal/healthcheck"
	"sneak.berlin/go/webhooker/internal/logger"
	"sneak.berlin/go/webhooker/internal/middleware"
	"sneak.berlin/go/webhooker/internal/server"
	"sneak.berlin/go/webhooker/internal/session"
)

// stopTimeout bounds the whole fx stop sequence, not each hook.
//
// fx defaults to 15s, which is longer than Docker's 10s default
// stop grace: the container would be SIGKILLed before the bound
// could fire, so nothing bounded by it would ever be observed.
// 5s leaves headroom inside that grace for signal delivery and
// process exit; the observed wedge case already exits at ~5.3s,
// so a larger bound would trade a rare skipped database close for
// a more common hard kill.
//
// The server's stop hook must fit inside it with room to spare: a
// hook that used the whole budget would exhaust it at that instant,
// and fx would skip every hook after the server — the delivery
// engine, the healthcheck, the webhook DB manager and the database
// close. That hook is the 3s HTTP drain plus the Sentry flush that
// follows it in the same hook, so the flush is clamped to the stop
// context's remaining time less server.TailHookReserve rather than
// running for its own fixed 2s; the reserve is what the tail hooks
// live on, and they are microsecond-scale in normal operation.
// TestStopTimeout_LeavesHeadroomForTailHooks pins the arithmetic
// across every drain length.
//
// This does not make the database close unconditional: the
// ArchiveSweeper and RetentionReaper hooks run before the server
// and can still consume the whole budget on their own.
const stopTimeout = 5 * time.Second

// Build-time variables set via -ldflags.
//
//nolint:gochecknoglobals // Build-time variables injected by the linker.
var (
	version = "dev"
	appname = "webhooker"
)

func main() {
	globals.Appname = appname
	globals.Version = version

	os.Exit(run(os.Stderr))
}

// run takes the exclusive DATA_DIR lock, then runs the application
// under it, and returns the process exit status.
//
// The lock is taken here rather than inside the fx graph because it has
// to be held before anything opens a database, and because a refusal
// has to reach the operator as a plain line on standard error rather
// than as one entry in an fx failure dump. It is released by the defer
// on a clean shutdown, and by the kernel closing the descriptor on any
// other exit — including the one fx performs itself when a start or
// stop hook fails, which skips deferred calls.
func run(stderr io.Writer) int {
	lock, err := datadir.Acquire(config.DataDir())
	if err != nil {
		_, _ = fmt.Fprintf(stderr, "%s: %v\n", appname, err)

		return 1
	}

	defer func() { _ = lock.Release() }()

	newApp().Run()

	return 0
}

// newApp builds the application graph. It is separate from main so
// a test can assert the options it carries.
func newApp() *fx.App {
	return fx.New(
		fx.StopTimeout(stopTimeout),
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
			database.New,
			database.NewWebhookDBManager,
			database.NewRetentionReaper,
			healthcheck.New,
			session.New,
			handlers.New,
			middleware.New,
			delivery.New,
			delivery.NewArchiveSweeper,
			// Wire *delivery.Engine as delivery.Notifier so the
			// webhook handler can notify the engine of new deliveries.
			func(e *delivery.Engine) delivery.Notifier { return e },
			// Wire *delivery.Engine as delivery.WebhookEvictor so
			// deleting a webhook releases its archive writer.
			func(e *delivery.Engine) delivery.WebhookEvictor {
				return e
			},
			server.New,
		),
		fx.Invoke(
			func(
				*server.Server,
				*delivery.Engine,
				*database.RetentionReaper,
				*delivery.ArchiveSweeper,
			) {
			},
		),
	)
}