feat: add reusable MySQL outbox and HTTP lifecycle example

examples/http-service/cmd/server/lifecycle.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"sync/atomic"
+	"time"
+)
+
+// component 不接管进程信号；宿主负责为每一类生命周期提供独立取消和等待。
+type component struct {
+	name string
+	run  func(context.Context) error
+}
+type completion struct {
+	name string
+	err  error
+}
+
+// serve 在HTTP监听已成功后启动后台组件；返回前完成HTTP→发送/执行→结果消费的关闭顺序。
+func serve(parent context.Context, listener net.Listener, server *http.Server, ready *atomic.Bool, workers []component, consumer component, grace time.Duration) error {
+	workCtx, stopWork := context.WithCancel(context.Background())
+	defer stopWork()
+	eventCtx, stopEvents := context.WithCancel(context.Background())
+	defer stopEvents()
+	workDone := make(chan completion, len(workers))
+	eventDone := make(chan completion, 1)
+	for _, c := range workers {
+		go func() { workDone <- completion{c.name, c.run(workCtx)} }()
+	}
+	go func() { eventDone <- completion{consumer.name, consumer.run(eventCtx)} }()
+	httpDone := make(chan error, 1)
+	ready.Store(true)
+	go func() { httpDone <- server.Serve(listener) }()
+	remaining := len(workers)
+	eventsPending := true
+	var result error
+	add := func(c completion) {
+		if c.err != nil {
+			result = errors.Join(result, fmt.Errorf("%s: %w", c.name, c.err))
+		}
+	}
+	select {
+	case <-parent.Done():
+	case err := <-httpDone:
+		if !errors.Is(err, http.ErrServerClosed) {
+			result = errors.Join(result, err)
+		}
+	case c := <-workDone:
+		remaining--
+		if c.err == nil {
+			c.err = errors.New("unexpected component exit")
+		}
+		add(c)
+	case c := <-eventDone:
+		eventsPending = false
+		if c.err == nil {
+			c.err = errors.New("unexpected component exit")
+		}
+		add(c)
+	}
+	ready.Store(false)
+	// 用新的关闭上下文；进程信号的context此时可能已取消，不能用它调用Shutdown。
+	shut, cancel := context.WithTimeout(context.Background(), grace)
+	if err := server.Shutdown(shut); err != nil {
+		result = errors.Join(result, fmt.Errorf("http shutdown: %w", err))
+		_ = server.Close()
+	}
+	cancel()
+	stopWork()
+	deadline := time.NewTimer(grace)
+	defer deadline.Stop()
+	for remaining > 0 {
+		select {
+		case c := <-workDone:
+			remaining--
+			add(c)
+		case <-deadline.C:
+			result = errors.Join(result, errors.New("background shutdown deadline exceeded"))
+			remaining = 0
+		}
+	}
+	// 结果消费器最后停止。仍未投递的结果会在重启后由持久订阅恢复，不以本地空闲判断全局完成。
+	stopEvents()
+	if eventsPending {
+		timer := time.NewTimer(grace)
+		defer timer.Stop()
+		select {
+		case c := <-eventDone:
+			add(c)
+		case <-timer.C:
+			result = errors.Join(result, errors.New("consumer shutdown deadline exceeded"))
+		}
+	}
+	return result
+}