fix(tasks): 任务队列 - 限制缓存回源并修复并发租约与过期写入

backend/internal/service/read_cache_test.go

@@ -0,0 +1,135 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestReadCacheCoalescesBurstAndCoolsFailures(t *testing.T) {
+	for _, fail := range []bool{false, true} {
+		cache := newBoundedReadCache[string, int](4, 1024, 2, time.Minute)
+		var calls atomic.Int32
+		loadErr := errors.New("database unavailable")
+		load := func(context.Context) (int, int, error) {
+			calls.Add(1)
+			if fail {
+				return 0, 0, loadErr
+			}
+			return 42, 256, nil
+		}
+		var wg sync.WaitGroup
+		for range 100 {
+			wg.Add(1)
+			go func() {
+				defer wg.Done()
+				value, err := cache.get(context.Background(), "hot", load)
+				if (fail && !errors.Is(err, loadErr)) || (!fail && (err != nil || value != 42)) {
+					t.Errorf("value=%d error=%v fail=%v", value, err, fail)
+				}
+			}()
+		}
+		wg.Wait()
+		if calls.Load() != 1 {
+			t.Fatalf("burst caused %d loads (fail=%v)", calls.Load(), fail)
+		}
+	}
+}
+
+func TestReadCacheBoundsLoadsAndInvalidation(t *testing.T) {
+	cache := newBoundedReadCache[string, int](2, 512, 1, time.Minute)
+	started, release, done := make(chan struct{}), make(chan struct{}), make(chan struct{})
+	go func() {
+		defer close(done)
+		_, _ = cache.get(context.Background(), "one", func(context.Context) (int, int, error) {
+			close(started)
+			<-release
+			return 1, 256, nil
+		})
+	}()
+	<-started
+	load := func(context.Context) (int, int, error) { return 2, 256, nil }
+	if _, err := cache.get(context.Background(), "two", load); !errors.Is(err, errReadCacheBusy) {
+		t.Fatalf("unbounded distinct load: %v", err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Millisecond)
+	defer cancel()
+	if _, err := cache.get(ctx, "one", load); !errors.Is(err, context.DeadlineExceeded) {
+		t.Fatalf("waiting reader did not cancel: %v", err)
+	}
+	cache.clear()
+	if _, err := cache.get(context.Background(), "two", load); !errors.Is(err, errReadCacheBusy) {
+		t.Fatalf("invalidation bypassed in-flight limit: %v", err)
+	}
+	close(release)
+	<-done
+	value, err := cache.get(context.Background(), "one", load)
+	if err != nil || value != 2 {
+		t.Fatalf("in-flight load repopulated invalidated cache: %d %v", value, err)
+	}
+}
+
+func TestReadCacheBudgetsExpiryAndNoStaleSuccess(t *testing.T) {
+	cache := newBoundedReadCache[int, int](3, 512, 1, time.Minute)
+	load := func(context.Context) (int, int, error) { return 1, 256, nil }
+	for i := range 100 {
+		if _, err := cache.get(context.Background(), i, load); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if len(cache.entries) > 2 || cache.bytes > 512 {
+		t.Fatalf("budget exceeded: entries=%d bytes=%d", len(cache.entries), cache.bytes)
+	}
+	cache.entries[99].expires = time.Now().Add(-time.Second)
+	wantErr := errors.New("load failed")
+	value, err := cache.get(context.Background(), 99, func(context.Context) (int, int, error) { return 0, 0, wantErr })
+	if value != 0 || !errors.Is(err, wantErr) {
+		t.Fatalf("stale success served: %d %v", value, err)
+	}
+	var calls int
+	for range 2 {
+		value, err = cache.get(context.Background(), 101, func(context.Context) (int, int, error) {
+			calls++
+			return 42, 1024, nil
+		})
+		if value != 42 || err != nil {
+			t.Fatalf("oversized load should still return to caller: %d %v", value, err)
+		}
+	}
+	if calls != 2 {
+		t.Fatal("oversized entry was retained")
+	}
+}
+
+func TestReadCacheCancelledLoadCanBeRetried(t *testing.T) {
+	cache := newBoundedReadCache[string, int](1, 512, 1, time.Minute)
+	_, err := cache.get(context.Background(), "key", func(context.Context) (int, int, error) { return 0, 0, context.Canceled })
+	if !errors.Is(err, context.Canceled) {
+		t.Fatal(err)
+	}
+	value, err := cache.get(context.Background(), "key", func(context.Context) (int, int, error) { return 7, 256, nil })
+	if err != nil || value != 7 {
+		t.Fatalf("cancellation poisoned cache: %d %v", value, err)
+	}
+}
+
+func TestReadCachePanicDoesNotLeakCapacity(t *testing.T) {
+	cache := newBoundedReadCache[string, int](1, 512, 1, time.Minute)
+	func() {
+		defer func() {
+			if recover() != "loader panic" {
+				t.Error("original panic was swallowed")
+			}
+		}()
+		_, _ = cache.get(context.Background(), "key", func(context.Context) (int, int, error) { panic("loader panic") })
+	}()
+	if cache.loads != 0 || len(cache.entries) != 0 {
+		t.Fatal("panic leaked load capacity")
+	}
+	if _, err := cache.get(context.Background(), "key", func(context.Context) (int, int, error) { return 1, 256, nil }); err != nil {
+		t.Fatal(err)
+	}
+}