Add batch

common/batch/batch.go

@@ -0,0 +1,105 @@
+package batch
+
+import (
+	"context"
+	"sync"
+)
+
+type Option[T any] func(b *Batch[T])
+
+type Result[T any] struct {
+	Value T
+	Err   error
+}
+
+type Error struct {
+	Key string
+	Err error
+}
+
+func WithConcurrencyNum[T any](n int) Option[T] {
+	return func(b *Batch[T]) {
+		q := make(chan struct{}, n)
+		for i := 0; i < n; i++ {
+			q <- struct{}{}
+		}
+		b.queue = q
+	}
+}
+
+// Batch similar to errgroup, but can control the maximum number of concurrent
+type Batch[T any] struct {
+	result map[string]Result[T]
+	queue  chan struct{}
+	wg     sync.WaitGroup
+	mux    sync.Mutex
+	err    *Error
+	once   sync.Once
+	cancel func()
+}
+
+func (b *Batch[T]) Go(key string, fn func() (T, error)) {
+	b.wg.Add(1)
+	go func() {
+		defer b.wg.Done()
+		if b.queue != nil {
+			<-b.queue
+			defer func() {
+				b.queue <- struct{}{}
+			}()
+		}
+
+		value, err := fn()
+		if err != nil {
+			b.once.Do(func() {
+				b.err = &Error{key, err}
+				if b.cancel != nil {
+					b.cancel()
+				}
+			})
+		}
+
+		ret := Result[T]{value, err}
+		b.mux.Lock()
+		defer b.mux.Unlock()
+		b.result[key] = ret
+	}()
+}
+
+func (b *Batch[T]) Wait() *Error {
+	b.wg.Wait()
+	if b.cancel != nil {
+		b.cancel()
+	}
+	return b.err
+}
+
+func (b *Batch[T]) WaitAndGetResult() (map[string]Result[T], *Error) {
+	err := b.Wait()
+	return b.Result(), err
+}
+
+func (b *Batch[T]) Result() map[string]Result[T] {
+	b.mux.Lock()
+	defer b.mux.Unlock()
+	copy := map[string]Result[T]{}
+	for k, v := range b.result {
+		copy[k] = v
+	}
+	return copy
+}
+
+func New[T any](ctx context.Context, opts ...Option[T]) (*Batch[T], context.Context) {
+	ctx, cancel := context.WithCancel(ctx)
+
+	b := &Batch[T]{
+		result: map[string]Result[T]{},
+	}
+
+	for _, o := range opts {
+		o(b)
+	}
+
+	b.cancel = cancel
+	return b, ctx
+}