Method ForEachShard

ring.go:723–756

ForEachShard concurrently calls the fn on each live shard in the ring. It returns the first error if any.

(
	ctx context.Context,
	fn func(ctx context.Context, client *Client) error,
)

// ForEachShard concurrently calls the fn on each live shard in the ring.
// It returns the first error if any.
func (c *Ring) ForEachShard(
	ctx context.Context,
	fn func(ctx context.Context, client *Client) error,
) error {
	// note: `c.List()` return a shadow copy of `[]*ringShard`.
	shards := c.sharding.List()
	var wg sync.WaitGroup
	errCh := make(chan error, 1)
	for _, shard := range shards {
		if shard.IsDown() {
			continue
		}

		wg.Add(1)
		go func(shard *ringShard) {
			defer wg.Done()
			err := fn(ctx, shard.Client)
			if err != nil {
				select {
				case errCh <- err:
				default:
				}
			}
		}(shard)
	}
	wg.Wait()

	select {
	case err := <-errCh:
		return err
	default:
		return nil
	}
}

func (c *Ring) cmdsInfo(ctx context.Context) (map[string]*CommandInfo, error) {
	// note: `c.List()` return a shadow copy of `[]*ringShard`.