// GetBlocks gets a list of blocks asynchronously and returns through
// the returned channel.
// NB: No guarantees are made about order.
func (s *BlockService) GetBlocks(ctx context.Context, ks []key.Key) <-chan *blocks.Block {
out := make(chan *blocks.Block, 0)
go func() {
defer close(out)
var misses []key.Key
for _, k := range ks {
hit, err := s.Blockstore.Get(k)
if err != nil {
misses = append(misses, k)
continue
}
select {
case out <- hit:
case <-ctx.Done():
return
}
}
rblocks, err := s.Exchange.GetBlocks(ctx, misses)
if err != nil {
// blocks not found are ignored. this is an optimistic call.
return
}
for b := range rblocks {
select {
case out <- b:
case <-ctx.Done():
return
}
}
}()
return out
}
func (e *offlineExchange) GetBlocks(ctx context.Context, ks []key.Key) (<-chan *blocks.Block, error) {
out := make(chan *blocks.Block, 0)
go func() {
defer close(out)
var misses []key.Key
for _, k := range ks {
hit, err := e.bs.Get(k)
if err != nil {
misses = append(misses, k)
// a long line of misses should abort when context is cancelled.
select {
// TODO case send misses down channel
case <-ctx.Done():
return
default:
continue
}
}
select {
case out <- hit:
case <-ctx.Done():
return
}
}
}()
return out, nil
}
// WithContext constructs and returns a Process that respects
// given context. It is the equivalent of:
//
// func ProcessWithContext(ctx context.Context) goprocess.Process {
// p := goprocess.WithParent(goprocess.Background())
// go func() {
// <-ctx.Done()
// p.Close()
// }()
// return p
// }
//
func WithContext(ctx context.Context) goprocess.Process {
if ctx == nil {
panic("nil Context")
}
p := goprocess.WithParent(goprocess.Background())
go func() {
<-ctx.Done()
p.Close()
}()
return p
}
// AllKeysChan runs a query for keys from the blockstore.
// this is very simplistic, in the future, take dsq.Query as a param?
//
// AllKeysChan respects context
func (bs *blockstore) AllKeysChan(ctx context.Context) (<-chan key.Key, error) {
// KeysOnly, because that would be _a lot_ of data.
q := dsq.Query{KeysOnly: true}
// datastore/namespace does *NOT* fix up Query.Prefix
q.Prefix = BlockPrefix.String()
res, err := bs.datastore.Query(q)
if err != nil {
return nil, err
}
// this function is here to compartmentalize
get := func() (k key.Key, ok bool) {
select {
case <-ctx.Done():
return k, false
case e, more := <-res.Next():
if !more {
return k, false
}
if e.Error != nil {
return k, false
}
// need to convert to key.Key using key.KeyFromDsKey.
k = key.KeyFromDsKey(ds.NewKey(e.Key))
// key must be a multihash. else ignore it.
_, err := mh.Cast([]byte(k))
if err != nil {
return "", true
}
return k, true
}
}
output := make(chan key.Key)
go func() {
defer func() {
res.Process().Close() // ensure exit (signals early exit, too)
close(output)
}()
for {
k, ok := get()
if !ok {
return
}
if k == "" {
continue
}
select {
case <-ctx.Done():
return
case output <- k:
}
}
}()
return output, nil
}