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sequence.go
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sequence.go
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package distribution
import (
"github.com/dgraph-io/badger"
"github.com/elliotcourant/arkdb/pkg/storage"
"github.com/elliotcourant/timber"
"sync"
)
type ObjectSequence struct {
sync.Mutex
barge Barge
objSeq *storage.ObjectSequence
key []byte
leased uint8
bandwidth uint8
}
func (r *boat) GetObjectSequence(key []byte, bandwidth uint8) (*ObjectSequence, error) {
switch {
case len(key) == 0:
return nil, badger.ErrEmptyKey
case bandwidth == 0:
return nil, badger.ErrZeroBandwidth
}
seq := &ObjectSequence{
barge: r,
key: key,
objSeq: &storage.ObjectSequence{
Key: key,
},
leased: 0,
bandwidth: bandwidth,
}
err := seq.updateLease()
return seq, err
}
func (s *ObjectSequence) updateLease() error {
tx, err := s.barge.Begin()
if err != nil {
return err
}
err = tx.Get(s.objSeq.Path(), s.objSeq)
if err == badger.ErrKeyNotFound {
if s.objSeq.Next > 0 {
timber.Warningf("sequence [%s] is missing, current val [%d] could not find stored val", s.key, s.objSeq.Next)
}
s.objSeq.Next = 0
} else if err != nil {
return err
}
s.objSeq.Key = s.key
lease := s.objSeq.Next + s.bandwidth
storeSeq := &storage.ObjectSequence{
Key: s.key,
Next: lease,
}
err = tx.Set(storeSeq.Path(), storeSeq)
if err != nil {
return err
}
err = tx.Commit()
if err != nil {
return err
}
s.leased = lease
return nil
}
func (s *ObjectSequence) Next() (uint8, error) {
s.Lock()
defer s.Unlock()
if s.objSeq.Next >= s.leased {
if err := s.updateLease(); err != nil {
return 0, err
}
}
s.objSeq.Next++
val := s.objSeq.Next
return val, nil
}