func (m *Multi) rebalanceFile(f meta.File, finderEntries map[[16]byte]FinderEntry) (bool, error) {
// search for the lowest free location that this file is stored on
var minI int
var minF int64
var minS store.Store
for i, l := range f.Locations {
fe, ok := finderEntries[l]
if !ok {
continue
}
if minS == nil || minF > fe.Free {
minS = fe.Store
minF = fe.Free
minI = i
}
}
if minS == nil {
return false, nil
}
// search for the highest free location that this file is NOT stored on
var maxF int64
var maxS store.Store
for id, fe := range finderEntries {
if fe.Dead {
continue
}
found := false
for _, locid := range f.Locations {
if locid == id {
found = true
break
}
}
if found {
continue
}
if maxS == nil || maxF < fe.Free {
maxF = fe.Free
maxS = fe.Store
}
}
if maxS == nil {
return false, nil
}
if maxF-minF < rebalanceMinDifference {
return false, nil
}
// we should move chunk minI on minS to maxS
err := m.db.RunTx(func(ctx kvl.Ctx) error {
l, err := meta.Open(ctx)
if err != nil {
return err
}
return l.WALMark(f.PrefixID)
})
if err != nil {
return false, err
}
defer func() {
// TODO: how to handle errors here?
m.db.RunTx(func(ctx kvl.Ctx) error {
l, err := meta.Open(ctx)
if err != nil {
return err
}
return l.WALClear(f.PrefixID)
})
}()
localKey := localKeyFor(&f, minI)
data, st, err := minS.Get(localKey, store.GetOptions{})
if err != nil {
return false, err
}
setCASV := store.CASV{
Present: true,
SHA256: st.SHA256,
Data: data,
}
err = maxS.CAS(localKey, store.MissingV, setCASV, nil)
if err != nil {
return false, err
}
newF := f
newF.Locations = make([][16]byte, len(f.Locations))
copy(newF.Locations, f.Locations)
newF.Locations[minI] = maxS.UUID()
err = m.db.RunTx(func(ctx kvl.Ctx) error {
l, err := meta.Open(ctx)
if err != nil {
return err
}
f2, err := l.GetFile(f.Path)
if err != nil {
return err
}
if f2.PrefixID != f.PrefixID {
return errModifiedDuringBalance
}
if len(f2.Locations) != len(f.Locations) {
return errModifiedDuringBalance
}
for i, floc := range f.Locations {
if floc != f2.Locations[i] {
return errModifiedDuringBalance
}
}
err = l.SetFile(&newF)
if err != nil {
return err
}
return nil
})
if err != nil {
maxS.CAS(localKey, setCASV, store.MissingV, nil) // ignore error
return false, err
}
err = minS.CAS(localKey, setCASV, store.MissingV, nil)
if err != nil {
log.Printf("Couldn't remove rebalanced chunk from old location %v: %v",
uuid.Fmt(maxS.UUID()), err)
}
fe := finderEntries[minS.UUID()]
fe.Free += int64(len(data))
finderEntries[minS.UUID()] = fe
fe = finderEntries[maxS.UUID()]
fe.Free -= int64(len(data))
finderEntries[maxS.UUID()] = fe
return true, nil
}
