func NewVar(uuid *common.VarUUId, exe *dispatcher.Executor, disk *mdbs.MDBServer, vm *VarManager) *Var {
v := newVar(uuid, exe, disk, vm)
clock := NewVectorClock().Bump(*v.UUId, 0)
written := NewVectorClock().Bump(*v.UUId, 0)
v.curFrame = NewFrame(nil, v, nil, nil, clock, written)
seg := capn.NewBuffer(nil)
varCap := msgs.NewRootVar(seg)
varCap.SetId(v.UUId[:])
v.varCap = &varCap
return v
}
func (v *Var) maybeWriteFrame(f *frame, action *localAction, positions *common.Positions) {
if v.writeInProgress != nil {
v.writeInProgress = func() {
v.writeInProgress = nil
v.maybeWriteFrame(f, action, positions)
}
return
}
v.writeInProgress = func() {
v.writeInProgress = nil
v.maybeMakeInactive()
}
oldVarCap := *v.varCap
varSeg := capn.NewBuffer(nil)
varCap := msgs.NewRootVar(varSeg)
v.varCap = &varCap
varCap.SetId(oldVarCap.Id())
if positions != nil {
varCap.SetPositions(capn.UInt8List(*positions))
} else {
varCap.SetPositions(oldVarCap.Positions())
}
varCap.SetWriteTxnId(f.frameTxnId[:])
varCap.SetWriteTxnClock(f.frameTxnClock.AddToSeg(varSeg))
varCap.SetWritesClock(f.frameWritesClock.AddToSeg(varSeg))
varData := server.SegToBytes(varSeg)
txnBytes := action.TxnRootBytes()
// to ensure correct order of writes, schedule the write from
// the current go-routine...
future := v.disk.ReadWriteTransaction(false, func(rwtxn *mdbs.RWTxn) (interface{}, error) {
if err := db.WriteTxnToDisk(rwtxn, f.frameTxnId, txnBytes); err != nil {
return nil, err
}
if err := rwtxn.Put(db.DB.Vars, v.UUId[:], varData, 0); err != nil {
return nil, err
}
if v.curFrameOnDisk != nil {
return nil, db.DeleteTxnFromDisk(rwtxn, v.curFrameOnDisk.frameTxnId)
}
return nil, nil
})
go func() {
// ... but process the result in a new go-routine to avoid blocking the executor.
if _, err := future.ResultError(); err != nil {
log.Println("Var error when writing to disk:", err)
return
}
// Switch back to the right go-routine
v.applyToVar(func() {
server.Log(v.UUId, "Wrote", f.frameTxnId)
v.curFrameOnDisk = f
for ancestor := f.parent; ancestor != nil && ancestor.DescendentOnDisk(); ancestor = ancestor.parent {
}
v.writeInProgress()
})
}()
}