func NewVar(uuid *common.VarUUId, exe *dispatcher.Executor, db *db.Databases, vm *VarManager) *Var {
v := newVar(uuid, exe, db, 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.db.ReadWriteTransaction(false, func(rwtxn *mdbs.RWTxn) interface{} {
if err := v.db.WriteTxnToDisk(rwtxn, f.frameTxnId, txnBytes); err == nil {
if err = rwtxn.Put(v.db.Vars, v.UUId[:], varData, 0); err == nil {
if v.curFrameOnDisk != nil {
v.db.DeleteTxnFromDisk(rwtxn, v.curFrameOnDisk.frameTxnId)
}
}
}
return true
})
go func() {
// ... but process the result in a new go-routine to avoid blocking the executor.
if ran, err := future.ResultError(); err != nil {
panic(fmt.Sprintf("Var error when writing to disk: %v\n", err))
} else if ran != nil {
// 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()
})
}
}()
}