.

wcfs/zodb.go

@@ -86,12 +86,6 @@ type Object interface {
 	PInvalidate()
 }
 
-// XXX
-type Stateful interface {
-	// XXX
-	DropState()
-}
-
 // PyObject is the interface that every in-RAM object representing Python ZODB object implements.
 type PyObject interface {
 	Object
@@ -99,21 +93,21 @@ type PyObject interface {
 	PyClass() pickle.Class // python class of this object
 //	PyState() interface{}  // object state. python passes this to pyclass.__new__().__setstate__()
 
-	PyStateful
+	// XXX want to hide from PyObject. Rationale: we do not want e.g. PySetState to
+	// be available to user who holds PyObject interface: it is confusing to have
+	// both PActivate and PySetState at the same time.
+//	PyStateful
 }
 
-// XXX
-type PyStateful interface {
-	Stateful
-
-	// PySetState should set Python state of the in-RAM object.
-	// Analog of __setstate__() in Python.
-	PySetState(pystate interface{}) error
+// ObjectState describe state of in-RAM object.
+type ObjectState int
 
-	// PyGetState should return Python state of in-RAM object.
-	// Analog of __getstate__() in Python.
-	//PyGetState() interface{}	XXX
-}
+const (
+	GHOST ObjectState = -1
+	UPTODATE          = 0
+	CHANGED           = 1
+	// no STICKY - we pin objects in RAM with PActivate
+)
 
 // object is common base for in-RAM implementations of ZODB objects.
 type object struct {
@@ -121,6 +115,8 @@ type object struct {
 	oid	zodb.Oid
 	serial	zodb.Tid
 
+	mu	sync.Mutex
+	state	ObjectState
 	refcnt	int32
 }
 
@@ -131,17 +127,50 @@ func (obj *object) PSerial() zodb.Tid	{ return obj.serial	}
 // pyObject is common base for in-RAM implementations of ZODB Python objects.
 type pyObject struct {
 	object
-
 	pyclass pickle.Class
-//	pystate  interface{}
+
+	// protected by object.mu
 	instance PyStateful
-	loaderr  error		// if there was error at state loading
-	ready    chan struct{}	// activation complete
+	loaded   *loaded
+//	loaderr  error		// if there was error at state loading
+//	ready    chan struct{}	// activation complete
 }
 
 func (pyobj *pyObject) PyClass() pickle.Class	{ return pyobj.pyclass	}
 //func (pyobj *pyObject) PyState() interface{}	{ return pyobj.pystate	}
 
+// loaded indicates object's load state/result.
+//
+// when !ready the loading is in progress.
+// when ready the loading has been completed.
+type loaded struct {
+	ready chan struct{} // closed when loading finishes
+
+	// error from the load.
+	// if there was no error loaded data goes to object state.
+	err   error
+}
+
+// XXX
+type Stateful interface {
+	// DropState should discard in-RAM object state.
+	DropState()
+}
+
+// PyStateful is the interface describing in-RAM object whose data state can be
+// exchanged as Python data.
+type PyStateful interface {
+	Stateful
+
+	// PySetState should set state of the in-RAM object from Python data.
+	// Analog of __setstate__() in Python.
+	PySetState(pystate interface{}) error
+
+	// PyGetState should return state of the in-RAM object as Python data.
+	// Analog of __getstate__() in Python.
+	//PyGetState() interface{}	XXX
+}
+
 
 // Connection represents a view of ZODB database.
 //
@@ -357,7 +386,7 @@ func registerClass(classPath string, classNew func(*pyObject)PyObject) {
 // newGhost creates new ghost object corresponding to pyclass and oid.
 func (conn *Connection) newGhost(pyclass pickle.Class, oid zodb.Oid) PyObject {
 	pyobj := &pyObject{
-		object:  object{jar: conn, oid: oid, serial: 0},
+		object:  object{jar: conn, oid: oid, serial: 0, state: GHOST},
 		pyclass: pyclass,
 	}
 
@@ -392,22 +421,16 @@ func (d *dummyPyInstance) PySetState(pystate interface{}) error	{
 
 // ----------------------------------------
 
-/*
-func (obj *object) PActivate(ctx context.Context) error {
-	// XXX
-}
-
-func (obj *object) PDeactivate() {
-	// XXX
-}
+// object's activate & friends that only manage base activation state, without actually loading data.
 
-// PInvalidate
-*/
-
-// object's pactivate & friends that only manage base activation state, without actually loading data.
-
-// XXX -> incref ?
-func (obj *object) pactivate() (load bool) {
+// activate increments object reference counter.
+//
+// it returns whether object data needs to be loaded.
+// must be called with .mu held.
+func (obj *object) activate() (load bool) {
+	obj.refcnt++
+	return (obj.refcnt == 1 && obj.state == GHOST)
+/*
 	nuse := atomic.AddInt32(&obj.refcnt, +1)
 	if nuse == 1 {
 		// we become responsible for loading object's data.
@@ -415,21 +438,28 @@ func (obj *object) pactivate() (load bool) {
 		return true
 	}
 	return false
+*/
 }
 
-// XXX -> decref ?
-func (obj *object) pdeactivate() (drop bool) {
-	nuse := atomic.AddInt32(&obj.refcnt, -1)
-	if nuse < 0 {
-		panic("pdeactivate: nuse < 0")
+// deactivate decrements object reference counter.
+//
+// it returns whether object data needs to be discarded.
+// must be called with .mu held.
+func (obj *object) deactivate() (drop bool) {
+	//nuse := atomic.AddInt32(&obj.refcnt, -1)
+	obj.refcnt--
+	if obj.refcnt < 0 {
+		panic("deactivate: refcnt < 0")
 	}
-	if nuse > 0 {
+	if obj.refcnt > 0 {
 		return // users still left
 	}
 
 	// no users left. Let's see whether we should transition this object to ghost.
-	// TODO state=modified -> don't drop.
 	drop = true
+	if obj.state >= CHANGED {
+		drop = false
+	}
 
 	// XXX -> pyObject?
 	if drop {
@@ -440,7 +470,7 @@ func (obj *object) pdeactivate() (drop bool) {
 
 	if drop {
 		obj.serial  = 0
-		//obj.insance.DropState()
+		obj.instance.DropState()
 	}
 
 	return drop
@@ -449,26 +479,35 @@ func (obj *object) pdeactivate() (drop bool) {
 
 // PActivate implements Object.
 func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
-	load := pyobj.object.pactivate()
+	pyobj.mu.Lock()
+	doload := pyobj.activate()
 	defer func() {
 		if err != nil {
 			// no need to check for drop - the state is already
 			// dropped - we just need to decref here.
-			pyobj.object.pdeactivate()
+			// XXX locking?
+			pyobj.deactivate()
 		}
 	}()
-	if !load {
+	if !doload {
+		loading := pyobj.loading
+		pyobj.mu.Unlock()
+
 		// someone else is already activated/activating the object.
 		// wait for its loading to complete and we are done.
 		select {
 		case <-ctx.Done():
 			return ctx.Err()	// XXX err ctx
-		case <-pyobj.ready:
-			return pyobj.loaderr		// XXX err ctx?
+		case <-loading.ready:
+			return loading.err	// XXX err ctx?
 		}
 	}
 
 	// we become responsible for loading the object
+	loading := &loading{ready: make(chan struct{})}
+	pyobj.loading = loading	// XXX assert before it was = nil ?
+	pyobj.mu.Unlock()
+
 	pyclass, pystate, serial, err := pyobj.jar.loadpy(ctx, pyobj.oid)
 	if err == nil && pyclass != pyobj.pyclass {
 		// complain pyclass changed
@@ -477,6 +516,8 @@ func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
 		pystate = nil
 	}
 
+	pyobj.mu.Lock()
+
 	pyobj.serial  = serial
 //	pyobj.pystate = pystate
 
@@ -487,16 +528,17 @@ func (pyobj *pyObject) PActivate(ctx context.Context) (err error) {
 		pyobj.instance.DropState()
 	}
 
-	pyobj.loaderr = err
+	// XXX unlock
 
-	close(pyobj.ready)
+	loading.err = err
+	close(loading.ready)
 	return err	// XXX err ctx
 }
 
 
 // PDeactivate implements Object.
 func (pyobj *pyObject) PDeactivate() {
-	drop := pyobj.object.pdeactivate()
+	drop := pyobj.pdeactivate()
 	if !drop {
 		return
 	}