MDBX bindings: remove finalizers (write tx require to be closed from …

…same thread) (#1579)

ethdb/mdbx/cursor.go

@@ -7,7 +7,6 @@ package mdbx
 */
 import "C"
 import (
-	"runtime"
 	"unsafe"
 )
 
@@ -106,7 +105,6 @@ func (c *Cursor) close() bool {
 // See mdb_cursor_close.
 func (c *Cursor) Close() {
 	if c.close() {
-		runtime.SetFinalizer(c, nil)
 	}
 }
 

ethdb/mdbx/env.go

@@ -540,19 +540,12 @@ func (env *Env) SetMaxDBs(size int) error {
 // methods, which assist in management of Txn objects and provide OS thread
 // locking required for write transactions.
 //
-// A finalizer detects unreachable, live transactions and logs thems to
-// standard error.  The transactions are aborted, but their presence should be
-// interpreted as an application error which should be patched so transactions
-// are terminated explicitly.  Unterminated transactions can adversly effect
+// Unterminated transactions can adversly effect
 // database performance and cause the database to grow until the map is full.
 //
 // See mdbx_txn_begin.
 func (env *Env) BeginTxn(parent *Txn, flags uint) (*Txn, error) {
-	txn, err := beginTxn(env, parent, flags)
-	if txn != nil {
-		runtime.SetFinalizer(txn, func(v interface{}) { v.(*Txn).finalize() })
-	}
-	return txn, err
+	return beginTxn(env, parent, flags)
 }
 
 // RunTxn creates a new Txn and calls fn with it as an argument.  Run commits

ethdb/mdbx/txn.go

@@ -9,7 +9,6 @@ import "C"
 
 import (
 	"log"
-	"runtime"
 	"time"
 	"unsafe"
 )
@@ -196,7 +195,6 @@ func (txn *Txn) Commit() (CommitLatency, error) {
 		panic("managed transaction cannot be committed directly")
 	}
 
-	runtime.SetFinalizer(txn, nil)
 	return txn.commit()
 }
 
@@ -242,7 +240,6 @@ func (txn *Txn) Abort() {
 		panic("managed transaction cannot be aborted directly")
 	}
 
-	runtime.SetFinalizer(txn, nil)
 	txn.abort()
 }
 
@@ -615,7 +612,6 @@ func (txn *Txn) Del(dbi DBI, key, val []byte) error {
 func (txn *Txn) OpenCursor(dbi DBI) (*Cursor, error) {
 	cur, err := openCursor(txn, dbi)
 	if cur != nil && txn.readonly {
-		runtime.SetFinalizer(cur, (*Cursor).close)
 	}
 	return cur, err
 }

ethdb/mdbx/txn_test.go

@@ -9,7 +9,6 @@ import (
 	"runtime"
 	"syscall"
 	"testing"
-	"time"
 )
 
 func TestTxn_ID(t *testing.T) {
@@ -100,7 +99,6 @@ func TestTxn_ID(t *testing.T) {
 }
 
 func TestTxn_errLogf(t *testing.T) {
-	t.Skip("to investigate")
 	env := setup(t)
 	defer clean(env, t)
 
@@ -116,37 +114,6 @@ func TestTxn_errLogf(t *testing.T) {
 	}
 }
 
-func TestTxn_finalizer(t *testing.T) {
-	env := setup(t)
-	defer clean(env, t)
-
-	runtime.LockOSThread()
-	defer runtime.UnlockOSThread()
-
-	called := make(chan struct{})
-	func() {
-		txn, err := env.BeginTxn(nil, 0)
-		if err != nil {
-			t.Error(err)
-		} else {
-			txn.errLogf = func(string, ...interface{}) {
-				close(called)
-			}
-		}
-	}()
-
-	// make sure that finalizer has a chance to get called.  it seems like this
-	// may not be consistent across versions of go.
-	runtime.GC()
-	runtime.Gosched()
-
-	select {
-	case <-called:
-	case <-time.After(time.Second):
-		t.Errorf("error logging function was not called")
-	}
-}
-
 func TestTxn_Drop(t *testing.T) {
 	env := setup(t)
 	defer clean(env, t)