From d737639c4acce7c9f28de22eabfd623d0ae7ed50 Mon Sep 17 00:00:00 2001
From: Chris Hines <chris.cs.guy@gmail.com>
Date: Mon, 24 Aug 2015 21:48:39 -0400
Subject: [PATCH] database/sql: close bad connections in commit or rollback:

Previously Tx.close always passed a nil error to tx.db.putConn. As a
result bad connections were reused, even if the driver returned
driver.ErrBadConn. Adding an err parameter to Tx.close allows it to
receive the driver error from Tx.Commit and Tx.Rollback and pass it
to tx.db.putConn.

Fixes #11264

Change-Id: I142b6b2509fa8d714bbc135cef7281a40803b3b8
Reviewed-on: https://go-review.googlesource.com/13912
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---
 src/database/sql/fakedb_test.go | 12 ++++++
 src/database/sql/sql.go         |  8 ++--
 src/database/sql/sql_test.go    | 71 +++++++++++++++++++++++++++++++++
 3 files changed, 87 insertions(+), 4 deletions(-)

diff --git a/src/database/sql/fakedb_test.go b/src/database/sql/fakedb_test.go
index 8cbbb29a7c..112f280ec5 100644
--- a/src/database/sql/fakedb_test.go
+++ b/src/database/sql/fakedb_test.go
@@ -699,13 +699,25 @@ func (s *fakeStmt) NumInput() int {
 	return s.placeholders
 }
 
+// hook to simulate broken connections
+var hookCommitBadConn func() bool
+
 func (tx *fakeTx) Commit() error {
 	tx.c.currTx = nil
+	if hookCommitBadConn != nil && hookCommitBadConn() {
+		return driver.ErrBadConn
+	}
 	return nil
 }
 
+// hook to simulate broken connections
+var hookRollbackBadConn func() bool
+
 func (tx *fakeTx) Rollback() error {
 	tx.c.currTx = nil
+	if hookRollbackBadConn != nil && hookRollbackBadConn() {
+		return driver.ErrBadConn
+	}
 	return nil
 }
 
diff --git a/src/database/sql/sql.go b/src/database/sql/sql.go
index aaa4ea28be..0120ae8abe 100644
--- a/src/database/sql/sql.go
+++ b/src/database/sql/sql.go
@@ -1103,12 +1103,12 @@ type Tx struct {
 
 var ErrTxDone = errors.New("sql: Transaction has already been committed or rolled back")
 
-func (tx *Tx) close() {
+func (tx *Tx) close(err error) {
 	if tx.done {
 		panic("double close") // internal error
 	}
 	tx.done = true
-	tx.db.putConn(tx.dc, nil)
+	tx.db.putConn(tx.dc, err)
 	tx.dc = nil
 	tx.txi = nil
 }
@@ -1134,13 +1134,13 @@ func (tx *Tx) Commit() error {
 	if tx.done {
 		return ErrTxDone
 	}
-	defer tx.close()
 	tx.dc.Lock()
 	err := tx.txi.Commit()
 	tx.dc.Unlock()
 	if err != driver.ErrBadConn {
 		tx.closePrepared()
 	}
+	tx.close(err)
 	return err
 }
 
@@ -1149,13 +1149,13 @@ func (tx *Tx) Rollback() error {
 	if tx.done {
 		return ErrTxDone
 	}
-	defer tx.close()
 	tx.dc.Lock()
 	err := tx.txi.Rollback()
 	tx.dc.Unlock()
 	if err != driver.ErrBadConn {
 		tx.closePrepared()
 	}
+	tx.close(err)
 	return err
 }
 
diff --git a/src/database/sql/sql_test.go b/src/database/sql/sql_test.go
index 432a641b85..b4135a3078 100644
--- a/src/database/sql/sql_test.go
+++ b/src/database/sql/sql_test.go
@@ -1564,6 +1564,77 @@ func TestErrBadConnReconnect(t *testing.T) {
 	simulateBadConn("stmt.Query exec", &hookQueryBadConn, stmtQuery)
 }
 
+// golang.org/issue/11264
+func TestTxEndBadConn(t *testing.T) {
+	db := newTestDB(t, "foo")
+	defer closeDB(t, db)
+	db.SetMaxIdleConns(0)
+	exec(t, db, "CREATE|t1|name=string,age=int32,dead=bool")
+	db.SetMaxIdleConns(1)
+
+	simulateBadConn := func(name string, hook *func() bool, op func() error) {
+		broken := false
+		numOpen := db.numOpen
+
+		*hook = func() bool {
+			if !broken {
+				broken = true
+			}
+			return broken
+		}
+
+		if err := op(); err != driver.ErrBadConn {
+			t.Errorf(name+": %v", err)
+			return
+		}
+
+		if !broken {
+			t.Error(name + ": Failed to simulate broken connection")
+		}
+		*hook = nil
+
+		if numOpen != db.numOpen {
+			t.Errorf(name+": leaked %d connection(s)!", db.numOpen-numOpen)
+		}
+	}
+
+	// db.Exec
+	dbExec := func(endTx func(tx *Tx) error) func() error {
+		return func() error {
+			tx, err := db.Begin()
+			if err != nil {
+				return err
+			}
+			_, err = tx.Exec("INSERT|t1|name=?,age=?,dead=?", "Gordon", 3, true)
+			if err != nil {
+				return err
+			}
+			return endTx(tx)
+		}
+	}
+	simulateBadConn("db.Tx.Exec commit", &hookCommitBadConn, dbExec((*Tx).Commit))
+	simulateBadConn("db.Tx.Exec rollback", &hookRollbackBadConn, dbExec((*Tx).Rollback))
+
+	// db.Query
+	dbQuery := func(endTx func(tx *Tx) error) func() error {
+		return func() error {
+			tx, err := db.Begin()
+			if err != nil {
+				return err
+			}
+			rows, err := tx.Query("SELECT|t1|age,name|")
+			if err == nil {
+				err = rows.Close()
+			} else {
+				return err
+			}
+			return endTx(tx)
+		}
+	}
+	simulateBadConn("db.Tx.Query commit", &hookCommitBadConn, dbQuery((*Tx).Commit))
+	simulateBadConn("db.Tx.Query rollback", &hookRollbackBadConn, dbQuery((*Tx).Rollback))
+}
+
 type concurrentTest interface {
 	init(t testing.TB, db *DB)
 	finish(t testing.TB)
-- 
2.48.1