tests/robustness: add issue72 reproducer

Signed-off-by: Wei Fu <fuweid89@gmail.com>
(cherry picked from commit 1b08078)
Signed-off-by: Wei Fu <fuweid89@gmail.com>

tests/failpoint/db_failpoint_test.go

@@ -94,3 +94,118 @@ func TestFailpoint_mLockFail_When_remap(t *testing.T) {
 
 	require.NoError(t, err)
 }
+
+// TestIssue72 reproduces issue 72.
+//
+// When bbolt is processing a `Put` invocation, the key might be concurrently
+// updated by the application which calls the `Put` API (although it shouldn't).
+// It might lead to a situation that bbolt use an old key to find a proper
+// position to insert the key/value pair, but actually inserts a new key.
+// Eventually it might break the rule that all keys should be sorted. In a
+// worse case, it might cause page elements to point to already freed pages.
+//
+// REF: https://github.com/etcd-io/bbolt/issues/72
+func TestIssue72(t *testing.T) {
+	db := btesting.MustCreateDBWithOption(t, &bolt.Options{PageSize: 4096})
+
+	bucketName := []byte(t.Name())
+	err := db.Update(func(tx *bolt.Tx) error {
+		_, txerr := tx.CreateBucket(bucketName)
+		return txerr
+	})
+	require.NoError(t, err)
+
+	// The layout is like:
+	//
+	//         +--+--+--+
+	//  +------+1 |3 |10+---+
+	//  |      +-++--+--+   |
+	//  |         |         |
+	//  |         |         |
+	// +v-+--+   +v-+--+  +-v+--+--+
+	// |1 |2 |   |3 |4 |  |10|11|12|
+	// +--+--+   +--+--+  +--+--+--+
+	//
+	err = db.Update(func(tx *bolt.Tx) error {
+		bk := tx.Bucket(bucketName)
+
+		for _, id := range []int{1, 2, 3, 4, 10, 11, 12} {
+			if txerr := bk.Put(idToBytes(id), make([]byte, 1000)); txerr != nil {
+				return txerr
+			}
+		}
+		return nil
+	})
+	require.NoError(t, err)
+
+	require.NoError(t, gofail.Enable("beforeBucketPut", `sleep(5000)`))
+
+	//         +--+--+--+
+	//  +------+1 |3 |1 +---+
+	//  |      +-++--+--+   |
+	//  |         |         |
+	//  |         |         |
+	// +v-+--+   +v-+--+  +-v+--+--+--+
+	// |1 |2 |   |3 |4 |  |1 |10|11|12|
+	// +--+--+   +--+--+  +--+--+--+--+
+	//
+	key := idToBytes(13)
+	updatedKey := idToBytes(1)
+	err = db.Update(func(tx *bolt.Tx) error {
+		bk := tx.Bucket(bucketName)
+
+		go func() {
+			time.Sleep(3 * time.Second)
+			copy(key, updatedKey)
+		}()
+		return bk.Put(key, make([]byte, 100))
+	})
+	require.NoError(t, err)
+
+	require.NoError(t, gofail.Disable("beforeBucketPut"))
+
+	// bbolt inserts 100 into last branch page. Since there are two `1`
+	// keys in branch, spill operation will update first `1` pointer and
+	// then last one won't be updated and continues to point to freed page.
+	//
+	//
+	//                  +--+--+--+
+	//  +---------------+1 |3 |1 +---------+
+	//  |               +--++-+--+         |
+	//  |                   |              |
+	//  |                   |              |
+	//  |        +--+--+   +v-+--+   +-----v-----+
+	//  |        |1 |2 |   |3 |4 |   |freed page |
+	//  |        +--+--+   +--+--+   +-----------+
+	//  |
+	// +v-+--+--+--+---+
+	// |1 |10|11|12|100|
+	// +--+--+--+--+---+
+	err = db.Update(func(tx *bolt.Tx) error {
+		return tx.Bucket(bucketName).Put(idToBytes(100), make([]byte, 100))
+	})
+	require.NoError(t, err)
+
+	defer func() {
+		if r := recover(); r != nil {
+			t.Logf("panic info:\n %v", r)
+		}
+	}()
+
+	// Add more keys to ensure branch node to spill.
+	err = db.Update(func(tx *bolt.Tx) error {
+		bk := tx.Bucket(bucketName)
+
+		for _, id := range []int{101, 102, 103, 104, 105} {
+			if txerr := bk.Put(idToBytes(id), make([]byte, 1000)); txerr != nil {
+				return txerr
+			}
+		}
+		return nil
+	})
+	require.NoError(t, err)
+}
+
+func idToBytes(id int) []byte {
+	return []byte(fmt.Sprintf("%010d", id))
+}