125 lines
3.2 KiB
Go
125 lines
3.2 KiB
Go
// Copyright 2016 The Cockroach Authors.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
|
|
// implied. See the License for the specific language governing
|
|
// permissions and limitations under the License.
|
|
//
|
|
// Author: Spencer Kimball (spencer@cockroachlabs.com)
|
|
|
|
package crdb
|
|
|
|
import (
|
|
"database/sql"
|
|
"fmt"
|
|
"sync"
|
|
"testing"
|
|
|
|
"github.com/cockroachdb/cockroach-go/testserver"
|
|
)
|
|
|
|
// TestExecuteTx verifies transaction retry using the classic
|
|
// example of write skew in bank account balance transfers.
|
|
func TestExecuteTx(t *testing.T) {
|
|
db, stop := testserver.NewDBForTest(t)
|
|
defer stop()
|
|
|
|
initStmt := `
|
|
CREATE DATABASE d;
|
|
CREATE TABLE d.t (acct INT PRIMARY KEY, balance INT);
|
|
INSERT INTO d.t (acct, balance) VALUES (1, 100), (2, 100);
|
|
`
|
|
if _, err := db.Exec(initStmt); err != nil {
|
|
t.Fatal(err)
|
|
}
|
|
|
|
type queryI interface {
|
|
Query(string, ...interface{}) (*sql.Rows, error)
|
|
}
|
|
|
|
getBalances := func(q queryI) (bal1, bal2 int, err error) {
|
|
var rows *sql.Rows
|
|
rows, err = q.Query(`SELECT balance FROM d.t WHERE acct IN (1, 2);`)
|
|
if err != nil {
|
|
return
|
|
}
|
|
defer rows.Close()
|
|
balances := []*int{&bal1, &bal2}
|
|
i := 0
|
|
for ; rows.Next(); i += 1 {
|
|
if err = rows.Scan(balances[i]); err != nil {
|
|
return
|
|
}
|
|
}
|
|
if i != 2 {
|
|
err = fmt.Errorf("expected two balances; got %d", i)
|
|
return
|
|
}
|
|
return
|
|
}
|
|
|
|
runTxn := func(wg *sync.WaitGroup, iter *int) <-chan error {
|
|
errCh := make(chan error, 1)
|
|
go func() {
|
|
*iter = 0
|
|
errCh <- ExecuteTx(db, func(tx *sql.Tx) error {
|
|
*iter++
|
|
bal1, bal2, err := getBalances(tx)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
// If this is the first iteration, wait for the other tx to also read.
|
|
if *iter == 1 {
|
|
wg.Done()
|
|
wg.Wait()
|
|
}
|
|
// Now, subtract from one account and give to the other.
|
|
if bal1 > bal2 {
|
|
if _, err := tx.Exec(`
|
|
UPDATE d.t SET balance=balance-100 WHERE acct=1;
|
|
UPDATE d.t SET balance=balance+100 WHERE acct=2;
|
|
`); err != nil {
|
|
return err
|
|
}
|
|
} else {
|
|
if _, err := tx.Exec(`
|
|
UPDATE d.t SET balance=balance+100 WHERE acct=1;
|
|
UPDATE d.t SET balance=balance-100 WHERE acct=2;
|
|
`); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
return nil
|
|
})
|
|
}()
|
|
return errCh
|
|
}
|
|
|
|
var wg sync.WaitGroup
|
|
wg.Add(2)
|
|
var iters1, iters2 int
|
|
txn1Err := runTxn(&wg, &iters1)
|
|
txn2Err := runTxn(&wg, &iters2)
|
|
if err := <-txn1Err; err != nil {
|
|
t.Errorf("expected success in txn1; got %s", err)
|
|
}
|
|
if err := <-txn2Err; err != nil {
|
|
t.Errorf("expected success in txn2; got %s", err)
|
|
}
|
|
if iters1+iters2 <= 2 {
|
|
t.Errorf("expected at least one retry between the competing transactions; "+
|
|
"got txn1=%d, txn2=%d", iters1, iters2)
|
|
}
|
|
bal1, bal2, err := getBalances(db)
|
|
if err != nil || bal1 != 100 || bal2 != 100 {
|
|
t.Errorf("expected balances to be restored without error; "+
|
|
"got acct1=%d, acct2=%d: %s", bal1, bal2, err)
|
|
}
|
|
}
|