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Posted to notifications@shardingsphere.apache.org by GitBox <gi...@apache.org> on 2022/09/05 06:36:19 UTC
[GitHub] [shardingsphere] nimo10050 opened a new issue, #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
nimo10050 opened a new issue, #20789:
URL: https://github.com/apache/shardingsphere/issues/20789
## Question
If there is write operation in the same thread and database connection, **all the following read operations are not from the master database to ensure data consistency.**
case:
```java
public class AccountService {
@Transactional
public void test(String userId, BigDecimal num) {
// step1, in current transaction, insert a data
accountMapper.insertAccount(new Account(userId, num));
// step2, start a new transaction, query all data
accountService2.test();
// step3, query all again.
accountMapper.selectAll();
}
}
public class AccountService2 {
@Transactional(propagation = Propagation.REQUIRES_NEW)
public void test() {
accountMapper.selectAll();
}
}
```
result：
step1：insert data to master db
step2：data from master db
step3： query data from slave db
when step1 and step3 in the same connection，step3 does not query data from master db。
why ? @terrymanu
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[GitHub] [shardingsphere] strongduanmu commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
strongduanmu commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1333330874
Since this issue has been fixed by https://github.com/apache/shardingsphere/pull/20814, I will close it now.
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[GitHub] [shardingsphere] FlyingZC commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
FlyingZC commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1284218224
Now tansactionHolder(or TransactionConnectionContext) is at the thread level. When the inner transaction commits, the inTransaction flag will be cleared, which will cause the inTransaction read by the outer transaction to be false, resulting in routing to the slave database.
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[GitHub] [shardingsphere] github-actions[bot] closed issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
github-actions[bot] closed issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
URL: https://github.com/apache/shardingsphere/issues/20789
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[GitHub] [shardingsphere] strongduanmu closed issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
strongduanmu closed issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
URL: https://github.com/apache/shardingsphere/issues/20789
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[GitHub] [shardingsphere] FlyingZC commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
FlyingZC commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1236696434
I want to investigate it, please assign to me.
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[GitHub] [shardingsphere] nimo10050 commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
nimo10050 commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1236705793
> The same with issue #20614.
yes, he's the one who really saw the problem.
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[GitHub] [shardingsphere] strongduanmu commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
strongduanmu commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1275437992
Hi @FlyingZC , could we finish this issue in 5.2.1?
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[GitHub] [shardingsphere] nimo10050 commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
nimo10050 commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1237824077
> The same with issue #20614.
for shardingsphere 5.1.0 , the souce code for determining routes are as follows:
```java
/**
* ReadwriteSplittingDataSourceRouter
* if return true, route to the master database
* else, route to the slave database
**/
private boolean isPrimaryRoute(final SQLStatementContext<?> sqlStatementContext) {
SQLStatement sqlStatement = sqlStatementContext.getSqlStatement();
return containsLockSegment(sqlStatement) || !(sqlStatement instanceof SelectStatement) || isHintWriteRouteOnly(sqlStatementContext) || TransactionHolder.isTransaction();
}
```
for the above case: https://github.com/apache/shardingsphere/issues/20789#issue-1361469079
For step 3, It seems like that the code that determine whether it routes master database is:
```TransactionHolder.isTransaction()```
So, when will it return true?
In our case, when encountering ```@Transaction``` annotation, the following code will be executed:
```java
// DataSourceTransactionManager
protected void doBegin(Object transaction, TransactionDefinition definition) {
if (con.getAutoCommit()) {
con.setAutoCommit(false);
}
}
// ShardingSphereConnection
public void setAutoCommit(final boolean autoCommit) throws SQLException {
if (!autoCommit) {
TransactionHolder.setInTransaction();
}
}
// TransactionHolder
public static void setInTransaction() {
TRANSACTION.set(true);
}
```
for code ```TransactionHolder.isTransaction()```,
step1 and step2 must be return true, then route to master database
step3 must be return false, , then route to slave database
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[GitHub] [shardingsphere] strongduanmu commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
strongduanmu commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1277016428
Since this task is not complete, I will move it to 5.2.2.
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[GitHub] [shardingsphere] FlyingZC commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
FlyingZC commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1236699876
The same with issue #20614.
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[GitHub] [shardingsphere] FlyingZC commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
FlyingZC commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1285636234
This bug has been fixed by #20814.Because the ConnectionContext is at the connection level, when the inner transaction commits, it will not affect the value of `inTransaction` in the outer transaction.But only local transactions support nesting transaction, xa transactions do not support nesting transaction, this is because xa transaction managers such as atomikos and narayana do not support this feature themselves.
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[GitHub] [shardingsphere] github-actions[bot] commented on issue #20789: If there is write operation in the same thread and database connection, all the following read operations are not from the master database to ensure data consistency.
Posted by GitBox <gi...@apache.org>.
github-actions[bot] commented on issue #20789:
URL: https://github.com/apache/shardingsphere/issues/20789#issuecomment-1272348615
Hello , this issue has not received a reply for several days.
This issue is supposed to be closed.
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