Call stored procedure on mysql slave using ReplicationDriver

Question

I have a Spring application that currently executes some queries utilizing stored procedures. The configuration is something like this:

Datasource:

<bean id="dataSource" destroy-method="close" class="org.apache.commons.dbcp.BasicDataSource">
    <property name="driverClassName" value="com.mysql.jdbc.ReplicationDriver"/>
    <property name="url" value="jdbc:mysql:replication://master,slave1,slave2/db?allowMultiQueries=true"/>
    <property name="username" value="${db.dbusername}"/>
    <property name="password" value="${db.dbpassword}"/>
    <property name="defaultReadOnly" value="true"/>
</bean>
<bean id="jdbcDeviceDAO" class="dao.jdbc.JdbcDeviceDAO">
    <property name="dataSource" ref="dataSource"/>
</bean>

DAO:

public class JdbcDeviceDAO implements DeviceDAO {
    // ...

    public void setDataSource(DataSource dataSource) {
        this.jdbcTemplate = new JdbcTemplate(dataSource);
        this.procGetCombinedDeviceRouting = new SimpleJdbcCall(jdbcTemplate)
                .withProcedureName("get_combined_device_routing");
        // ...
    }

    public CombinedDeviceRouting getCombinedDeviceRouting(String deviceName, String deviceNameType) {
        SqlParameterSource in = createParameters(deviceName, deviceNameType);

        Map<String, Object> results = this.procGetCombinedDeviceRouting.execute(in);

        return extractResults(results);
    }

Now when I call getCombinedDeviceRouting(...) it fails with the following exception:

org.springframework.dao.TransientDataAccessResourceException: CallableStatementCallback; SQL [{call get_combined_device_routing()}]; Connection is read-only. Queries leading to data modification are not allowed; nested exception is java.sql.SQLException: Connection is read-only. Queries leading to data modification are not allowed

I know the connection is read-only and I need it to be that way so the queries are load-balanced between slave hosts. But the stored procedure is actually read only, it's just a lot of SELECT statements, in fact I tried adding READS SQL DATA to its definition but it didn't work.

Finally I came to the point of reading the mysql's connector code and I found this:

protected boolean checkReadOnlySafeStatement() throws SQLException {
    synchronized (checkClosed().getConnectionMutex()) {
        return this.firstCharOfStmt == 'S' || !this.connection.isReadOnly();
    }
}

It sounds naive, but is the connector checking whether my statement is read-only by just matching the first character with 'S'? If this is the case, it seems like there's no way of calling a stored procedure on a slave host, because the statement starts with 'C' (CALL ...).

Does anyone know if there's a workaround for this problem? Or maybe I'm wrong assuming this first character check?

Answer 1

看来这是驱动程序的错误，我看了一下代码，看是否有一个简单的扩展点，但是看来您必须扩展很多类才能影响此行为:(