Mysql with Hibernate AbstractMultiTenantConnectionProvider with C3P0ConnectionProvider throws GenericJDBCException: Could not open connection

Question

I am working on implementing multitenancy="DATABASE", ie single connection pool with per tenant database/schema (mysql database and schema are synonymous).

I have got MultiTenantConnectionProviderImpl.java

public class MultiTenantConnectionProviderImpl extends AbstractMultiTenantConnectionProvider implements
    ServiceRegistryAwareService {

private static final long serialVersionUID = 1234567890L;

private final HashMap<String, C3P0ConnectionProvider> connProviderMap = new HashMap<>();
private Map<String, String> originalSettings;
private ServiceRegistryImplementor serviceRegistry;

public MultiTenantConnectionProviderImpl() {
}

@Override
protected C3P0ConnectionProvider getAnyConnectionProvider() {
    return selectConnectionProvider(TenantContext.getTenantId());
}

@Override
protected C3P0ConnectionProvider selectConnectionProvider(String tenantId) {
    if (tenantId == null || !tenantId.equals(TenantContext.getTenantId())) {
        throw new TenantStateException(
                "Cannot get connection. Cause: tenant_id is not defined.");
    }

    C3P0ConnectionProvider connectionProvider = connProviderMap.get(tenantId);
    if (connectionProvider == null) {
        // create the new connection and register it
        Map<String, String> settings = new HashMap<>(originalSettings);
        // alter connection by changing user / password of the connection
        Properties properties = new PropertiesBuilder().withScope("database").build();
        settings.put("hibernate.connection.user", DatabaseConnectionProperties.getUser());
        settings.put("hibernate.connection.password", DatabaseConnectionProperties.getPassword());
        settings.put("hibernate.connection.url", DatabaseConnectionProperties.getConnectionUrl());
        settings.put("hibernate.connection.driver_class", properties.getProperty("hibernate.connection.driver_class"));

        connectionProvider = new C3P0ConnectionProvider();
        connectionProvider.injectServices(serviceRegistry);
        connectionProvider.configure(settings);
        connProviderMap.put(tenantId, connectionProvider);
    }

    return connectionProvider;
}

@Override
public void injectServices(ServiceRegistryImplementor serviceRegistry) {
    this.serviceRegistry = serviceRegistry;
    originalSettings = serviceRegistry.getService(ConfigurationService.class).getSettings();
    C3P0ConnectionProvider connectionProvider = new C3P0ConnectionProvider();
    connectionProvider.injectServices(serviceRegistry);
    connectionProvider.configure(originalSettings);
    connProviderMap.put(TenantContext.getTenantId(), connectionProvider);
}
}

And connection user is as follows

String.format("jdbc:mysql://%s/%s", databaseHost, databaseName)

This is failing with

rg.hibernate.exception.GenericJDBCException: Could not open connection
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)
...

  at org.hibernate.engine.jdbc.internal.LogicalConnectionImpl.obtainConnection(LogicalConnectionImpl.java:297) ~[hibernate-core-4.1.12.Final.jar:4.1.12.Final]
    ... 43 common frames omitted
   Caused by:     com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool  could not acquire a resource from its primary factory or source.

I have tried to override getConnection(String tenantId) to execute "use tenantId" to get the right database. However it didn't help and I reverted to the original way of specifying the database using connection url.

Anyone else encountered this problem?

Answer 1

I ended up implementing MultiTenantConnectionProvider instead, with an initial connection to default schema followed by schema alteration to tenant schema

public class MultiTenantConnectionProviderImpl implements MultiTenantConnectionProvider,
    ServiceRegistryAwareService {

private static final long serialVersionUID = 12345567890;

C3P0ConnectionProvider connectionProvider = null;

@Override
public void injectServices(ServiceRegistryImplementor serviceRegistry) {
    Map<String, String> originalSettings = serviceRegistry
        .getService(ConfigurationService.class).getSettings();
    connectionProvider = new C3P0ConnectionProvider();
    connectionProvider.injectServices(serviceRegistry);
    connectionProvider.configure(originalSettings);
}

@Override
public Connection getAnyConnection() throws SQLException {
    try {
        Class.forName("com.mysql.jdbc.Driver");
        final Connection connection = DriverManager.getConnection(
            DatabaseConnectionProperties.getConnectionUrl(),
            DatabaseConnectionProperties.getUser(), DatabaseConnectionProperties.getPassword());
        return connection;
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
    return connectionProvider.getConnection();
}

@Override
public void releaseAnyConnection(Connection connection) throws SQLException {
    try {
        connection.createStatement().execute("use default_tenant");
    }
    catch (SQLException e) {
        throw new HibernateException("Could not alter JDBC connection to specified schema [public]", e);
    }
    connectionProvider.closeConnection(connection);
}

@Override
public Connection getConnection(String tenantIdentifier) throws SQLException {
    final Connection connection = getAnyConnection();
    try {
        connection.createStatement().execute("use " + tenantIdentifier);
    }
    catch (SQLException e) {
        throw new HibernateException("Could not alter JDBC connection to specified schema ["
            + tenantIdentifier + "]", e);
    }
    return connection;
}

@Override
public void releaseConnection(String tenantIdentifier, Connection connection)
        throws SQLException {
    releaseAnyConnection(connection);
}

@Override
public boolean supportsAggressiveRelease() {
    return false;
}

@Override
public boolean isUnwrappableAs(Class unwrapType) {
    return false;
}

@Override
public <T> T unwrap(Class<T> unwrapType) {
    return null;
}
}