使用未包装的 oracle.jdbc.driver.T4CConnection 导致 HikariCP 连接泄漏

Question

我在使用 HikariCP 和未包装连接时遇到资源泄漏问题。然后是代码的一些解释。

我必须使用展开的连接来访问 oracle.sql.BFILE 的 Oracle 方法。这是从 Oracle 目录中流式传输二进制文件。

数据源示例：

private static DataSource unwrapDatasource;
public static synchronized DataSource getUnwrappedDataSource() {
    if (unwrapDatasource == null) {
        HikariConfig config = new HikariConfig();
        config.setMaximumPoolSize(50);
        config.setLeakDetectionThreshold(120000);
        config.setJdbcUrl(DATABASEURL);
        config.addDataSourceProperty("user", USERNAME);
        config.addDataSourceProperty("password", DBPASSWORD);
        config.addDataSourceProperty("driverType", "thin");
        config.setDriverClassName("oracle.jdbc.pool.OracleDataSource");
        config.setMaxLifetime(300000);
        config.setPoolName("UNWRAP");
        unwrapDatasource = new HikariDataSource(config);
    }

    return unwrapDatasource;
}

  public static Connection getUnwrappedConnection() {
    Connection con = null;
    try {
        con = this.getUnwrappedDataSource().getConnection().unwrap(oracle.jdbc.driver.OracleConnection.class);
    } catch (SQLException ex) {
        //logger junk ommitted for brevity
    }
    return con;
}

使用 HikariCP-java7-2.4.12 作为应用程序非常旧并且在 tomcat-6 上运行。以下是报告为泄漏的连接示例

    com.zaxxer.hikari.pool.ProxyLeakTask.run(poolProxyLeak.java:91) : <Connection leak detection triggered for {}, stack trace follows>
java.lang.Exception: Apparent connection leak detected
    at myapp.package.obfuscated.getUnwrapConnection(DataSourceConstants.java:253)
    at myapp.package.obfuscated.BB.execute(DatabaseCallingClass2.java:106)
    at myapp.package.obfuscated.BB.execute(DatabaseCallingClass2.java:85)
    at myapp.package.obfuscated.AA.execute(DataBaseCallingClass.java:52)
    at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:425)
    at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:228)
    at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
    at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:462)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:643)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.displaytag.filter.ResponseOverrideFilter.doFilter(ResponseOverrideFilter.java:123)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:563)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:610)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:503)
    at java.lang.Thread.run(Thread.java:745)

这是连接及其使用方法：

     Connection con = null;
     PreparedStatement pstmt = null;
     OracleResultSet rs = null;
     InputStream inputStream = null;
     StringBuilder stringBuilder = new StringBuilder(128);
     try {
            con = DataSourceConstants.getUnwrappedConnection();

            pstmt = con.prepareStatement("SELECT BFILENAME('ORACLE_DIR', 'fileDownload.12345') AS BFILE from dual" );  //hardcoded for example
            rs = (OracleResultSet) pstmt.executeQuery();

            rs.next();  //Assumption if rs.next() blows up, catch would grab it and resources would all attempt to close in finally block

            bfile = rs.getBFILE(1);
            bfile.open();
            inputStream = bfile.getBinaryStream();
            char c;
            long size = bfile.length();

            int i = 0;
            do {
                c= (char) inputStream.read();
                stringBuilder.append(c);
            } while (++i < size);

            } catch (Exception ex) {
              //logger ommitted but not throwing here
            } finally {
             //cleanup resources
             try { inputStream.close(); } catch (Exception ex) {}
             try { bfile.close(); } catch (Exception ex) {}
             try { rs.close(); } catch (Exception ex) {}
             try { pstmt.close(); } catch (Exception ex) {}
             try {con.close();  } catch (Exception ex){}
            }
       //use stringBuilder later in built output.

因此，上面检索了一个未包装的 T4CConnection，以便我可以使用 OracleResultSet 和 BFILE / getBFILE()。这有效，我得到了我想要的结果，但是使用此结构检索 BFILE 的两个单独的类都泄漏，并且不使用 BFILE 但使用未包装连接来使用 OracleCallableStatement 的另一种方法也泄漏。我已经实例化了 3 个数据源，以按类型/功能拆分所有连接器，唯一泄漏的池是使用 Datasource.getConnection().unwrap(oracle.jdbc.driver.OracleConnection.class) 作为其连接器的池。

我在未包装的连接上做错了什么吗？为什么只有这个泄漏？这是一个已知的驱动程序错误吗？（我还没有拿出任何关于它的文章）BFILE似乎不是很受欢迎......

Answer 1

您正在做的事情getUnwrappedConnection()不是您应该做的事情：如果您正在展开，那么您需要确保还保留连接池连接，因为关闭该连接会将其返回到池中。因此，首先从池中获取连接，并且仅在您真正需要它时解包，然后，完成后，关闭从数据源获取的原始连接。

不要关闭未包装的连接，因为这将关闭实际的物理连接，并且会破坏使用连接池的目的。

简而言之：

try (Connection connection = dataSource.getConnection()) {
    OracleConnection unwrapped = connection.unwrap(oracle.jdbc.driver.OracleConnection.class)

    ...

    // Do not close (or use try-with-resources) on unwrapped
}