[英]Too many connections error using DB pooling
因此,我正在開發應該處理大量負載的Web服務。 而且我使用了snaq DBpooling。 但問題是我總是會收到錯誤
com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Data source rejected
establishment of connection, message from server: "Too many connections"
我檢查了其他線程,大部分問題是由於conn.close()調用不正確。 但是在這里,我在各地建議的finally方法中調用它。 這是我的代碼。 您能建議出什么問題嗎。
public class ExampleServlet extends HttpServlet {
public static final String MESSAGE = "message";
private String message;
private ConnectionPool pool;
@Override
public void init(final ServletConfig config) throws ServletException {
super.init(config);
message = config.getInitParameter(MESSAGE);
try {
Class c = Class.forName("com.mysql.jdbc.Driver");
Driver driver = (Driver) c.newInstance();
DriverManager.registerDriver(driver);
String url = "jdbc:mysql://localhost/db15619";
pool = new ConnectionPool("local", 20, 25, 30, 180, url, "root", "db15319root");
} catch (/*InstantiationException | ClassNotFoundException | SQLException */ Exception ex) {
System.out.println("Error:" + ex.toString());
}
}
@Override
protected void doGet(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {
PrintWriter writer = resp.getWriter();
//System.out.println(req.getQueryString());
String[] string_key = req.getQueryString().split("=|\\&");
//exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain");
string_key[3] = string_key[3].replace('+', ' ');
String query_str = "select tweetid,score,tweettext from tweets where userid = '" + string_key[1] + "' and dttm = '" + string_key[3] + "';";
Connection conn = null;
long timeout = 10000;
try {
conn = pool.getConnection();
} catch (SQLException ex) {
System.out.println("Error While Creating Connection :=> " + ex.toString());
}
if (conn != null) {
try {
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(query_str);
String str = "CloudNinjas," + "0369-8371-3735" + "," + "9830-4777-6269" + "," + "3472-5239-0207" + "\n";
while (rs.next()) {
for (int i = 1; i <= 3; i++) {
str = str + rs.getString(i);
if (i != 3) {
str = str + ":";
} else {
str = str + "\n";
}
}
}
byte[] bytes = str.getBytes(Charset.forName("UTF-8"));
System.out.println(str);
System.out.println(bytes);
writer.write(str);
} catch (SQLException ex) {
System.out.println("Error While Creating Connection :=> " + ex.toString());
} finally {
if (conn != null) {
try {
conn.close();
} catch (SQLException ex) {
}
}
}
}
writer.close();
}
@Override
protected void doPost(final HttpServletRequest req, final HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
太多的客戶端同時訪問該池,或者某些客戶端沒有退還其連接。 我認為是后者。
您可以嘗試通過使用一個較小的存儲池(例如5)順序進行單個呼叫並查看問題是否在第6個呼叫上發生來進行測試。 這表明客戶端沒有正確清理。
之所以創建JDK7資源嘗試功能,是因為有很多人遇到相同的問題(例如: 我應該如何在JDBC中使用try-with-resources? )。
我還看到您沒有關閉Statement
或Resultset
(請參閱JDBC Resultsset和Statements是否必須先關閉,盡管Connection隨后會關閉嗎? ),這可能是相關的或導致了其他問題。
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