CommunicationsException when connecting from GAE to MySQL Instance

Question

I'm trying to connect from inside GAE (Google App Engine) to my MySQL DB instance, also on GAE. It works fine from the outside.

After a week of searching, I cannot seem to find the problem.

Without the MySQL connection code, the servlet works fine without errors on GAE.

Here is the simple servlet:

public class DBServlet extends HttpServlet {
        @Override
        public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
            try {
                Class.forName("com.mysql.jdbc.GoogleDriver");
                Connection conn = DriverManager.getConnection("jdbc:google:mysql://cloud-2280:mysql/account", "root", "");
                //Connection conn = DriverManager.getConnection("jdbc:google:mysql://cloud-1180:mysql/account?user=root");
            } catch (ClassNotFoundException ex) {
                Logger.getLogger(DBServlet.class.getName()).log(Level.SEVERE, null, ex);
            } catch (SQLException ex) {
                Logger.getLogger(DBServlet.class.getName()).log(Level.SEVERE, null, ex);
            } finally {
                try {
                        conn.close();
                    } catch (SQLException ex) {
                        Logger.getLogger(DBServlet.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

When tying this on GAE, I get this in the GAE logs:

com.conversedynamics.NewServlet doPost: null com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:46) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1117) at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:668) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1078) at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2417) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2450) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2235) at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:818) at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:46) at com.mysql.jdbc.Util.handleNewInstance(Util.java:411) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:404) at com.mysql.jdbc.GoogleNonRegisteringDriver$JdbcWrapper.getInstance(GoogleNonRegisteringDriver.java:282) at com.mysql.jdbc.GoogleNonRegisteringDriver.connect(GoogleNonRegisteringDriver.java:252) at java.sql.DriverManager.getConnection(DriverManager.java:571) at java.sql.DriverManager.getConnection(DriverManager.java:233) at com.conversedynamics.NewServlet.doPost(NewServlet.java:90) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542) at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:923) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at com.google.tracing.TraceContext$TraceContextRunnable.runInContext(TraceContext.java:437) at com.google.tracing.TraceContext$TraceContextRunnable$1.run(TraceContext.java:444) at com.google.tracing.CurrentContext.runInContext(CurrentContext.java:256) at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContextNoUnref(TraceContext.java:308) at com.google.tracing.TraceContext$AbstractTraceContextCallback.runInInheritedContext(TraceContext.java:300) at com.google.tracing.TraceContext$TraceContextRunnable.run(TraceContext.java:441) at java.lang.Thread.run(Thread.java:745) Caused by: java.io.EOFException: Can not read response from server. Expected to read 4 bytes, read 0 bytes before connection was unexpectedly lost. at com.mysql.jdbc.MysqlIO.readFully(MysqlIO.java:3039) at com.mysql.jdbc.MysqlIO.readPacket(MysqlIO.java:592)

And here is the appengine-web.xml

<application>cloud-2280</application>
    <version>1</version>
    <!--    <ssl-enabled>false</ssl-enabled>
    <sessions-enabled>true</sessions-enabled>
    -->
    <threadsafe>false</threadsafe>
    <use-google-connector-j>true</use-google-connector-j>
</appengine-web-app>

UPDATE: Screen shot in relation to koma's answer:

Answer 1

You are using a second generation cloud sql instance. These are not accessible from app engine yet. Use a first generation instance and you can add your app as an authorized app. I had the same problem.

Answer 2

Communications link failure usually indicates that you have no permission to connect.

Did you grant access to your CloudSQL instance for your GAE application ?

https://cloud.google.com/sql/docs/access-control#appengine