Hi everyone,
I was using Hadoop command line interface to access HDFS with a non-root user. After successfully running kinit, Hadoop FsShell fails with GSSException: No valid credentials provided (Mechanism level: Failed to find any Kerberos tgt). After using a subclassed Krb5LoginModule to print out necessary debug info, I found that the login module's login method failed because permissions of some jars in classpath are not properly set and process doesn't have read permissions to them. A java.lang.ExceptionInInitializerError is thrown. Because the login method is invoked via reflection in LoginContext, the ExceptionInInitializerError is wrapped in an InvocationTargetException and is caught in LoginContext#invoke. Since this Kerberos login module is optional and the following login module logins successfully, the exception is logged nowhere and the ExceptionInInitializerError thrown from deep in the call stack is completely swallowed silently, making debugging this problem extremely hard. My point here is that codes in LoginModule are not supposed to catch and process java.lang.Error, and I am confused by the way that reflection method invocation in LoginContext#invoke just swallows silently errors thrown by the method invoked. When an Error occurs, it means something really bad happened. I think LoginContext#invoke should either propagate errors to upper codes, or at least log such events. This error-swallowing behavior is consistent from jdk 7 to jdk 11. I would like to have some expert comments on this to help me understand this design. Thanks. Wenxiang Qiu
