Remove exception from sun.rmi.runtime.Log#getSource()

[Philippe Marschall]

Hello

First time contributor here.

We have exception tracing enabled in production and see thousands of
exceptions in sun.rmi.runtime.Log#getSource() to get the caller class.
In my option this should use StackWalker introduced in Java 9. I could
find no corresponding bug in JBS.

I created a and uploaded webrev here [1] and also added the patch inline
below. As for the implementation I created a custom StackWalker to be
able to pass in the estimated number of frames that we traverse. For
variable naming conventions I tried to stick with other StackWalker
users I could find in the JDK. The stream formatting tries to follow the
LVTI style guidelines.

I have not written a test as the method is private. I ran the tier1
tests and they passed.

I have signed the OCA.

What are the next steps?


--- old/src/java.rmi/share/classes/sun/rmi/runtime/Log.java	2019-08-21
14:16:47.381544386 +0200
+++ new/src/java.rmi/share/classes/sun/rmi/runtime/Log.java	2019-08-21
14:16:47.249545585 +0200
@@ -30,6 +30,7 @@
  import java.io.OutputStream;
  import java.rmi.server.LogStream;
  import java.security.PrivilegedAction;
+import java.util.Set;
  import java.util.logging.Handler;
  import java.util.logging.SimpleFormatter;
  import java.util.logging.Level;
@@ -62,6 +63,8 @@
      public static final Level BRIEF = Level.FINE;
      public static final Level VERBOSE = Level.FINER;

+    private static final StackWalker WALKER =
StackWalker.getInstance(Set.of(), 4);
+
      /* selects log implementation */
      private static final LogFactory logFactory;
      static {
@@ -444,10 +447,10 @@
       * Obtain class and method names of code calling a log method.
       */
      private static String[] getSource() {
-        StackTraceElement[] trace = (new Exception()).getStackTrace();
-        return new String[] {
-            trace[3].getClassName(),
-            trace[3].getMethodName()
-        };
+        return WALKER.walk(s -> s
+                                 .skip(3)
+                                 .map(f -> new String[]
{f.getClassName(), f.getMethodName()})
+                                 .findFirst()
+                                 .get());
      }
  }

  [1]
https://github.com/marschall/webrevs/raw/master/Log-getSource/webrev.zip

Cheers
Philippe Marschall