--- a/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/AsmBasedInstrumentor.java	Tue Jan 26 10:18:13 2016 -0500
+++ b/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/AsmBasedInstrumentor.java	Tue Feb 02 12:13:27 2016 -0500
@@ -69,8 +69,8 @@
             return data;
 
         } catch (Exception e) {
-            System.err.println("Error transforming: " + className);
-            e.printStackTrace();
+            Debug.printlnError("Error transforming: " + className);
+            Debug.printStackTrace(e);
             throw new AssertionError(e);
         }
     }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/Debug.java	Tue Feb 02 12:13:27 2016 -0500
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2012-2015 Red Hat, Inc.
+ *
+ * This file is part of Thermostat.
+ *
+ * Thermostat is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2, or (at your
+ * option) any later version.
+ *
+ * Thermostat is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Thermostat; see the file COPYING.  If not see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Linking this code with other modules is making a combined work
+ * based on this code.  Thus, the terms and conditions of the GNU
+ * General Public License cover the whole combination.
+ *
+ * As a special exception, the copyright holders of this code give
+ * you permission to link this code with independent modules to
+ * produce an executable, regardless of the license terms of these
+ * independent modules, and to copy and distribute the resulting
+ * executable under terms of your choice, provided that you also
+ * meet, for each linked independent module, the terms and conditions
+ * of the license of that module.  An independent module is a module
+ * which is not derived from or based on this code.  If you modify
+ * this code, you may extend this exception to your version of the
+ * library, but you are not obligated to do so.  If you do not wish
+ * to do so, delete this exception statement from your version.
+ */
+
+package com.redhat.thermostat.vm.profiler.agent.jvm;
+
+/**
+ * Central place for debugging so we can control whether output is displayed or
+ * not. In general, it's not a good idea to display output to stdout/stderr of a
+ * random program since it may not be expected at all.
+ */
+public class Debug {
+
+    private static boolean printEnabled = false;
+
+    private Debug() {
+        // do not instantiate
+    }
+
+    public static void setPrintEnabled(boolean enabled) {
+        Debug.printEnabled = enabled;
+    }
+
+    public static boolean getPrintEnabled() {
+        return printEnabled;
+    }
+
+    public static void println(String message) {
+        if (printEnabled) {
+            System.out.println(message);
+        }
+    }
+
+    public static void printlnError(String message) {
+        if (printEnabled) {
+            System.err.println(message);
+        }
+    }
+
+    public static void printStackTrace(Throwable t) {
+        if (printEnabled) {
+            t.printStackTrace();
+        }
+    }
+
+}

--- a/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/InstrumentationControl.java	Tue Jan 26 10:18:13 2016 -0500
+++ b/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/InstrumentationControl.java	Tue Feb 02 12:13:27 2016 -0500
@@ -144,21 +144,21 @@
         }
 
         if (toTransform.size() > 0) {
-            System.out.println("AGENT: Retransforming " + toTransform.size() + " classes");
+            Debug.println("AGENT: Retransforming " + toTransform.size() + " classes");
             for (Class<?> klass : toTransform) {
                 try {
                     instrumentation.retransformClasses(klass);
                 } catch (UnmodifiableClassException e) {
                     throw new AssertionError("Tried to modify an unmodifiable class", e);
                 } catch (Error e) {
-                    System.err.println("Failed to trasnform: " + klass.getName());
-                    System.err.println("Unable to retransform all classes. Some classes may not have been instrumented correctly!");
-                    e.printStackTrace();
+                    Debug.printlnError("Failed to transform: " + klass.getName());
+                    Debug.printlnError("Unable to retransform all classes. Some classes may not have been instrumented correctly!");
+                    Debug.printStackTrace(e);
                 }
             }
         }
         long end = System.nanoTime();
-        System.out.println("AGENT: Retansforming took: " + (end - start) + "ns");
+        Debug.println("AGENT: Retansforming took: " + (end - start) + "ns");
     }
 
     private void writeResultsToDiskIfNotWritten() {
@@ -175,7 +175,7 @@
             try {
                 out = resultsFile.getWriter();
                 Map<String, AtomicLong> data = recorder.getData();
-                System.out.println("AGENT: Writing " + data.size() + " results to: " + path);
+                Debug.println("AGENT: Writing " + data.size() + " results to: " + path);
                 for (Map.Entry<String, AtomicLong> entry : data.entrySet()) {
                     out.write(entry.getValue().get() + "\t" + entry.getKey() + "\n");
                 }
@@ -188,11 +188,11 @@
                     }
                 } catch (IOException e) {
                     // well, we are screwed
-                    e.printStackTrace();
+                    Debug.printStackTrace(e);
                 }
             }
         } catch (IOException e) {
-            e.printStackTrace();
+            Debug.printStackTrace(e);
         }
     }
 

--- a/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/Main.java	Tue Jan 26 10:18:13 2016 -0500
+++ b/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/Main.java	Tue Feb 02 12:13:27 2016 -0500
@@ -64,8 +64,8 @@
             ObjectName name = new ObjectName("com.redhat.thermostat:type=InstrumentationControl");
             server.registerMBean(control, name);
         } catch (Exception e) {
-            System.err.println("Unable to attach agent");
-            e.printStackTrace();
+            Debug.printlnError("Unable to attach agent");
+            Debug.printStackTrace(e);
         }
     }
 

--- a/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/ProfilerAgent.java	Tue Jan 26 10:18:13 2016 -0500
+++ b/vm-profiler/jvm-agent/src/main/java/com/redhat/thermostat/vm/profiler/agent/jvm/ProfilerAgent.java	Tue Feb 02 12:13:27 2016 -0500
@@ -59,7 +59,7 @@
 
     private static void initializeAgent(String args, Instrumentation instrumentation) {
 
-        System.out.println("AGENT: loaded");
+        Debug.println("AGENT: loaded");
 
         // This is the saner approach, but for now we are brute-forcing a
         // hardcoded path using a manifest entry
@@ -70,7 +70,7 @@
     }
 
     private static void addJarsToClassPath(String jars, Instrumentation instrumentation) throws AssertionError {
-        // System.out.println("Classpath: " + System.getProperty("java.class.path"));
+        Debug.println("Classpath: " + System.getProperty("java.class.path"));
         boolean addToBoot = true;
         String[] jarPaths = jars.split(":");
         for (String jarPath : jarPaths) {
@@ -83,7 +83,7 @@
                 } else {
                     instrumentation.appendToSystemClassLoaderSearch(jarFile);
                 }
-                System.out.println("AGENT: Added" + jarPath + " to " + (addToBoot ? "bootstrap" : "system") + " classpath");
+                Debug.println("AGENT: Added '" + jarPath + "' to " + (addToBoot ? "bootstrap" : "system") + " classpath");
             } catch (IOException e) {
                 throw new AssertionError(jarFile + " not found!");
             }
@@ -99,23 +99,23 @@
             Method runMethod = klass.getMethod("run");
             runMethod.invoke(main);
         } catch (ClassNotFoundException e) {
-            e.printStackTrace();
-            System.err.println("Unable to initialize agent");
+            Debug.printStackTrace(e);
+            Debug.printlnError("Unable to initialize agent");
         } catch (NoSuchMethodException e) {
-            e.printStackTrace();
-            System.err.println("Unable to initialize agent");
+            Debug.printStackTrace(e);
+            Debug.printlnError("Unable to initialize agent");
         } catch (IllegalAccessException e) {
-            e.printStackTrace();
-            System.err.println("Unable to initialize agent");
+            Debug.printStackTrace(e);
+            Debug.printlnError("Unable to initialize agent");
         } catch (InstantiationException e) {
-            e.printStackTrace();
-            System.err.println("Unable to initialize agent");
+            Debug.printStackTrace(e);
+            Debug.printlnError("Unable to initialize agent");
         } catch (InvocationTargetException e) {
-            e.printStackTrace();
-            System.err.println("Unable to initialize agent");
+            Debug.printStackTrace(e);
+            Debug.printlnError("Unable to initialize agent");
         } catch (SecurityException e) {
-            e.printStackTrace();
-            System.err.println("Unable to initialize agent");
+            Debug.printStackTrace(e);
+            Debug.printlnError("Unable to initialize agent");
         }
     }
 

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/vm-profiler/jvm-agent/src/test/java/com/redhat/thermostat/vm/profiler/agent/jvm/DebugTest.java	Tue Feb 02 12:13:27 2016 -0500
@@ -0,0 +1,94 @@
+/*
+ * Copyright 2012-2015 Red Hat, Inc.
+ *
+ * This file is part of Thermostat.
+ *
+ * Thermostat is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2, or (at your
+ * option) any later version.
+ *
+ * Thermostat is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Thermostat; see the file COPYING.  If not see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Linking this code with other modules is making a combined work
+ * based on this code.  Thus, the terms and conditions of the GNU
+ * General Public License cover the whole combination.
+ *
+ * As a special exception, the copyright holders of this code give
+ * you permission to link this code with independent modules to
+ * produce an executable, regardless of the license terms of these
+ * independent modules, and to copy and distribute the resulting
+ * executable under terms of your choice, provided that you also
+ * meet, for each linked independent module, the terms and conditions
+ * of the license of that module.  An independent module is a module
+ * which is not derived from or based on this code.  If you modify
+ * this code, you may extend this exception to your version of the
+ * library, but you are not obligated to do so.  If you do not wish
+ * to do so, delete this exception statement from your version.
+ */
+
+package com.redhat.thermostat.vm.profiler.agent.jvm;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+import java.io.PrintStream;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class DebugTest {
+
+    private PrintStream originalSystemOut;
+    private PrintStream originalSystemErr;
+    private boolean originalPrintEnabled;
+
+    private PrintStream systemOut;
+    private PrintStream systemErr;
+
+    @Before
+    public void setup() {
+        originalPrintEnabled = Debug.getPrintEnabled();
+
+        originalSystemOut = System.out;
+        systemOut = mock(PrintStream.class);
+        System.setOut(systemOut);
+
+        originalSystemErr = System.err;
+        systemErr = mock(PrintStream.class);
+        System.setErr(systemErr);
+    }
+
+    @After
+    public void tearDown() {
+        System.setErr(originalSystemErr);
+        System.setOut(originalSystemOut);
+
+        Debug.setPrintEnabled(originalPrintEnabled);
+    }
+
+    @Test
+    public void verifyNoOutputWhenPrintingIsDisabled() throws Exception {
+        Debug.setPrintEnabled(false);
+        Debug.println("foobar!");
+        verifyNoMoreInteractions(systemErr, systemOut);
+    }
+
+    @Test
+    public void verifyOutputWhenPrintingIsEnabled() throws Exception {
+        Debug.setPrintEnabled(true);
+        Debug.printlnError("foobar!");
+        verify(systemErr).println("foobar!");
+        verifyNoMoreInteractions(systemOut);
+    }
+
+}