azkaban-developers

diff --git a/azkaban-common/src/main/java/azkaban/utils/PatternLayoutEscaped.java b/azkaban-common/src/main/java/azkaban/utils/PatternLayoutEscaped.java
index ff5ad87..089dba9 100644
--- a/azkaban-common/src/main/java/azkaban/utils/PatternLayoutEscaped.java
+++ b/azkaban-common/src/main/java/azkaban/utils/PatternLayoutEscaped.java
@@ -4,23 +4,34 @@ import org.apache.log4j.PatternLayout;
 import org.apache.log4j.spi.LoggingEvent;
 
 /**
- * When we use log4j to send a JSON message the official PatternLayout will send corrupt JSON if certain characters are
- * present. We use this PatternLayoutEscaped class as a thin interface around PatternLayout to escape all these
- * characters.
+ * When we use the log4j Kafka appender, it seems that the appender simply does not log the stack trace anywhere
+ * Seeing as the stack trace is a very important piece of information, we create our own PatternLayout class that
+ * appends the stack trace to the log message that reported it, so that all the information regarding that error
+ * can be found one in place.
  */
 public class PatternLayoutEscaped extends PatternLayout {
+  @Override
   public String format(final LoggingEvent event) {
     if (event.getMessage() instanceof String) {
-      return super.format(copyAndEscapeEvent(event));
+      return super.format(appendStackTraceToEvent(event));
     }
     return super.format(event);
   }
 
   /**
-   * Create a copy of event, but escape backslashes, tabs, newlines and quotes in its message
+   * Create a copy of event, but append a stack trace to the message (if it exists).
+   * Then it escapes the backslashes, tabs, newlines and quotes in its message as we are sending it as JSON and we
+   * don't want any corruption of the JSON object.
    */
-  private LoggingEvent copyAndEscapeEvent(LoggingEvent event) {
+  private LoggingEvent appendStackTraceToEvent(LoggingEvent event) {
     String message = event.getMessage().toString();
+    // If there is a stack trace available, print it out
+    if (event.getThrowableInformation() != null) {
+      String[] s = event.getThrowableStrRep();
+      for (String line: s) {
+        message += "\n" + line;
+      }
+    }
     message = message
         .replace("\\", "\\\\")
         .replace("\n", "\\n")

diff --git a/azkaban-common/src/test/java/azkaban/utils/PatternLayoutEscapedTest.java b/azkaban-common/src/test/java/azkaban/utils/PatternLayoutEscapedTest.java
index b92b233..2cd3cf3 100644
--- a/azkaban-common/src/test/java/azkaban/utils/PatternLayoutEscapedTest.java
+++ b/azkaban-common/src/test/java/azkaban/utils/PatternLayoutEscapedTest.java
@@ -28,7 +28,7 @@ import static org.junit.Assert.assertTrue;
 
 /**
  * Test output of PatternLayoutEscapedTest
- * It should be escaping new lines, quotes, tabs and backslashes
+ * It should be appending stack traces, escaping new lines, quotes, tabs and backslashes
  * This is necessary when we are logging these messages out as JSON objects
  */
 public class PatternLayoutEscapedTest {
@@ -41,6 +41,17 @@ public class PatternLayoutEscapedTest {
   }
 
   @Test
+  public void testWithException() {
+    try {
+      throw new Exception("This is an exception");
+    } catch (Exception e) {
+      LoggingEvent event = createEventWithException("There was an exception", e);
+      // Stack trace might change if the codebase changes, but this prefix should always remain the same
+      assertTrue(layout.format(event).startsWith("There was an exception\\njava.lang.Exception: This is an exception"));
+    }
+  }
+
+  @Test
   public void testNewLine() {
     LoggingEvent event = createMessageEvent("This message contains \n new lines");
     assertTrue(layout.format(event).equals("This message contains \\n new lines"));
@@ -65,11 +76,15 @@ public class PatternLayoutEscapedTest {
   }
 
   private LoggingEvent createMessageEvent(String message) {
+    return createEventWithException(message, null);
+  }
+
+  private LoggingEvent createEventWithException(String message, Exception e) {
     return new LoggingEvent(this.getClass().getCanonicalName(),
         logger,
         0,
         Level.toLevel("INFO"),
         message,
-        new Exception());
+        e);
   }
 }