fix event_id ordering and remove happened_at

bin/cqlsh

@@ -1023,7 +1023,7 @@ class Shell(cmd.Cmd):
     def print_trace(self, session_id):
         out = self.query_out
         out.write('\nTracing session: %s\n\n' % session_id)
-        self.perform_statement_untraced("SELECT activity, happened_at, source, source_elapsed FROM system_traces.events WHERE session_id = '%s'" % session_id)
+        self.perform_statement_untraced("SELECT activity, source, source_elapsed FROM system_traces.events WHERE session_id = '%s'" % session_id)
 
     # these next two functions are not guaranteed perfect; just checks if the
     # statement parses fully according to cqlsh's own understanding of the

src/java/org/apache/cassandra/config/CFMetaData.java

@@ -197,7 +197,6 @@ public final class CFMetaData
                                                                + "  source inet,"
                                                                + "  thread text,"
                                                                + "  activity text,"
-                                                               + "  happened_at timestamp,"
                                                                + "  source_elapsed int,"
                                                                + "  PRIMARY KEY (session_id, event_id)"
                                                                + ");", Tracing.TRACE_KS);

src/java/org/apache/cassandra/tracing/TracingAppender.java

@@ -49,18 +49,15 @@ public class TracingAppender extends AppenderSkeleton
             return;
 
         final int elapsed = state.elapsed();
-        final String threadName = event.getThreadName();
+        final ByteBuffer eventId = ByteBufferUtil.bytes(UUIDGen.makeType1UUIDFromHost(FBUtilities.getBroadcastAddress()));
         StageManager.getStage(Stage.TRACING).execute(new WrappedRunnable()
         {
             public void runMayThrow() throws Exception
             {
-                ByteBuffer eventId = ByteBufferUtil.bytes(UUIDGen.makeType1UUIDFromHost(FBUtilities
-                        .getBroadcastAddress()));
                 CFMetaData cfMeta = CFMetaData.TraceEventsCf;
                 ColumnFamily cf = ColumnFamily.create(cfMeta);
                 addColumn(cf, buildName(cfMeta, eventId, bytes("source")), FBUtilities.getBroadcastAddress());
-                addColumn(cf, buildName(cfMeta, eventId, bytes("thread")), threadName);
-                addColumn(cf, buildName(cfMeta, eventId, bytes("happened_at")), event.getTimeStamp());
+                addColumn(cf, buildName(cfMeta, eventId, bytes("thread")), event.getThreadName());
                 addColumn(cf, buildName(cfMeta, eventId, bytes("source_elapsed")), elapsed);
                 addColumn(cf, buildName(cfMeta, eventId, bytes("activity")), event.getMessage());
                 RowMutation mutation = new RowMutation(Tracing.TRACE_KS, state.sessionIdBytes);