fix for daemon race condition (#1918)

test/daemon-test.sh

@@ -3,7 +3,7 @@
 #
 NAME='vw-daemon-test'
 
-export PATH="vowpalwabbit:../vowpalwabbit:${PATH}"
+export PATH="vowpalwabbit:../build/vowpalwabbit:${PATH}"
 # The VW under test
 VW=`which vw`
 
@@ -59,7 +59,6 @@ else
     exit 1
 fi
 
-
 # A command (+pattern) that is unlikely to match anything but our own test
 DaemonCmd="$VW -t -i $MODEL --daemon $Foreground --num_children 1 --quiet --port $PORT"
 # libtool may wrap vw with '.libs/lt-vw' so we need to be flexible
@@ -142,22 +141,24 @@ fi
 # Test on train-set
 # OpenBSD netcat quits immediately after stdin EOF
 # nc.traditional does not, so let's use -q 1.
-#$NETCAT -q 1 localhost $PORT < $TRAINSET > $PREDOUT
+$NETCAT -q 1 localhost $PORT < $TRAINSET > $PREDOUT
 #wait
+
+# JohnLangford: I'm unable to make the following work on Ubuntu 16.04.  Without -q 1, netcat appears to sometimes early terminate with STATUS an empty string.
 # However, GNU netcat does not know -q, so let's do a work-around
-touch $PREDOUT
-( $NETCAT localhost $PORT < $TRAINSET > $PREDOUT; STATUS=$?; echo $STATUS > $NETCAT_STATUS ) &
+#touch $PREDOUT
+#( $NETCAT localhost $PORT < $TRAINSET > $PREDOUT; STATUS=$?; echo $STATUS > $NETCAT_STATUS ) &
 # Wait until we recieve a prediction from the vw daemon then kill netcat
-until [ `wc -l < $PREDOUT` -eq 2 ]; do
-    if [ -f $NETCAT_STATUS ]; then
-        STATUS=`cat $NETCAT_STATUS`
-        if [ $STATUS -ne 0 ]; then
-            echo "$NAME: netcat failed with status code $STATUS"
-            stop_daemon
-            exit 1
-        fi
-    fi
-done
+#until [ `wc -l < $PREDOUT` -eq 2 ]; do
+#    if [ -f $NETCAT_STATUS ]; then
+#        STATUS=`cat $NETCAT_STATUS`
+#        if [ $STATUS -ne 0 ]; then
+#            echo "$NAME: netcat failed with status code $STATUS"
+#            stop_daemon
+#            exit 1
+#        fi
+#    fi
+#done
 $PKILL -9 $NETCAT
 
 # We should ignore small (< $Epsilon) floating-point differences (fuzzy compare)
@@ -176,4 +177,3 @@ case $? in
         exit 2
         ;;
 esac
-