[SPARK-3584] sbin/slaves doesn't work when we use password authentication for SSH

Author: Kousuke Saruta <sarutak@oss.nttdata.co.jp>

Closes #2444 from sarutak/slaves-scripts-modification and squashes the following commits:

eff7394 [Kousuke Saruta] Improve the description about Cluster Launch Script in docs/spark-standalone.md
7858225 [Kousuke Saruta] Modified sbin/slaves to use the environment variable "SPARK_SSH_FOREGROUND" as a flag
53d7121 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into slaves-scripts-modification
e570431 [Kousuke Saruta] Added a description for SPARK_SSH_FOREGROUND variable
7120a0c [Kousuke Saruta] Added a description about default host for sbin/slaves
1bba8a9 [Kousuke Saruta] Added SPARK_SSH_FOREGROUND flag to sbin/slaves
88e2f17 [Kousuke Saruta] Merge branch 'master' of git://git.apache.org/spark into slaves-scripts-modification
297e75d [Kousuke Saruta] Modified sbin/slaves not to export HOSTLIST

1 files changed, 22 insertions, 9 deletions

diff --git a/sbin/slaves.sh b/sbin/slaves.sh
index 1d4dc5edf9..cdad47ee2e 100755
--- a/sbin/slaves.sh
+++ b/sbin/slaves.sh
@@ -44,7 +44,9 @@ sbin="`cd "$sbin"; pwd`"
 # If the slaves file is specified in the command line,
 # then it takes precedence over the definition in
 # spark-env.sh. Save it here.
-HOSTLIST="$SPARK_SLAVES"
+if [ -f "$SPARK_SLAVES" ]; then
+  HOSTLIST=`cat "$SPARK_SLAVES"`
+fi
 
 # Check if --config is passed as an argument. It is an optional parameter.
 # Exit if the argument is not a directory.
@@ -67,23 +69,34 @@ fi
 
 if [ "$HOSTLIST" = "" ]; then
   if [ "$SPARK_SLAVES" = "" ]; then
-    export HOSTLIST="${SPARK_CONF_DIR}/slaves"
+    if [ -f "${SPARK_CONF_DIR}/slaves" ]; then
+      HOSTLIST=`cat "${SPARK_CONF_DIR}/slaves"`
+    else
+      HOSTLIST=localhost
+    fi
   else
-    export HOSTLIST="${SPARK_SLAVES}"
+    HOSTLIST=`cat "${SPARK_SLAVES}"`
   fi
 fi
 
+
+
 # By default disable strict host key checking
 if [ "$SPARK_SSH_OPTS" = "" ]; then
   SPARK_SSH_OPTS="-o StrictHostKeyChecking=no"
 fi
 
-for slave in `cat "$HOSTLIST"|sed  "s/#.*$//;/^$/d"`; do
- ssh $SPARK_SSH_OPTS "$slave" $"${@// /\\ }" \
-   2>&1 | sed "s/^/$slave: /" &
- if [ "$SPARK_SLAVE_SLEEP" != "" ]; then
-   sleep $SPARK_SLAVE_SLEEP
- fi
+for slave in `echo "$HOSTLIST"|sed  "s/#.*$//;/^$/d"`; do
+  if [ -n "${SPARK_SSH_FOREGROUND}" ]; then
+    ssh $SPARK_SSH_OPTS "$slave" $"${@// /\\ }" \
+      2>&1 | sed "s/^/$slave: /"
+  else
+    ssh $SPARK_SSH_OPTS "$slave" $"${@// /\\ }" \
+      2>&1 | sed "s/^/$slave: /" &
+  fi
+  if [ "$SPARK_SLAVE_SLEEP" != "" ]; then
+    sleep $SPARK_SLAVE_SLEEP
+  fi
 done
 
 wait