SPARK-1286: Make usage of spark-env.sh idempotent

Various spark scripts load spark-env.sh. This can cause growth of any variables that may be appended to (SPARK_CLASSPATH, SPARK_REPL_OPTS) and it makes the precedence order for options specified in spark-env.sh less clear.

One use-case for the latter is that we want to set options from the command-line of spark-shell, but these options will be overridden by subsequent loading of spark-env.sh. If we were to load the spark-env.sh first and then set our command-line options, we could guarantee correct precedence order.

Note that we use SPARK_CONF_DIR if available to support the sbin/ scripts, which always set this variable from sbin/spark-config.sh. Otherwise, we default to the ../conf/ as usual.

Author: Aaron Davidson <aaron@databricks.com>

Closes #184 from aarondav/idem and squashes the following commits:

e291f91 [Aaron Davidson] Use "private" variables in load-spark-env.sh
8da8360 [Aaron Davidson] Add .sh extension to load-spark-env.sh
93a2471 [Aaron Davidson] SPARK-1286: Make usage of spark-env.sh idempotent

1 files changed, 35 insertions, 0 deletions

diff --git a/bin/load-spark-env.sh b/bin/load-spark-env.sh
new file mode 100644
index 0000000000..476dd82655
--- /dev/null
+++ b/bin/load-spark-env.sh
@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# This script loads spark-env.sh if it exists, and ensures it is only loaded once.
+# spark-env.sh is loaded from SPARK_CONF_DIR if set, or within the current directory's
+# conf/ subdirectory.
+
+if [ -z "$SPARK_ENV_LOADED" ]; then
+  export SPARK_ENV_LOADED=1
+
+  # Returns the parent of the directory this script lives in.
+  parent_dir="$(cd `dirname $0`/..; pwd)"
+
+  use_conf_dir=${SPARK_CONF_DIR:-"$parent_dir/conf"}
+
+  if [ -f "${use_conf_dir}/spark-env.sh" ]; then
+    . "${use_conf_dir}/spark-env.sh"
+  fi
+fi