Spark-submit脚本解读

#!/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.
#

# NOTE: Any changes in this file must be reflected in SparkSubmitDriverBootstrapper.scala!

#Spark的安装目录
export SPARK_HOME="$(cd `dirname $0`/..; pwd)"
#将参数已数组的形式赋值给ORIG_ARGS 
ORIG_ARGS=("$@")

#根据不同的参数项，把对应的参数值赋给对应的环境变量

while (($#)); do
  if [ "$1" = "--deploy-mode" ]; then
    SPARK_SUBMIT_DEPLOY_MODE=$2
  elif [ "$1" = "--properties-file" ]; then
    SPARK_SUBMIT_PROPERTIES_FILE=$2
  elif [ "$1" = "--driver-memory" ]; then
    export SPARK_SUBMIT_DRIVER_MEMORY=$2
  elif [ "$1" = "--driver-library-path" ]; then
    export SPARK_SUBMIT_LIBRARY_PATH=$2
  elif [ "$1" = "--driver-class-path" ]; then
    export SPARK_SUBMIT_CLASSPATH=$2
  elif [ "$1" = "--driver-java-options" ]; then
    export SPARK_SUBMIT_OPTS=$2
  fi
  shift
done

#定义一些默认的变量，会被用户的自定义参数覆盖
# :- 同 nvl
DEFAULT_PROPERTIES_FILE="$SPARK_HOME/conf/spark-defaults.conf"
export SPARK_SUBMIT_DEPLOY_MODE=${SPARK_SUBMIT_DEPLOY_MODE:-"client"}
export SPARK_SUBMIT_PROPERTIES_FILE=${SPARK_SUBMIT_PROPERTIES_FILE:-"$DEFAULT_PROPERTIES_FILE"}

# For client mode, the driver will be launched in the same JVM that launches
# SparkSubmit, so we may need to read the properties file for any extra class
# paths, library paths, java options and memory early on. Otherwise, it will
# be too late by the time the driver JVM has started.

#从spark-defaults.conf文件中获取"spark.driver.extra*|spark.driver.memory" 两个变量的值

if [[ "$SPARK_SUBMIT_DEPLOY_MODE" == "client" && -f "$SPARK_SUBMIT_PROPERTIES_FILE" ]]; then
  # Parse the properties file only if the special configs exist
  contains_special_configs=$(
    grep -e "spark.driver.extra*|spark.driver.memory" "$SPARK_SUBMIT_PROPERTIES_FILE" | 
    grep -v "^[[:space:]]*#"
  )
  if [ -n "$contains_special_configs" ]; then
    export SPARK_SUBMIT_BOOTSTRAP_DRIVER=1
  fi
fi
#将参数传递spark-class
#exec命令在执行时会把当前的shell process关闭，然后换到后面的命令继续执行
exec $SPARK_HOME/bin/spark-class org.apache.spark.deploy.SparkSubmit "${ORIG_ARGS[@]}"