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== [[AbstractCommandBuilder]] AbstractCommandBuilder

AbstractCommandBuilder is the base command builder for[SparkSubmitCommandBuilder] and SparkClassCommandBuilder specialized command builders.

AbstractCommandBuilder expects that command builders define buildCommand.

.AbstractCommandBuilder Methods [cols="1,2",options="header",width="100%"] |=== | Method | Description | buildCommand | The only abstract method that subclasses have to define. | <> | | <> | | <> | Loads the configuration file for a Spark application, be it the user-specified properties file or spark-defaults.conf file under the Spark configuration directory. |===

=== [[buildJavaCommand]] buildJavaCommand Internal Method

[source, java]

List buildJavaCommand(String extraClassPath)

buildJavaCommand builds the Java command for a Spark application (which is a collection of elements with the path to java executable, JVM options from java-opts file, and a class path).

If javaHome is set, buildJavaCommand adds [javaHome]/bin/java to the result Java command. Otherwise, it uses JAVA_HOME or, when no earlier checks succeeded, falls through to java.home Java's system property.

CAUTION: FIXME Who sets javaHome internal property and when?

buildJavaCommand loads extra Java options from the java-opts file in <> if the file exists and adds them to the result Java command.

Eventually, buildJavaCommand <> (with the extra class path if non-empty) and adds it as -cp to the result Java command.

=== [[buildClassPath]] buildClassPath method

[source, java]

List buildClassPath(String appClassPath)

buildClassPath builds the classpath for a Spark application.

NOTE: Directories always end up with the OS-specific file separator at the end of their paths.

buildClassPath adds the following in that order:

  1. SPARK_CLASSPATH environment variable
  2. The input appClassPath
  3. The[configuration directory]
  4. (only with SPARK_PREPEND_CLASSES set or SPARK_TESTING being 1) Locally compiled Spark classes in classes, test-classes and Core's jars. + CAUTION: FIXME Elaborate on "locally compiled Spark classes".

  5. (only with SPARK_SQL_TESTING being 1) ... + CAUTION: FIXME Elaborate on the SQL testing case

  6. HADOOP_CONF_DIR environment variable

  7. YARN_CONF_DIR environment variable

  8. SPARK_DIST_CLASSPATH environment variable

NOTE: childEnv is queried first before System properties. It is always empty for AbstractCommandBuilder (and SparkSubmitCommandBuilder, too).

=== [[loadPropertiesFile]] Loading Properties File -- loadPropertiesFile Internal Method

[source, java]

Properties loadPropertiesFile()

loadPropertiesFile is part of AbstractCommandBuilder private API that loads Spark settings from a properties file (when specified on the command line) or[spark-defaults.conf] in the <>.

It loads the settings from the following files starting from the first and checking every location until the first properties file is found:

  1. propertiesFile (if specified using --properties-file command-line option or set by AbstractCommandBuilder.setPropertiesFile).
  2. [SPARK_CONF_DIR]/spark-defaults.conf
  3. [SPARK_HOME]/conf/spark-defaults.conf

NOTE: loadPropertiesFile reads a properties file using UTF-8.

=== [[getConfDir]][[configuration-directory]] Spark's Configuration Directory -- getConfDir Internal Method

AbstractCommandBuilder uses getConfDir to compute the current configuration directory of a Spark application.

It uses SPARK_CONF_DIR (from childEnv which is always empty anyway or as a environment variable) and falls through to [SPARK_HOME]/conf (with SPARK_HOME from <getSparkHome internal method>>).

=== [[getSparkHome]][[home-directory]] Spark's Home Directory -- getSparkHome Internal Method

AbstractCommandBuilder uses getSparkHome to compute Spark's home directory for a Spark application.

It uses SPARK_HOME (from childEnv which is always empty anyway or as a environment variable).

If SPARK_HOME is not set, Spark throws a IllegalStateException:

Spark home not found; set it explicitly or use the SPARK_HOME environment variable.

Last update: 2020-10-06