Add Scala as --build-arg

docs/using/specifics.md

@@ -46,14 +46,13 @@ You can build a `pyspark-notebook` image (and also the downstream `all-spark-not
 
   - `spark_version`: The Spark version to install (`3.3.0`).
   - `hadoop_version`: The Hadoop version (`3.2`).
-  - `scala_version`: The Scala version (`2.13`).
+  - `scala_version`: The Scala version (`2.13`, optional).
   - `spark_checksum`: The package checksum (`BFE4540...`).
   - `openjdk_version`: The version of the OpenJDK (JRE headless) distribution (`17`).
     - This version needs to match the version supported by the Spark distribution used above.
     - See [Spark Overview](https://spark.apache.org/docs/latest/#downloading) and [Ubuntu packages](https://packages.ubuntu.com/search?keywords=openjdk).
 
-- Starting with _Spark >= 3.2_ the distribution file contains Scala version, hence building older Spark will not work.
-- Building older version requires modification to the Dockerfile or using it's older version of the Dockerfile.
+- Starting with _Spark >= 3.2_ the distribution file might contain Scala version.
 
 For example here is how to build a `pyspark-notebook` image with Spark `3.2.0`, Hadoop `3.2` and OpenJDK `11`.
 

pyspark-notebook/Dockerfile

@@ -17,8 +17,8 @@ USER root
 # (ARGS are in lower case to distinguish them from ENV)
 ARG spark_version="3.3.0"
 ARG hadoop_version="3"
-ARG scala_version="2.13"
-ARG spark_checksum="4c09dac70e22bf1d5b7b2cabc1dd92aba13237f52a5b682c67982266fc7a0f5e0f964edff9bc76adbd8cb444eb1a00fdc59516147f99e4e2ce068420ff4881f0"
+ARG scala_version
+ARG spark_checksum="1e8234d0c1d2ab4462d6b0dfe5b54f2851dcd883378e0ed756140e10adfb5be4123961b521140f580e364c239872ea5a9f813a20b73c69cb6d4e95da2575c29c"
 ARG openjdk_version="17"
 
 ENV APACHE_SPARK_VERSION="${spark_version}" \
@@ -32,22 +32,29 @@ RUN apt-get update --yes && \
 
 # Spark installation
 WORKDIR /tmp
-RUN wget -q "https://archive.apache.org/dist/spark/spark-${APACHE_SPARK_VERSION}/spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}.tgz" && \
-    echo "${spark_checksum} *spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}.tgz" | sha512sum -c - && \
-    tar xzf "spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}.tgz" -C /usr/local --owner root --group root --no-same-owner && \
-    rm "spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}.tgz"
 
-WORKDIR /usr/local
+RUN if [ -z "${scala_version}" ]; then \
+    wget -qO "spark.tgz" "https://archive.apache.org/dist/spark/spark-${APACHE_SPARK_VERSION}/spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}.tgz"; \
+  else \
+    wget -qO "spark.tgz" "https://archive.apache.org/dist/spark/spark-${APACHE_SPARK_VERSION}/spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}.tgz"; \
+  fi && \
+  echo "${spark_checksum} *spark.tgz" | sha512sum -c - && \
+  tar xzf "spark.tgz" -C /usr/local --owner root --group root --no-same-owner && \
+  rm "spark.tgz"
 
 # Configure Spark
 ENV SPARK_HOME=/usr/local/spark
 ENV SPARK_OPTS="--driver-java-options=-Xms1024M --driver-java-options=-Xmx4096M --driver-java-options=-Dlog4j.logLevel=info" \
     PATH="${PATH}:${SPARK_HOME}/bin"
 
-RUN ln -s "spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}" spark && \
-    # Add a link in the before_notebook hook in order to source automatically PYTHONPATH
-    mkdir -p /usr/local/bin/before-notebook.d && \
-    ln -s "${SPARK_HOME}/sbin/spark-config.sh" /usr/local/bin/before-notebook.d/spark-config.sh
+RUN if [ -z "${scala_version}" ]; then \
+    ln -s "spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}" "${SPARK_HOME}"; \
+  else \
+    ln -s "spark-${APACHE_SPARK_VERSION}-bin-hadoop${HADOOP_VERSION}-scala${scala_version}" "${SPARK_HOME}"; \
+  fi && \
+  # Add a link in the before_notebook hook in order to source automatically PYTHONPATH && \
+  mkdir -p /usr/local/bin/before-notebook.d && \
+  ln -s "${SPARK_HOME}/sbin/spark-config.sh" /usr/local/bin/before-notebook.d/spark-config.sh
 
 # Configure IPython system-wide
 COPY ipython_kernel_config.py "/etc/ipython/"