site/docs/3.5.0/README.html

<p>Welcome to the Spark documentation!</p>

<p>This readme will walk you through navigating and building the Spark documentation, which is included
here with the Spark source code. You can also find documentation specific to release versions of
Spark at https://spark.apache.org/documentation.html.</p>

<p>Read on to learn more about viewing documentation in plain text (i.e., markdown) or building the
documentation yourself. Why build it yourself? So that you have the docs that correspond to
whichever version of Spark you currently have checked out of revision control.</p>

<h2 id="prerequisites">Prerequisites</h2>

<p>The Spark documentation build uses a number of tools to build HTML docs and API docs in Scala, Java,
Python, R and SQL.</p>

<p>You need to have <a href="https://www.ruby-lang.org/en/documentation/installation/">Ruby</a> and
<a href="https://docs.python.org/2/using/unix.html#getting-and-installing-the-latest-version-of-python">Python</a>
installed. Make sure the <code class="language-plaintext highlighter-rouge">bundle</code> command is available, if not install the Gem containing it:</p>

<div class="language-sh highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">$ </span><span class="nb">sudo </span>gem <span class="nb">install </span>bundler
</code></pre></div></div>

<p>After this all the required ruby dependencies can be installed from the <code class="language-plaintext highlighter-rouge">docs/</code> directory via the Bundler:</p>

<div class="language-sh highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">$ </span><span class="nb">cd </span>docs
<span class="nv">$ </span>bundle <span class="nb">install</span>
</code></pre></div></div>

<p>Note: If you are on a system with both Ruby 1.9 and Ruby 2.0 you may need to replace gem with gem2.0.</p>

<h3 id="sql-and-python-api-documentation-optional">SQL and Python API Documentation (Optional)</h3>

<p>To generate SQL and Python API docs, you&#8217;ll need to install these libraries:</p>

<!--
TODO(SPARK-32407): Sphinx 3.1+ does not correctly index nested classes.
See also https://github.com/sphinx-doc/sphinx/issues/7551.

TODO(SPARK-35375): Jinja2 3.0.0+ causes error when building with Sphinx.
See also https://issues.apache.org/jira/browse/SPARK-35375.
-->
<p>Run the following command from $SPARK_HOME:</p>
<div class="language-sh highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">$ </span>pip <span class="nb">install</span> <span class="nt">--upgrade</span> <span class="nt">-r</span> dev/requirements.txt
</code></pre></div></div>

<h3 id="r-api-documentation-optional">R API Documentation (Optional)</h3>

<p>If you&#8217;d like to generate R API documentation, you&#8217;ll need to <a href="https://pandoc.org/installing.html">install Pandoc</a>
and install these libraries:</p>

<div class="language-sh highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">$ </span><span class="nb">sudo </span>Rscript <span class="nt">-e</span> <span class="s1">'install.packages(c("knitr", "devtools", "testthat", "rmarkdown"), repos="https://cloud.r-project.org/")'</span>
<span class="nv">$ </span><span class="nb">sudo </span>Rscript <span class="nt">-e</span> <span class="s1">'devtools::install_version("roxygen2", version = "7.1.2", repos="https://cloud.r-project.org/")'</span>
<span class="nv">$ </span><span class="nb">sudo </span>Rscript <span class="nt">-e</span> <span class="s2">"devtools::install_version('pkgdown', version='2.0.1', repos='https://cloud.r-project.org')"</span>
<span class="nv">$ </span><span class="nb">sudo </span>Rscript <span class="nt">-e</span> <span class="s2">"devtools::install_version('preferably', version='0.4', repos='https://cloud.r-project.org')"</span>
</code></pre></div></div>

<p>Note: Other versions of roxygen2 might work in SparkR documentation generation but <code class="language-plaintext highlighter-rouge">RoxygenNote</code> field in <code class="language-plaintext highlighter-rouge">$SPARK_HOME/R/pkg/DESCRIPTION</code> is 7.1.2, which is updated if the version is mismatched.</p>

<h2 id="generating-the-documentation-html">Generating the Documentation HTML</h2>

<p>We include the Spark documentation as part of the source (as opposed to using a hosted wiki, such as
the github wiki, as the definitive documentation) to enable the documentation to evolve along with
the source code and be captured by revision control (currently git). This way the code automatically
includes the version of the documentation that is relevant regardless of which version or release
you have checked out or downloaded.</p>

<p>In this directory you will find text files formatted using Markdown, with an &#8220;.md&#8221; suffix. You can
read those text files directly if you want. Start with <code class="language-plaintext highlighter-rouge">index.md</code>.</p>

<p>Execute <code class="language-plaintext highlighter-rouge">SKIP_API=1 bundle exec jekyll build</code> from the <code class="language-plaintext highlighter-rouge">docs/</code> directory to compile the site. Compiling the site with
Jekyll will create a directory called <code class="language-plaintext highlighter-rouge">_site</code> containing <code class="language-plaintext highlighter-rouge">index.html</code> as well as the rest of the
compiled files.</p>

<div class="language-sh highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">$ </span><span class="nb">cd </span>docs
<span class="c"># Skip generating API docs (which takes a while)</span>
<span class="nv">$ SKIP_API</span><span class="o">=</span>1 bundle <span class="nb">exec </span>jekyll build
</code></pre></div></div>

<p>You can also generate the default Jekyll build with API Docs as follows:</p>

<div class="language-sh highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nv">$ </span>bundle <span class="nb">exec </span>jekyll build

<span class="c"># Serve content locally on port 4000</span>
<span class="nv">$ </span>bundle <span class="nb">exec </span>jekyll serve <span class="nt">--watch</span>

<span class="c"># Build the site with extra features used on the live page</span>
<span class="nv">$ PRODUCTION</span><span class="o">=</span>1 bundle <span class="nb">exec </span>jekyll build
</code></pre></div></div>

<h2 id="api-docs-scaladoc-javadoc-sphinx-roxygen2-mkdocs">API Docs (Scaladoc, Javadoc, Sphinx, roxygen2, MkDocs)</h2>

<p>You can build just the Spark scaladoc and javadoc by running <code class="language-plaintext highlighter-rouge">./build/sbt unidoc</code> from the <code class="language-plaintext highlighter-rouge">$SPARK_HOME</code> directory.</p>

<p>Similarly, you can build just the PySpark docs by running <code class="language-plaintext highlighter-rouge">make html</code> from the
<code class="language-plaintext highlighter-rouge">$SPARK_HOME/python/docs</code> directory. Documentation is only generated for classes that are listed as
public in <code class="language-plaintext highlighter-rouge">__init__.py</code>. The SparkR docs can be built by running <code class="language-plaintext highlighter-rouge">$SPARK_HOME/R/create-docs.sh</code>, and
the SQL docs can be built by running <code class="language-plaintext highlighter-rouge">$SPARK_HOME/sql/create-docs.sh</code>
after <a href="https://github.com/apache/spark#building-spark">building Spark</a> first.</p>

<p>When you run <code class="language-plaintext highlighter-rouge">bundle exec jekyll build</code> in the <code class="language-plaintext highlighter-rouge">docs</code> directory, it will also copy over the scaladoc and javadoc for the various
Spark subprojects into the <code class="language-plaintext highlighter-rouge">docs</code> directory (and then also into the <code class="language-plaintext highlighter-rouge">_site</code> directory). We use a
jekyll plugin to run <code class="language-plaintext highlighter-rouge">./build/sbt unidoc</code> before building the site so if you haven&#8217;t run it (recently) it
may take some time as it generates all of the scaladoc and javadoc using <a href="https://github.com/sbt/sbt-unidoc">Unidoc</a>.
The jekyll plugin also generates the PySpark docs using <a href="http://sphinx-doc.org/">Sphinx</a>, SparkR docs
using <a href="https://cran.r-project.org/web/packages/roxygen2/index.html">roxygen2</a> and SQL docs
using <a href="https://www.mkdocs.org/">MkDocs</a>.</p>

<p>NOTE: To skip the step of building and copying over the Scala, Java, Python, R and SQL API docs, run <code class="language-plaintext highlighter-rouge">SKIP_API=1
bundle exec jekyll build</code>. In addition, <code class="language-plaintext highlighter-rouge">SKIP_SCALADOC=1</code>, <code class="language-plaintext highlighter-rouge">SKIP_PYTHONDOC=1</code>, <code class="language-plaintext highlighter-rouge">SKIP_RDOC=1</code> and <code class="language-plaintext highlighter-rouge">SKIP_SQLDOC=1</code> can be used
to skip a single step of the corresponding language. <code class="language-plaintext highlighter-rouge">SKIP_SCALADOC</code> indicates skipping both the Scala and Java docs.</p>