Spark 3883: SSL support for HttpServer and Akka

SPARK-3883: SSL support for Akka connections and Jetty based file servers.

This story introduced the following changes:
- Introduced SSLOptions object which holds the SSL configuration and can build the appropriate configuration for Akka or Jetty. SSLOptions can be created by parsing SparkConf entries at a specified namespace.
- SSLOptions is created and kept by SecurityManager
- All Akka actor address creation snippets based on interpolated strings were replaced by a dedicated methods from AkkaUtils. Those methods select the proper Akka protocol - whether akka.tcp or akka.ssl.tcp
- Added tests cases for AkkaUtils, FileServer, SSLOptions and SecurityManager
- Added a way to use node local SSL configuration by executors and driver in standalone mode. It can be done by specifying spark.ssl.useNodeLocalConf in SparkConf.
- Made CoarseGrainedExecutorBackend not overwrite the settings which are executor startup configuration - they are passed anyway from Worker

Refer to https://github.com/apache/spark/pull/3571 for discussion and details

Author: Jacek Lewandowski <lewandowski.jacek@gmail.com>
Author: Jacek Lewandowski <jacek.lewandowski@datastax.com>

Closes #3571 from jacek-lewandowski/SPARK-3883-master and squashes the following commits:

9ef4ed1 [Jacek Lewandowski] Merge pull request #2 from jacek-lewandowski/SPARK-3883-docs2
fb31b49 [Jacek Lewandowski] SPARK-3883: Added SSL setup documentation
2532668 [Jacek Lewandowski] SPARK-3883: Refactored AkkaUtils.protocol method to not use Try
90a8762 [Jacek Lewandowski] SPARK-3883: Refactored methods to resolve Akka address and made it possible to easily configure multiple communication layers for SSL
72b2541 [Jacek Lewandowski] SPARK-3883: A reference to the fallback SSLOptions can be provided when constructing SSLOptions
93050f4 [Jacek Lewandowski] SPARK-3883: SSL support for HttpServer and Akka

1 files changed, 80 insertions, 0 deletions

diff --git a/docs/configuration.md b/docs/configuration.md
index 08c6befaf3..62d3fca937 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -1242,6 +1242,86 @@ Apart from these, the following properties are also available, and may be useful
 </tr>
 </table>
 
+#### Encryption
+
+<table class="table">
+    <tr><th>Property Name</th><th>Default</th><th>Meaning</th></tr>
+    <tr>
+        <td><code>spark.ssl.enabled</code></td>
+        <td>false</td>
+        <td>
+            <p>Whether to enable SSL connections on all supported protocols.</p>
+
+            <p>All the SSL settings like <code>spark.ssl.xxx</code> where <code>xxx</code> is a
+            particular configuration property, denote the global configuration for all the supported
+            protocols. In order to override the global configuration for the particular protocol,
+            the properties must be overwritten in the protocol-specific namespace.</p>
+
+            <p>Use <code>spark.ssl.YYY.XXX</code> settings to overwrite the global configuration for
+            particular protocol denoted by <code>YYY</code>. Currently <code>YYY</code> can be
+            either <code>akka</code> for Akka based connections or <code>fs</code> for broadcast and
+            file server.</p>
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.keyStore</code></td>
+        <td>None</td>
+        <td>
+            A path to a key-store file. The path can be absolute or relative to the directory where
+            the component is started in.
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.keyStorePassword</code></td>
+        <td>None</td>
+        <td>
+            A password to the key-store.
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.keyPassword</code></td>
+        <td>None</td>
+        <td>
+            A password to the private key in key-store.
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.trustStore</code></td>
+        <td>None</td>
+        <td>
+            A path to a trust-store file. The path can be absolute or relative to the directory
+            where the component is started in.
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.trustStorePassword</code></td>
+        <td>None</td>
+        <td>
+            A password to the trust-store.
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.protocol</code></td>
+        <td>None</td>
+        <td>
+            A protocol name. The protocol must be supported by JVM. The reference list of protocols
+            one can find on <a href="https://blogs.oracle.com/java-platform-group/entry/diagnosing_tls_ssl_and_https">this</a>
+            page.
+        </td>
+    </tr>
+    <tr>
+        <td><code>spark.ssl.enabledAlgorithms</code></td>
+        <td>Empty</td>
+        <td>
+            A comma separated list of ciphers. The specified ciphers must be supported by JVM.
+            The reference list of protocols one can find on
+            <a href="https://blogs.oracle.com/java-platform-group/entry/diagnosing_tls_ssl_and_https">this</a>
+            page.
+        </td>
+    </tr>
+</table>
+
+
 #### Spark Streaming
 <table class="table">
 <tr><th>Property Name</th><th>Default</th><th>Meaning</th></tr>