[SPARK-11140][CORE] Transfer files using network lib when using NettyRpcEnv.

This change abstracts the code that serves jars / files to executors so that
each RpcEnv can have its own implementation; the akka version uses the existing
HTTP-based file serving mechanism, while the netty versions uses the new
stream support added to the network lib, which makes file transfers benefit
from the easier security configuration of the network library, and should also
reduce overhead overall.

The change includes a small fix to TransportChannelHandler so that it propagates
user events to downstream handlers.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #9530 from vanzin/SPARK-11140.

1 files changed, 2 insertions, 0 deletions

diff --git a/docs/configuration.md b/docs/configuration.md
index c496146e3e..4de202d7f7 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -1020,6 +1020,7 @@ Apart from these, the following properties are also available, and may be useful
   <td>(random)</td>
   <td>
     Port for the executor to listen on. This is used for communicating with the driver.
+    This is only relevant when using the Akka RPC backend.
   </td>
 </tr>
 <tr>
@@ -1027,6 +1028,7 @@ Apart from these, the following properties are also available, and may be useful
   <td>(random)</td>
   <td>
     Port for the driver's HTTP file server to listen on.
+    This is only relevant when using the Akka RPC backend.
   </td>
 </tr>
 <tr>