[SPARK-7997][CORE] Remove Akka from Spark Core and Streaming

- Remove Akka dependency from core. Note: the streaming-akka project still uses Akka.
- Remove HttpFileServer
- Remove Akka configs from SparkConf and SSLOptions
- Rename `spark.akka.frameSize` to `spark.rpc.message.maxSize`. I think it's still worth to keep this config because using `DirectTaskResult` or `IndirectTaskResult`  depends on it.
- Update comments and docs

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #10854 from zsxwing/remove-akka.

1 files changed, 1 insertions, 1 deletions

diff --git a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala
index 31fa53e24b..21ac04dc76 100644
--- a/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala
+++ b/yarn/src/main/scala/org/apache/spark/deploy/yarn/ExecutorRunnable.scala
@@ -166,7 +166,7 @@ class ExecutorRunnable(
 
     // Certain configs need to be passed here because they are needed before the Executor
     // registers with the Scheduler and transfers the spark configs. Since the Executor backend
-    // uses Akka to connect to the scheduler, the akka settings are needed as well as the
+    // uses RPC to connect to the scheduler, the RPC settings are needed as well as the
     // authentication settings.
     sparkConf.getAll
       .filter { case (k, v) => SparkConf.isExecutorStartupConf(k) }