[SPARK-8958] Dynamic allocation: change cached timeout to infinity

pwendell and I discussed this a little more offline and concluded that it would be good to keep it more conservative. Losing cached blocks may be very expensive and we should only allow it if the user knows what he/she is doing.

FYI harishreedharan sryza.

Author: Andrew Or <[email protected]>

Closes #7329 from andrewor14/da-cached-timeout and squashes the following commits:

cef0b4e [Andrew Or] Change timeout to infinity

Author: Andrew Or

core/src/main/scala/org/apache/spark/ExecutorAllocationManager.scala

@@ -102,7 +102,7 @@ private[spark] class ExecutorAllocationManager(
     "spark.dynamicAllocation.executorIdleTimeout", "60s")
 
   private val cachedExecutorIdleTimeoutS = conf.getTimeAsSeconds(
-    "spark.dynamicAllocation.cachedExecutorIdleTimeout", s"${2 * executorIdleTimeoutS}s")
+    "spark.dynamicAllocation.cachedExecutorIdleTimeout", s"${Integer.MAX_VALUE}s")
 
   // During testing, the methods to actually kill and add executors are mocked out
   private val testing = conf.getBoolean("spark.dynamicAllocation.testing", false)

docs/configuration.md

@@ -1206,7 +1206,7 @@ Apart from these, the following properties are also available, and may be useful
 </tr>
 <tr>
   <td><code>spark.dynamicAllocation.cachedExecutorIdleTimeout</code></td>
-  <td>2 * executorIdleTimeout</td>
+  <td>infinity</td>
   <td>
     If dynamic allocation is enabled and an executor which has cached data blocks has been idle for more than this duration,
     the executor will be removed. For more details, see this
@@ -1222,7 +1222,7 @@ Apart from these, the following properties are also available, and may be useful
 </tr>
 <tr>
   <td><code>spark.dynamicAllocation.maxExecutors</code></td>
-  <td>Integer.MAX_VALUE</td>
+  <td>infinity</td>
   <td>
     Upper bound for the number of executors if dynamic allocation is enabled.
   </td>