[SPARK-17663][CORE] SchedulableBuilder should handle invalid data access via scheduler.allocation.file

## What changes were proposed in this pull request?

If `spark.scheduler.allocation.file` has invalid `minShare` or/and `weight` values, these cause :
- `NumberFormatException` due to `toInt` function
- `SparkContext` can not be initialized.
- It does not show meaningful error message to user.

In a nutshell, this functionality can be more robust by selecting one of the following flows :

**1-** Currently, if `schedulingMode` has an invalid value, a warning message is logged and default value is set as `FIFO`. Same pattern can be used for `minShare`(default: 0) and `weight`(default: 1) as well
**2-** Meaningful error message can be shown to the user for all invalid cases.

PR offers :
- `schedulingMode` handles just empty values. It also needs to be supported for **whitespace**, **non-uppercase**(fair, FaIr etc...) or `SchedulingMode.NONE` cases by setting default value(`FIFO`)
- `minShare` and `weight` handle just empty values. They also need to be supported for **non-integer** cases by setting default values.
- Some refactoring of `PoolSuite`.

**Code to Reproduce :**

```
val conf = new SparkConf().setAppName("spark-fairscheduler").setMaster("local")
conf.set("spark.scheduler.mode", "FAIR")
conf.set("spark.scheduler.allocation.file", "src/main/resources/fairscheduler-invalid-data.xml")
val sc = new SparkContext(conf)
```

**fairscheduler-invalid-data.xml :**

```
<allocations>
    <pool name="production">
        <schedulingMode>FIFO</schedulingMode>
        <weight>invalid_weight</weight>
        <minShare>2</minShare>
    </pool>
</allocations>
```

**Stacktrace :**

```
Exception in thread "main" java.lang.NumberFormatException: For input string: "invalid_weight"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.parseInt(Integer.java:615)
    at scala.collection.immutable.StringLike$class.toInt(StringLike.scala:272)
    at scala.collection.immutable.StringOps.toInt(StringOps.scala:29)
    at org.apache.spark.scheduler.FairSchedulableBuilder$$anonfun$org$apache$spark$scheduler$FairSchedulableBuilder$$buildFairSchedulerPool$1.apply(SchedulableBuilder.scala:127)
    at org.apache.spark.scheduler.FairSchedulableBuilder$$anonfun$org$apache$spark$scheduler$FairSchedulableBuilder$$buildFairSchedulerPool$1.apply(SchedulableBuilder.scala:102)
```
## How was this patch tested?

Added Unit Test Case.

Author: erenavsarogullari <erenavsarogullari@gmail.com>

Closes #15237 from erenavsarogullari/SPARK-17663.

1 files changed, 45 insertions, 25 deletions

diff --git a/core/src/main/scala/org/apache/spark/scheduler/SchedulableBuilder.scala b/core/src/main/scala/org/apache/spark/scheduler/SchedulableBuilder.scala
index 96325a0329..f8bee3eea5 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/SchedulableBuilder.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/SchedulableBuilder.scala
@@ -20,10 +20,11 @@ package org.apache.spark.scheduler
 import java.io.{FileInputStream, InputStream}
 import java.util.{NoSuchElementException, Properties}
 
-import scala.xml.XML
+import scala.xml.{Node, XML}
 
 import org.apache.spark.SparkConf
 import org.apache.spark.internal.Logging
+import org.apache.spark.scheduler.SchedulingMode.SchedulingMode
 import org.apache.spark.util.Utils
 
 /**
@@ -102,38 +103,57 @@ private[spark] class FairSchedulableBuilder(val rootPool: Pool, conf: SparkConf)
     for (poolNode <- (xml \\ POOLS_PROPERTY)) {
 
       val poolName = (poolNode \ POOL_NAME_PROPERTY).text
-      var schedulingMode = DEFAULT_SCHEDULING_MODE
-      var minShare = DEFAULT_MINIMUM_SHARE
-      var weight = DEFAULT_WEIGHT
-
-      val xmlSchedulingMode = (poolNode \ SCHEDULING_MODE_PROPERTY).text
-      if (xmlSchedulingMode != "") {
-        try {
-          schedulingMode = SchedulingMode.withName(xmlSchedulingMode)
-        } catch {
-          case e: NoSuchElementException =>
-            logWarning(s"Unsupported schedulingMode: $xmlSchedulingMode, " +
-              s"using the default schedulingMode: $schedulingMode")
-        }
-      }
 
-      val xmlMinShare = (poolNode \ MINIMUM_SHARES_PROPERTY).text
-      if (xmlMinShare != "") {
-        minShare = xmlMinShare.toInt
-      }
+      val schedulingMode = getSchedulingModeValue(poolNode, poolName, DEFAULT_SCHEDULING_MODE)
+      val minShare = getIntValue(poolNode, poolName, MINIMUM_SHARES_PROPERTY, DEFAULT_MINIMUM_SHARE)
+      val weight = getIntValue(poolNode, poolName, WEIGHT_PROPERTY, DEFAULT_WEIGHT)
 
-      val xmlWeight = (poolNode \ WEIGHT_PROPERTY).text
-      if (xmlWeight != "") {
-        weight = xmlWeight.toInt
-      }
+      rootPool.addSchedulable(new Pool(poolName, schedulingMode, minShare, weight))
 
-      val pool = new Pool(poolName, schedulingMode, minShare, weight)
-      rootPool.addSchedulable(pool)
       logInfo("Created pool %s, schedulingMode: %s, minShare: %d, weight: %d".format(
         poolName, schedulingMode, minShare, weight))
     }
   }
 
+  private def getSchedulingModeValue(
+      poolNode: Node,
+      poolName: String,
+      defaultValue: SchedulingMode): SchedulingMode = {
+
+    val xmlSchedulingMode = (poolNode \ SCHEDULING_MODE_PROPERTY).text.trim.toUpperCase
+    val warningMessage = s"Unsupported schedulingMode: $xmlSchedulingMode, using the default " +
+      s"schedulingMode: $defaultValue for pool: $poolName"
+    try {
+      if (SchedulingMode.withName(xmlSchedulingMode) != SchedulingMode.NONE) {
+        SchedulingMode.withName(xmlSchedulingMode)
+      } else {
+        logWarning(warningMessage)
+        defaultValue
+      }
+    } catch {
+      case e: NoSuchElementException =>
+        logWarning(warningMessage)
+        defaultValue
+    }
+  }
+
+  private def getIntValue(
+      poolNode: Node,
+      poolName: String,
+      propertyName: String, defaultValue: Int): Int = {
+
+    val data = (poolNode \ propertyName).text.trim
+    try {
+      data.toInt
+    } catch {
+      case e: NumberFormatException =>
+        logWarning(s"Error while loading scheduler allocation file. " +
+          s"$propertyName is blank or invalid: $data, using the default $propertyName: " +
+          s"$defaultValue for pool: $poolName")
+        defaultValue
+    }
+  }
+
   override def addTaskSetManager(manager: Schedulable, properties: Properties) {
     var poolName = DEFAULT_POOL_NAME
     var parentPool = rootPool.getSchedulableByName(poolName)