FLUME-2997. Fix flaky test in SpillableMemoryChannel

When the mock sinks are slower than sources, testParallelSingleSourceAndSink sometimes fails.
In such situations the channel can get full, thus uncaught ChannelFullException breaks the test.

Since testCapacityWithOverflow was designed to cover such a scenario, we
can safely fix the test by increasing the channel capacity to make sure it won't get full.

This commit does the previously mentioned change.

Reviewers: Bessenyei Balázs Donát

(Attila Simon via Bessenyei Balázs Donát)

flume-ng-channels/flume-spillable-memory-channel/src/test/java/org/apache/flume/channel/TestSpillableMemoryChannel.java

@@ -805,7 +805,7 @@ public void testParallelMultipleSourcesAndSinks() throws InterruptedException {
 
     Map<String, String> params = new HashMap<String, String>();
     params.put("memoryCapacity", "0");
-    params.put("overflowCapacity", "500020");
+    params.put("overflowCapacity", String.valueOf(eventCount));
     params.put("overflowTimeout", "3");
     startChannel(params);
 
@@ -822,12 +822,11 @@ public void testParallelMultipleSourcesAndSinks() throws InterruptedException {
 
     watch.elapsed();
 
-    System.out.println("Total puts " + channel.drainOrder.totalPuts);
-
     System.out.println("Max Queue size " + channel.getMaxMemQueueSize());
-    System.out.println(channel.memQueue.size());
 
-    System.out.println("done");
+    Assert.assertEquals(eventCount, channel.drainOrder.totalPuts);
+    Assert.assertEquals("Channel not fully drained", 0, channel.getTotalStored());
+    System.out.println("testParallelMultipleSourcesAndSinks done");
   }
 
   static class StopWatch {