Fixes HUDI-38: Reduce memory overhead of WriteStatus

- For implicit indexes (e.g BloomIndex), don't buffer up written records
 - By default, only collect 10% of failing records to avoid OOMs
 - Improves debuggability via above, since data errors can now show up in collect()
 - Unit tests & fixing subclasses & adjusting tests

hoodie-client/src/test/java/com/uber/hoodie/TestWriteStatus.java

@@ -0,0 +1,53 @@
+/*
+ *  Copyright (c) 2019 Uber Technologies, Inc. (hoodie-dev-group@uber.com)
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *           http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package com.uber.hoodie;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import com.uber.hoodie.common.model.HoodieRecord;
+import java.io.IOException;
+import org.junit.Test;
+import org.mockito.Mockito;
+
+public class TestWriteStatus {
+  @Test
+  public void testFailureFraction() throws IOException  {
+    WriteStatus status = new WriteStatus(true, 0.1);
+    Throwable t = new Exception("some error in writing");
+    for (int i = 0; i < 1000; i++) {
+      status.markFailure(Mockito.mock(HoodieRecord.class), t, null);
+    }
+    assertTrue(status.getFailedRecords().size() > 0);
+    assertTrue(status.getFailedRecords().size() < 150); //150 instead of 100, to prevent flaky test
+    assertTrue(status.hasErrors());
+  }
+
+  @Test
+  public void testSuccessRecordTracking() {
+    WriteStatus status = new WriteStatus(false, 1.0);
+    Throwable t = new Exception("some error in writing");
+    for (int i = 0; i < 1000; i++) {
+      status.markSuccess(Mockito.mock(HoodieRecord.class), null);
+      status.markFailure(Mockito.mock(HoodieRecord.class), t, null);
+    }
+    assertEquals(1000, status.getFailedRecords().size());
+    assertTrue(status.hasErrors());
+    assertTrue(status.getWrittenRecords().isEmpty());
+    assertEquals(2000, status.getTotalRecords());
+  }
+}