diff --git a/indexing-service/src/main/java/org/apache/druid/indexing/overlord/sampler/InputSourceSampler.java b/indexing-service/src/main/java/org/apache/druid/indexing/overlord/sampler/InputSourceSampler.java
index 1b25279ef0d..c9984c42965 100644
--- a/indexing-service/src/main/java/org/apache/druid/indexing/overlord/sampler/InputSourceSampler.java
+++ b/indexing-service/src/main/java/org/apache/druid/indexing/overlord/sampler/InputSourceSampler.java
@@ -103,90 +103,102 @@ public class InputSourceSampler
     final File tempDir = FileUtils.createTempDir();
     closer.register(() -> FileUtils.deleteDirectory(tempDir));
 
-    final InputSourceReader reader = buildReader(
-        nonNullSamplerConfig,
-        nonNullDataSchema,
-        inputSource,
-        inputFormat,
-        tempDir
-    );
-    try (final CloseableIterator<InputRowListPlusRawValues> iterator = reader.sample();
-         final IncrementalIndex<Aggregator> index = buildIncrementalIndex(nonNullSamplerConfig, nonNullDataSchema);
-         final Closer closer1 = closer) {
-      List<SamplerResponseRow> responseRows = new ArrayList<>(nonNullSamplerConfig.getNumRows());
-      int numRowsIndexed = 0;
-
-      while (responseRows.size() < nonNullSamplerConfig.getNumRows() && iterator.hasNext()) {
-        final InputRowListPlusRawValues inputRowListPlusRawValues = iterator.next();
-
-        final List<Map<String, Object>> rawColumnsList = inputRowListPlusRawValues.getRawValuesList();
-
-        final ParseException parseException = inputRowListPlusRawValues.getParseException();
-        if (parseException != null) {
-          if (rawColumnsList != null) {
-            // add all rows to response
-            responseRows.addAll(rawColumnsList.stream()
-                                              .map(rawColumns -> new SamplerResponseRow(rawColumns, null, true, parseException.getMessage()))
-                                              .collect(Collectors.toList()));
-          } else {
-            // no data parsed, add one response row
-            responseRows.add(new SamplerResponseRow(null, null, true, parseException.getMessage()));
-          }
-          continue;
-        }
-
-        List<InputRow> inputRows = inputRowListPlusRawValues.getInputRows();
-        if (inputRows == null) {
-          continue;
-        }
-
-        for (int i = 0; i < inputRows.size(); i++) {
-          // InputRowListPlusRawValues guarantees the size of rawColumnsList and inputRows are the same
-          Map<String, Object> rawColumns = rawColumnsList == null ? null : rawColumnsList.get(i);
-          InputRow row = inputRows.get(i);
-
-          //keep the index of the row to be added to responseRows for further use
-          final int rowIndex = responseRows.size();
-          IncrementalIndexAddResult addResult = index.add(new SamplerInputRow(row, rowIndex), true);
-          if (addResult.hasParseException()) {
-            responseRows.add(new SamplerResponseRow(rawColumns, null, true, addResult.getParseException().getMessage()));
-          } else {
-            // store the raw value; will be merged with the data from the IncrementalIndex later
-            responseRows.add(new SamplerResponseRow(rawColumns, null, null, null));
-            numRowsIndexed++;
-          }
-        }
-      }
-
-      final List<String> columnNames = index.getColumnNames();
-      columnNames.remove(SamplerInputRow.SAMPLER_ORDERING_COLUMN);
-
-      for (Row row : index) {
-        Map<String, Object> parsed = new HashMap<>();
-
-        columnNames.forEach(k -> parsed.put(k, row.getRaw(k)));
-        parsed.put(ColumnHolder.TIME_COLUMN_NAME, row.getTimestampFromEpoch());
-
-        Number sortKey = row.getMetric(SamplerInputRow.SAMPLER_ORDERING_COLUMN);
-        if (sortKey != null) {
-          responseRows.set(sortKey.intValue(), responseRows.get(sortKey.intValue()).withParsed(parsed));
-        }
-      }
-
-      // make sure size of responseRows meets the input
-      if (responseRows.size() > nonNullSamplerConfig.getNumRows()) {
-        responseRows = responseRows.subList(0, nonNullSamplerConfig.getNumRows());
-      }
-
-      int numRowsRead = responseRows.size();
-      return new SamplerResponse(
-          numRowsRead,
-          numRowsIndexed,
-          responseRows.stream()
-                      .filter(Objects::nonNull)
-                      .filter(x -> x.getParsed() != null || x.isUnparseable() != null)
-                      .collect(Collectors.toList())
+    try {
+      final InputSourceReader reader = buildReader(
+          nonNullSamplerConfig,
+          nonNullDataSchema,
+          inputSource,
+          inputFormat,
+          tempDir
       );
+      try (final CloseableIterator<InputRowListPlusRawValues> iterator = reader.sample();
+           final IncrementalIndex<Aggregator> index = buildIncrementalIndex(nonNullSamplerConfig, nonNullDataSchema);
+           final Closer closer1 = closer) {
+        List<SamplerResponseRow> responseRows = new ArrayList<>(nonNullSamplerConfig.getNumRows());
+        int numRowsIndexed = 0;
+
+        while (responseRows.size() < nonNullSamplerConfig.getNumRows() && iterator.hasNext()) {
+          final InputRowListPlusRawValues inputRowListPlusRawValues = iterator.next();
+
+          final List<Map<String, Object>> rawColumnsList = inputRowListPlusRawValues.getRawValuesList();
+
+          final ParseException parseException = inputRowListPlusRawValues.getParseException();
+          if (parseException != null) {
+            if (rawColumnsList != null) {
+              // add all rows to response
+              responseRows.addAll(rawColumnsList.stream()
+                                                .map(rawColumns -> new SamplerResponseRow(
+                                                    rawColumns,
+                                                    null,
+                                                    true,
+                                                    parseException.getMessage()
+                                                ))
+                                                .collect(Collectors.toList()));
+            } else {
+              // no data parsed, add one response row
+              responseRows.add(new SamplerResponseRow(null, null, true, parseException.getMessage()));
+            }
+            continue;
+          }
+
+          List<InputRow> inputRows = inputRowListPlusRawValues.getInputRows();
+          if (inputRows == null) {
+            continue;
+          }
+
+          for (int i = 0; i < inputRows.size(); i++) {
+            // InputRowListPlusRawValues guarantees the size of rawColumnsList and inputRows are the same
+            Map<String, Object> rawColumns = rawColumnsList == null ? null : rawColumnsList.get(i);
+            InputRow row = inputRows.get(i);
+
+            //keep the index of the row to be added to responseRows for further use
+            final int rowIndex = responseRows.size();
+            IncrementalIndexAddResult addResult = index.add(new SamplerInputRow(row, rowIndex), true);
+            if (addResult.hasParseException()) {
+              responseRows.add(new SamplerResponseRow(
+                  rawColumns,
+                  null,
+                  true,
+                  addResult.getParseException().getMessage()
+              ));
+            } else {
+              // store the raw value; will be merged with the data from the IncrementalIndex later
+              responseRows.add(new SamplerResponseRow(rawColumns, null, null, null));
+              numRowsIndexed++;
+            }
+          }
+        }
+
+        final List<String> columnNames = index.getColumnNames();
+        columnNames.remove(SamplerInputRow.SAMPLER_ORDERING_COLUMN);
+
+        for (Row row : index) {
+          Map<String, Object> parsed = new HashMap<>();
+
+          columnNames.forEach(k -> parsed.put(k, row.getRaw(k)));
+          parsed.put(ColumnHolder.TIME_COLUMN_NAME, row.getTimestampFromEpoch());
+
+          Number sortKey = row.getMetric(SamplerInputRow.SAMPLER_ORDERING_COLUMN);
+          if (sortKey != null) {
+            responseRows.set(sortKey.intValue(), responseRows.get(sortKey.intValue()).withParsed(parsed));
+          }
+        }
+
+        // make sure size of responseRows meets the input
+        if (responseRows.size() > nonNullSamplerConfig.getNumRows()) {
+          responseRows = responseRows.subList(0, nonNullSamplerConfig.getNumRows());
+        }
+
+        int numRowsRead = responseRows.size();
+        return new SamplerResponse(
+            numRowsRead,
+            numRowsIndexed,
+            responseRows.stream()
+                        .filter(Objects::nonNull)
+                        .filter(x -> x.getParsed() != null || x.isUnparseable() != null)
+                        .collect(Collectors.toList())
+        );
+      }
     }
     catch (Exception e) {
       throw new SamplerException(e, "Failed to sample data: %s", e.getMessage());