[Test] Added test to verify the avoidance of infnite accumulation

Author: andsel

logstash-core/src/test/java/org/logstash/common/BufferedTokenizerWithSizeLimitTest.java

@@ -26,7 +26,7 @@
 import java.util.List;
 
 import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.containsString;
+import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThrows;
 import static org.logstash.common.BufferedTokenizerTest.toList;
@@ -128,4 +128,26 @@ public void givenFragmentThatHasTheSecondTokenOverrunsSizeLimitThenAnErrorIsThro
         // third token resumes
         assertEquals("ccc", tokensIterator.next());
     }
+
+    @Test
+    public void givenSequenceOfFragmentsWithoutSeparatorThenDoesntGenerateOutOfMemory() {
+        final String neverEndingData = generate(8, "a");
+        for (int i = 0; i < 10; i++) {
+            sut.extract(neverEndingData);
+        }
+
+        assertThat("Accumulator include only a part of an exploding payload", sut.flush().length(), is(lessThan(10)));
+
+        Iterable<String> tokensIterable = sut.extract("\nbbb\n");
+        Iterator<String> tokensIterator = tokensIterable.iterator();
+        // send a token delimiter and check an error is raised
+        Exception exception = assertThrows(IllegalStateException.class, () -> {
+            tokensIterator.next();
+        });
+        assertThat(exception.getMessage(), containsString("input buffer full"));
+    }
+
+    private static String generate(int length, String fillChar) {
+        return fillChar.repeat(length);
+    }
 }