Add Histogram deserialization test

Add an addition test to the HistogramSerDeTest which tests that
histogram deserialization roundtrips even when the serialized size
exceeds the initial buffer.

benchmark-framework/src/test/java/io/openmessaging/benchmark/worker/jackson/HistogramSerDeTest.java

@@ -18,6 +18,9 @@
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.Random;
+
 import org.HdrHistogram.Histogram;
 import org.junit.jupiter.api.Test;
 
@@ -41,4 +44,62 @@ void deserialize() throws IOException {
 
         assertThat(deserialized).isEqualTo(value);
     }
+
+    /**
+     * Create a random histogram and insert the given number of samples.
+     *
+     * @param samples the number of samples to record into the histogram
+     * @return a Histogram with the given number of samples
+     */
+    private Histogram randomHisto(int samples) {
+        Random r = new Random(0xBADBEEF);
+        Histogram h = new org.HdrHistogram.Histogram(5);
+        for (int i = 0; i < samples; i++) {
+            h.recordValue(r.nextInt(10000000));
+        }
+
+        return h;
+    }
+
+    byte[] serializeRandomHisto(int samples, int initialBufferSize) throws Exception {
+        ByteBuffer inbuffer = ByteBuffer.allocate(initialBufferSize);
+        Histogram inHisto = randomHisto(samples);
+        byte[] serialBytes = HistogramSerializer.toByteArray(HistogramSerializer.serializeHistogram(inHisto, inbuffer));
+
+        // check roundtrip
+        Histogram outHisto = Histogram.decodeFromCompressedByteBuffer(ByteBuffer.wrap(serialBytes), Long.MIN_VALUE);
+        assertThat(inHisto).isEqualTo(outHisto);
+
+        return serialBytes;
+    }
+
+    @Test
+    public void testHistogram() throws Exception {
+
+        // in the worker it's 8 MB but it takes a while to make a histogram that big
+        final int bufSize = 1002;
+
+        int samples = 300;
+
+        // we do an exponential search to fit the crossover point where we need to grow the buffer
+        while (true) {
+            byte[] serialBytes = serializeRandomHisto(samples, bufSize);
+            // System.out.println("Samples: " + samples + ", histogram size: " + serialBytes.length);
+            if (serialBytes.length >= bufSize) {
+                break;
+            }
+            samples *= 1.05;
+        }
+
+        // then walk backwards across the point linearly with increment of 1 to check the boundary
+        // carefully
+        while (true) {
+            samples--;
+            byte[] serialBytes = serializeRandomHisto(samples, bufSize);
+            // System.out.println("Samples: " + samples + ", histogram size: " + serialBytes.length);
+            if (serialBytes.length < bufSize - 10) {
+                break;
+            }
+        }
+    }
 }