diff --git a/java/google/registry/monitoring/metrics/FibonacciFitter.java b/java/google/registry/monitoring/metrics/FibonacciFitter.java
new file mode 100644
index 000000000..c03a2cdc6
--- /dev/null
+++ b/java/google/registry/monitoring/metrics/FibonacciFitter.java
@@ -0,0 +1,64 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.monitoring.metrics;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableSortedSet;
+
+/**
+ * A {@link DistributionFitter} with intervals of increasing size using the Fibonacci sequence.
+ *
+ *
A Fibonacci fitter is useful in situations where you want more precision on the low end than
+ * an {@link ExponentialFitter} with exponent base 2 would provide without the hassle of dealing
+ * with non-integer boundaries, such as would be created by an exponential fitter with a base of
+ * less than 2. Fibonacci fitters are ideal for integer metrics that are bounded across a certain
+ * range, e.g. integers between 1 and 1,000.
+ *
+ *
The interval boundaries are chosen as {@code (-inf, 0), [0, 1), [1, 2), [2, 3), [3, 5), [5,
+ * 8), [8, 13)}, etc., up to {@code [fibonacciFloor(maxBucketSize), inf)}.
+ */
+@AutoValue
+public abstract class FibonacciFitter implements DistributionFitter {
+
+ /**
+ * Returns a new {@link FibonacciFitter}.
+ *
+ * @param maxBucketSize the maximum bucket size to create (rounded down to the nearest Fibonacci
+ * number)
+ * @throws IllegalArgumentException if {@code maxBucketSize <= 0}
+ */
+ public static FibonacciFitter create(long maxBucketSize) {
+ checkArgument(maxBucketSize > 0, "maxBucketSize must be greater than 0");
+
+ ImmutableSortedSet.Builder boundaries = ImmutableSortedSet.naturalOrder();
+ boundaries.add(Double.valueOf(0));
+ long i = 1;
+ long j = 2;
+ long k = 3;
+ while (i <= maxBucketSize) {
+ boundaries.add(Double.valueOf(i));
+ i = j;
+ j = k;
+ k = i + j;
+ }
+
+ return new AutoValue_FibonacciFitter(boundaries.build());
+ }
+
+ @Override
+ public abstract ImmutableSortedSet boundaries();
+}
diff --git a/javatests/google/registry/monitoring/metrics/ExponentialFitterTest.java b/javatests/google/registry/monitoring/metrics/ExponentialFitterTest.java
index 8790e5b66..df80e9d7b 100644
--- a/javatests/google/registry/monitoring/metrics/ExponentialFitterTest.java
+++ b/javatests/google/registry/monitoring/metrics/ExponentialFitterTest.java
@@ -22,7 +22,7 @@ import org.junit.rules.ExpectedException;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;
-/** Tests for implementations of {@link DistributionFitter}. */
+/** Unit tests for {@link ExponentialFitter}. */
@RunWith(JUnit4.class)
public class ExponentialFitterTest {
diff --git a/javatests/google/registry/monitoring/metrics/FibonacciFitterTest.java b/javatests/google/registry/monitoring/metrics/FibonacciFitterTest.java
new file mode 100644
index 000000000..7b2d57ade
--- /dev/null
+++ b/javatests/google/registry/monitoring/metrics/FibonacciFitterTest.java
@@ -0,0 +1,83 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// 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 google.registry.monitoring.metrics;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.fail;
+
+import com.google.common.collect.ImmutableList;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Unit tests for {@link FibonacciFitter}. */
+@RunWith(JUnit4.class)
+public class FibonacciFitterTest {
+
+ @Test
+ public void testCreate_maxBucketSizeNegative_throwsException() {
+ try {
+ FibonacciFitter.create(-1);
+ fail("Expected exception");
+ } catch (IllegalArgumentException e) {
+ assertThat(e).hasMessageThat().isEqualTo("maxBucketSize must be greater than 0");
+ }
+ }
+
+ @Test
+ public void testCreate_maxBucketSizeZero_throwsException() {
+ try {
+ FibonacciFitter.create(0);
+ fail("Expected exception");
+ } catch (IllegalArgumentException e) {
+ assertThat(e).hasMessageThat().isEqualTo("maxBucketSize must be greater than 0");
+ }
+ }
+
+ @Test
+ public void testCreate_maxBucketSizeOne_createsTwoBoundaries() {
+ assertThat(FibonacciFitter.create(1).boundaries()).containsExactly(0.0, 1.0).inOrder();
+ }
+
+ @Test
+ public void testCreate_maxBucketSizeTwo_createsThreeBoundaries() {
+ assertThat(FibonacciFitter.create(2).boundaries()).containsExactly(0.0, 1.0, 2.0).inOrder();
+ }
+
+ @Test
+ public void testCreate_maxBucketSizeThree_createsFourBoundaries() {
+ assertThat(FibonacciFitter.create(3).boundaries())
+ .containsExactly(0.0, 1.0, 2.0, 3.0)
+ .inOrder();
+ }
+
+ @Test
+ public void testCreate_maxBucketSizeFour_createsFourBoundaries() {
+ assertThat(FibonacciFitter.create(4).boundaries())
+ .containsExactly(0.0, 1.0, 2.0, 3.0)
+ .inOrder();
+ }
+
+ @Test
+ public void testCreate_maxBucketSizeLarge_createsFibonacciSequenceBoundaries() {
+ ImmutableList expectedBoundaries =
+ ImmutableList.of(
+ 0.0, 1.0, 2.0, 3.0, 5.0, 8.0, 13.0, 21.0, 34.0, 55.0, 89.0, 144.0, 233.0, 377.0, 610.0,
+ 987.0);
+ assertThat(FibonacciFitter.create(1000).boundaries())
+ .containsExactlyElementsIn(expectedBoundaries)
+ .inOrder();
+ }
+}
diff --git a/javatests/google/registry/monitoring/metrics/LinearFitterTest.java b/javatests/google/registry/monitoring/metrics/LinearFitterTest.java
index 8716f2597..8955029eb 100644
--- a/javatests/google/registry/monitoring/metrics/LinearFitterTest.java
+++ b/javatests/google/registry/monitoring/metrics/LinearFitterTest.java
@@ -22,7 +22,7 @@ import org.junit.rules.ExpectedException;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;
-/** Tests for {@link LinearFitter}. */
+/** Unit tests for {@link LinearFitter}. */
@RunWith(JUnit4.class)
public class LinearFitterTest {