Added bucket creation method with custom buckets in ValueBuckets and …

…DurationBuckets (#35)

* Added custom buckets for Value and Duration

core/src/main/java/com/uber/m3/tally/DurationBuckets.java

@@ -103,4 +103,23 @@ public static DurationBuckets exponential(Duration start, double factor, int num
 
         return new DurationBuckets(buckets);
     }
+
+    /**
+     * Allows to create bucket with finer bucket creation control
+     *
+     * @param sortedDurations sorted values (ascending) of upper bound of the buckets
+     * @return {@link DurationBuckets} of the specified parameters
+     */
+    public static DurationBuckets custom(Duration... sortedDurations) {
+        if (sortedDurations == null || sortedDurations.length == 0) {
+            throw new IllegalArgumentException("at least one upper bucket value has to be specified");
+        }
+
+        for (int i = 0; i < sortedDurations.length - 1; i++) {
+            if (sortedDurations[i].compareTo(sortedDurations[i + 1]) >= 0) {
+                throw new IllegalArgumentException("bucketUpperMillis has to be sorted in ascending order with unique values");
+            }
+        }
+        return new DurationBuckets(sortedDurations);
+    }
 }

core/src/main/java/com/uber/m3/tally/ValueBuckets.java

@@ -103,4 +103,27 @@ public static ValueBuckets exponential(double start, double factor, int numBucke
 
         return new ValueBuckets(buckets);
     }
+
+    /**
+     * Helper function to create {@link ValueBuckets} with custom buckets.
+     *
+     * @param sortedBucketUpperValues sorted (ascending order) values of bucket's upper bound
+     * @return {@link ValueBuckets} of the specified paramters
+     */
+    public static ValueBuckets custom(double... sortedBucketUpperValues) {
+        if (sortedBucketUpperValues == null || sortedBucketUpperValues.length == 0) {
+            throw new IllegalArgumentException("Must have a positive number of buckets");
+        }
+        for (int i = 0; i < sortedBucketUpperValues.length - 1; i++) {
+            if (sortedBucketUpperValues[i] >= sortedBucketUpperValues[i + 1]) {
+                throw new IllegalArgumentException("bucketUpperValues has to be sorted and unique values in ascending order");
+            }
+        }
+
+        Double[] buckets = new Double[sortedBucketUpperValues.length];
+        for (int i = 0; i < sortedBucketUpperValues.length; i++) {
+            buckets[i] = sortedBucketUpperValues[i];
+        }
+        return new ValueBuckets(buckets);
+    }
 }

core/src/test/java/com/uber/m3/tally/DurationBucketsTest.java

@@ -20,18 +20,21 @@
 
 package com.uber.m3.tally;
 
-import com.uber.m3.util.Duration;
-import org.junit.Test;
-
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.ListIterator;
 
+import org.hamcrest.CoreMatchers;
+import org.junit.Test;
+
+import com.uber.m3.util.Duration;
+
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertThat;
 
 public class DurationBucketsTest {
     @Test
@@ -203,6 +206,45 @@ public void exponential() {
         ));
     }
 
+    @Test
+    public void custom() {
+        DurationBuckets expectedBuckets = new DurationBuckets(
+                new Duration[] {
+                        Duration.ofMillis(1),
+                        Duration.ofMillis(2),
+                        Duration.ofMillis(3),
+                        Duration.ofMillis(5),
+                        Duration.ofMillis(7),
+                        Duration.ofMillis(10),
+                }
+        );
+
+        assertThat("custom buckets are created as per our expectations",
+                DurationBuckets.custom(
+                        Duration.ofMillis(1),
+                        Duration.ofMillis(2),
+                        Duration.ofMillis(3),
+                        Duration.ofMillis(5),
+                        Duration.ofMillis(7),
+                        Duration.ofMillis(10)
+                ),
+                CoreMatchers.equalTo(expectedBuckets));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void customFailWithEmptyBuckets() {
+        DurationBuckets.custom();
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void customFailWithUnsortedBuckets() {
+        DurationBuckets.custom(
+                Duration.ofMillis(1),
+                Duration.ofMillis(3),
+                Duration.ofMillis(2)
+        );
+    }
+
     @Test
     public void testToString() {
         DurationBuckets buckets = DurationBuckets.linear(Duration.ZERO, Duration.ofMillis(10), 6);

core/src/test/java/com/uber/m3/tally/ValueBucketsTest.java

@@ -20,13 +20,16 @@
 
 package com.uber.m3.tally;
 
-import com.uber.m3.util.Duration;
+import org.hamcrest.CoreMatchers;
 import org.junit.Test;
 
+import com.uber.m3.util.Duration;
+
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertThat;
 
 public class ValueBucketsTest {
     @Test
@@ -110,6 +113,30 @@ public void exponential() {
         ));
     }
 
+    @Test
+    public void custom() {
+        ValueBuckets expectedBuckets = new ValueBuckets(new Double[] {
+            1d,
+            2d,
+            3d,
+            5d,
+            7d
+        });
+        assertThat("Buckets are created as per our expectations",
+                ValueBuckets.custom(1D, 2D, 3D, 5D, 7D),
+                CoreMatchers.equalTo(expectedBuckets));
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void customFailOnEmptyBucket() {
+        ValueBuckets.custom();
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void customFailOnUnsortedBuckets() {
+        ValueBuckets.custom(1, 3, 2);
+    }
+
     @Test
     public void testToString() {
         ValueBuckets buckets = ValueBuckets.linear(0, 10, 6);