Merge branch 'release/v1.0.1'

README.md

@@ -83,6 +83,20 @@ $renderer = new RenderTextFormat();
 $result = $renderer->render($registry->getMetricFamilySamples());
 ```
 
+### Advanced Usage
+
+#### Advanced Histogram Usage
+On passing an empty array for the bucket parameter on instantiation, a set of default buckets will be used instead.
+Whilst this is a good base for a typical web application, there is named constructor to assist in the generation of
+exponential / geometric buckets.
+
+Eg:
+```
+Histogram::exponentialBuckets(0.05, 1.5, 10);
+``` 
+
+This will start your buckets with a value of 1.5, grow them by a factor of 1.5 per bucket across a set of 10 buckets. 
+
 Also look at the [examples](examples).
 
 ## Development

composer.json

@@ -1,15 +1,7 @@
 {
     "name": "endclothing/prometheus_client_php",
-    "version": "1.0.0",
+    "version": "1.0.1",
     "authors": [
-        {
-            "name": "Joscha",
-            "email": "[email protected]"
-        },
-        {
-            "name": "Jan Brauer",
-            "email": "[email protected]"
-        },
         {
             "name": "Daniel Noel-Davies",
             "email": "[email protected]"

src/Prometheus/Histogram.php

@@ -1,5 +1,5 @@
 <?php
-declare(strict_types = 1);
+declare(strict_types=1);
 
 namespace Prometheus;
 
@@ -62,6 +62,36 @@ public static function getDefaultBuckets(): array
         ];
     }
 
+    /**
+     * @param float $start
+     * @param float $growthFactor
+     * @param int $numberOfBuckets
+     * @return array
+     */
+    public static function exponentialBuckets(float $start, float $growthFactor, int $numberOfBuckets): array
+    {
+        if ($numberOfBuckets < 1) {
+            throw new InvalidArgumentException('Number of buckets must be a positive integer');
+        }
+
+        if ($start <= 0) {
+            throw new InvalidArgumentException('The starting position of a set of buckets must be a positive integer');
+        }
+
+        if ($growthFactor <= 1) {
+            throw new InvalidArgumentException('The growth factor must greater than 1');
+        }
+
+        $buckets = [];
+
+        for ($i = 0; $i < $numberOfBuckets; $i++) {
+            $buckets[$i] = $start;
+            $start *= $growthFactor;
+        }
+
+        return $buckets;
+    }
+
     /**
      * @param double $value e.g. 123
      * @param array $labels e.g. ['status', 'opcode']

tests/Test/Prometheus/AbstractHistogramTest.php

@@ -455,6 +455,37 @@ public function isShouldAcceptAnySequenceOfBasicLatinCharactersForLabelValues($v
         }
     }
 
+    /**
+     * @test
+     */
+    public function itShouldBeAbleToGenerateExponentialBucketsGivenSpecificBounds()
+    {
+        $start = 0.05;
+        $growthFactor = 1.5;
+        $numberOfbuckets = 14;
+
+        $generatedBuckets = Histogram::exponentialBuckets($start, $growthFactor, $numberOfbuckets);
+
+        $expectedBuckets = [
+            0.05,
+            0.075,
+            0.1125,
+            0.16875,
+            0.253125,
+            0.3796875,
+            0.56953125,
+            0.854296875,
+            1.2814453125,
+            1.92216796875,
+            2.883251953125,
+            4.3248779296875,
+            6.4873168945313,
+            9.7309753417969,
+        ];
+
+        self::assertEquals($generatedBuckets, $expectedBuckets);
+    }
+
     /**
      * @return array
      * @see isShouldAcceptArbitraryLabelValues