feat(flags): Locally evaluate all cohorts (#63)

PostHog · Mar 13, 2024 · 07e3875 · 07e3875
1 parent 04f7509
commit 07e3875
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Showing 5 changed files with 523 additions and 111 deletions.
diff --git a/lib/Client.php b/lib/Client.php
@@ -57,6 +57,12 @@ class Client
      */
     public $groupTypeMapping;
 
+    /**
+     * @var array
+     */
+    public $cohorts;
+
+
     /**
      * @var SizeLimitedHash
      */
@@ -92,6 +98,7 @@ public function __construct(
         $this->featureFlagsRequestTimeout = (int) ($options['feature_flag_request_timeout_ms'] ?? 3000);
         $this->featureFlags = [];
         $this->groupTypeMapping = [];
+        $this->cohorts = [];
         $this->distinctIdsFeatureFlagsReported = new SizeLimitedHash(SIZE_LIMIT);
 
         // Populate featureflags and grouptypemapping if possible
@@ -375,7 +382,7 @@ private function computeFlagLocally(
             $focusedGroupProperties = $groupProperties[$groupName];
             return FeatureFlag::matchFeatureFlagProperties($featureFlag, $groups[$groupName], $focusedGroupProperties);
         } else {
-            return FeatureFlag::matchFeatureFlagProperties($featureFlag, $distinctId, $personProperties);
+            return FeatureFlag::matchFeatureFlagProperties($featureFlag, $distinctId, $personProperties, $this->cohorts);
         }
     }
 
@@ -413,14 +420,15 @@ public function loadFlags()
 
         $this->featureFlags = $payload['flags'] ?? [];
         $this->groupTypeMapping = $payload['group_type_mapping'] ?? [];
+        $this->cohorts = $payload['cohorts'] ?? [];
     }
 
 
     public function localFlags()
     {
 
         return $this->httpClient->sendRequest(
-            '/api/feature_flag/local_evaluation?token=' . $this->apiKey,
+            '/api/feature_flag/local_evaluation?send_cohorts&token=' . $this->apiKey,
             null,
             [
                 // Send user agent in the form of {library_name}/{library_version} as per RFC 7231.

diff --git a/lib/FeatureFlag.php b/lib/FeatureFlag.php
@@ -96,6 +96,102 @@ public static function matchProperty($property, $propertyValues)
         return false;
     }
 
+    public static function matchCohort($property, $propertyValues, $cohortProperties)
+    {
+        $cohortId = strval($property["value"]);
+        if (!array_key_exists($cohortId, $cohortProperties)) {
+            throw new InconclusiveMatchException("can't match cohort without a given cohort property value");
+        }
+
+        $propertyGroup = $cohortProperties[$cohortId];
+        return FeatureFlag::matchPropertyGroup($propertyGroup, $propertyValues, $cohortProperties);
+
+    }
+
+    public static function matchPropertyGroup($propertyGroup, $propertyValues, $cohortProperties)
+    {
+        if (!$propertyGroup) {
+            return true;
+        }
+
+        $propertyGroupType = $propertyGroup["type"];
+        $properties = $propertyGroup["values"];
+
+        if (!$properties || count($properties) === 0) {
+            // empty groups are no-ops, always match
+            return true;
+        }
+
+        $errorMatchingLocally = false;
+
+        if (array_key_exists("values", $properties[0])) {
+            // a nested property group
+            foreach ($properties as $prop) {
+                try {
+                    $matches = FeatureFlag::matchPropertyGroup($prop, $propertyValues, $cohortProperties);
+                    if ($propertyGroupType === 'AND') {
+                        if (!$matches) {
+                            return false;
+                        }
+                    } else {
+                        // OR group
+                        if ($matches) {
+                            return true;
+                        }
+                    }
+                } catch (InconclusiveMatchException $err) {
+                    $errorMatchingLocally = true;
+                }
+            }
+
+            if ($errorMatchingLocally) {
+                throw new InconclusiveMatchException("Can't match cohort without a given cohort property value");
+            }
+            // if we get here, all matched in AND case, or none matched in OR case
+            return $propertyGroupType === 'AND';
+        } else {
+            foreach ($properties as $prop) {
+                try {
+                    $matches = false;
+                    if ($prop["type"] === 'cohort') {
+                        $matches = FeatureFlag::matchCohort($prop, $propertyValues, $cohortProperties);
+                    } else {
+                        $matches = FeatureFlag::matchProperty($prop, $propertyValues);
+                    }
+
+                    $negation = $prop["negation"] ?? false;
+
+                    if ($propertyGroupType === 'AND') {
+                        // if negated property, do the inverse
+                        if (!$matches && !$negation) {
+                            return false;
+                        }
+                        if ($matches && $negation) {
+                            return false;
+                        }
+                    } else {
+                        // OR group
+                        if ($matches && !$negation) {
+                            return true;
+                        }
+                        if (!$matches && $negation) {
+                            return true;
+                        }
+                    }
+                } catch (InconclusiveMatchException $err) {
+                    $errorMatchingLocally = true;
+                }
+            }
+
+            if ($errorMatchingLocally) {
+                throw new InconclusiveMatchException("can't match cohort without a given cohort property value");
+            }
+
+            // if we get here, all matched in AND case, or none matched in OR case
+            return $propertyGroupType === 'AND';
+        }
+    }
+
     public static function relativeDateParseForFeatureFlagMatching($value)
     {
         $regex = "/^-?(?<number>[0-9]+)(?<interval>[a-z])$/";
@@ -239,7 +335,7 @@ private static function compareFlagConditions($conditionA, $conditionB)
         }
     }
 
-    public static function matchFeatureFlagProperties($flag, $distinctId, $properties)
+    public static function matchFeatureFlagProperties($flag, $distinctId, $properties, $cohorts = [])
     {
         $flagConditions = ($flag["filters"] ?? [])["groups"] ?? [];
         $isInconclusive = false;
@@ -275,7 +371,7 @@ function ($conditionA, $conditionB) {
         foreach ($flagConditionsWithIndexes as $conditionWithIndex) {
             $condition = $conditionWithIndex[0];
             try {
-                if (FeatureFlag::isConditionMatch($flag, $distinctId, $condition, $properties)) {
+                if (FeatureFlag::isConditionMatch($flag, $distinctId, $condition, $properties, $cohorts)) {
                     $variantOverride = $condition["variant"] ?? null;
                     $flagVariants = (($flag["filters"] ?? [])["multivariate"] ?? [])["variants"] ?? [];
                     $variantKeys = array_map(function ($variant) {
@@ -300,13 +396,20 @@ function ($conditionA, $conditionB) {
         return false;
     }
 
-    private static function isConditionMatch($featureFlag, $distinctId, $condition, $properties)
+    private static function isConditionMatch($featureFlag, $distinctId, $condition, $properties, $cohorts)
     {
         $rolloutPercentage = array_key_exists("rollout_percentage", $condition) ? $condition["rollout_percentage"] : null;
 
         if (count($condition['properties'] ?? []) > 0) {
             foreach ($condition['properties'] as $property) {
-                if (!FeatureFlag::matchProperty($property, $properties)) {
+                $matches = false;
+                if ($property['type'] == 'cohort') {
+                    $matches = FeatureFlag::matchCohort($property, $properties, $cohorts);
+                } else {
+                    $matches = FeatureFlag::matchProperty($property, $properties);
+                }
+
+                if (!$matches) {
                     return false;
                 }
             }