Moirai 3.x Redesign

* Move config-reading abstract methods from each decider into a
  ConfigReader Interface
* Add featureGroup support to control what features use the same hashing
  for proportionOfUsers decider
* Move the provided config decider predicates to a single class as
  static factory methods that depend on a ConfigReader instead of separate
  abstract classes that must be implemented in a specific config module

README.md

@@ -24,20 +24,20 @@ import com.nike.moirai.ConfigFeatureFlagChecker;
 import com.nike.moirai.FeatureCheckInput;
 import com.nike.moirai.FeatureFlagChecker;
 import com.nike.moirai.Suppliers;
+import com.nike.moirai.config.ConfigDeciders;
 import com.nike.moirai.resource.FileResourceLoaders;
 import com.nike.moirai.resource.reload.ResourceReloader;
-import com.nike.moirai.typesafeconfig.TypesafeConfigDecider;
-import com.nike.moirai.typesafeconfig.TypesafeConfigReader;
+import com.nike.moirai.typesafeconfig.TypesafeConfigLoader;
 import com.typesafe.config.Config;
 
 import java.io.File;
 import java.util.function.Supplier;
 
-import static com.nike.moirai.Suppliers.supplierAndThen;
+import static com.nike.moirai.typesafeconfig.TypesafeConfigReader.TYPESAFE_CONFIG_READER;
 
 public class Usage {
     Supplier<String> fileSupplier = FileResourceLoaders.forFile(new File("/path/to/conf/file/moirai.conf"));
-    Supplier<Config> configSupplier = supplierAndThen(fileSupplier, TypesafeConfigReader.FROM_STRING);
+    Supplier<Config> configSupplier = Suppliers.supplierAndThen(fileSupplier, TypesafeConfigReader.FROM_STRING);
 
     ResourceReloader<Config> resourceReloader = ResourceReloader.withDefaultSettings(
         Suppliers.async(configSupplier),
@@ -46,7 +46,7 @@ public class Usage {
 
     FeatureFlagChecker featureFlagChecker = ConfigFeatureFlagChecker.forReloadableResource(
         resourceReloader,
-        TypesafeConfigDecider.ENABLED_USERS.or(TypesafeConfigDecider.PROPORTION_OF_USERS)
+        ConfigDeciders.enabledUsers(TYPESAFE_CONFIG_READER).or(ConfigDeciders.proportionOfUsers(TYPESAFE_CONFIG_READER))
     );
 
     public int getNumber(String userIdentity) {

build.sbt

@@ -1,7 +1,7 @@
 import sbt.Keys.javacOptions
 import Dependencies._
 
-lazy val commonSettings = Seq(
+val commonSettings = Seq(
   organization := "com.nike.moirai",
   organizationName := "Nike",
   organizationHomepage := Some(url("http://engineering.nike.com")),
@@ -85,6 +85,7 @@ lazy val `moirai-typesafeconfig` = project
     libraryDependencies ++= Seq(
       typesafeConfig,
       scalaTest,
+      scalaCheck,
       logback
     )
   )

moirai-core/src/main/java/com/nike/moirai/FeatureCheckInput.java

@@ -17,7 +17,7 @@ public class FeatureCheckInput {
     public enum DimensionKey {
         USER_ID, DATE_TIME;
 
-        private static Set<String> KEYS = Arrays.stream(DimensionKey.values()).map(DimensionKey::name).collect(Collectors.toSet());
+        private static final Set<String> KEYS = Arrays.stream(DimensionKey.values()).map(DimensionKey::name).collect(Collectors.toSet());
     }
 
     private final Map<String, ?> dimensions;

moirai-core/src/main/java/com/nike/moirai/config/ConfigDeciderSupport.java

@@ -0,0 +1,37 @@
+package com.nike.moirai.config;
+
+import com.nike.moirai.FeatureCheckInput;
+
+import java.util.function.Predicate;
+
+/**
+ * Support functions for creating a {@link java.util.function.Predicate} for {@link ConfigDecisionInput}.
+ */
+public class ConfigDeciderSupport {
+    /**
+     * Apply a predicate to the userId from a feature check input.
+     *
+     * @param featureCheckInput the input to check
+     * @param userIdCheck       the predicate to apply
+     * @return false if there is no userId in the input, otherwise the result of the predicate applied to the userId
+     */
+    public static boolean userIdCheck(FeatureCheckInput featureCheckInput, Predicate<String> userIdCheck) {
+        return featureCheckInput.getUserId().map(userIdCheck::test).orElse(false);
+    }
+
+    /**
+     * Apply a predicate to the dimension value from a feature check input.
+     *
+     * @param featureCheckInput the input to check
+     * @param dimensionKey      the dimension to check
+     * @param dimensionCheck    the predicate to apply
+     * @return false if there is no userId in the input, otherwise the result of the predicate applied to the userId
+     */
+    public static boolean customDimensionCheck(FeatureCheckInput featureCheckInput, String dimensionKey, Predicate<Object> dimensionCheck) {
+        return featureCheckInput.getDimension(dimensionKey).map(dimensionCheck::test).orElse(false);
+    }
+
+    private ConfigDeciderSupport() {
+        // Prevent instantiation
+    }
+}

moirai-core/src/main/java/com/nike/moirai/config/ConfigDeciders.java

@@ -2,33 +2,51 @@
 
 import com.nike.moirai.FeatureCheckInput;
 
+import java.util.Collection;
+import java.util.Optional;
 import java.util.function.Predicate;
 
+import static com.nike.moirai.config.ConfigDeciderSupport.userIdCheck;
+
 /**
- * Useful methods for implementing a Predicate<ConfigDecisionInput<T>>
+ * {@link Predicate} factories given a {@link ConfigReader}
  */
 public class ConfigDeciders {
-    /**
-     * Apply a predicate to the userId from a feature check input.
-     *
-     * @param featureCheckInput the input to check
-     * @param userIdCheck the predicate to apply
-     * @return false if there is no userId in the input, otherwise the result of the predicate applied to the userId
-     */
-    public static boolean userIdCheck(FeatureCheckInput featureCheckInput, Predicate<String> userIdCheck) {
-        return featureCheckInput.getUserId().map(userIdCheck::test).orElse(false);
+    public static <C> Predicate<ConfigDecisionInput<C>> featureEnabled(ConfigReader<C> configReader) {
+        return configDecisionInput ->
+            configReader.featureEnabled(configDecisionInput.getConfig(), configDecisionInput.getFeatureIdentifier()).orElse(false);
+    }
+
+    public static <C> Predicate<ConfigDecisionInput<C>> enabledUsers(ConfigReader<C> configReader) {
+        return new EnabledValuesConfigDecider<C, String>() {
+            @Override
+            protected Collection<String> enabledValues(C config, String featureIdentifier) {
+                return configReader.enabledUsers(config, featureIdentifier);
+            }
+
+            @Override
+            protected boolean checkValue(FeatureCheckInput featureCheckInput, Predicate<String> check) {
+                return userIdCheck(featureCheckInput, check);
+            }
+        };
+    }
+
+    public static <C> Predicate<ConfigDecisionInput<C>> proportionOfUsers(ConfigReader<C> configReader) {
+        return configDecisionInput ->
+            userIdCheck(configDecisionInput.getFeatureCheckInput(), userId ->
+                configReader.enabledProportion(configDecisionInput.getConfig(), configDecisionInput.getFeatureIdentifier()).map(enabledProportion ->
+                    userHashEnabled(
+                        userId,
+                        configDecisionInput.getFeatureIdentifier(),
+                        configReader.featureGroup(configDecisionInput.getConfig(), configDecisionInput.getFeatureIdentifier()),
+                        enabledProportion)
+                ).orElse(false)
+            );
     }
 
-    /**
-     * Apply a predicate to the dimension value from a feature check input.
-     *
-     * @param featureCheckInput the input to check
-     * @param dimensionKey the dimension to check
-     * @param dimensionCheck the predicate to apply
-     * @return false if there is no userId in the input, otherwise the result of the predicate applied to the userId
-     */
-    public static boolean customDimensionCheck(FeatureCheckInput featureCheckInput, String dimensionKey, Predicate<Object> dimensionCheck) {
-        return featureCheckInput.getDimension(dimensionKey).map(dimensionCheck::test).orElse(false);
+    @SuppressWarnings("OptionalUsedAsFieldOrParameterType")
+    private static boolean userHashEnabled(String userId, String featureIdentifier, Optional<String> featureGroup, double proportion) {
+        return (Math.abs((userId + featureGroup.orElse(featureIdentifier)).hashCode()) % 100) / 100.0 < proportion;
     }
 
     private ConfigDeciders() {

moirai-core/src/main/java/com/nike/moirai/config/ConfigReader.java

@@ -0,0 +1,48 @@
+package com.nike.moirai.config;
+
+import java.util.Collection;
+import java.util.Optional;
+
+public interface ConfigReader<C> {
+    /**
+     * Provide the collection of users that should have the given feature enabled. Return an empty list if no configuration is provided for the feature.
+     *
+     * @param config the config source
+     * @param featureIdentifier the feature
+     * @return the collection of userIds that should be enabled for the feature
+     */
+    Collection<String> enabledUsers(C config, String featureIdentifier);
+
+    /**
+     * Provide the boolean value on whether the feature should be enabled.
+     * Returning Optional.empty() is equivalent to false.
+     *
+     * @param config the config source
+     * @param featureIdentifier the feature
+     * @return true, false, or {@link Optional#empty()}
+     */
+    Optional<Boolean> featureEnabled(C config, String featureIdentifier);
+
+    /**
+     * Provide the proportion of users that should be enabled for the given feature. The proportion should be a double from 0.0 to 1.0.
+     * 0.0 means no users will have the feature enabled, and 1.0 will mean that all users will have the feature enabled.
+     * Values below zero will be treated the same as 0.0 and values above 1.0 will be treated the same as 1.0.
+     * Returning Optional.empty() is equivalent to 0.0; both will return false for all users.
+     *
+     * @param config the config source
+     * @param featureIdentifier the feature
+     * @return some proportion between 0.0 and 1.0, or {@link Optional#empty()}
+     */
+    Optional<Double> enabledProportion(C config, String featureIdentifier);
+
+    /**
+     * Provide the featureGroup that the feature should belong to. This will affect the {@link ConfigDeciders#proportionOfUsers(ConfigReader)} so that
+     * if two features with the same featureGroup have the same enabled proportion, the same users will be included in that proportion.
+     * Returning Optional.empty() will result in the feature being grouped by itself (the featureIdentifier will be used as the featureGroup).
+     *
+     * @param config the config source
+     * @param featureIdentifier the feature
+     * @return the identifier of the feature group or {@link Optional#empty()}
+     */
+    Optional<String> featureGroup(C config, String featureIdentifier);
+}

moirai-core/src/main/java/com/nike/moirai/config/EnabledCustomDimensionConfigDecider.java

@@ -6,7 +6,7 @@
 
 import java.util.function.Predicate;
 
-import static com.nike.moirai.config.ConfigDeciders.customDimensionCheck;
+import static com.nike.moirai.config.ConfigDeciderSupport.customDimensionCheck;
 
 /**
  * Returns true for a configured collection of values for some custom dimension.
@@ -15,6 +15,7 @@
  * @param <V> the type of value for the dimension
  */
 public abstract class EnabledCustomDimensionConfigDecider<C, V> extends EnabledValuesConfigDecider<C, V> {
+
     private final Logger logger = LoggerFactory.getLogger(this.getClass());
 
     @Override