Add finer grain rollouts to experiments

service/src/main/java/org/whispersystems/textsecuregcm/configuration/dynamic/DynamicExperimentEnrollmentConfiguration.java

@@ -6,6 +6,7 @@
 package org.whispersystems.textsecuregcm.configuration.dynamic;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.annotations.VisibleForTesting;
 
 import javax.validation.Valid;
 import javax.validation.constraints.Max;
@@ -16,21 +17,52 @@ import java.util.UUID;
 
 public class DynamicExperimentEnrollmentConfiguration {
 
+  public static class UuidSelector {
+
     @JsonProperty
     @Valid
-    private Set<UUID> enrolledUuids = Collections.emptySet();
+    private Set<UUID> uuids = Collections.emptySet();
 
+    /**
+     * What percentage of enrolled UUIDs should the experiment be enabled for.
+     * <p>
+     * Unlike {@link this#enrollmentPercentage}, this is not stable by UUID. The same UUID may be
+     * enrolled/unenrolled across calls.
+     */
     @JsonProperty
     @Valid
     @Min(0)
     @Max(100)
-    private int enrollmentPercentage = 0;
+    private int uuidEnrollmentPercentage = 100;
 
-    public Set<UUID> getEnrolledUuids() {
-        return enrolledUuids;
+    public Set<UUID> getUuids() {
+      return uuids;
     }
 
-    public int getEnrollmentPercentage() {
-        return enrollmentPercentage;
+    public int getUuidEnrollmentPercentage() {
+      return uuidEnrollmentPercentage;
     }
+
+  }
+
+  private UuidSelector uuidSelector = new UuidSelector();
+
+  /**
+   * If the UUID is not enrolled via {@link UuidSelector#uuids}, what is the percentage chance it should be enrolled.
+   * <p>
+   * This is stable by UUID, for a given configuration if a UUID is enrolled it will always be enrolled on every call.
+   */
+  @JsonProperty
+  @Valid
+  @Min(0)
+  @Max(100)
+  private int enrollmentPercentage = 0;
+
+  public int getEnrollmentPercentage() {
+    return enrollmentPercentage;
+  }
+
+  public UuidSelector getUuidSelector() {
+    return uuidSelector;
+  }
 }

service/src/main/java/org/whispersystems/textsecuregcm/experiment/ExperimentEnrollmentManager.java

@@ -6,7 +6,10 @@
 package org.whispersystems.textsecuregcm.experiment;
 
 import java.util.Optional;
+import java.util.Random;
 import java.util.UUID;
+import java.util.concurrent.ThreadLocalRandom;
+import com.google.common.annotations.VisibleForTesting;
 import org.whispersystems.textsecuregcm.configuration.dynamic.DynamicConfiguration;
 import org.whispersystems.textsecuregcm.configuration.dynamic.DynamicExperimentEnrollmentConfiguration;
 import org.whispersystems.textsecuregcm.configuration.dynamic.DynamicPreRegistrationExperimentEnrollmentConfiguration;
@@ -16,9 +19,20 @@ import org.whispersystems.textsecuregcm.util.Util;
 public class ExperimentEnrollmentManager {
 
   private final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager;
+  private final Random random;
 
-  public ExperimentEnrollmentManager(final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager) {
+
+  public ExperimentEnrollmentManager(
+      final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager) {
+    this(dynamicConfigurationManager, ThreadLocalRandom.current());
+  }
+
+  @VisibleForTesting
+  ExperimentEnrollmentManager(
+      final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager,
+      final Random random) {
     this.dynamicConfigurationManager = dynamicConfigurationManager;
+    this.random = random;
   }
 
   public boolean isEnrolled(final UUID accountUuid, final String experimentName) {
@@ -28,8 +42,9 @@ public class ExperimentEnrollmentManager {
 
     return maybeConfiguration.map(config -> {
 
-      if (config.getEnrolledUuids().contains(accountUuid)) {
-        return true;
+      if (config.getUuidSelector().getUuids().contains(accountUuid)) {
+        final int r = random.nextInt(100);
+        return r < config.getUuidSelector().getUuidEnrollmentPercentage();
       }
 
       return isEnrolled(accountUuid, config.getEnrollmentPercentage(), experimentName);