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;
+  }
 }