[featureflag]: use float to check for flag probability

CHANGELOG.md

@@ -9,6 +9,8 @@ release.
 
 * update PHP quoteservice to use 1.0.0
   ([#1236](https://github.com/open-telemetry/opentelemetry-demo/pull/1236))
+* Add ability to do probabilistic A/B testing with feature flags
+  ([#1237](https://github.com/open-telemetry/opentelemetry-demo/pull/1237))
 * add env var for pinning trace-based test tool version
   ([#1239](https://github.com/open-telemetry/opentelemetry-demo/pull/1239))
 * [cartservice] Add .NET memory, CPU, and thread metrics

src/featureflagservice/lib/featureflagservice/feature_flags/feature_flag.ex

@@ -1,14 +1,13 @@
 # Copyright The OpenTelemetry Authors
 # SPDX-License-Identifier: Apache-2.0
 
-
 defmodule Featureflagservice.FeatureFlags.FeatureFlag do
   use Ecto.Schema
   import Ecto.Changeset
 
   schema "featureflags" do
     field :description, :string
-    field :enabled, :boolean, default: false
+    field :enabled, :float, default: 0.0
     field :name, :string
 
     timestamps()
@@ -19,6 +18,7 @@ defmodule Featureflagservice.FeatureFlags.FeatureFlag do
     feature_flag
     |> cast(attrs, [:name, :description, :enabled])
     |> validate_required([:name, :description, :enabled])
+    |> validate_number(:enabled, greater_than_or_equal_to: 0.0, less_than_or_equal_to: 1.0)
     |> unique_constraint(:name)
   end
 end

src/featureflagservice/lib/featureflagservice_web/templates/feature_flag/form.html.heex

@@ -29,10 +29,15 @@
   <%= text_input f, :description %>
   <%= error_tag f, :description %>
 
-  <div class="float-right">
-    <%= checkbox f, :enabled %>
-    <%= label f, :enabled, class: "label-inline" %>
-  </div>
+  <%= label f, :enabled %>
+  <%= number_input f, :enabled, min: 0, max: 1, step: 0.01, "aria-describedby": "enabled_help_text" %>
+  <p id="enabled_help_text" style="font-size: smaller; margin-top: -10px;">
+    A decimal value between 0 and 1 (inclusive)<br />
+    0.0 is always disabled<br />
+    1.0 is always enabled<br />
+    All values between set a percentage chance on each request<br />
+    example: 0.55 is enabled 55% of the time<br />
+  </p>
   <%= error_tag f, :enabled %>
 
   <%= submit "Save" %>

src/featureflagservice/priv/repo/migrations/20220524172636_create_featureflags.exs

@@ -1,13 +1,11 @@
-
-
 defmodule Featureflagservice.Repo.Migrations.CreateFeatureflags do
   use Ecto.Migration
 
   def change do
     create table(:featureflags) do
       add :name, :string
       add :description, :string
-      add :enabled, :boolean, default: false, null: false
+      add :enabled, :float, default: 0.0, null: false
 
       timestamps()
     end
@@ -21,22 +19,26 @@ defmodule Featureflagservice.Repo.Migrations.CreateFeatureflags do
     repo().insert(%Featureflagservice.FeatureFlags.FeatureFlag{
       name: "productCatalogFailure",
       description: "Fail product catalog service on a specific product",
-      enabled: false})
+      enabled: 0.0
+    })
 
     repo().insert(%Featureflagservice.FeatureFlags.FeatureFlag{
       name: "recommendationCache",
       description: "Cache recommendations",
-      enabled: false})
+      enabled: 0.0
+    })
 
     repo().insert(%Featureflagservice.FeatureFlags.FeatureFlag{
       name: "adServiceFailure",
       description: "Fail ad service requests sporadically",
-      enabled: false})
+      enabled: 0.0
+    })
 
     repo().insert(%Featureflagservice.FeatureFlags.FeatureFlag{
       name: "cartServiceFailure",
       description: "Fail cart service requests sporadically",
-      enabled: false})
+      enabled: 0.0
+    })
   end
 
   defp execute_down do

src/featureflagservice/src/ffs_service.erl

@@ -17,56 +17,64 @@
 -behaviour(ffs_service_bhvr).
 
 -export([get_flag/2,
-         create_flag/2,
-         update_flag/2,
-         list_flags/2,
-         delete_flag/2]).
+  create_flag/2,
+  update_flag/2,
+  list_flags/2,
+  delete_flag/2]).
 
 -include_lib("grpcbox/include/grpcbox.hrl").
 
 -include_lib("opentelemetry_api/include/otel_tracer.hrl").
 
 -spec get_flag(ctx:t(), ffs_demo_pb:get_flag_request()) ->
-    {ok, ffs_demo_pb:get_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
+  {ok, ffs_demo_pb:get_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
 get_flag(Ctx, #{name := Name}) ->
-    case 'Elixir.Featureflagservice.FeatureFlags':get_feature_flag_by_name(Name) of
-        nil ->
-            {grpc_error, {?GRPC_STATUS_NOT_FOUND, <<"the requested feature flag does not exist">>}};
-        #{'__struct__' := 'Elixir.Featureflagservice.FeatureFlags.FeatureFlag',
-          description := Description,
-          enabled := Enabled,
-          inserted_at := CreatedAt,
-          updated_at := UpdatedAt
-         } ->
-            ?set_attribute('app.featureflag.name', Name),
-            ?set_attribute('app.featureflag.enabled', Enabled),
-            {ok, Epoch} = 'Elixir.NaiveDateTime':from_erl({{1970, 1, 1}, {0, 0, 0}}),
-            CreatedAtSeconds = 'Elixir.NaiveDateTime':diff(CreatedAt, Epoch),
-            UpdatedAtSeconds = 'Elixir.NaiveDateTime':diff(UpdatedAt, Epoch),
-            Flag = #{name => Name,
-                     description => Description,
-                     enabled => Enabled,
-                     created_at => #{seconds => CreatedAtSeconds, nanos => 0},
-                     updated_at => #{seconds => UpdatedAtSeconds, nanos => 0}},
-            {ok, #{flag => Flag}, Ctx}
-    end.
+  case 'Elixir.Featureflagservice.FeatureFlags':get_feature_flag_by_name(Name) of
+    nil ->
+      {grpc_error, {?GRPC_STATUS_NOT_FOUND, <<"the requested feature flag does not exist">>}};
+    #{'__struct__' := 'Elixir.Featureflagservice.FeatureFlags.FeatureFlag',
+      description := Description,
+      enabled := Enabled,
+      inserted_at := CreatedAt,
+      updated_at := UpdatedAt
+    } ->
+      RandomNumber = rand:uniform(100), % Generate a random number between 0 and 100
+      Probability = trunc(Enabled * 100), % Convert the Enabled value to a percentage
+      FlagEnabledValue = RandomNumber =< Probability, % Determine if the random number falls within the probability range
+
+      ?set_attribute('app.featureflag.name', Name),
+      ?set_attribute('app.featureflag.raw_value', Enabled),
+      ?set_attribute('app.featureflag.enabled', FlagEnabledValue),
+
+      {ok, Epoch} = 'Elixir.NaiveDateTime':from_erl({{1970, 1, 1}, {0, 0, 0}}),
+      CreatedAtSeconds = 'Elixir.NaiveDateTime':diff(CreatedAt, Epoch),
+      UpdatedAtSeconds = 'Elixir.NaiveDateTime':diff(UpdatedAt, Epoch),
+
+      Flag = #{name => Name,
+        description => Description,
+        enabled => FlagEnabledValue,
+        created_at => #{seconds => CreatedAtSeconds, nanos => 0},
+        updated_at => #{seconds => UpdatedAtSeconds, nanos => 0}},
+
+      {ok, #{flag => Flag}, Ctx}
+  end.
 
 -spec create_flag(ctx:t(), ffs_demo_pb:create_flag_request()) ->
-    {ok, ffs_demo_pb:create_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
+  {ok, ffs_demo_pb:create_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
 create_flag(_Ctx, _) ->
-    {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to create flags.">>}}.
+  {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to create flags.">>}}.
 
 -spec update_flag(ctx:t(), ffs_demo_pb:update_flag_request()) ->
-    {ok, ffs_demo_pb:update_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
+  {ok, ffs_demo_pb:update_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
 update_flag(_Ctx, _) ->
-    {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to update flags.">>}}.
+  {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to update flags.">>}}.
 
 -spec list_flags(ctx:t(), ffs_demo_pb:list_flags_request()) ->
-    {ok, ffs_demo_pb:list_flags_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
+  {ok, ffs_demo_pb:list_flags_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
 list_flags(_Ctx, _) ->
-    {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to view all flags.">>}}.
+  {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to view all flags.">>}}.
 
 -spec delete_flag(ctx:t(), ffs_demo_pb:delete_flag_request()) ->
-    {ok, ffs_demo_pb:delete_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
+  {ok, ffs_demo_pb:delete_flag_response(), ctx:t()} | grpcbox_stream:grpc_error_response().
 delete_flag(_Ctx, _) ->
-    {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to delete flags.">>}}.
+  {grpc_error, {?GRPC_STATUS_UNIMPLEMENTED, <<"use the web interface to delete flags.">>}}.