[FFM-9925] - Testgrid - % rollout - Ruby SDK - Fix MM3 hash (#33)

What
Various fixes to MM3 hash to bring it in alignment with GoLang SDK

    Fix input to MM3 hash to use <ATTR>:<VALUE> instead of <VALUE>:<ATTR>
    Set MM3 seed to 0
    Ignore 0 weighted distributions
    If bucket_by attribute is missing, fall back to identifier + log new SDK code
    Additional debug statements for easier diagnostics

Also

    Remove some IDE files that shouldn't be checked in
    Bump main version number
    Loosen Gem dependency requirements

Why
Review SDKs to make sure Murmur3 hash calculations are consistent across SDKs and buckets mappings align for customers that rely on this feature.

Testing
New percentage rollout tests added to testgrid, these will be committed later

---------

Co-authored-by: Erdi Rowlands <[email protected]>

CHANGELOG.md

@@ -1,3 +1,10 @@
+# [1.2.0] ** BREAKING **
+
+- [FFM-9804] - The percentage rollout hash algorithm was slightly different compared to other Feature Flags SDKs, which resulted 
+in a different bucket allocation for the same target. While the overall percentage distribution was correct with the previous
+algorithm; this fix ensures that the same target will get the same allocation per SDK. We are marking as a breaking change
+as existing targets may get different allocations in a percentage rollout flag. 
+
 # [1.1.0]
 
 - [FFM-7285] - Remove Metrics queue and implement Map for better memory usage

Gemfile

@@ -9,19 +9,19 @@ gem "minitest", "~> 5.0"
 gem "standard", "~> 1.3"
 
 # Caching support:
-gem "rufus-scheduler"
-gem "libcache"
-gem "jwt"
-gem "moneta"
+gem "rufus-scheduler", "~> 3.8"
+gem "libcache", "0.4.2"
+gem "jwt", "~> 2.3"
+gem "moneta", "~> 1.4"
 
 # SSE support:
-gem "rest-client"
+gem "rest-client", "~> 2.1"
 
 # Concurrency support:
-gem "concurrent-ruby", "1.1.10", require: "concurrent"
+gem "concurrent-ruby", "~> 1.1", require: "concurrent"
 
 # Evaluator dependencies:
-gem "murmurhash3"
+gem "murmurhash3", "~> 0.1.6"
 
 gem "typhoeus"
 

lib/ff/ruby/server/sdk/api/evaluator.rb

@@ -181,20 +181,24 @@ def find_variation(variations, identifier)
   end
 
   def get_normalized_number(property, bucket_by)
-
-    joined = property.to_s + ":" + bucket_by.to_s
-    hash = MurmurHash3::V32.str_hash(joined, joined.length)
+    joined = bucket_by.to_s + ":" + property.to_s
+    hash = MurmurHash3::V32.str_hash(joined, 0)
     (hash % 100) + 1
   end
 
   def is_enabled(target, bucket_by, percentage)
-
     property = get_attr_value(target, bucket_by)
 
-    if property != nil
+    if property == nil
+      old_bb = bucket_by
+      bucket_by = "identifier"
+      property = get_attr_value(target, bucket_by)
+      SdkCodes.warn_bucket_by_attr_not_found @logger, old_bb, property
+    end
 
+    if property != nil
       bucket_id = get_normalized_number(property, bucket_by)
-
+      @logger.debug "MM3 percentage_check=%s bucket_by=%s value=%s bucket=%s" % [percentage, bucket_by, property, bucket_id]
       return percentage > 0 && bucket_id <= percentage
     end
 
@@ -206,13 +210,11 @@ def evaluate_distribution(distribution, target)
     if distribution != nil
 
       variation = nil
-
+      total_percentage = 0
       distribution.variations.each do |weighted_variation|
-
         variation = weighted_variation.variation
-
-        if is_enabled(target, distribution.bucket_by, weighted_variation.weight)
-
+        total_percentage = total_percentage + weighted_variation.weight
+        if is_enabled(target, distribution.bucket_by, total_percentage)
           return variation
         end
       end

lib/ff/ruby/server/sdk/common/sdk_codes.rb

@@ -54,6 +54,13 @@ def self.warn_default_variation_served(logger, identifier, target, default)
     logger.warn SdkCodes.sdk_err_msg(6001, "identifier=%s, target=%s, default=%s" % [identifier, target.identifier, default])
   end
 
+  def self.warn_bucket_by_attr_not_found(logger, attr_name, new_value)
+    if new_value == nil
+      new_value = "NOT FOUND"
+    end
+    logger.warn SdkCodes.sdk_err_msg(6002, "missing=%s, using value=%s" % [attr_name, new_value])
+  end
+
   private
 
   @map =
@@ -77,6 +84,7 @@ def self.warn_default_variation_served(logger, identifier, target, default)
       # SDK_EVAL_6xxx
       6000 => "Evaluated variation successfully",
       6001 => "Default variation was served",
+      6002 => "BucketBy attribute not found in target attributes, falling back to 'identifier':",
       # SDK_METRICS_7xxx
       7000 => "Metrics thread started",
       7001 => "Metrics thread exited",

lib/ff/ruby/server/sdk/version.rb

@@ -5,7 +5,7 @@ module Ruby
     module Server
       module Sdk
 
-        VERSION = "1.1.4"
+        VERSION = "1.2.0"
       end
     end
   end

scripts/sdk_specs.sh

@@ -1,4 +1,4 @@
 #!/bin/bash
 
 export ff_ruby_sdk="ff-ruby-server-sdk"
-export ff_ruby_sdk_version="1.1.4"
+export ff_ruby_sdk_version="1.2.0"