From add0abb5055141c5a39beeb01c8eb1b3129b147c Mon Sep 17 00:00:00 2001
From: Simon Tomlinson <stomlinson@gitlab.com>
Date: Wed, 4 Sep 2024 16:23:08 -0500
Subject: [PATCH] Flipper per-pod actor
Adds Feature.current_pod, a flipper actor that is the same for a given
kubernetes pod.
---
lib/feature.rb | 16 +++++++++++++
spec/lib/feature_spec.rb | 52 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 68 insertions(+)
diff --git a/lib/feature.rb b/lib/feature.rb
index b9307ce66dd1a..e2b2039a04f7e 100644
--- a/lib/feature.rb
+++ b/lib/feature.rb
@@ -44,6 +44,16 @@ def flipper_id
end
end
+ # Generates the same flipper_id for a given kubernetes pod,
+ # or for the entire gitlab application if deployed on a single host.
+ class FlipperPod
+ attr_reader :flipper_id
+
+ def initialize
+ @flipper_id = "FlipperPod:#{Socket.gethostname}".freeze
+ end
+ end
+
# Generates a unique flipper_id for the current GitLab instance.
class FlipperGitlabInstance
attr_reader :flipper_id
@@ -253,6 +263,10 @@ def current_request
end
end
+ def current_pod
+ @flipper_pod ||= FlipperPod.new
+ end
+
def gitlab_instance
@flipper_gitlab_instance ||= FlipperGitlabInstance.new
end
@@ -290,6 +304,8 @@ def sanitized_thing(thing)
gitlab_instance
when :request, :current_request
current_request
+ when :pod, :current_pod
+ current_pod
else
thing
end
diff --git a/spec/lib/feature_spec.rb b/spec/lib/feature_spec.rb
index acf39fbbe5350..b2bc24970a1df 100644
--- a/spec/lib/feature_spec.rb
+++ b/spec/lib/feature_spec.rb
@@ -55,6 +55,29 @@ def wrap_all_methods_with_flag_check(lb, flag)
end
end
+ describe '.current_pod' do
+ it 'returns a FlipperPod with a flipper_id' do
+ expect(described_class.current_pod).to respond_to(:flipper_id)
+ end
+
+ it 'is the same flipper_id within a process' do
+ previous_id = described_class.current_pod.flipper_id
+
+ expect(previous_id).to eq(described_class.current_pod.flipper_id)
+ end
+
+ it 'is a different flipper_id in a new host' do
+ previous_id = described_class.current_pod.flipper_id
+
+ # Simulate a new process by changing host,
+ previous_host = Socket.gethostname
+ allow(Socket).to receive(:gethostname).and_return("#{previous_host}-1")
+
+ new_id = Feature::FlipperPod.new.flipper_id # Bypass caching
+ expect(previous_id).not_to eq(new_id)
+ end
+ end
+
describe '.gitlab_instance' do
it 'returns a FlipperGitlabInstance with a flipper_id' do
flipper_request = described_class.gitlab_instance
@@ -407,6 +430,35 @@ def wrap_all_methods_with_flag_check(lb, flag)
end
end
+ context 'with :pod actor' do
+ before do
+ stub_feature_flag_definition(:enabled_feature_flag)
+ end
+
+ it 'returns the same value in the same host' do
+ described_class.enable(:enabled_feature_flag, :current_pod)
+
+ expect(described_class.enabled?(:enabled_feature_flag, :current_pod)).to be_truthy
+ end
+
+ it 'returns different values in different hosts' do
+ number_of_times = 1_000
+ percentage = 50
+ described_class.enable_percentage_of_actors(:enabled_feature_flag, percentage)
+ results = { true => 0, false => 0 }
+ original_hostname = Socket.gethostname
+ number_of_times.times do |i|
+ allow(Socket).to receive(:gethostname).and_return("#{original_hostname}-#{i}")
+ flipper_thing = Feature::FlipperPod.new # Create a new one to bypass caching, we are simulating many different pods
+ result = described_class.enabled?(:enabled_feature_flag, flipper_thing)
+ results[result] += 1
+ end
+
+ percent_true = (results[true].to_f / (results[true] + results[false])) * 100
+ expect(percent_true).to be_within(5).of(percentage)
+ end
+ end
+
context 'with a group member' do
let(:key) { :awesome_feature }
let(:guinea_pigs) { create_list(:user, 3) }
--
GitLab