Add latest changes from gitlab-org/gitlab@master

1 files changed, 83 insertions, 0 deletions

diff --git a/app/experiments/application_experiment.rb b/app/experiments/application_experiment.rb
new file mode 100644
index 00000000000..e8f7d22bf77
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+++ b/app/experiments/application_experiment.rb
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+# frozen_string_literal: true
+
+class ApplicationExperiment < Gitlab::Experiment
+  def publish(_result)
+    track(:assignment) # track that we've assigned a variant for this context
+    Gon.global.push({ experiment: { name => signature } }, true) # push to client
+  end
+
+  def track(action, **event_args)
+    return if excluded? # no events for opted out actors or excluded subjects
+
+    Gitlab::Tracking.event(name, action.to_s, **event_args.merge(
+      context: (event_args[:context] || []) << SnowplowTracker::SelfDescribingJson.new(
+        'iglu:com.gitlab/gitlab_experiment/jsonschema/0-3-0', signature
+      )
+    ))
+  end
+
+  private
+
+  def resolve_variant_name
+    variant_names.first if Feature.enabled?(name, self, type: :experiment)
+  end
+
+  # Cache is an implementation on top of Gitlab::Redis::SharedState that also
+  # adheres to the ActiveSupport::Cache::Store interface and uses the redis
+  # hash data type.
+  #
+  # Since Gitlab::Experiment can use any type of caching layer, utilizing the
+  # long lived shared state interface here gives us an efficient way to store
+  # context keys and the variant they've been assigned -- while also giving us
+  # a simple way to clean up an experiments data upon resolution.
+  #
+  # The data structure:
+  #   key: experiment.name
+  #   fields: context key => variant name
+  #
+  # The keys are expected to be `experiment_name:context_key`, which is the
+  # default cache key strategy. So running `cache.fetch("foo:bar", "value")`
+  # would create/update a hash with the key of "foo", with a field named
+  # "bar" that has "value" assigned to it.
+  class Cache < ActiveSupport::Cache::Store
+    # Clears the entire cache for a given experiment. Be careful with this
+    # since it would reset all resolved variants for the entire experiment.
+    def clear(key:)
+      key = hkey(key)[0] # extract only the first part of the key
+      pool do |redis|
+        case redis.type(key)
+        when 'hash', 'none' then redis.del(key)
+        else raise ArgumentError, 'invalid call to clear a non-hash cache key'
+        end
+      end
+    end
+
+    private
+
+    def pool
+      raise ArgumentError, 'missing block' unless block_given?
+
+      Gitlab::Redis::SharedState.with { |redis| yield redis }
+    end
+
+    def hkey(key)
+      key.split(':') # this assumes the default strategy in gitlab-experiment
+    end
+
+    def read_entry(key, **options)
+      value = pool { |redis| redis.hget(*hkey(key)) }
+      value.nil? ? nil : ActiveSupport::Cache::Entry.new(value)
+    end
+
+    def write_entry(key, entry, **options)
+      return false unless Feature.enabled?(:caching_experiments)
+      return false if entry.value.blank? # don't cache any empty values
+
+      pool { |redis| redis.hset(*hkey(key), entry.value) }
+    end
+
+    def delete_entry(key, **options)
+      pool { |redis| redis.hdel(*hkey(key)) }
+    end
+  end
+end