1 files changed, 65 insertions, 0 deletions
diff --git a/lib/gitlab/ci/runner_releases.rb b/lib/gitlab/ci/runner_releases.rb
new file mode 100644
index 00000000000..944c24ca128
--- /dev/null
+++ b/lib/gitlab/ci/runner_releases.rb
@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    class RunnerReleases
+      include Singleton
+
+      RELEASES_VALIDITY_PERIOD = 1.day
+      RELEASES_VALIDITY_AFTER_ERROR_PERIOD = 5.seconds
+
+      INITIAL_BACKOFF = 5.seconds
+      MAX_BACKOFF = 1.hour
+      BACKOFF_GROWTH_FACTOR = 2.0
+
+      def initialize
+        reset!
+      end
+
+      # Returns a sorted list of the publicly available GitLab Runner releases
+      #
+      def releases
+        return @releases unless Time.now.utc >= @expire_time
+
+        @releases = fetch_new_releases
+      end
+
+      def reset!
+        @expire_time = Time.now.utc
+        @releases = nil
+        @backoff_count = 0
+      end
+
+      public_class_method :instance
+
+      private
+
+      def fetch_new_releases
+        response = Gitlab::HTTP.try_get(::Gitlab::CurrentSettings.current_application_settings.public_runner_releases_url)
+
+        releases = response.success? ? extract_releases(response) : nil
+      ensure
+        @expire_time = (releases ? RELEASES_VALIDITY_PERIOD : next_backoff).from_now
+      end
+
+      def extract_releases(response)
+        response.parsed_response.map { |release| parse_runner_release(release) }.sort!
+      end
+
+      def parse_runner_release(release)
+        ::Gitlab::VersionInfo.parse(release['name'].delete_prefix('v'))
+      end
+
+      def next_backoff
+        return MAX_BACKOFF if @backoff_count >= 11 # optimization to prevent expensive exponentiation and possible overflows
+
+        backoff = (INITIAL_BACKOFF * (BACKOFF_GROWTH_FACTOR**@backoff_count))
+          .clamp(INITIAL_BACKOFF, MAX_BACKOFF)
+          .seconds
+        @backoff_count += 1
+
+        backoff
+      end
+    end
+  end
+end