1 files changed, 55 insertions, 0 deletions
diff --git a/lib/gitlab/ci/trace/backoff.rb b/lib/gitlab/ci/trace/backoff.rb
new file mode 100644
index 00000000000..c13d88cced1
--- /dev/null
+++ b/lib/gitlab/ci/trace/backoff.rb
@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    class Trace
+      ##
+      # Trace::Backoff class is responsible for calculating a backoff value
+      # for when to be able to retry archiving a build's trace
+      #
+      # Because we're updating `last_archival_attempt_at` timestamp with every
+      # failed archival attempt, we need to be sure that sum of the backoff values
+      # for 1..MAX_ATTEMPTS is under 7 days(CHUNK_REDIS_TTL).
+      #
+      class Backoff
+        include Gitlab::Utils::StrongMemoize
+
+        MAX_JITTER_VALUE = 4
+
+        attr_reader :archival_attempts
+
+        def initialize(archival_attempts)
+          @archival_attempts = archival_attempts
+        end
+
+        def value
+          (((chunks_ttl / (3.5 * max_attempts)) * archival_attempts) / 1.hour).hours
+        end
+
+        # This formula generates an increasing delay between executions
+        # 9.6, 19.2, 28.8, 38.4, 48.0 + a random amount of time to
+        # change the order of execution for the jobs.
+        # With maximum value for each call to rand(4), this sums up to 6.8 days
+        # and with minimum values is 6 days.
+        #
+        def value_with_jitter
+          value + jitter
+        end
+
+        private
+
+        def jitter
+          rand(MAX_JITTER_VALUE).hours
+        end
+
+        def chunks_ttl
+          ::Ci::BuildTraceChunks::RedisBase::CHUNK_REDIS_TTL
+        end
+
+        def max_attempts
+          ::Ci::BuildTraceMetadata::MAX_ATTEMPTS
+        end
+      end
+    end
+  end
+end