Refactor retry exponential backoff

Author: Matt Muller

gems/smithy-client/lib/smithy-client/plugins/retry_errors.rb

@@ -33,15 +33,37 @@ class RetryErrors < Plugin
           DOCS
 
         option(
-          :retry_backoff,
-          default: Retry::EXPONENTIAL_BACKOFF,
-          doc_default: 'Smithy::Client::Retry::EXPONENTIAL_BACKOFF',
-          doc_type: 'lambda',
+          :retry_max_delay,
+          default: 20,
+          docstring: <<~DOCS)
+            The maximum delay, in seconds, between retry attempts. This option is ignored
+            if a custom `retry_backoff` is provided. Used in the `standard` and `adaptive`
+            retry strategies.
+          DOCS
+
+        option(
+          :retry_base_delay,
+          default: 2,
           docstring: <<~DOCS)
+            The base delay, in seconds, used to calculate the exponential backoff for
+            retry attempts. This option is ignored if a custom `retry_backoff` is provided.
+            Used in the `standard` and `adaptive` retry strategies.
+          DOCS
+
+        option(
+          :retry_backoff,
+          doc_default: 'Smithy::Client::Retry::ExponentialBackoff.new',
+          doc_type: '#call(attempts)',
+          docstring: <<~DOCS) do |config|
             A callable object that calculates a backoff delay for a retry attempt. The callable
             should accept a single argument, `attempts`, that represents the number of attempts
             that have been made. Used in the `standard` and `adaptive` retry strategies.
           DOCS
+          Retry::ExponentialBackoff.new(
+            retry_base_delay: config.retry_base_delay,
+            retry_max_delay: config.retry_max_delay
+          )
+        end
 
         option(
           :adaptive_retry_wait_to_fill,

gems/smithy-client/lib/smithy-client/retry.rb

@@ -2,35 +2,7 @@
 
 require_relative 'retry/adaptive'
 require_relative 'retry/client_rate_limiter'
+require_relative 'retry/exponential_backoff'
 require_relative 'retry/quota'
 require_relative 'retry/standard'
-
-module Smithy
-  module Client
-    module Retry
-      # The maximum backoff delay for retrying requests.
-      MAX_BACKOFF = 20
-
-      # The default backoff for retrying requests.
-      EXPONENTIAL_BACKOFF = lambda do |attempts|
-        [Kernel.rand * (2**attempts), MAX_BACKOFF].min || 0
-      end
-
-      # Represents a token that can be used to retry an operation.
-      class Token
-        def initialize
-          @retry_count = 0
-          @retry_delay = 0
-        end
-
-        # The number of times the operation has been retried.
-        # @return [Integer]
-        attr_accessor :retry_count
-
-        # The delay before the next retry.
-        # @return [Numeric]
-        attr_accessor :retry_delay
-      end
-    end
-  end
-end
+require_relative 'retry/token'

gems/smithy-client/lib/smithy-client/retry/adaptive.rb

@@ -5,7 +5,7 @@ module Client
     module Retry
       # Adaptive retry strategy for retrying requests.
       class Adaptive
-        # @option [#call] :backoff (EXPONENTIAL_BACKOFF) A callable object that
+        # @option [#call] :backoff (ExponentialBackoff.new) A callable object that
         #  calculates a backoff delay for a retry attempt.
         # @option [Integer] :max_attempts (3) The maximum number of attempts that
         #  will be made for a single request, including the initial attempt.
@@ -15,7 +15,10 @@ class Adaptive
         #  not retry instead of sleeping.
         def initialize(options = {})
           super()
-          @backoff = options[:backoff] || EXPONENTIAL_BACKOFF
+          @backoff = options[:backoff] || ExponentialBackoff.new(
+            base_delay: options[:base_delay],
+            max_delay: options[:max_delay]
+          )
           @max_attempts = options[:max_attempts] || 3
           @wait_to_fill = options[:wait_to_fill] || true
           @client_rate_limiter = ClientRateLimiter.new

gems/smithy-client/lib/smithy-client/retry/exponential_backoff.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Smithy
+  module Client
+    module Retry
+      # Default exponential backoff retry strategy for retrying requests.
+      class ExponentialBackoff
+        def initialize(options = {})
+          @base_delay = options[:base_delay] || 2
+          @max_delay = options[:max_delay] || 20
+        end
+
+        # Calculates a delay based on exponential backoff strategy. Uses full jitter approach.
+        # @param [Integer] attempts
+        # @return [Float] delay in seconds
+        def call(attempts)
+          delay = (@base_delay**attempts)
+          [delay, @max_delay].min * Kernel.rand
+        end
+      end
+    end
+  end
+end

gems/smithy-client/lib/smithy-client/retry/standard.rb

@@ -5,13 +5,16 @@ module Client
     module Retry
       # Standard retry strategy for retrying requests.
       class Standard
-        # @option [#call] :backoff (EXPONENTIAL_BACKOFF) A callable object that
+        # @option [#call] :backoff (ExponentialBackoff.new) A callable object that
         #  calculates a backoff delay for a retry attempt.
         # @option [Integer] :max_attempts (3) The maximum number of attempts that
         #  will be made for a single request, including the initial attempt.
         def initialize(options = {})
           super()
-          @backoff = options[:backoff] || EXPONENTIAL_BACKOFF
+          @backoff = options[:backoff] || ExponentialBackoff.new(
+            base_delay: options[:base_delay],
+            max_delay: options[:max_delay]
+          )
           @max_attempts = options[:max_attempts] || 3
           @quota = Quota.new
           @capacity_amount = 0

gems/smithy-client/lib/smithy-client/retry/token.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Smithy
+  module Client
+    module Retry
+      # Represents a token that can be used to retry an operation.
+      class Token
+        def initialize
+          @retry_count = 0
+          @retry_delay = 0
+        end
+
+        # The number of times the operation has been retried.
+        # @return [Integer]
+        attr_accessor :retry_count
+
+        # The delay before the next retry.
+        # @return [Numeric]
+        attr_accessor :retry_delay
+      end
+    end
+  end
+end

gems/smithy-client/spec/smithy-client/plugins/retry_errors_spec.rb

@@ -203,8 +203,8 @@ module Plugins
             end
 
             it 'does not exceed the max backoff time' do
+              config.retry_strategy = Retry::Standard.new(max_delay: 3)
               retry_strategy.instance_variable_set(:@max_attempts, 5)
-              stub_const('Smithy::Client::Retry::MAX_BACKOFF', 3)
 
               test_case_def = [
                 {