added retry_after option to the retries plugin

lib/httpx/plugins/retries.rb

@@ -25,6 +25,17 @@ module HTTPX
 
       def self.extra_options(options)
         Class.new(options.class) do
+          # number of seconds after which one can retry the request
+          def_option(:retry_after) do |num|
+            # return early if callable
+            return num if num.respond_to?(:call)
+
+            num = Integer(num)
+            raise Error, ":retry_after must be positive" unless num.positive?
+
+            num
+          end
+
           def_option(:max_retries) do |num|
             num = Integer(num)
             raise Error, ":max_retries must be positive" unless num.positive?
@@ -63,8 +74,7 @@ module HTTPX
             log { "failed to get response, #{request.retries} tries to go..." }
             request.transition(:idle)
             connection = find_connection(request, connections, options)
-            connection.send(request)
-            set_request_timeout(connection, request, options)
+            __retry_request(connection, request, options)
             return
           end
           response
@@ -77,6 +87,23 @@ module HTTPX
         def __retryable_error?(ex)
           RETRYABLE_ERRORS.any? { |klass| ex.is_a?(klass) }
         end
+
+        def __retry_request(connection, request, options)
+          retry_after = options.retry_after
+          unless retry_after
+            connection.send(request)
+            set_request_timeout(connection, request, options)
+            return
+          end
+
+          retry_after = retry_after.call(request) if retry_after.respond_to?(:call)
+          log { "retrying after #{retry_after} secs..." }
+          pool.after(retry_after) do
+            log { "retrying!!" }
+            connection.send(request)
+            set_request_timeout(connection, request, options)
+          end
+        end
       end
 
       module RequestMethods

test/support/requests/plugins/retries.rb

@@ -46,6 +46,38 @@ module Requests
         assert retries_session.calls.zero?, "expect request not to be retried (it was, #{retries_session.calls} times)"
       end
 
+      def test_plugin_retries_retry_after
+        before_time = Process.clock_gettime(Process::CLOCK_MONOTONIC, :second)
+        retries_session = HTTPX
+                          .plugin(RequestInspector)
+                          .plugin(:retries, retry_after: 2)
+                          .timeout(total_timeout: 3)
+                          .max_retries(1)
+        retries_response = retries_session.get(build_uri("/delay/10"))
+        after_time = Process.clock_gettime(Process::CLOCK_MONOTONIC, :second)
+        total_time = after_time - before_time
+
+        assert retries_response.is_a?(HTTPX::ErrorResponse)
+        assert_in_delta 3 + 2 + 3, total_time, 1, "request didn't take as expected to retry (#{total_time} secs)"
+      end
+
+      def test_plugin_retries_retry_after_callable
+        retries = 0
+        exponential = ->(_) { (retries += 1) * 2 }
+        before_time = Process.clock_gettime(Process::CLOCK_MONOTONIC, :second)
+        retries_session = HTTPX
+                          .plugin(RequestInspector)
+                          .plugin(:retries, retry_after: exponential)
+                          .timeout(total_timeout: 3)
+                          .max_retries(2)
+        retries_response = retries_session.get(build_uri("/delay/10"))
+        after_time = Process.clock_gettime(Process::CLOCK_MONOTONIC, :second)
+        total_time = after_time - before_time
+
+        assert retries_response.is_a?(HTTPX::ErrorResponse)
+        assert_in_delta 3 + 2 + 3 + 4 + 3, total_time, 1, "request didn't take as expected to retry (#{total_time} secs)"
+      end
+
       module RequestInspector
         module InstanceMethods
           attr_reader :calls