Add support for the RateLimit-Reset header

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2022-01-04 18:53:25 UTC using RuboCop version 1.23.0.
+# on 2022-06-07 14:20:20 UTC using RuboCop version 1.21.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -17,6 +17,11 @@ Lint/AmbiguousBlockAssociation:
 Metrics/AbcSize:
   Max: 26
 
+# Offense count: 1
+# Configuration parameters: CountComments, CountAsOne.
+Metrics/ClassLength:
+  Max: 105
+
 # Offense count: 2
 # Configuration parameters: CountComments, CountAsOne, ExcludedMethods, IgnoredMethods.
 Metrics/MethodLength:
@@ -49,7 +54,7 @@ RSpec/InstanceVariable:
 RSpec/MultipleExpectations:
   Max: 3
 
-# Offense count: 9
+# Offense count: 11
 # Configuration parameters: AllowSubject.
 RSpec/MultipleMemoizedHelpers:
   Max: 9

README.md

@@ -96,11 +96,14 @@ retry_options = {
 }
 ```
 
-#### Automatically handle the `Retry-After` header
+#### Automatically handle the `Retry-After` and `RateLimit-Reset` headers
 
-Some APIs, like the [Slack API](https://api.slack.com/docs/rate-limits), will inform you when you reach their API limits by replying with a response status code of `429` and a response header of `Retry-After` containing a time in seconds. You should then only retry querying after the amount of time provided by the `Retry-After` header, otherwise you won't get a response.
+Some APIs, like the [Slack API](https://api.slack.com/docs/rate-limits), will inform you when you reach their API limits by replying with a response status code of `429`
+and a response header of `Retry-After` containing a time in seconds. You should then only retry querying after the amount of time provided by the `Retry-After` header,
+otherwise you won't get a response. Other APIs communicate their rate limits via the [RateLimit-xxx](https://tools.ietf.org/id/draft-polli-ratelimit-headers-00.html#rfc.section.3.3) headers
+where `RateLimit-Reset` behaves similarly to the `Retry-After`.
 
-You can automatically handle this and have Faraday pause and retry for the right amount of time by including the `429` status code in the retry statuses list:
+You can automatically handle both headers and have Faraday pause and retry for the right amount of time by including the `429` status code in the retry statuses list:
 
 ```ruby
 retry_options = {

lib/faraday/retry/middleware.rb

@@ -126,7 +126,7 @@ def initialize(app, options = nil)
       end
 
       def calculate_sleep_amount(retries, env)
-        retry_after = calculate_retry_after(env)
+        retry_after = [calculate_retry_after(env), calculate_rate_limit_reset(env)].compact.max
         retry_interval = calculate_retry_interval(retries)
 
         return if retry_after && retry_after > @options.max_interval
@@ -212,21 +212,16 @@ def rewind_files(body)
         end
       end
 
+      # RFC for RateLimit Header Fields for HTTP:
+      # https://tools.ietf.org/id/draft-polli-ratelimit-headers-00.html#rfc.section.3.3
+      def calculate_rate_limit_reset(env)
+        parse_retry_header(env, 'RateLimit-Reset')
+      end
+
       # MDN spec for Retry-After header:
       # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Retry-After
       def calculate_retry_after(env)
-        response_headers = env[:response_headers]
-        return unless response_headers
-
-        retry_after_value = env[:response_headers]['Retry-After']
-
-        # Try to parse date from the header value
-        begin
-          datetime = DateTime.rfc2822(retry_after_value)
-          datetime.to_time - Time.now.utc
-        rescue ArgumentError
-          retry_after_value.to_f
-        end
+        parse_retry_header(env, 'Retry-After')
       end
 
       def calculate_retry_interval(retries)
@@ -239,6 +234,21 @@ def calculate_retry_interval(retries)
 
         current_interval + random_interval
       end
+
+      def parse_retry_header(env, header)
+        response_headers = env[:response_headers]
+        return unless response_headers
+
+        retry_after_value = env[:response_headers][header]
+
+        # Try to parse date from the header value
+        begin
+          datetime = DateTime.rfc2822(retry_after_value)
+          datetime.to_time - Time.now.utc
+        rescue ArgumentError
+          retry_after_value.to_f
+        end
+      end
     end
   end
 end

spec/faraday/retry/middleware_spec.rb

@@ -245,8 +245,15 @@
       conn.get('/unstable')
     end
 
-    context 'when retry_after bigger than interval' do
-      let(:headers) { { 'Retry-After' => '0.5' } }
+    context 'when Retry-After bigger than RateLimit-Reset' do
+      let(:headers) { { 'Retry-After' => '0.5', 'RateLimit-Reset' => '0.1' } }
+      let(:options) { [{ max: 1, interval: 0.1, retry_statuses: 504 }] }
+
+      it { expect(elapsed).to be > 0.5 }
+    end
+
+    context 'when RateLimit-Reset bigger than Retry-After' do
+      let(:headers) { { 'Retry-After' => '0.1', 'RateLimit-Reset' => '0.5' } }
       let(:options) { [{ max: 1, interval: 0.1, retry_statuses: 504 }] }
 
       it { expect(elapsed).to be > 0.5 }
@@ -259,6 +266,13 @@
       it { expect(elapsed).to be > 0.2 }
     end
 
+    context 'when RateLimit-Reset is a timestamp' do
+      let(:headers) { { 'Retry-After' => '0.1', 'RateLimit-Reset' => (Time.now.utc + 2).strftime('%a, %d %b %Y %H:%M:%S GMT') } }
+      let(:options) { [{ max: 1, interval: 0.1, retry_statuses: 504 }] }
+
+      it { expect(elapsed).to be > 1 }
+    end
+
     context 'when retry_after is a timestamp' do
       let(:headers) { { 'Retry-After' => (Time.now.utc + 2).strftime('%a, %d %b %Y %H:%M:%S GMT') } }
       let(:options) { [{ max: 1, interval: 0.1, retry_statuses: 504 }] }