From ad93a6ab60524b6e563ad64c4c3a386c0c5a3127 Mon Sep 17 00:00:00 2001
From: Tim Morgan <tim@timmorgan.org>
Date: Sun, 28 Feb 2021 09:46:52 -0600
Subject: [PATCH] Automatically handle rate limiting errors

We will sleep the prescribed number of seconds, then retry the request.

To disable, you can set retry_when_rate_limited to false.
---
 README.md                     | 11 +++++++++
 lib/pco/api.rb                |  7 +++---
 lib/pco/api/endpoint.rb       | 23 ++++++++++++++++++-
 spec/pco/api/endpoint_spec.rb | 42 +++++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index 14a08a8..3c598d2 100644
--- a/README.md
+++ b/README.md
@@ -231,6 +231,17 @@ In the case of validation errors, the `message` is a summary string built from t
 Alternatively, you may rescue `PCO::API::Errors::BaseError` and branch your code based on
 the status code returned by calling `error.status`.
 
+### TooManyRequests Error
+
+By default, PCO::API::Endpoint will sleep and retry a request that fails with TooManyRequests due
+to rate limiting. If you would rather catch and handle such errors yourself, you can disable this
+behavior like this:
+
+```ruby
+api = PCO::API.new(...)
+api.retry_when_rate_limited = false
+```
+
 ## Copyright & License
 
 Copyright Ministry Centered Technologies. Licensed MIT.
diff --git a/lib/pco/api.rb b/lib/pco/api.rb
index 962bc51..79d3c54 100644
--- a/lib/pco/api.rb
+++ b/lib/pco/api.rb
@@ -3,9 +3,10 @@
 
 module PCO
   module API
-    module_function
-    def new(**args)
-      Endpoint.new(**args)
+    class << self
+      def new(**args)
+        Endpoint.new(**args)
+      end
     end
   end
 end
diff --git a/lib/pco/api/endpoint.rb b/lib/pco/api/endpoint.rb
index 86053d9..8415825 100644
--- a/lib/pco/api/endpoint.rb
+++ b/lib/pco/api/endpoint.rb
@@ -12,6 +12,8 @@ class Response < Hash
     class Endpoint
       attr_reader :url, :last_result
 
+      attr_accessor :retry_when_rate_limited
+
       def initialize(url: URL, oauth_access_token: nil, basic_auth_token: nil, basic_auth_secret: nil, connection: nil)
         @url = url
         @oauth_access_token = oauth_access_token
@@ -19,6 +21,7 @@ def initialize(url: URL, oauth_access_token: nil, basic_auth_token: nil, basic_a
         @basic_auth_secret = basic_auth_secret
         @connection = connection || _build_connection
         @cache = {}
+        @retry_when_rate_limited = true
       end
 
       def method_missing(method_name, *_args)
@@ -29,7 +32,7 @@ def [](id)
         _build_endpoint(id.to_s)
       end
 
-      def respond_to?(method_name)
+      def respond_to?(method_name, _include_all = false)
         endpoint = _build_endpoint(method_name.to_s)
         begin
           endpoint.get
@@ -43,6 +46,8 @@ def respond_to?(method_name)
       def get(params = {})
         @last_result = @connection.get(@url, params)
         _build_response(@last_result)
+      rescue Errors::TooManyRequests => e
+        _retry_after_timeout?(e) ? retry : raise
       end
 
       def post(body = {})
@@ -50,6 +55,8 @@ def post(body = {})
           req.body = _build_body(body)
         end
         _build_response(@last_result)
+      rescue Errors::TooManyRequests => e
+        _retry_after_timeout?(e) ? retry : raise
       end
 
       def patch(body = {})
@@ -57,6 +64,8 @@ def patch(body = {})
           req.body = _build_body(body)
         end
         _build_response(@last_result)
+      rescue Errors::TooManyRequests => e
+        _retry_after_timeout?(e) ? retry : raise
       end
 
       def delete
@@ -66,6 +75,8 @@ def delete
         else
           _build_response(@last_result)
         end
+      rescue Errors::TooManyRequests => e
+        _retry_after_timeout?(e) ? retry : raise
       end
 
       private
@@ -135,6 +146,16 @@ def _build_connection
           faraday.adapter :excon
         end
       end
+
+      def _retry_after_timeout?(e)
+        if @retry_when_rate_limited
+          secs = e.headers['Retry-After']
+          Kernel.sleep(secs ? secs.to_i : 1)
+          true
+        else
+          false
+        end
+      end
     end
   end
 end
diff --git a/spec/pco/api/endpoint_spec.rb b/spec/pco/api/endpoint_spec.rb
index 7bc9ad7..0a77df4 100644
--- a/spec/pco/api/endpoint_spec.rb
+++ b/spec/pco/api/endpoint_spec.rb
@@ -124,6 +124,48 @@
         }.to raise_error(PCO::API::Errors::ServerError)
       end
     end
+
+    context 'given a 429 error due to rate limiting' do
+      subject { base.people.v2 }
+
+      let(:result) do
+        {
+          'type'  => 'Organization',
+          'id'    => '1',
+          'name'  => 'Ministry Centered Technologies',
+          'links' => {}
+        }
+      end
+
+      before do
+        stub_request(:get, 'https://api.planningcenteronline.com/people/v2')
+          .to_return([
+            { status: 429, headers: { 'retry-after' => '2' } },
+            { status: 200, body: { data: result }.to_json, headers: { 'Content-Type' => 'application/vnd.api+json' } }
+          ])
+      end
+
+      context 'given retry_when_rate_limited is true' do
+        before do
+          subject.retry_when_rate_limited = true
+        end
+
+        it 'sleeps, then makes the call again' do
+          expect(Kernel).to receive(:sleep).with(2)
+          expect(subject.get).to be_a(Hash)
+        end
+      end
+
+      context 'given retry_when_rate_limited is false' do
+        before do
+          subject.retry_when_rate_limited = false
+        end
+
+        it 'raises the TooManyRequests error' do
+          expect { subject.get }.to raise_error(PCO::API::Errors::TooManyRequests)
+        end
+      end
+    end
   end
 
   describe '#post' do