Fastly edge caching: use PURGE HTTP method instead of POST (#12627)

* Add :fastly_http_purge feature flag

* Add fastly.purge to EdgeCache::Bust::Fasty

* Update app/services/edge_cache/bust/fastly.rb

Co-authored-by: Michael Kohl <citizen428@dev.to>

* Update app/services/edge_cache/bust/fastly.rb

Co-authored-by: Michael Kohl <citizen428@dev.to>

* Update spec/lib/data_update_scripts/add_fastly_http_purge_feature_flag_spec.rb

Co-authored-by: Michael Kohl <citizen428@dev.to>

* Improve specs applying the feedback

* Deploy to BHC

* Undo Travis changes

Co-authored-by: Michael Kohl <citizen428@dev.to>
Co-authored-by: Mac Siri <krairit.siri@gmail.com>

app/services/edge_cache/bust/fastly.rb

@@ -1,24 +1,37 @@
 module EdgeCache
   class Bust
     class Fastly
+      # [@forem/systems] Fastly-enabled Forems don't need "flexible" domains.
       def self.call(path)
-        # TODO: (Alex Smith) - It would be "nice to have" the ability to use the
-        # Fastly gem here instead of custom API calls.
+        api_key = ApplicationConfig["FASTLY_API_KEY"]
+        return fastly_purge(api_key, path) if FeatureFlag.enabled?(:fastly_http_purge)
 
-        # @forem/systems Fastly-enabled forems don't need "flexible" domains.
-        HTTParty.post(
-          "https://api.fastly.com/purge/https://#{URL.domain}#{path}",
-          headers: {
-            "Fastly-Key" => ApplicationConfig["FASTLY_API_KEY"]
-          },
-        )
-        HTTParty.post(
-          "https://api.fastly.com/purge/https://#{URL.domain}#{path}?i=i",
-          headers: {
-            "Fastly-Key" => ApplicationConfig["FASTLY_API_KEY"]
-          },
-        )
+        fastly_post(api_key, path)
       end
+
+      def self.fastly_post(api_key, path)
+        urls(path).map do |url|
+          HTTParty.post("https://api.fastly.com/purge/#{url}", headers: { "Fastly-Key" => api_key })
+        end
+      end
+      private_class_method :fastly_post
+
+      def self.fastly_purge(api_key, path)
+        fastly = ::Fastly.new(api_key: api_key)
+
+        urls(path).map do |url|
+          fastly.purge(url)
+        end
+      end
+      private_class_method :fastly_purge
+
+      def self.urls(path)
+        [
+          URL.url(path),
+          URL.url("#{path}?i=i"),
+        ]
+      end
+      private_class_method :fastly_purge
     end
   end
 end

lib/data_update_scripts/20210209152726_add_fastly_http_purge_feature_flag.rb

@@ -0,0 +1,7 @@
+module DataUpdateScripts
+  class AddFastlyHttpPurgeFeatureFlag
+    def run
+      FeatureFlag.add(:fastly_http_purge)
+    end
+  end
+end

spec/lib/data_update_scripts/add_fastly_http_purge_feature_flag_spec.rb

@@ -0,0 +1,24 @@
+require "rails_helper"
+require Rails.root.join(
+  "lib/data_update_scripts/20210209152726_add_fastly_http_purge_feature_flag.rb",
+)
+
+describe DataUpdateScripts::AddFastlyHttpPurgeFeatureFlag do
+  after do
+    FeatureFlag.remove(:fastly_http_purge)
+  end
+
+  it "adds the :fastly_http_purge flag", :aggregate_failures do
+    expect do
+      described_class.new.run
+    end.to change { FeatureFlag.exist?(:fastly_http_purge) }.from(false).to(true)
+  end
+
+  it "works if the flag is already available" do
+    FeatureFlag.add(:fastly_http_purge)
+
+    expect do
+      described_class.new.run
+    end.not_to change { FeatureFlag.exist?(:fastly_http_purge) }
+  end
+end