feat: Return 204 from GET requests to an event function, to support health checks (#128)

Author: dazuma

functions_framework.gemspec

@@ -45,7 +45,7 @@ version = ::FunctionsFramework::VERSION
   spec.executables = ["functions-framework", "functions-framework-ruby"]
 
   spec.required_ruby_version = ">= 2.5.0"
-  spec.add_dependency "cloud_events", ">= 0.6.0", "< 2.a"
+  spec.add_dependency "cloud_events", ">= 0.7.0", "< 2.a"
   spec.add_dependency "puma", ">= 4.3.0", "< 6.a"
   spec.add_dependency "rack", "~> 2.1"
 

lib/functions_framework/server.rb

@@ -364,6 +364,10 @@ def notfound_response
         string_response "Not found", 404
       end
 
+      def no_content_response
+        [204, [], []]
+      end
+
       def string_response string, status, content_type: nil
         string.force_encoding ::Encoding::ASCII_8BIT unless string.valid_encoding?
         if string.encoding == ::Encoding::ASCII_8BIT
@@ -403,7 +407,7 @@ def call env
         return notfound_response if excluded_path? env
         response =
           begin
-            logger = env["rack.logger"] ||= @config.logger
+            logger = env[::Rack::RACK_LOGGER] ||= @config.logger
             request = ::Rack::Request.new env
             logger.info "FunctionsFramework: Handling HTTP #{request.request_method} request"
             @function.call request, globals: @globals, logger: logger
@@ -426,7 +430,8 @@ def initialize function, globals, config
 
       def call env
         return notfound_response if excluded_path? env
-        logger = env["rack.logger"] ||= @config.logger
+        return no_content_response if env[::Rack::REQUEST_METHOD] == "GET"
+        logger = env[::Rack::RACK_LOGGER] ||= @config.logger
         event = decode_event env
         response =
           case event
@@ -448,9 +453,8 @@ def decode_event env
         begin
           @cloud_events.decode_event env
         rescue ::CloudEvents::NotCloudEventError
-          env["rack.input"].rewind rescue nil
-          @legacy_events.decode_rack_env(env) ||
-            raise(::CloudEvents::CloudEventsError, "Unrecognized event format")
+          env[::Rack::RACK_INPUT].rewind rescue nil
+          @legacy_events.decode_rack_env(env) || ::CloudEvents::CloudEventsError.new("Unrecognized event format")
         end
       rescue ::CloudEvents::CloudEventsError => e
         e

test/test_server.rb

@@ -287,4 +287,13 @@ def query_server_with_retry server
     assert_match(/Unrecognized event format/, response.body)
     assert_equal "text/plain; charset=utf-8", response["Content-Type"]
   end
+
+  it "returns no content when an event server receives a get" do
+    response = query_server_with_retry event_server do
+      ::Net::HTTP.get_response URI("#{server_url}/")
+    end
+    refute_nil response
+    assert_equal "204", response.code
+    assert_nil response.body
+  end
 end