Implementing connection pooling for HTTP clients for Mediaflux::Http:…

…:Request (#517)

* Implementing connection pooling for HTTP clients for Mediaflux::Http::Request

* Ensuring that the HTTP client is shutdown at the level of the Mediaflux::Http::Request Class destructor

app/models/mediaflux/http/request.rb

@@ -2,6 +2,22 @@
 module Mediaflux
   module Http
     class Request
+      # This ensures that, once the Class is out of scope, the Net::HTTP::Persistent connection is closed
+      class << self
+        def self.create_finalizer
+          proc {
+            @http_client.shutdown unless @http_client.nil?
+          }
+        end
+
+        def initialize(**args)
+          super
+
+          finalizer = self.class.create_finalizer
+          ObjectSpace.define_finalizer(self, finalizer)
+        end
+      end
+
       # As this is an abstract class, this should be overridden to specify the Mediaflux API service
       def self.service
         raise(NotImplementedError, "#{self} is an abstract class, please override #{self}.service")
@@ -60,17 +76,25 @@ def self.default_xml_namespace_uri
         "http://tigerdata.princeton.edu"
       end
 
+      # Constructs and memoizes a new instance of the Net::HTTP::Persistent object at the level of the Class
+      # @returns http_client [Net::HTTP::Persistent] HTTP client for transmitting requests to the Mediaflux server API
+      def self.find_or_create_http_client
+        @http_client ||= begin
+                           @http_client = Net::HTTP::Persistent.new
+                           # https is not working correctly on td-meta1 we should not need this, but we do...
+                           @http_client.verify_mode = OpenSSL::SSL::VERIFY_NONE
+                           @http_client
+                         end
+      end
+
       attr_reader :session_token
 
       # Constructor
       # @param file [File] any upload file required for the POST request
       # @param session_token [String] the API token for the authenticated session
       # @param http_client [Net::HTTP::Persistent] HTTP client for transmitting requests to the Mediaflux server API
       def initialize(file: nil, session_token: nil, http_client: nil)
-        @http_client = http_client || Net::HTTP::Persistent.new
-        # https is not working correctly on td-meta1 we should not need this, but we do...
-        @http_client.verify_mode = OpenSSL::SSL::VERIFY_NONE
-
+        @http_client = http_client || self.class.find_or_create_http_client
         @file = file
         @session_token = session_token
       end
@@ -79,8 +103,6 @@ def initialize(file: nil, session_token: nil, http_client: nil)
       # @return [Net::HTTP]
       def resolve
         @http_response = @http_client.request self.class.uri, http_request
-        @http_client.shutdown
-        @http_response
       end
 
       # Determines whether or not the request has been resolved
@@ -127,12 +149,8 @@ def response_error
       delegate :to_s, to: :response_xml
 
       def xml_payload( name: self.class.service)
-        @payloads ||= {}
-        @payloads[name] ||= begin
-                        body = build_http_request_body(name: )
-                        body.to_xml
-                       end
-        @payloads[name]              
+        body = build_http_request_body(name: )
+        xml_payload = body.to_xml
       end
 
       private