commit 11710c003493cde39b0db39b26be3a2e5c45b36d
Author: Justin Bull <me@justinbull.ca>
Date:   Fri Jan 24 08:49:14 2020 -0500

    Don't set 'Connection: close' by default if #started? is false
    
    This causes divergent and unexpected behaviour from other ways of using of
    Net::HTTP, and sending requests with 'Connection: close' causes a drain on
    server resources. Consumers of this Ruby class may unintentionally invoke it in
    such a way where they intend to send many many requests to a server, but
    unfortunately all of them closing the connection.
    
    For example, this causes 50 TIME_WAIT tcp connections on the server because the
    'Connection: close' header was set every time:
    
    ```
    net = Net::HTTP.new('example.com')
    50.times { net.get('/') } # causes many TIME_WAIT TCP sockets server-side
    ```
    
    Meanwhile neither of these invocations have this behaviour, which (for HTTP
    servers >= 1.1) benefit from the default behaviour of a keep-alive/persistent
    TCP connection:
    
    ```
    50.times { Net::HTTP.get(URI('http://example.com/')) } # no TIME_WAIT sockets
    
    net = Net::HTTP.new('example.com')
    50.times { net.start { net.get('/') } } # no TIME_WAIT sockets
    
    net = Net::HTTP.new('example.com')
    net.start
    50.times { net.get('/') } # no TIME_WAIT sockets
    net.finish
    ```
    
    Indeed using cURL, which one can assume represents one-off HTTP requests, does
    not set the header either way-- defering to the server which is keep-alive/
    persistence on 1.1 and greater.

diff --git a/lib/net/http.rb b/lib/net/http.rb
index de9963d18c..6b96bcc569 100644
--- a/lib/net/http.rb
+++ b/lib/net/http.rb
@@ -1233,6 +1233,9 @@ def edit_path(path)
     # +dest+ argument is obsolete.
     # It still works but you must not use it.
     #
+    # If called before the connection has started, this method will open the
+    # connection and finish it once complete.
+    #
     # This method never raises an exception.
     #
     #     response = http.get('/index.html')
@@ -1258,6 +1261,9 @@ def get(path, initheader = nil, dest = nil, &block) # :yield: +body_segment+
     #
     # This method returns a Net::HTTPResponse object.
     #
+    # If called before the connection has started, this method will open the
+    # connection and finish it once complete.
+    #
     # This method never raises an exception.
     #
     #     response = nil
@@ -1280,6 +1286,9 @@ def head(path, initheader = nil)
     # the socket.  Note that in this case, the returned response
     # object will *not* contain a (meaningful) body.
     #
+    # If called before the connection has started, this method will open the
+    # connection and finish it once complete.
+    #
     # +dest+ argument is obsolete.
     # It still works but you must not use it.
     #
@@ -1484,14 +1493,14 @@ def send_request(name, path, data = nil, header = nil)
     # the block can process it using HTTPResponse#read_body,
     # if desired.
     #
+    # If called before the connection has started, this method will open the
+    # connection and finish it once complete.
+    #
     # This method never raises Net::* exceptions.
     #
     def request(req, body = nil, &block)  # :yield: +response+
       unless started?
-        start {
-          req['connection'] ||= 'close'
-          return request(req, body, &block)
-        }
+        start { return request(req, body, &block) }
       end
       if proxy_user()
         req.proxy_basic_auth proxy_user(), proxy_pass() unless use_ssl?
@@ -1585,10 +1594,6 @@ def begin_transport(req)
         end
       end
 
-      if not req.response_body_permitted? and @close_on_empty_response
-        req['connection'] ||= 'close'
-      end
-
       req.update_uri address, port, use_ssl?
       req['host'] ||= addr_port()
     end