Add rack.after_reply functionality

BlakeWilliams · Eric Wong · commit 673c15e3f020 · 2020-12-09T21:58:33.000Z
This adds `rack.after_reply` functionality which allows rack middleware
to pass lambdas that will be executed after the client connection has
been closed.

This was driven by a need to perform actions in a request that shouldn't
block the request from completing but also don't make sense as
background jobs.

There is prior art of this being supported found in a few gems, as well
as this functionality existing in other rack based servers (e.g. Puma).

[ew: check if `env' is set in ensure statement]

Acked-by: Eric Wong &lt;e@80x24.org&gt;
diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb
@@ -629,6 +629,8 @@ def process_client(client)
       end
     end
 
+    env["rack.after_reply"] = []
+
     status, headers, body = @app.call(env)
 
     begin
@@ -651,6 +653,8 @@ def process_client(client)
     end
   rescue => e
     handle_error(client, e)
+  ensure
+    env["rack.after_reply"].each(&:call) if env
   end
 
   def nuke_listeners!(readers)
diff --git a/test/unit/test_server.rb b/test/unit/test_server.rb
@@ -34,6 +34,24 @@ def call(env)
   end
 end
 
+class TestRackAfterReply
+  def initialize
+    @called = false
+  end
+
+  def call(env)
+    while env['rack.input'].read(4096)
+    end
+
+    env["rack.after_reply"] << -> { @called = true }
+
+    [200, { 'Content-Type' => 'text/plain' }, ["after_reply_called: #{@called}"]]
+  rescue Unicorn::ClientShutdown, Unicorn::HttpParserError => e
+    $stderr.syswrite("#{e.class}: #{e.message} #{e.backtrace.empty?}\n")
+    raise e
+  end
+end
+
 class WebServerTest < Test::Unit::TestCase
 
   def setup
@@ -114,6 +132,32 @@ def test_early_hints
     assert_match %r{^HTTP/1.[01] 200\b}, responses
   end
 
+  def test_after_reply
+    teardown
+
+    redirect_test_io do
+      @server = HttpServer.new(TestRackAfterReply.new,
+                               :listeners => [ "127.0.0.1:#@port"])
+      @server.start
+    end
+
+    sock = TCPSocket.new('127.0.0.1', @port)
+    sock.syswrite("GET / HTTP/1.0\r\n\r\n")
+
+    responses = sock.read(4096)
+    assert_match %r{\AHTTP/1.[01] 200\b}, responses
+    assert_match %r{^after_reply_called: false}, responses
+
+    sock = TCPSocket.new('127.0.0.1', @port)
+    sock.syswrite("GET / HTTP/1.0\r\n\r\n")
+
+    responses = sock.read(4096)
+    assert_match %r{\AHTTP/1.[01] 200\b}, responses
+    assert_match %r{^after_reply_called: true}, responses
+
+    sock.close
+  end
+
   def test_broken_app
     teardown
     app = lambda { |env| raise RuntimeError, "hello" }
