From 57909fb76dd0bcf95bed94ec41933ec85afda885 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Tue, 4 May 2010 13:23:38 -0700
Subject: eventmachine: add app.deferred?(env) support as middleware

Merb (and possibly other) frameworks that support conditionally
deferred app dispatch can now use it just like Ebb and Thin.

http://brainspl.at/articles/2008/04/18/deferred-requests-with-merb-ebb-and-thin
---
 lib/rainbows/event_machine.rb | 23 ++++++++++++++++++++++
 t/app_deferred.ru             | 22 +++++++++++++++++++++
 t/t0700-app-deferred.sh       | 45 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 90 insertions(+)
 create mode 100644 t/app_deferred.ru
 create mode 100755 t/t0700-app-deferred.sh

diff --git a/lib/rainbows/event_machine.rb b/lib/rainbows/event_machine.rb
index 3dd329a..4b852c9 100644
--- a/lib/rainbows/event_machine.rb
+++ b/lib/rainbows/event_machine.rb
@@ -34,6 +34,11 @@ module Rainbows
   # which allows each request to run inside its own \Fiber after
   # all request processing is complete.
   #
+  # Merb (and other frameworks/apps) supporting +deferred?+ execution as
+  # documented at http://brainspl.at/articles/2008/04/18/deferred-requests-with-merb-ebb-and-thin
+  # will also get the ability to conditionally defer request processing
+  # to a separate thread.
+  #
   # This model does not implement as streaming "rack.input" which allows
   # the Rack application to process data as it arrives.  This means
   # "rack.input" will be fully buffered in memory or to a temporary file
@@ -200,11 +205,29 @@ module Rainbows
       end
     end
 
+    # Middleware that will run the app dispatch in a separate thread.
+    # This middleware is automatically loaded by Rainbows! when using
+    # EventMachine and if the app responds to the +deferred?+ method.
+    class TryDefer < Struct.new(:app)
+      def call(env)
+        if app.deferred?(env)
+          EM.defer(proc { catch(:async) { app.call(env) } },
+                   env[EvCore::ASYNC_CALLBACK])
+          # all of the async/deferred stuff breaks Rack::Lint :<
+          nil
+        else
+          app.call(env)
+        end
+      end
+    end
+
     # runs inside each forked worker, this sits around and waits
     # for connections and doesn't die until the parent dies (or is
     # given a INT, QUIT, or TERM signal)
     def worker_loop(worker)
       init_worker_process(worker)
+      G.server.app.respond_to?(:deferred?) and
+        G.server.app = TryDefer[G.server.app]
 
       # enable them both, should be non-fatal if not supported
       EM.epoll
diff --git a/t/app_deferred.ru b/t/app_deferred.ru
new file mode 100644
index 0000000..179ac95
--- /dev/null
+++ b/t/app_deferred.ru
@@ -0,0 +1,22 @@
+#\-E none
+# can't use non-compatible middleware that doesn't pass "deferered?" calls
+#
+# used for testing deferred actions for Merb and possibly other frameworks
+# ref: http://brainspl.at/articles/2008/04/18/deferred-requests-with-merb-ebb-and-thin
+
+class DeferredApp < Struct.new(:app)
+  def deferred?(env)
+    env["PATH_INFO"] == "/deferred"
+  end
+
+  def call(env)
+    body = "#{Thread.current.inspect}\n"
+    headers = {
+      "Content-Type" => "text/plain",
+      "Content-Length" => body.size.to_s,
+    }
+    [ 200, headers, [ body ] ]
+  end
+end
+
+run DeferredApp.new
diff --git a/t/t0700-app-deferred.sh b/t/t0700-app-deferred.sh
new file mode 100755
index 0000000..8d4b4e2
--- /dev/null
+++ b/t/t0700-app-deferred.sh
@@ -0,0 +1,45 @@
+#!/bin/sh
+. ./test-lib.sh
+case $model in
+EventMachine) ;;
+*)
+	t_info "skipping $T since it's not compatible with $model"
+	exit 0
+	;;
+esac
+
+t_plan 5 "basic test for app.deferred? usage"
+
+CONFIG_RU=app_deferred.ru
+
+t_begin "setup and start" && {
+	rainbows_setup
+	rtmpfiles deferred_err deferred_out sync_err sync_out
+	rainbows -D -c $unicorn_config $CONFIG_RU
+	rainbows_wait_start
+}
+
+t_begin "synchronous requests run in the same thread" && {
+	curl --no-buffer -sSf http://$listen/ >> $sync_out 2>> $sync_err &
+	curl --no-buffer -sSf http://$listen/ >> $sync_out 2>> $sync_err &
+	curl --no-buffer -sSf http://$listen/ >> $sync_out 2>> $sync_err &
+	wait
+	test ! -s $sync_err
+	test 3 -eq "$(wc -l < $sync_out)"
+	test 1 -eq "$(uniq < $sync_out | wc -l)"
+}
+
+t_begin "deferred requests run in a different thread" && {
+	curl -sSf http://$listen/deferred >> $deferred_out 2>> $deferred_err
+	test ! -s $deferred_err
+	sync_thread="$(uniq < $sync_out)"
+	test x"$(uniq < $deferred_out)" != x"$sync_thread"
+}
+
+t_begin "termination signal sent" && {
+	kill $rainbows_pid
+}
+
+t_begin "no errors in stderr" && check_stderr
+
+t_done
-- 
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