fire EM connection error at next tick

this simplifies the API

A problem is that the error callback should fire before setting it up.
Hence, if we are in a fiber, and if we expected to yield after setting up
callbacks/errbacks. We would resume the fiber before yielding it,
generating a double resume error.
We work around this problem by calling :close/:on_error at next tick.
Hence, the errback's fiber will predictably be EM's reactor fiber.

examples/fibered-http.rb

@@ -33,6 +33,10 @@ def async_fetch(url)
     puts "Setting up HTTP request #2"
     data = async_fetch('http://www.yahoo.com/')
     puts "Fetched page #2: #{data.response_header.status}"
+
+    puts "Setting up HTTP request #3"
+    data = async_fetch('http://non-existing.domain/')
+    puts "Fetched page #3: #{data.response_header.status}"
 
     EventMachine.stop
   }.resume

lib/em-http/http_connection.rb

@@ -64,17 +64,21 @@ def activate_connection(client)
       rescue EventMachine::ConnectionError => e
         #
         # Currently, this can only fire on initial connection setup
-        # since #connect is a synchronous method. Hence, rescue the
-        # exception, and return a failed deferred which will immediately
-        # fail any client request.
+        # since #connect is a synchronous method. Hence, rescue the exception,
+        # and return a failed deferred which fail any client request at next
+        # tick.  We fail at next tick to keep a consistent API when the newly
+        # created HttpClient is failed. This approach has the advantage to
+        # remove a state check of @deferred_status after creating a new
+        # HttpRequest. The drawback is that users may setup a callback which we
+        # know won't be used.
         #
         # Once there is async-DNS, then we'll iterate over the outstanding
         # client requests and fail them in order.
         #
         # Net outcome: failed connection will invoke the same ConnectionError
         # message on the connection deferred, and on the client deferred.
         #
-        client.close(e.message)
+        EM.next_tick{client.close(e.message)}
       end
     end
 

spec/client_fiber_spec.rb

@@ -0,0 +1,21 @@
+require 'helper'
+require 'fiber'
+
+describe EventMachine::HttpRequest do
+  context "with fibers" do
+    it "should be transparent to connexion errors" do
+      EventMachine.run do
+        Fiber.new do
+          f = Fiber.current
+          http = EventMachine::HttpRequest.new('http://non-existing.domain/').get
+          http.callback {failed(http)}
+          http.errback {f.resume}
+          Fiber.yield
+          EventMachine.stop
+        end.resume
+      end
+    end
+  end
+end
+
+