Fixed: Applications or middleware that didn't call the WSGI

start_response function before returning an iterator weren't handled
properly.

src/zc/resumelb/README.txt

@@ -242,6 +242,10 @@ maintaining ZooKeeper trees.
 Change History
 ==============
 
+- Fixed: Applications or middleware that didn't call the WSGI
+  start_response function before returning an iterator weren't handled
+  properly.
+
 0.7.3 (2014-06-04)
 ------------------
 

src/zc/resumelb/tests.py

@@ -25,6 +25,7 @@
 import os
 import pprint
 import re
+import sys
 import time
 import traceback
 import unittest
@@ -89,6 +90,16 @@ def gsleep(dur=0):
 def app():
     return bobo.Application(bobo_resources=__name__)
 
+def generator_app(env, start):
+    start('200 OK', [('Content-type', 'text/plain'), ('Content-length', '2')])
+    yield 'h'
+    yield 'i'
+
+def generator_app0(env, start):
+    start('200 OK', [('Content-type', 'text/plain'), ('Content-length', '0')])
+    if False:
+        yield 'hi'
+
 #
 ###############################################################################
 
@@ -122,7 +133,7 @@ def print_response(worker_socket, rno, size_only=False):
             if size_only:
                 size += len(data)
             else:
-                print data,
+                sys.stdout.write(data)
         else:
             break
     if size_only:
@@ -401,6 +412,31 @@ def dont_reset_worker_backlogs_if_they_already_have_them():
     9
     """
 
+def generator_apps():
+    r"""PEP 333 allows WSGI apps to be implemented as generators.
+
+    This means that start_response may not becalled until after an app
+    has returned it's iterator (but before the first value is yielded.
+
+    Let's make sure workers handle this correctly.
+
+    >>> worker = zc.resumelb.worker.Worker(
+    ...   zc.resumelb.tests.generator_app, ('127.0.0.1', 0))
+    >>> worker_socket = gevent.socket.create_connection(worker.addr)
+    >>> from zc.resumelb.util import read_message, write_message
+    >>> read_message(worker_socket)
+    (0, {})
+    >>> env = newenv('', '/')
+    >>> write_message(worker_socket, 1, env, '')
+    >>> print_response(worker_socket, 1)
+    1 200 OK
+    Content-length: 2
+    Content-type: text/plain
+    <BLANKLINE>
+    hi
+
+    """
+
 def test_classifier(env):
     return "yup, it's a test"
 

src/zc/resumelb/worker.py

@@ -68,14 +68,25 @@ def start_response(status, headers, exc_info=None):
                 response[0] = (status, headers)
 
             try:
-                body = app(env, start_response)
+                body = iter(app(env, start_response))
+                try:
+                    first = body.next()
+                except StopIteration:
+                    first = ''
+                    if hasattr(body, 'close'):
+                        body.close()
+                    body = ()
             except Exception:
                 error("Uncaught application exception for %s" % trno)
                 import webob
-                body = webob.Response(
-                    'A system error occurred', status=500)(env, start_response)
+                body = iter(
+                    webob.Response(
+                        'A system error occurred', status=500
+                        )(env, start_response)
+                    )
+                first = body.next()
 
-            return response[0], body
+            return response[0], first, body
 
         if tracelog:
             info = logging.getLogger(tracelog).info
@@ -101,7 +112,7 @@ def log(self, msg=None, code='-'):
             def call_app_w_tracelog(trno, env):
                 log(trno, 'C')
                 env[tracelog_key] = ApplicationTraceLog(trno)
-                response, body = call_app(trno, env)
+                response, first, body = call_app(trno, env)
                 content_length = [v for (h, v) in response[1]
                                   if h.lower() == 'content-length']
                 content_length = content_length[-1] if content_length else '?'
@@ -114,7 +125,7 @@ def body_iter():
                         if hasattr(body, 'close'):
                             body.close()
                         log(trno, 'E')
-                return response, body_iter()
+                return response, first, body_iter()
 
             if threads:
                 def call_app_w_threads(trno, env):
@@ -232,12 +243,16 @@ def handle(self, conn, rno, get, env):
             if tracelog:
                 tracelog(trno, 'I', env.get('CONTENT_LENGTH') or '0')
 
-            response, body = self.call_app(trno, env)
+            response, first, body = self.call_app(trno, env)
             try:
                 requests = conn.readers
                 if rno not in requests:
                     return # cancelled
                 conn.put((rno, response))
+                if rno not in requests:
+                    return # cancelled
+                if first:
+                    conn.put((rno, first))
                 for data in body:
                     if rno not in requests:
                         return # cancelled