Obtain a session with a pre-request

This fix the problem explained in the previous commit:
When we run a job, we don't wait for the answer. So when we don't have
any cookie yet, we send a GET on a very fast controller route which will
return a cookie, used for all the subsequents calls to runjob.

This effectively prevent to create one session file per job.

It still needs intensive testing.

Fixes OCA#44

queue_job/controllers/main.py

@@ -64,6 +64,18 @@ def _try_perform_job(self, env, job):
         http.request.env.cr.commit()
         _logger.debug('%s done', job)
 
+    @http.route('/queue_job/session', type='http', auth="none")
+    def session(self):
+        """ Used by the jobrunner to spawn a session
+
+        The queue jobrunner uses anonymous sessions when it calls
+        ``/queue_job/runjob``.  To avoid having thousands of anonymous
+        sessions, before running jobs, it creates a ``requests.Session``
+        and does a GET on ``/queue_job/session``, providing it a cookie
+        which will be used for subsequent calls to runjob.
+        """
+        return ''
+
     @http.route('/queue_job/runjob', type='http', auth='none')
     def runjob(self, db, job_uuid, **kw):
         http.request.session.db = db

queue_job/jobrunner/runner.py

@@ -149,6 +149,9 @@
 _logger = logging.getLogger(__name__)
 
 
+session = requests.Session()
+
+
 # Unfortunately, it is not possible to extend the Odoo
 # server command line arguments, so we resort to environment variables
 # to configure the runner (channels mostly).
@@ -180,6 +183,13 @@ def _odoo_now():
 
 
 def _async_http_get(scheme, host, port, user, password, db_name, job_uuid):
+    if not session.cookies:
+        # obtain an anonymous session
+        _logger.info("obtaining an anonymous session for the job runner")
+        url = ('http://localhost:%s/queue_job/session' % (port,))
+        response = session.get(url, timeout=30)
+        response.raise_for_status()
+
     # Method to set failed job (due to timeout, etc) as pending,
     # to avoid keeping it as enqueued.
     def set_job_pending():
@@ -215,6 +225,7 @@ def urlopen():
             set_job_pending()
         except:
             _logger.exception("exception in GET %s", url)
+            session.cookies.clear()
             set_job_pending()
     thread = threading.Thread(target=urlopen)
     thread.daemon = True