commit bc41d1c23137900ffef33ef0c08bc3a96736e652
author Prathmesh Prabhu <pprabhu@chromium.org> Thu Jul 12 17:50:49 2018 -0700
committer chrome-bot <chrome-bot@chromium.org> Wed Jul 18 01:40:06 2018 -0700
tree 573a4e703f537feb30b76768bc254a0c9435a930
parent f2e818c88f240da22f8cd9aae005e35f39aa90fe

rpm: Extract _queue_once()

in preparation for replacement RPCs for queue_requests()

BUG=chromium:863217
TEST=Locally run rpmserver and ensure behaviour matches
     prod for both DUT and servo.

Change-Id: Ib1d37df1ef99c9889be10f2f40cbd3a1f09ac0f7
Reviewed-on: https://chromium-review.googlesource.com/1136025
Commit-Ready: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>

site_utils/rpm_control_system/frontend_server.py

diff --git a/site_utils/rpm_control_system/frontend_server.py b/site_utils/rpm_control_system/frontend_server.py
index 794c2b6..805a53f 100755
--- a/site_utils/rpm_control_system/frontend_server.py
+++ b/site_utils/rpm_control_system/frontend_server.py
@@ -44,6 +44,10 @@
 LRU_SIZE = rpm_config.getint('RPM_INFRASTRUCTURE', 'lru_size')
 
 
+class DispatcherDownException(Exception):
+    """Raised when a particular RPMDispatcher is down."""
+
+
 class RPMFrontendServer(object):
     """
     This class is the frontend server of the RPM Infrastructure. All clients
@@ -102,8 +106,8 @@
 
         This call will block until the forwarded request returns.
 
-        @param device_hostname: Hostname of the device whose power state we want to
-                             change.
+        @param device_hostname: Hostname of the device whose power state we want
+                                to change.
         @param new_state: [ON, OFF, CYCLE] State to which we want to set the
                           device's outlet to.
 
@@ -124,6 +128,15 @@
         logging.info('Received request to set device: %s to state: %s',
                      device_hostname, new_state)
         powerunit_info = self._get_powerunit_info(device_hostname)
+        try:
+            return self._queue_once(powerunit_info, new_state)
+        except DispatcherDownException:
+            # Retry forwarding the request.
+            return self.queue_request(device_hostname, new_state)
+
+
+    def _queue_once(self, powerunit_info, new_state):
+        """Queue one request to the dispatcher."""
         dispatcher_uri = self._get_dispatcher(powerunit_info)
         if not dispatcher_uri:
             # No dispatchers available.
@@ -146,8 +159,7 @@
             logging.error('Unregistering %s due to error. Recommend resetting '
                           'that dispatch server.', dispatcher_uri)
             self.unregister_dispatcher(dispatcher_uri)
-            # Retry forwarding the request.
-            return self.queue_request(device_hostname, new_state)
+            raise DispatcherDownException(dispatcher_uri)
 
 
     def is_network_infrastructure_down(self):