Support server node weights.

Support setting a weighting value for each node that will determine
the proportion of load balancing requests that it receives in relation
to the other defined servers and their weights.

Also adds a file describing the worker JSON message versioning.

Fixes bug 1117349

Change-Id: Ie1460c165f03b0523ee28d864b74ea9e5858b256

WORKER_MSG_FMT_VERSIONS

@@ -0,0 +1,29 @@
+# The worker versions the JSON messages that it comprehends. This version
+# is used for the DISCOVER message that can be sent by the API server. E.g.,
+#
+#      { 'hpcs_action': 'DISCOVER' }
+#
+# And an example response from the worker:
+#
+#      {
+#        'hpcs_action': 'DISCOVER',
+#        'version': '1.0',
+#        'hpcs_response': 'PASS'
+#      }
+#
+# The version number is set in the method:
+#
+#      libra.worker.controller._action_discover()
+#
+# Version format is: <major>.<minor>
+#
+# A change to the <minor> value means that a change has been made, but
+# we are still backwards compatible. A change to the <major> value means
+# a significant change was made and we are no longer compatible with older
+# versions.
+
+[Version 1.1]
+  - Accept node 'weight' values.
+
+[Version 1.0]
+  - Initial version.

libra/worker/controller.py

@@ -75,7 +75,7 @@ class LBaaSController(object):
         version this worker supports.
         """
         # Version of the JSON message format that this worker understands.
-        msg_fmt_version = "1.0"
+        msg_fmt_version = "1.1"
         self.msg['version'] = msg_fmt_version
         self.msg[self.RESPONSE_FIELD] = self.RESPONSE_SUCCESS
         return self.msg

libra/worker/drivers/base.py

@@ -48,7 +48,7 @@ class LoadBalancerDriver(object):
         """ Add a supported protocol and listening port for the instance. """
         raise NotImplementedError()
 
-    def add_server(self, protocol, host, port):
+    def add_server(self, protocol, host, port, weight):
         """ Add a server for the protocol for which we will proxy. """
         raise NotImplementedError()
 

libra/worker/drivers/haproxy/driver.py

@@ -92,9 +92,9 @@ class HAProxyDriver(LoadBalancerDriver):
             if proto == 'http':
                 output.append('    cookie SERVERID rewrite')
 
-            for (addr, port) in protocfg['servers']:
+            for (addr, port, weight) in protocfg['servers']:
-                output.append('    server server%d %s:%s' %
+                output.append('    server server%d %s:%s weight %d' %
-                              (serv_num, addr, port))
+                              (serv_num, addr, port, weight))
                 serv_num += 1
 
         return '\n'.join(output) + '\n'
@@ -123,11 +123,20 @@ class HAProxyDriver(LoadBalancerDriver):
         else:
             self._bind(proto, '0.0.0.0', port)
 
-    def add_server(self, protocol, host, port):
+    def add_server(self, protocol, host, port, weight=1):
         proto = protocol.lower()
+
+        try:
+            weight = int(weight)
+        except ValueError:
+            raise Exception("Non-integer 'weight' value: '%s'" % weight)
+
+        if weight > 256:
+            raise Exception("Server 'weight' %d exceeds max of 256" % weight)
+
         if 'servers' not in self._config[proto]:
             self._config[proto]['servers'] = []
-        self._config[proto]['servers'].append((host, port))
+        self._config[proto]['servers'].append((host, port, weight))
 
     def set_algorithm(self, protocol, algo):
         proto = protocol.lower()

tests/test_haproxy_driver.py

@@ -41,8 +41,8 @@ class TestHAProxyDriver(testtools.TestCase):
         self.assertIn('servers', self.driver._config[proto])
         servers = self.driver._config[proto]['servers']
         self.assertEqual(len(servers), 2)
-        self.assertEqual(servers[0], ('1.2.3.4', 7777))
+        self.assertEqual(servers[0], ('1.2.3.4', 7777, 1))
-        self.assertEqual(servers[1], ('5.6.7.8', 8888))
+        self.assertEqual(servers[1], ('5.6.7.8', 8888, 1))
 
     def testSetAlgorithm(self):
         """ Test the HAProxy set_algorithm() method """
@@ -56,3 +56,35 @@ class TestHAProxyDriver(testtools.TestCase):
         self.assertEqual(self.driver._config[proto]['algorithm'], 'leastconn')
         e = self.assertRaises(Exception, self.driver.set_algorithm, proto, 99)
         self.assertEqual("Invalid algorithm: http", e.message)
+
+    def testServerWeightInt(self):
+        """ Test setting integer server weights """
+        proto = 'http'
+        self.driver.add_protocol(proto, None)
+        self.driver.add_server(proto, '1.2.3.4', 7777, 10)
+        servers = self.driver._config[proto]['servers']
+        self.assertEqual(len(servers), 1)
+        self.assertEqual(servers[0], ('1.2.3.4', 7777, 10))
+
+    def testServerWeightStr(self):
+        """ Test setting string server weights """
+        proto = 'http'
+        self.driver.add_protocol(proto, None)
+        self.driver.add_server(proto, '1.2.3.4', 7777, "20")
+        servers = self.driver._config[proto]['servers']
+        self.assertEqual(len(servers), 1)
+        self.assertEqual(servers[0], ('1.2.3.4', 7777, 20))
+
+    def testServerWeightInvalid(self):
+        """ Test setting string server weights """
+        proto = 'http'
+        self.driver.add_protocol(proto, None)
+        e = self.assertRaises(
+                Exception,
+                self.driver.add_server, proto, '1.2.3.4', 7777, 257)
+        self.assertEqual("Server 'weight' 257 exceeds max of 256", e.message)
+
+        e = self.assertRaises(
+                Exception,
+                self.driver.add_server, proto, '1.2.3.4', 7777, "abc")
+        self.assertEqual("Non-integer 'weight' value: 'abc'", e.message)

tools/test-requires

@@ -1,6 +1,8 @@
+fixtures>=0.3.12
 pep8
 mock
 httplib2
+python-subunit
 sphinx>=1.1.2
 testrepository>=0.0.8
 testtools>=0.9.22