Add Monitoring.http_address to expose Prometheus stats server (#993)

* Allow stats server to listen on TCP port

This commit allows the stats server to bind to the
port for outside network sources to use (Kubernetes Service).

* Add configuration item to bind monitoring address

PR revision: Instead of exposing the monitoring address we opt
to have users indicate via configuration option
`Monitoring.http_address` the server address to bind to.

CHANGELOG

@@ -5,6 +5,8 @@
 * Introduced Server.grr_binaries_readonly configuration option (set to False
   by default). When set to True, binaries and python hacks can't be overriden
   or deleted.
+* Added configuration option Monitoring.http_address to specify server address
+  of stats server. Default value will remain 127.0.0.1.
 
 ## 3.4.3.1
 

grr/core/grr_response_core/config/logging.py

@@ -48,8 +48,11 @@
         description="The email address to notify in an emergency.",
         default="grr-emergency@localhost"))
 
+config_lib.DEFINE_string("Monitoring.http_address", "::1",
+    "IP address for stats monitoring server.")
+
 config_lib.DEFINE_integer("Monitoring.http_port", 0,
-                          "Port for stats monitoring server.")
+    "Port for stats monitoring server.")
 
 config_lib.DEFINE_integer(
     "Monitoring.http_port_max", None,

grr/server/grr_response_server/base_stats_server.py

@@ -28,12 +28,14 @@ class BaseStatsServer(metaclass=abc.ABCMeta):
     port: The TCP port that the server should listen to.
   """
 
-  def __init__(self, port):
+  def __init__(self, address, port):
     """Instantiates a new BaseStatsServer.
 
     Args:
+      address: The IP address of the server to bind.
       port: The TCP port that the server should listen to.
     """
+    self.address = address
     self.port = port
 
   @abc.abstractmethod

grr/server/grr_response_server/stats_server.py

@@ -31,20 +31,21 @@ class IPv6HTTPServer(http_server.HTTPServer):
 class StatsServer(base_stats_server.BaseStatsServer):
   """A statistics server that exposes a minimal, custom /varz route."""
 
-  def __init__(self, port):
+  def __init__(self, address, port):
     """Instantiates a new StatsServer.
 
     Args:
+      address: The IP address of the server to bind.
       port: The TCP port that the server should listen to.
     """
-    super().__init__(port)
+    super().__init__(address, port)
     self._http_server = None
     self._server_thread = None
 
   def Start(self):
     """Start HTTPServer."""
     try:
-      self._http_server = IPv6HTTPServer(("::1", self.port), StatsServerHandler)
+      self._http_server = IPv6HTTPServer((self.address, self.port), StatsServerHandler)
     except socket.error as e:
       if e.errno == errno.EADDRINUSE:
         raise base_stats_server.PortInUseError(self.port)
@@ -72,6 +73,8 @@ def InitializeStatsServerOnce():
   a default one.
   """
 
+  address = config.CONFIG["Monitoring.http_address"]
+
   # Figure out which port to use.
   port = config.CONFIG["Monitoring.http_port"]
   if not port:
@@ -99,8 +102,8 @@ def InitializeStatsServerOnce():
 
   for port in range(port, max_port + 1):
     try:
-      logging.info("Starting monitoring server on port %d.", port)
-      server_obj = server_cls(port)
+      logging.info("Starting monitoring server on address %s and port %d.", address, port)
+      server_obj = server_cls(address, port)
       server_obj.Start()
       return
     except base_stats_server.PortInUseError as e:

grr/server/grr_response_server/stats_server_test.py

@@ -23,7 +23,7 @@ class StatsServerTest(base_stats_server_test.StatsServerTestMixin,
                       test_lib.GRRBaseTest):
 
   def setUpStatsServer(self, port):
-    return stats_server.StatsServer(port)
+    return stats_server.StatsServer("::1", port)
 
   def testPrometheusIntegration(self):
     registry = prometheus_client.CollectorRegistry(auto_describe=True)
@@ -38,7 +38,7 @@ def testPrometheusIntegration(self):
 
     with mock.patch.object(stats_server.StatsServerHandler, "registry",
                            registry):
-      server = stats_server.StatsServer(port)
+      server = stats_server.StatsServer("::1", port)
       server.Start()
       self.addCleanup(server.Stop)
       res = requests.get("http://[::1]:{}/metrics".format(port))