From 3a09bd43dc1514f285f6fd69317756ccd4068611 Mon Sep 17 00:00:00 2001
From: Bernhard Ehlers <be@bernhard-ehlers.de>
Date: Tue, 13 Feb 2018 11:31:04 +0100
Subject: [PATCH] Implement a minimum interval between psutil calls. Fixes
 #2262

---
 .../handlers/api/compute/project_handler.py   |  8 +--
 gns3server/notification_queue.py              | 17 ++-----
 gns3server/utils/ping_stats.py                | 50 +++++++++++++++++++
 3 files changed, 56 insertions(+), 19 deletions(-)
 create mode 100644 gns3server/utils/ping_stats.py

diff --git a/gns3server/handlers/api/compute/project_handler.py b/gns3server/handlers/api/compute/project_handler.py
index 73662ca7..a7d8f760 100644
--- a/gns3server/handlers/api/compute/project_handler.py
+++ b/gns3server/handlers/api/compute/project_handler.py
@@ -19,12 +19,12 @@ import aiohttp
 import asyncio
 import json
 import os
-import psutil
 import tempfile
 
 from gns3server.web.route import Route
 from gns3server.compute.project_manager import ProjectManager
 from gns3server.compute import MODULES
+from gns3server.utils.ping_stats import PingStats
 
 from gns3server.schemas.project import (
     PROJECT_OBJECT_SCHEMA,
@@ -186,11 +186,7 @@ class ProjectHandler:
 
         :returns: hash
         """
-        stats = {}
-        # Non blocking call in order to get cpu usage. First call will return 0
-        stats["cpu_usage_percent"] = psutil.cpu_percent(interval=None)
-        stats["memory_usage_percent"] = psutil.virtual_memory().percent
-        return {"action": "ping", "event": stats}
+        return {"action": "ping", "event": PingStats.get()}
 
     @Route.get(
         r"/projects/{project_id}/files",
diff --git a/gns3server/notification_queue.py b/gns3server/notification_queue.py
index 88cbaec3..2412d5cb 100644
--- a/gns3server/notification_queue.py
+++ b/gns3server/notification_queue.py
@@ -17,7 +17,8 @@
 
 import asyncio
 import json
-import psutil
+
+from gns3server.utils.ping_stats import PingStats
 
 
 class NotificationQueue(asyncio.Queue):
@@ -38,24 +39,14 @@ class NotificationQueue(asyncio.Queue):
         # At first get we return a ping so the client immediately receives data
         if self._first:
             self._first = False
-            return ("ping", self._getPing(), {})
+            return ("ping", PingStats.get(), {})
 
         try:
             (action, msg, kwargs) = yield from asyncio.wait_for(super().get(), timeout)
         except asyncio.futures.TimeoutError:
-            return ("ping", self._getPing(), {})
+            return ("ping", PingStats.get(), {})
         return (action, msg, kwargs)
 
-    def _getPing(self):
-        """
-        Return the content of the ping notification
-        """
-        msg = {}
-        # Non blocking call in order to get cpu usage. First call will return 0
-        msg["cpu_usage_percent"] = psutil.cpu_percent(interval=None)
-        msg["memory_usage_percent"] = psutil.virtual_memory().percent
-        return msg
-
     @asyncio.coroutine
     def get_json(self, timeout):
         """
diff --git a/gns3server/utils/ping_stats.py b/gns3server/utils/ping_stats.py
new file mode 100644
index 00000000..3252f9c2
--- /dev/null
+++ b/gns3server/utils/ping_stats.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2018 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import psutil
+import time
+
+
+class PingStats:
+    """
+    Ping messages are regularly sent to the client to keep the connection open.
+    We send with it some information about server load.
+    """
+
+    _last_measurement = 0.0		# time of last measurement
+    _last_cpu_percent = 0.0		# last cpu_percent
+    _last_mem_percent = 0.0		# last virtual_memory().percent
+
+    @classmethod
+    def get(cls):
+        """
+        Get ping statistics
+
+        :returns: hash
+        """
+        stats = {}
+        cur_time = time.time()
+        # minimum interval for getting CPU and memory statistics
+        if cur_time < cls._last_measurement or \
+           cur_time > cls._last_measurement + 1.9:
+            cls._last_measurement = cur_time
+            # Non blocking call to get cpu usage. First call will return 0
+            cls._last_cpu_percent = psutil.cpu_percent(interval=None)
+            cls._last_mem_percent = psutil.virtual_memory().percent
+        stats["cpu_usage_percent"] = cls._last_cpu_percent
+        stats["memory_usage_percent"] = cls._last_mem_percent
+        return stats