From 10bb2592484f529cf5a9d926d0546c9bae625aea Mon Sep 17 00:00:00 2001
From: Bernhard Ehlers <none@bernhard-ehlers.de>
Date: Sun, 19 Apr 2020 20:42:46 +0200
Subject: [PATCH] Implement a minimum interval between cpu_percent() calls.
 Fixes #1738

---
 .../handlers/api/compute/project_handler.py   |  3 +-
 .../handlers/api/compute/server_handler.py    |  3 +-
 gns3server/notification_queue.py              |  4 +-
 gns3server/utils/cpu_percent.py               | 48 +++++++++++++++++++
 4 files changed, 55 insertions(+), 3 deletions(-)
 create mode 100644 gns3server/utils/cpu_percent.py

diff --git a/gns3server/handlers/api/compute/project_handler.py b/gns3server/handlers/api/compute/project_handler.py
index fed82210..d8eb0e11 100644
--- a/gns3server/handlers/api/compute/project_handler.py
+++ b/gns3server/handlers/api/compute/project_handler.py
@@ -25,6 +25,7 @@ import tempfile
 from gns3server.web.route import Route
 from gns3server.compute.project_manager import ProjectManager
 from gns3server.compute import MODULES
+from gns3server.utils.cpu_percent import CpuPercent
 
 from gns3server.schemas.project import (
     PROJECT_OBJECT_SCHEMA,
@@ -208,7 +209,7 @@ class ProjectHandler:
         """
         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["cpu_usage_percent"] = CpuPercent.get(interval=None)
         stats["memory_usage_percent"] = psutil.virtual_memory().percent
         return {"action": "ping", "event": stats}
 
diff --git a/gns3server/handlers/api/compute/server_handler.py b/gns3server/handlers/api/compute/server_handler.py
index 4f043f95..c158a55d 100644
--- a/gns3server/handlers/api/compute/server_handler.py
+++ b/gns3server/handlers/api/compute/server_handler.py
@@ -23,6 +23,7 @@ from gns3server.config import Config
 from gns3server.schemas.version import VERSION_SCHEMA
 from gns3server.schemas.server_statistics import SERVER_STATISTICS_SCHEMA
 from gns3server.compute.port_manager import PortManager
+from gns3server.utils.cpu_percent import CpuPercent
 from gns3server.version import __version__
 from aiohttp.web import HTTPConflict
 from psutil._common import bytes2human
@@ -57,7 +58,7 @@ class ServerHandler:
             swap_total = psutil.swap_memory().total
             swap_free = psutil.swap_memory().free
             swap_used = psutil.swap_memory().used
-            cpu_percent = int(psutil.cpu_percent())
+            cpu_percent = int(CpuPercent.get())
             load_average_percent = [int(x / psutil.cpu_count() * 100) for x in psutil.getloadavg()]
             memory_percent = int(psutil.virtual_memory().percent)
             swap_percent = int(psutil.swap_memory().percent)
diff --git a/gns3server/notification_queue.py b/gns3server/notification_queue.py
index a3eab916..d81a2a2b 100644
--- a/gns3server/notification_queue.py
+++ b/gns3server/notification_queue.py
@@ -19,6 +19,8 @@ import asyncio
 import json
 import psutil
 
+from gns3server.utils.cpu_percent import CpuPercent
+
 
 class NotificationQueue(asyncio.Queue):
     """
@@ -51,7 +53,7 @@ class NotificationQueue(asyncio.Queue):
         """
         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["cpu_usage_percent"] = CpuPercent.get(interval=None)
         msg["memory_usage_percent"] = psutil.virtual_memory().percent
         return msg
 
diff --git a/gns3server/utils/cpu_percent.py b/gns3server/utils/cpu_percent.py
new file mode 100644
index 00000000..441b7efb
--- /dev/null
+++ b/gns3server/utils/cpu_percent.py
@@ -0,0 +1,48 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2020 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 CpuPercent:
+    """
+    Ensures a minumum interval between two cpu_percent() calls
+    """
+
+    _last_measurement = None		# time of last measurement
+    _last_cpu_percent = 0.0		# last cpu_percent
+
+    @classmethod
+    def get(cls, interval=None):
+        """
+        Get CPU utilization as a percentage
+
+        :returns: float
+        """
+
+        if interval:
+            cls._last_cpu_percent = psutil.cpu_percent(interval=interval)
+            cls._last_measurement = time.monotonic()
+        else:
+            cur_time = time.monotonic()
+            if cls._last_measurement is None or \
+               (cur_time - cls._last_measurement) >= 1.9:
+                cls._last_cpu_percent = psutil.cpu_percent(interval=None)
+                cls._last_measurement = cur_time
+
+        return cls._last_cpu_percent