Implement a minimum interval between psutil calls. Fixes #2262

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