Add ProcessMonitor class

refs: #3641

Change-Id: I88bf88081038360170532d3c4bf11f1bc2650bda
diff --git a/ndn/process_monitor.py b/ndn/process_monitor.py
new file mode 100644
index 0000000..2392aff
--- /dev/null
+++ b/ndn/process_monitor.py
@@ -0,0 +1,53 @@
+# -*- Mode:python; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+#
+# Copyright (C) 2015-2016, The University of Memphis,
+#                          Arizona Board of Regents,
+#                          Regents of the University of California.
+#
+# This file is part of Mini-NDN.
+# See AUTHORS.md for a complete list of Mini-NDN authors and contributors.
+#
+# Mini-NDN 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.
+#
+# Mini-NDN 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 Mini-NDN, e.g., in COPYING.md file.
+# If not, see <http://www.gnu.org/licenses/>.
+
+import time
+
+from subprocess import call
+from threading import Timer
+
+class ProcessMonitor:
+    def __init__(self, processId, processName, outputDir, interval=1):
+        self._processId = processId.strip()
+        self._processName = processName
+        self._statFile = "/proc/{}/stat".format(self._processId)
+        self._logFile = "{}/{}-{}-stat.txt".format(outputDir, self._processName, self._processId)
+        self._interval = interval
+
+    def _recordStats(self):
+        try:
+            with open(self._statFile, "r") as stat:
+                currentTime = int(time.time())
+                with open(self._logFile, "a") as log:
+                    for line in stat:
+                        log.write("{} {}".format(currentTime, line))
+        except IOError as e:
+            print "I/O error({0}): {1}".format(e.errno, e.strerror)
+            print "No process with PID={}".format(self._processId)
+            return
+
+        self.start() # Reschedule event
+
+    def start(self):
+        self._timer = Timer(self._interval, self._recordStats)
+        self._timer.start()