[modules/ping] Re-enable ping module

Show RTT measured by ICMP echo request/replies for a given host.

For that to work correctly, change the "full_text" callback for a widget
so that the widget itself is also passed as argument in the callback
method. That actually makes a lot of sense, since the widget can now be
used as a repository of state information.

see #23

bumblebee/modules/ping.py

@@ -0,0 +1,81 @@
+# pylint: disable=C0111,R0903
+
+"""Periodically checks the RTT of a configurable host using ICMP echos
+
+Parameters:
+    * ping.interval: Time in seconds between two RTT checks (defaults to 60)
+    * ping.address : IP address to check
+    * ping.timeout : Timeout for waiting for a reply (defaults to 5.0)
+    * ping.probes  : Number of probes to send (defaults to 5)
+    * ping.warning : Threshold for warning state, in seconds (defaults to 1.0)
+    * ping.critical: Threshold for critical state, in seconds (defaults to 2.0)
+"""
+
+import re
+import time
+import threading
+
+import bumblebee.input
+import bumblebee.output
+import bumblebee.engine
+
+def get_rtt(module, widget):
+
+    main = None
+    for thread in threading.enumerate():
+        if thread.name == "MainThread":
+            main = thread
+
+    interval = widget.get("interval")
+    next_check = 0
+    while main.is_alive():
+        try:
+            if int(time.time()) < next_check:
+                time.sleep(1)
+                continue
+            widget.set("rtt-unreachable", False)
+            res = bumblebee.util.execute("ping -n -q -c {} -W {} {}".format(
+                widget.get("rtt-probes"), widget.get("rtt-timeout"), widget.get("address")
+            ))
+            next_check = int(time.time()) + interval
+
+            for line in res.split("\n"):
+                if not line.startswith("rtt"): continue
+                m = re.search(r'([0-9\.]+)/([0-9\.]+)/([0-9\.]+)/([0-9\.]+)\s+(\S+)', line)
+
+                widget.set("rtt-min", float(m.group(1)))
+                widget.set("rtt-avg", float(m.group(2)))
+                widget.set("rtt-max", float(m.group(3)))
+                widget.set("rtt-unit", m.group(5))
+        except Exception as e:
+            widget.set("rtt-unreachable", True)
+
+class Module(bumblebee.engine.Module):
+    def __init__(self, engine, config):
+        widget = bumblebee.output.Widget(full_text=self.rtt)
+        super(Module, self).__init__(engine, config, widget)
+
+        widget.set("address", self.parameter("address", "8.8.8.8"))
+        widget.set("interval", self.parameter("interval", 60))
+        widget.set("rtt-probes", self.parameter("probes", 5))
+        widget.set("rtt-timeout", self.parameter("timeout", 5.0))
+        widget.set("rtt-avg", 0.0)
+        widget.set("rtt-unit", "")
+
+        self._thread = threading.Thread(target=get_rtt, args=(self,widget,))
+        self._thread.start()
+
+    def rtt(self, widget):
+        if widget.get("rtt-unreachable"):
+            return "{}: unreachable".format(widget.get("address"))
+        return "{}: {:.1f}{}".format(
+            widget.get("address"),
+            widget.get("rtt-avg"),
+            widget.get("rtt-unit")
+        )
+
+    def state(self, widget):
+        if widget.get("rtt-unreachable"): return ["critical"]
+        return self.threshold_state(widget.get("rtt-avg"), 1000.0, 2000.0)
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4