Log error when client probe takes a 185.0 reading

this indicates some power issue with the probe(s) and does not really mean
that's the temperature.  so we don't want the server to send out "high temp"
email etc. but rather just a technical error email

https://www.controlbyweb.com/support/faq/temp-sensor-reading-error.html

rattail_tempmon/client.py

@@ -72,46 +72,60 @@ class TempmonClient(Daemon):
 
         # main loop: take readings, pause, repeat
         while True:
+            self.take_readings(client_uuid)
+            time.sleep(self.delay)
 
-            session = Session()
+    def take_readings(self, client_uuid):
+        """
+        Take new readings for all enabled probes on this client.
+        """
+        session = Session()
 
+        try:
+            client = session.query(tempmon.Client).get(client_uuid)
+            self.delay = client.delay or 60
+            if client.enabled:
+                for probe in client.enabled_probes():
+                    self.take_reading(session, probe)
+
+        except:
+            log.exception("Failed to read/record temperature data (but will keep trying)")
+            session.rollback()
+
+        else:
+            # make sure we show as being online
+            if not client.online:
+                client.online = True
             try:
-                client = session.query(tempmon.Client).get(client_uuid)
+                session.commit()
-                self.delay = client.delay or 60
-                if client.enabled:
-                    for probe in client.enabled_probes():
-                        self.take_reading(session, probe)
-
             except:
                 log.exception("Failed to read/record temperature data (but will keep trying)")
                 session.rollback()
 
-            else:
+        finally:
-                # make sure we show as being online
+            session.close()
-                if not client.online:
-                    client.online = True
-                try:
-                    session.commit()
-                except:
-                    log.exception("Failed to read/record temperature data (but will keep trying)")
-                    session.rollback()
-
-            finally:
-                session.close()
-
-            time.sleep(self.delay)
 
     def take_reading(self, session, probe):
         """
         Take a single reading and add to Rattail database.
         """
         reading = tempmon.Reading()
-        reading.client = probe.client
-        reading.probe = probe
         reading.degrees_f = self.read_temp(probe)
-        reading.taken = datetime.datetime.utcnow()
+
-        session.add(reading)
+        # a reading of 185.0 °F indicates some sort of power issue.  when this
-        return reading
+        # happens we log an error (which sends basic email) but do not record
+        # the temperature.  that way the server doesn't see the 185.0 reading
+        # and send out a "false alarm" about the temperature being too high.
+        # https://www.controlbyweb.com/support/faq/temp-sensor-reading-error.html
+        if reading.degrees_f == 185.0:
+            log.error("got reading of 185.0 from probe: %s", probe.description)
+
+        else: # we have a good reading
+            reading.client = probe.client
+            reading.probe = probe
+            reading.taken = datetime.datetime.utcnow()
+            session.add(reading)
+            return reading
 
     def read_temp(self, probe):
         """
@@ -126,7 +140,9 @@ class TempmonClient(Daemon):
         equals_pos = lines[1].find('t=')
         if equals_pos != -1:
             temp_string = lines[1][equals_pos+2:]
+            # temperature data comes in as celsius
             temp_c = float(temp_string) / 1000.0
+            # convert celsius to fahrenheit
             temp_f = temp_c * 9.0 / 5.0 + 32.0
             return round(temp_f,4)