From b3c5a042f23aa1631b972e0bbdd985e78b972f5f Mon Sep 17 00:00:00 2001
From: Jason Jackson <jake1164@hotmail.com>
Date: Sun, 27 Aug 2023 10:26:50 -0400
Subject: [PATCH] Added multiple NTP server support

---
 README.md         | 12 ++++++++----
 src/network.py    | 22 ++++++++++++++--------
 src/settings.toml |  5 +++--
 3 files changed, 25 insertions(+), 14 deletions(-)

diff --git a/README.md b/README.md
index fccb69f..57610ef 100644
--- a/README.md
+++ b/README.md
@@ -9,15 +9,19 @@ Go to the [OWM sign up](https://openweathermap.org/appid) and using the free sub
 Put the token from the [OWM API Keys page](https://home.openweathermap.org/api_keys) into the settings.toml file in the OWM_API_TOKEN="" setting.
 OWM uses your geolocation which gets looked up via the Geolocation api, for this you need to provide your zipcode and the Country under OWM settings listed below.
 
+### NTP Servers 
+You can define up to 3 NTP servers, one primary and two fallbacks, to use for time syncronization. The servers are separated by a "pipe" | character. You can find 
+a list of [NTP Servers](https://timetoolsltd.com/information/public-ntp-server/) to use if you need something closer. 
+
 ## Settings
 Requires a settings.toml file with the following settings in settings file:
 
 * WIFI_SSID="your ssid"
 * WIFI_PASSWORD="yoursupersecretpassword"
-* NTP_HOST="0.adafruit.pool.ntp.org"
-* TZ_OFFSET=<timezone offset> ie TZ_OFFSET=-5
-* NTP_INTERVAL=6
-* UNITS="imperial" # imperial or metric
+* NTP_HOST="0.adafruit.pool.ntp.org|0.us.pool.ntp.org"
+* TZ_OFFSET=-5 
+* NTP_INTERVAL=21600 **ie 21600 = 6hr, 43200 = 12hr, 86400 = 24hr**
+* UNITS="imperial" **ie imperial or metric**
 
 ### openweathermap.org Data Authorization
 * OWM_API_TOKEN="Your Token"
diff --git a/src/network.py b/src/network.py
index c721278..c3912b4 100644
--- a/src/network.py
+++ b/src/network.py
@@ -18,12 +18,14 @@ def __init__(self) -> None:
 
         # NTP specific constants
         self.TZ = os.getenv('TZ_OFFSET')
-        self.NTP_HOST = os.getenv('NTP_HOST')
+        # Offer up to 3 ntp api's.
+        self.NTP_HOST = os.getenv('NTP_HOST').split('|', 2)
         self.INTERVAL = os.getenv('NTP_INTERVAL')
 
         if self.TZ is None or self.NTP_HOST is None or self.INTERVAL is None:
             raise Exception("NTP_HOST, NTP_INTERVAL & TZ_OFFSET are stored in settings.toml, please add them")
         
+        self._last_ntp_sync = None
         self.connect()
 
 
@@ -46,14 +48,18 @@ def connect(self) -> bool:
 
 
     def get_time(self):
-        # Need better connection testing
-        # has IP before connecting.
-        #if wifi.radio.ipv4_address is None:
-        #self.connect() # This just feels wrong to connect every time.
         pool = socketpool.SocketPool(wifi.radio)
-        ntp = adafruit_ntp.NTP(pool, tz_offset=self.TZ, server=self.NTP_HOST)
-        return ntp.datetime
-                    
+        ntp_try = 0
+        while ntp_try < len(self.NTP_HOST):
+            try:
+                ntp = adafruit_ntp.NTP(pool, tz_offset=self.TZ, server=self.NTP_HOST[ntp_try])
+                self._last_ntp_sync = ntp.datetime
+                return ntp.datetime
+            except Exception as ex:
+                print(f'Unable to connect to NTP Server {self.NTP_HOST[ntp_try]} with exception:', ex)
+                ntp_try += 1
+        raise Exception("Unable to contact NTP servers")
+                                                
 
     def getJson(self, url):
         try:
diff --git a/src/settings.toml b/src/settings.toml
index d3883a9..d627015 100644
--- a/src/settings.toml
+++ b/src/settings.toml
@@ -1,8 +1,9 @@
 WIFI_SSID="yourWIFI"
 WIFI_PASSWORD="YourPassword"
-NTP_HOST="0.adafruit.pool.ntp.org"
+NTP_HOST="0.adafruit.pool.ntp.org|0.us.pool.ntp.org"
 TZ_OFFSET=-5
-NTP_INTERVAL=60
+# 21600 = 6hr, 43200 = 12hr, 86400 = 24hr
+NTP_INTERVAL=21600 
 
 # weather settings # imperial or metric
 UNITS="imperial"