From b4571b0c1e5a904286619e6929bbbe157461b1d4 Mon Sep 17 00:00:00 2001
From: "rtrp@factory1" <rtrp@factory1.com>
Date: Wed, 27 Jan 2021 21:59:51 +0000
Subject: [PATCH 1/2] create a Systemd service file.

This file is used to start the program at startup. It, also, restarts the
program if it crashes or throws an exception. The usual scenario which
causes the program to crash is the 'max. requests exceeded' exception in
the 'requests' module (Python). When that happens, this 'restart' service
has a 60 seconds wait period -- which acts as a 'backoff' period.

You will need to copy the .service file to the appropriate systemd
location, 'daemon-reload' systemctl, enable the service and start the
service. You will need to look-up how to do that -- this info. is beyond
the scope of this commmit.
---
 light-meter.service | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 light-meter.service

diff --git a/light-meter.service b/light-meter.service
new file mode 100644
index 0000000..281b5b7
--- /dev/null
+++ b/light-meter.service
@@ -0,0 +1,16 @@
+[Unit]
+Description=Light-Meter service for Return to Ritherdon project by Nicola Ellis
+After=network.service
+
+[Service]
+Type=simple
+ExecStart=bash /home/rtrp/repos/light-meter/startup.sh
+WorkingDirectory=/home/rtrp/repos/light-meter
+StandardOutput=inherit
+StandardError=inherit
+Restart=always
+RestartSec=60
+user=rtrp
+
+[Install]
+WantedBy=multi-user.target

From 56e05dceaf14996f11ef48eee4cb4f01ca429777 Mon Sep 17 00:00:00 2001
From: "rtrp@factory1" <rtrp@factory1.com>
Date: Fri, 5 Feb 2021 16:54:31 +0000
Subject: [PATCH 2/2] use session to persist REST calls and expand exception
 handling.

Previously, the light-meter was creating a new HTTP request to send every new reading. This now
uses a persistant session to reduce the amount of requests made to the server -- and reduce low
on the system.

The extra exceptions listed and expanded on are mostly for testing. At the time of writing, the
system as a whole is hanging at various parts throughout the day and the intention is to monitor
the Light Meter to see if any of the new exceptions are the cause (or contributing) to the
hanging. The current trains-of-thought at the minute are too many requests (system load too
high) and requests not timing out properly.
---
 cli_meter.py | 33 +++++++++++++++++++--------------
 startup.sh   |  2 +-
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/cli_meter.py b/cli_meter.py
index f1ee85f..15018ca 100755
--- a/cli_meter.py
+++ b/cli_meter.py
@@ -39,7 +39,7 @@ a_pin = 18  # Charges the capacitor.
 b_pin = 23  # Discharges the capacitor.
 
 device_id = platform.node()  # For servers logs.
-
+session = requests.Session() # Persist connection for REST calls.
 
 def get_api_url():
     # Yes, I know I could do this better. Stop moaning.
@@ -56,7 +56,6 @@ def discharge():
     GPIO.output(b_pin, False)
     time.sleep(0.01)  # 0.01 -- initial/default value.
 
-
 def charge_time():
     GPIO.setup(b_pin, GPIO.IN)
     GPIO.setup(a_pin, GPIO.OUT)
@@ -67,12 +66,10 @@ def charge_time():
     t2 = time.time()
     return (t2 - t1) * 1000000
 
-
 def analog_read():
     discharge()
     return charge_time()
 
-
 def read_resistance():
     n = 20
     total = 0
@@ -82,23 +79,20 @@ def read_resistance():
     resistance = reading * 6.05 - 939
     return resistance
 
-
 def light_from_r(R):
     return math.log(1000000.0/R) * 10.0
 
-
 def get_timestamp():
     return datetime.now().strftime(("%Y-%m-%d %H:%M:%S"))
 
-
 def push_reading(lvalue):
     time = get_timestamp()
     headers = {"content-type": "application/json"}
     payload = {"reading": int(lvalue), "time": time,
                "token": "QWERTYuiopasdfghjklzxcvbnm_1234567890"}
-    # print(payload) # For testing.
-    res = requests.post(api_url, data=json.dumps(payload), headers=headers)
-
+    print(payload) # For testing.
+    # res = requests.post(api_url, data=json.dumps(payload), headers=headers)
+    res = session.post(api_url, data=json.dumps(payload), headers=headers)
 
 def update_reading():
     light = light_from_r(read_resistance())
@@ -113,11 +107,22 @@ def main():
             # pdb.set_trace() # For testing.
             update_reading()
     except KeyboardInterrupt:
-        print("Keyboard Interrupt: quitting program.")
-    except:
-        print("Error updating light reading...")
+        print("[INFO] KEYBOARD INTERRUPT: quitting program.")
+    except requests.exceptions.ConnectionError:
+        pause = 60
+        time.sleep(60)
+        print(f"[WARNING] MAX. REQUESTS EXCEEDED: Pausing requests for {pause} seconds...")
+        pass
+    except requests.exceptions.Timeout:
+        t_stamp = datetime.datetime.now()
+        print(f"[WARNING] TIMEOUT EXCEPTION: Request timed-out at {t_stamp}.")
+        time.sleep(60)
+        pass
+    except Exception as e:
+        print(f"[ERROR] GENERAL EXCEPTION: {e}")
     finally:
-        print("Cleaning up GPIO before closing...")
+        print("[INFO] Terminating relay.py...")
+        print("[INFO] Cleaning up GPIO before closing...")
         GPIO.cleanup()
 
 
diff --git a/startup.sh b/startup.sh
index 0d5d912..9af3fcb 100755
--- a/startup.sh
+++ b/startup.sh
@@ -20,7 +20,7 @@
 # times".
 
 
-sleep 60
+# sleep 60
 
 logDate=$(date '+%Y-%m-%dT%TZ')
 logFile="/home/rtrp/logs/startup-logs.txt"