Add caching mechanism

solaredge.py

@@ -2,8 +2,10 @@
 
 import bottle
 import datetime
+import logging
 import requests
 from collections import defaultdict
+from sys import stderr
 
 api_key = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
 site_id = 4143190
@@ -12,7 +14,9 @@ inverter = '7B0E5700-E0'
 
 endpoint = "https://monitoringapi.solaredge.com/"
 
-delta = datetime.timedelta(minutes=20)
+query_delta = datetime.timedelta(minutes=20)
+freshness_delta = datetime.timedelta(minutes=20)
+cache = {}
 
 numeric_modes = {
     'OFF': 0,
@@ -40,6 +44,11 @@ metric_data = {
     'ac_cos_phi': ["gauge", "AC Phase factor"] 
 }
 
+last_ts = {}
+
+def is_fresh(date):
+    return (datetime.datetime.now()) - date < freshness_delta
+
 def numeric_mode(s):
     if s in numeric_modes:
         return numeric_modes[s]
@@ -55,7 +64,7 @@ def ptime(s):
 def get(path, params={}, **kw):
     r = requests.get(endpoint + path, params | { "api_key": api_key }, **kw)
     r.raise_for_status()
-    return r.json()
+    return r.json() | { 'fetch_time': datetime.datetime.now().timestamp() }
     
 def details():
     return get(f"site/{site_id}/details.json")
@@ -69,22 +78,39 @@ def get_inverters():
 def energy(**kw):
     return get(f"site/{site_id}/energyDetails.json",
     kw | {"timeUnit": "QUARTER_OF_AN_HOUR"})
-
+11
 def tech_data(**kw):
     return get(f"equipment/{site_id}/{inverter}/data.json", kw)
 
 def meters(**kw):
-    return get(f"site/{site_id}/meters.json", kw)
+    return get(f"site/{site_id}/meters.json", kw | {"timeUnit": "QUARTER_OF_AN_HOUR"})
 
-def latest(method, **kw):
+def latest(method, timefn, **kw):
+    name = method.__name__
+    if name in cache and is_fresh(timefn(cache[name])):
+        logging.info("Cache for {} is fresh", method.__name__)
+        return cache[name]
+
+    logging.info("Cache for {} is stale, requesting", method.__name__)
     end = datetime.datetime.now()
-    start = end - delta
+    start = end - query_delta
-    return method(startTime=time(start), endTime=time(end), **kw)
+    data = method(startTime=time(start), endTime=time(end), **kw)
+    cache[name] = data
+    return data
+
+def tech_check(c):
+        if c['data']['telemetries']:
+            return ptime(c['data']['telemetries'][-1]['date'])
+        else:
+            return datetime.datetime.fromtimestamp(c['fetch_time'])
+
+
+def meters_check(c):
+    return ptime(c['meterEnergyDetails']['meters'][0]['values'][-1]['date'])
 
 def collect():
-    tech = latest(tech_data)['data']['telemetries']
+    tech = latest(tech_data, tech_check)['data']['telemetries']
-    ms = latest(meters)['meterEnergyDetails']['meters']
+    ms = latest(meters, meters_check)['meterEnergyDetails']['meters']
-
     if len(tech):
         point = tech[-1]
         date = ptime(point['date'])
@@ -111,7 +137,7 @@ def collect():
         date = ptime(point['date'])
         yield (date, 'meter_energy_watthours_total', {'meter': m['meterType'].lower()}, point['value'])
 
-def format_metrics(entries):
+def format_metrics(entries, timestamps=False):
     collected = defaultdict(list)
     for entry in entries:
         collected[entry[1]].append(entry)
@@ -127,7 +153,10 @@ def format_metrics(entries):
             attr_s = ""
             if attrs:
                 attr_s = "{" + ','.join('{}="{}"'.format(k, attrs[k]) for k in attrs ) + "}"
+            if timestamps:
                 yield f"{metric} {attr_s} {value} {time_s}\n"
+            else:
+                yield f"{metric} {attr_s} {value}\n"
 
 @bottle.route('/')
 def root():