Simple vitals endpoint for external integration

[rawslaw]

I have rooftop solar with PW3 and soon to have two EV chargers of different brands utilizing a software-based load sharing. My design has Home Assistant / NodeRed querying pypowerwall to execute decision paths to manage the load sharing via smart amperage control on the charging units.

My current design uses pypowerwall's proxy, but I've been annoyed at the overcomplexity of multiple endpoints, size of payloads discarded, and the engineer in me is concerned about multiple points of failure. Probably negligible, but querying at high frequency and not confident about the receivers' garbage collection techniques, I thought I would try to simplify it.

I'm currently querying

• /api/meters/aggregates for .solar.instant_power
• /api/meters/aggregates for .battery.instant_power
• /api/meters/aggregates for .load.instant_power
• /api/meters/aggregates for .site.instant_power
• /soe for .percentage
• /pod for .time_remaining_hours

I was prepared to write my own, but then a few weeks ago I was diving into the release notes and noticed a /csv endpoint appear and thought, that's exactly what I need-- but it’s csv. One endpoint that directly pulls from the internal proxy cache with a single point of failure in case of future breaking changes. And actually, /csv/v2 is slightly better, but that incorporation is less clean.

{
  "grid_w": -3184,
  "home_w": 2006.5000000000002,
  "solar_w": 5145,
  "battery_w": 40,
  "soc": 100
}

Beautiful - I was able to mock up a code change for extending /csv endpoint to produce json instead, but wanted to inquire with codeowner(s) where the enhancement makes sense. Here's what I did (and I don't like it, but it is POC)

--- a/proxy/server.py
+++ b/proxy/server.py
@@ -395,11 +395,10 @@ class Handler(BaseHTTPRequestHandler):
         elif request_path == '/api/system_status/grid_status':
             # Grid Status - JSON
             message: str = pw.poll('/api/system_status/grid_status', jsonformat=True)
-        elif request_path.startswith('/csv') or request_path.startswith('/csv/v2'):
+        elif request_path.startswith('/csv') or request_path.startswith('/csv/v2') or request_path == '/ha':
             # CSV Output - Grid,Home,Solar,Battery,Level
             # CSV2 Output - Grid,Home,Solar,Battery,Level,GridStatus,Reserve
             # Add ?headers to include CSV headers, e.g. http://localhost:8675/csv?headers
-            contenttype = 'text/plain; charset=utf-8'
             batterylevel = pw.level() or 0
             grid = pw.grid() or 0
             solar = pw.solar() or 0
@@ -409,21 +408,29 @@ class Handler(BaseHTTPRequestHandler):
                 solar = 0
                 # Shift energy from solar to load
                 home -= solar
-            if request_path.startswith('/csv/v2'):
-                gridstatus = 1 if pw.grid_status() == 'UP' else 0
-                reserve = pw.get_reserve() or 0
-                message = ""
-                if "headers" in request_path:
-                    message += "Grid,Home,Solar,Battery,BatteryLevel,GridStatus,Reserve\n"
-                message += "%0.2f,%0.2f,%0.2f,%0.2f,%0.2f,%d,%d\n" \
-                    % (grid, home, solar, battery, batterylevel, 
-                        gridstatus, reserve)
+            if request_path == '/ha':
+                # Key Power Data for Home Assistant REST API input - JSON
+                # Same data as CSV endpoint, but in json for Home Assistant
+                keyPower = {'grid_w': grid, 'home_w': home, 'solar_w': solar,
+                            'battery_w': battery, 'soc': batterylevel}
+                message: str = json.dumps(keyPower)
             else:
-                message = ""
-                if "headers" in request_path:
-                    message += "Grid,Home,Solar,Battery,BatteryLevel\n"
-                message += "%0.2f,%0.2f,%0.2f,%0.2f,%0.2f\n" \
-                    % (grid, home, solar, battery, batterylevel)
+                contenttype = 'text/plain; charset=utf-8'
+                if request_path.startswith('/csv/v2'):
+                    gridstatus = 1 if pw.grid_status() == 'UP' else 0
+                    reserve = pw.get_reserve() or 0
+                    message = ""
+                    if "headers" in request_path:
+                        message += "Grid,Home,Solar,Battery,BatteryLevel,GridStatus,Reserve\n"
+                    message += "%0.2f,%0.2f,%0.2f,%0.2f,%0.2f,%d,%d\n" \
+                               % (grid, home, solar, battery, batterylevel,
+                                  gridstatus, reserve)
+                else:
+                    message = ""
+                    if "headers" in request_path:
+                        message += "Grid,Home,Solar,Battery,BatteryLevel\n"
+                    message += "%0.2f,%0.2f,%0.2f,%0.2f,%0.2f\n" \
+                               % (grid, home, solar, battery, batterylevel)
         elif request_path == '/vitals':

I dislike placing it in the conditional block with request_path.startswith('/csv') or request_path.startswith('/csv/v2') in proxy/server.py because that block is entirely about csv. But! that block already makes the python calls to populate the values. Placing it outside this block would be duplicate code (bad) [question mark].

Any suggestion on where to put this logic? There's not already a /json endpoint, so that is an option. But I also want to think about larger implications / implementations with this conditional. /csv/v2/json seems like a silly name, but organizationally, that is where it would go. Welcome to suggestions!

For now a local implementation is allowing me to continue development and testing on the integration pieces, but I'm prepared to take suggestions in order to contribute this enhancement so that I can continue to cleanly take future changes from upstream.

[jasonacox]

Nice! Thanks for raising this.

We should do a top level route. Maybe something like:

        elif request_path in ['/ha', '/json']:
            # JSON - Grid,Home,Solar,Battery,Level,GridStatus,Reserve
            values = {
                'grid': pw.grid() or 0,
                'home': pw.home() or 0, 
                'solar': pw.solar() or 0,
                'battery': pw.battery() or 0,
                'soc': pw.level() or 0,
                'grid_status': int(pw.grid_status() == 'UP'),
                'reserve': pw.get_reserve() or 0
            }
            if not neg_solar and values['solar'] < 0:
                # Shift negative solar to load
                values['home'] -= values['solar']
                values['solar'] = 0
            message: str = json.dumps(values)

[erikgieseler]

I opened a PR: #174

[rawslaw]

Thanks for your help @jasonacox @erikgieseler!