Sanic Config loading with Consul

consul_sanic_example.py

from sanic import Sanic
from consul.aio import Consul

import default_settings
import asyncio


"""
Initialize application
"""
app = Sanic()
app.config.from_object(default_settings)

async def load_config_from_consul():
    """
    Load config from Consul.
    Pings the Consul service every 30 or so seconds for changes
    
    This version will iterate over each key of the app and look for individaul Consul entries for them.
    A bit more complex, but allows for lighter-weight, fine grained updates.
    """
    consul = Consul(loop=app.loop)
    conf = { attr: None for (attr, value) in app.config.items() }
    
    async def update_key(key):
        print(f"consul:{key}:Reading Value")
        index, data = await consul.kv.get("/".join(key.lower().split("_")), index=conf[key])
        if bool(data):
            val = data['Value'].decode("utf-8") 
            if app.config[key] != val:
                app.config[key] = val
                print(f"consul:{key}:{val}")
            else:
                print(f"consul:{key}:Value Unchanged")
        else:
            print(f"consul:{key}:Value Not Found")
        conf[key] = index

    while True:
        for attr, val in app.config.items():
            await update_key(attr)
        await asyncio.sleep(30)

@app.listener('before_server_start')
def before(app, loop):
    app.add_task(load_config_from_consul)

if __name__ == "__main__":
    app.run(host="localhost", port=54658, debug=True)

consul_sanic_example_full.py

from sanic import Sanic
from consul.aio import Consul

import default_settings
import asyncio
import json


"""
Initialize application
"""
app = Sanic()
app.config.from_object(default_settings)

async def load_config_from_consul():
    """
    Load config from Consul.
    Pings the Consul service every 30 or so seconds for changes
    
    This version will look for a single config entry for the entire app.  Whenever something
    of it changes, it'll reload the entire thing.  The config should be stored as json, for easy parsing.
    """
    consul = Consul(loop=app.loop)
    
    index = None
    while True:
        index, data = await consul.kv.get("myapp.properties", index=index)
        if bool(data):
            val = data['Value'].decode("utf-8")
            obj = json.loads(val)
            app.config.update(obj)
            print("consul:config:App Updated")
            await asyncio.sleep(30)

@app.listener('before_server_start')
def before(app, loop):
    app.add_task(load_config_from_consul)

if __name__ == "__main__":
    app.run(host="localhost", port=54658, debug=True)

default_settings.py

"""
Default configuration values for the app.
Production should pull accurate values from Consul, but this is fine for local development and to get the app started

Sanic requires settings to be in all upper-case.
We translate underscores into / for consul, allowing us to have organized paths for configuration when using
the per key loader, else this is how key-value pairs should appear in a json stored in Consul.
"""
NEO4J_HOST = "http://localhost:7474/data/db/"
NEO4J_USERNAME = "neo4j"
NEO4J_PASSWORD = "neo4j"