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mqtt-tools
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Cache last value for each topic and only insert into DB on change 

Reduces database size
master
0xee 2020-12-21 22:22:27 +01:00
parent adf4e564d9
commit b88fcb2f04
2 changed files with 16 additions and 6 deletions
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2
default.nix
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@ -1,7 +1,7 @@
{ python3 }: { python3 }:
with python3.pkgs; with python3.pkgs;
buildPythonPackage rec { buildPythonPackage rec {
name = "mqtt-config"; name = "mqtt-tools";
src = ./.; src = ./.;
propagatedBuildInputs = [ pyyaml paho-mqtt ]; propagatedBuildInputs = [ pyyaml paho-mqtt ];
buildInputs = []; buildInputs = [];

20
mqtt-collect
View File

@ -7,6 +7,7 @@ import paho.mqtt.client
import sqlite3 import sqlite3
import datetime import datetime
MAX_VALUE_CACHE_SIZE = 1024
def init_db(path, topics): def init_db(path, topics):
db = sqlite3.connect(path) db = sqlite3.connect(path)
@ -31,6 +32,8 @@ def main():
def on_disconnect(client, userdata, rc): def on_disconnect(client, userdata, rc):
client.reconnect() client.reconnect()
current_values = {}
def on_message(client, userdata, msg): def on_message(client, userdata, msg):
try: try:
c = db.cursor() c = db.cursor()
@ -48,11 +51,18 @@ def main():
else: else:
value = float(msg.payload) value = float(msg.payload)
print(f"{table}: {value} ") print(f"{table}: {value} ")
c.execute(f'CREATE TABLE IF NOT EXISTS "{table}" '
'(timestamp timestamp, value real)') if current_values.get(table, None) != value:
c.execute(f'INSERT INTO "{table}" VALUES (?, ?)', (ts, value)) current_values[table] = value
#c.execute(f'SELECT * from "{table}"') if len(current_values) > MAX_VALUE_CACHE_SIZE:
db.commit() first_entry = current_values.keys().next()
del current_values[first_entry]
c.execute(f'CREATE TABLE IF NOT EXISTS "{table}" '
'(timestamp timestamp, value real)')
c.execute(f'INSERT INTO "{table}" VALUES (?, ?)', (ts, value))
db.commit()
except Exception as e: except Exception as e:
print(f'Error writing to database: {e}') print(f'Error writing to database: {e}')