Lag when MQTT Server is down (possible workaround)

[ascillato]

Hi

It is a known Tasmota issue (Wiki) that when a Sonoff try to connect to a MQTT server that is DOWN (IP and Port, both down), the pubsubclient library hangs for 5 second on each reconnection attempt making a Sonoff unresponsive.

So, looking for a work around for this, found this other MQTT Library (https://github.com/i-n-g-o/esp-mqtt-arduino). I tested on ESP8266 and with Home Assistant, and it has no lag when losing connection to MQTT Server. It has a different approach for conecting to an MQTT Server that is not using the wificlient library like pubsubclient.

What about changing the library so as to make Tasmota faster?

[Jason2866]

Hello, no offend
what is the use case of a mqtt device (sonoff) without a mqtt broker?
Users who want to use it without mqtt can turn it permant off (for example to use with Alexa)

[ascillato]

Hi, no offend taken. I just post an idea to be discussed ;)

May be I wasn't clear. I'm not saying of taking out MQTT from tasmota. No. That's not the idea. You are right. Will be useless that. What I'm saying is changing the MQTT library from pubsubclient to esp-mqtt-arduino. Just using another library for MQTT on Tasmota Firmware.

The actual library (pubsubclient) is a generic MQTT library to be used for any Arduino compatible device. So it is NOT optimized for ESP8266. However, esp-mqtt-arduino library is a MQTT library optimized for ESP8266.

So, I tested both libraries and pubsubclient has a 5 second lag when there is not a MQTT server active while the other has not that bug and remains fast responsive.

When I say MQTT Server Down I meant the case where you are using the MQTT feature and because a Wifi disconnection or a problem in a MQTT server, a Sonoff disconnects from the server. Using pubsubclient, Tasmota gets unresponsive for 5 seconds each 10 seconds. With the other library, this bug should be resolved.

So, @arendst, What do you think about changing the library from pubsubclient to esp-mqtt-arduino?

[arendst]

I'll take a look at it.

[emontnemery]

This sounds really nice! WAF is very low when the wall switches are not working because the WIFI is acting up..

[arendst]

UPDATE:

Installed patched esp-mqtt-arduino as the original does not support LWT like Tasmota does and I want it to be compatible with PubSubClient. It adds 5k to the code base while using the same amount of ram so that's fine. It does not support TLS using WifiClientSecure as PubSubClient does so it is only a replacement for non-TLS configurations. Blocking is indeed gone so that's positive.

I also tried ESP8266MQTTClient but that only seems to support TLS which is very code hungry: +52k code and exceptions everywhere. So that's no way to go.

I'll tune/rewrite/strip the current esp-mqtt-arduino library and will release a TasmotaMQTT library being a wrapper around slightly modified TuanPmt code and to be used on non-TLS sytems.

TO BE CONTINUED.

[ascillato]

Work really well !!! Thanks 👍

@arendst please put the TasmotaMQTT as default option. Works really good.

[ascillato]

Issue solved. Closing...

[jeylites]

@ascillato
A noob question is this alternative by default in v5.12.0d or something has to be done in the script for it to taken effect?

Update:

Nevermind, I found it in user config.h

/*********************************************************************************************\
 * Select ONE of possible MQTT library types below
\*********************************************************************************************/
// Default MQTT driver for both non-TLS and TLS connections. Blocks network if MQTT server is unavailable.
#define MQTT_LIBRARY_TYPE      1                 // Use PubSubClient library
// Alternative MQTT driver does not block network when MQTT server is unavailable. No TLS support
//#define MQTT_LIBRARY_TYPE      2                 // Use TasmotaMqtt library (+4k4 code, +4k mem) - non-TLS only
// Alternative MQTT driver does not block network when MQTT server is unavailable. No TLS support
//#define MQTT_LIBRARY_TYPE      3                 // Use (patched) esp-mqtt-arduino library (+4k8 code, +4k mem) - non-TLS only

[ascillato]

great!!! 👍

[Kepete]

Run into the same lag problem when MQTT Broker is down. So I changed the Default MQTT driver to
MQTT_TASMOTAMQTT. But it didn't help, the lag is still present.
Version 6.2.1