Slowness at reading many retained messages

[leandronsp]

Hey!

I'm around an issue which I'm not sure if it's related how I use the lib or something else on its internals.
By trying the following process:

@mqtt_client = PahoMqtt::Client.new(
  client_id: client_id,             
  username: username,               
  password: password                
)

@mqtt_client.connect(
  host=@mqtt_host,   
  port=@mqtt_port,   
  keep_alive=60,     
  persistent=true    
)

@mqtt_client.subscribe(['v1/some_topic'], 1) 

@mqtt_client.on_message do |message|                                       
  # print the retained/received message
end

At first, it will print all retained messages on the broker, around ~80 on ours.
It takes 10 seconds to load all 80 retained messages, which it seems to be very slow on our requirements.

Then I changed to use the foreground alternative.

@mqtt_client.connect(
  host=@mqtt_host,   
  port=@mqtt_port,   
  keep_alive=60,     
  persistent=true ,
  blocking=true  
)

def foreground_mode                                     
  [:loop_read, :loop_write, :loop_misc].each do |method|
    Thread.new do                                       
      while @mqtt_client.connected? do                  
        @mqtt_client.send(method)                       
      end                                               
    end                                                 
  end                                                   
end                                                     

# will spawn a different Thread for each loop
foreground_mode

Even so, this solution is even worse, taking 40 seconds, and I think it's related to the GIL maybe.

In addition, I compared along with the paho.mqtt.python lib, which in turn takes just 1 second instead to load all 80 retained messages. I'd gently ask you guys for some clue, am I missing something, some tweak to be made, already an known issue?

Thanks in advance!