@startuml
:MQTT service starts;
start

if (certificate expired) then
    #pink:raise error;
    kill
endif
:start accepting connections;
:check certificate;

if (expiring soon) then (yes)
    :generate new certificate;
    :send to clients;

    if (confirmation NOK) then
        #pink:raise error;
        kill
    endif
    :restart MQTT;

else (no)
    :continue;
endif

stop
@enduml