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Migrations

Change between version 1.x and 2.0

Most breaking change should break loudly and should not be missed. The most significant one which affect everyone is the versioned user callbacks. Other breaking change might not effect your usage of paho-mqtt.

The list of breaking change (detailed below) are:

  • Add version to user callbacks (on_publish, on_connect...). tl; dr: add mqtt.CallbackAPIVersion.VERSION1 as first argument to Client()
  • Drop support for older Python.
  • Dropped some deprecated and no used argument or method. If you used them, you can just drop them.
  • Removed from public interface few function/class
  • Renamed ReasonCodes to ReasonCode
  • Improved typing which resulted in few type change. It might no affect you, see below for detail.
  • Fixed connect_srv, which changed its signature.
  • Added new properties, which could conflict with sub-class

Versioned the user callbacks

Version 2.0 of paho-mqtt introduced versioning of user-callback. To fix some inconsistency in callback arguments and to provide better support for MQTTv5, version 2.0 changed the arguments passed to user-callback.

You can still use old version of callback, you are just require to tell paho-mqtt that you opt for this version. For that just change your client creation from:

# OLD code
>>> mqttc = mqtt.Client()

# NEW code
>>> mqttc = mqtt.Client(mqtt.CallbackAPIVersion.VERSION1)

That it, remaining of the code could stay unchanged.

The version 1 of callback is deprecated, but is still supported in version 2.x. If you want to upgrade to newer version of API callback, you will need to update your callbacks:

on_connect

# OLD code for MQTTv3
def on_connect(client, userdata, flags, rc):
    if flags["session present"] == 1:
        # ...
    if rc == 0:
        # success connect
    if rc > 0:
        # error processing

# OLD code for MQTTv5
def on_connect(client, userdata, flags, reason_code, properties):
    if flags["session present"] == 1:
        # ...
    if reason_code == 0:
        # success connect

# NEW code for both version
def on_connect(client, userdata, flags, reason_code, properties):
    if flags.session_present:
        # ...
    if reason_code == 0:
        # success connect
    if reason_code > 0:
        # error processing

Be careful that for MQTTv3, rc (an integer) changed to reason_code (an instance of ReasonCode), and the numeric value changed. The numeric value 0 means success for both, so as in above example, using reason_code == 0, reason_code != 0 or other comparison with zero is fine. But if you had comparison with other value, you will need to update the code. It's recommended to compare to string value:

# OLD code for MQTTv3
def on_connect(client, userdata, flags, rc):
    if rc == 1:
        # handle bad protocol version
    if rc == CONNACK_REFUSED_IDENTIFIER_REJECTED:
        # handle bad identifier

# NEW code
def on_connect(client, userdata, flags, reason_code, properties):
    if rc == "Unsupported protocol version":
        # handle bad protocol version
    if rc == "Client identifier not valid":
        # handle bad identifier

on_disconnect

# OLD code for MQTTv3
def on_disconnect(client, userdata, rc):
    if rc == 0:
        # success disconnect
    if rc > 0:
        # error processing

# OLD code for MQTTv5
def on_disconnect(client, userdata, reason_code, properties):
    if reason_code:
        # error processing

# NEW code for both version
def on_disconnect(client, userdata, flags, reason_code, properties):
    if reason_code == 0:
        # success disconnect
    if reason_code > 0:
        # error processing

on_subscribe

# OLD code for MQTTv3
def on_subscribe(client, userdata, mid, granted_qos):
    for sub_result in granted_qos:
        if sub_result == 1:
            # process QoS == 1
        if sub_result == 0x80:
            # error processing

# OLD code for MQTTv5
def on_disconnect(client, userdata, mid, reason_codes, properties):
    for sub_result in reason_codes:
        if sub_result == 1:
            # process QoS == 1
        # Any reason code >= 128 is a failure.
        if sub_result >= 128:
            # error processing

# NEW code for both version
def on_subscribe(client, userdata, mid, reason_codes, properties):
    for sub_result in reason_codes:
        if sub_result == 1:
            # process QoS == 1
        # Any reason code >= 128 is a failure.
        if sub_result >= 128:
            # error processing

on_unsubscribe

# OLD code for MQTTv3
def on_unsubscribe(client, userdata, mid):
    # ...

# OLD code for MQTTv5
def on_unsubscribe(client, userdata, mid, properties, reason_codes):
    # In OLD version, reason_codes could be a list or a single ReasonCode object
    if isinstance(reason_codes, list):
        for unsub_result in reason_codes:
            # Any reason code >= 128 is a failure.
            if reason_codes[0] >= 128:
                # error processing
    else:
        # Any reason code >= 128 is a failure.
        if reason_codes > 128:
            # error processing


# NEW code for both version
def on_subscribe(client, userdata, mid, reason_codes, properties):
    # In NEW version, reason_codes is always a list. Empty for MQTTv3
    for unsub_result in reason_codes:
        # Any reason code >= 128 is a failure.
        if reason_codes[0] >= 128:
            # error processing

on_publish

# OLD code
def on_publish(client, userdata, mid):
    # ...


# NEW code
def on_publish(client, userdata, mid, reason_codes, properties):
    # ...

on_message

No change for this callback:

# OLD & NEW code
def on_message(client, userdata, message):
    # ...

Drop support for older Python

paho-mqtt support Python 3.7 to 3.12. If you are using an older Python version, including Python 2.x you will need to kept running the 1.x version of paho-mqtt.

Drop deprecated argument and method

The following are dropped:

  • max_packets argument in loop(), loop_write() and loop_forever() is removed
  • force argument in loop_stop() is removed
  • method message_retry_set() is removed

They were not used in previous version, so you can just remove them if you used them.

Stop exposing private function/class

Some private function or class are not longer exposed. The following are removed:

  • function base62
  • class WebsocketWrapper
  • enum ConnectionState

Renamed ReasonCodes to ReasonCode

The class ReasonCodes that was used to represent one reason code response from broker or generated by the library is now named ReasonCode.

This should work without any change as ReasonCodes (plural, the old name) is still present but deprecated.

Improved typing

Version 2.0 improved typing, but this would be compatible with existing code. The most likely issue are some integer that are now better type, like dup on MQTTMessage.

That means that code that used if msg.dup == 1: will need to be change to if msg.dup: (the later version for with both paho-mqtt 1.x and 2.0).

Fix connect_srv

connect_srv() didn't took the same argument as connect(). Fixed this, which means the signaure changed. But since connect_srv was broken in previous version, this should not have any negative impact.

Added new properties

The Client class added few new properties. If you are using a sub-class of Client and also defined a attribute, method or properties with the same name, it will conflict.

The added properties are:

  • host
  • port
  • keepalive
  • transport
  • protocol
  • connect_timeout
  • username
  • password
  • max_inflight_messages
  • max_queued_messages
  • will_topic
  • will_payload
  • logger