Publish/Subscribe API for PubNub Python-Tornado SDK

Python version support

Python SDK versions 5.0.0 and higher no longer support Python v2.7 and the Twisted and Tornado frameworks. If you require support for any of these, use SDK version 4.8.1.

Note that PubNub will stop supporting versions of Python lower than 3.7 by the end of 2021.

Publish

Description

The publish() function is used to send a message to all subscribers of a channel. To publish a message you must first specify a valid publish_key at initialization. A successfully published message is replicated across the PubNub Real-Time Network and sent simultaneously to all subscribed clients on a channel.

Messages in transit can be secured from potential eavesdroppers with SSL/TLS by setting ssl to true during initialization.

Important

The new Jackson parser does not recognize JSONObject. Please use ObjectNode instead.

Publish Anytime

It's not required to be subscribed to a channel in order to publish to that channel.

Message Data:

The message argument can contain any JSON serializable data, including: Objects, Arrays, Ints and Strings. data should not contain special Python-Tornado classes or functions as these will not serialize. String content can include any single-byte or multi-byte UTF-8 character.

Don't JSON serialize!

It is important to note that you should not JSON serialize when sending signals/messages via PUBNUB. Why? Because the serialization is done for you automatically. Instead just pass the full object as the message payload. PubNub takes care of everything for you.

Message Size:

The maximum number of characters per message is 32 KiB by default. The maximum message size is based on the final escaped character count, including the channel name. An ideal message size is under 1800 bytes which allows a message to be compressed and sent using single IP datagram (1.5 KiB) providing optimal network performance.

If the message you publish exceeds the configured size, you will receive the following message:

Message Too Large Error

["PUBLISHED",[0,"Message Too Large","13524237335750949"]]

For further details please check: https://support.pubnub.com/hc/en-us/articles/360051495932-Calculating-Message-Payload-Size-Before-Publish

Message Publish Rate:

Messages can be published as fast as bandwidth conditions will allow. There is a soft limit based on max throughput since messages will be discarded if the subscriber can't keep pace with the publisher.

For example, if 200 messages are published simultaneously before a subscriber has had a chance to receive any messages, the subscriber may not receive the first 100 messages because the message queue has a limit of only 100 messages stored in memory.

Publishing to Multiple Channels:

It is not possible to publish a message to multiple channels simultaneously. The message must be published to one channel at a time.

Publishing Messages Reliably:

There are some best practices to ensure messages are delivered when publishing to a channel:

Publish to any given channel in a serial manner (not concurrently).
Check that the return code is success (e.g. [1,"Sent","136074940..."])
Publish the next message only after receiving a success return code.
If a failure code is returned ([0,"blah","<timetoken>"]), retry the publish.
Avoid exceeding the in-memory queue's capacity of 100 messages. An overflow situation (aka missed messages) can occur if slow subscribers fail to keep up with the publish pace in a given period of time.
Throttle publish bursts in accordance with your app's latency needs e.g. Publish no faster than 5 msgs per second to any one channel.

Method(s)

To Publish a message you can use the following method(s) in the Python-Tornado SDK:

pubnub.publish().channel(String).message(Object).should_store(Boolean).meta(dict).use_post(Boolean)

Parameter	Type	Required	Defaults	Description
`channel`	String	Yes		Destination of `message`.
`message`	Object	Yes		The payload.
`should_store`	Boolean	Optional	`account default`	Store in history
`meta`	Object	Optional	`None`	Meta data object which can be used with the filtering ability.

Basic Usage

Publish a message to a channel:

from pubnub.exceptions import PubNubException

try:
    envelope = yield pubnub.publish().channel("my_channel").message({
        'name': 'Alex',
        'online': True
    }).future()
    print("publish timetoken: %d" % envelope.result.timetoken)
except PubNubException as e:
    handle_exception(e)

Note

Before running the above publish example, either using the Debug Console or in a separate script running in a separate terminal window, subscribe to the same channel that is being published to.

Returns

The publish() operation returns a PNPublishResult which contains the following fields:

Field	Type	Description
timetoken	`Int`	an `int` representation of the timetoken when the message was published

Other Examples

Publish with metadata

envelope = yield pubnub.publish()\
    .channel("my_channel")\
    .message(["hello", "there"])\
    .meta({'name': 'Alex'})\
    .future()

# handle publish result, status always present, result if successful
# envelope.status.is_error() to see if error happened

Fire

Description

The fire endpoint allows the client to send a message to PubNub Functions Event Handlers. These messages will go directly to any Event Handlers registered on the channel that you fire to and will trigger their execution. The content of the fired request will be available for processing within the Event Handler. The message sent via fire() isn't replicated, and so won't be received by any subscribers to the channel. The message is also not stored in history.

Method(s)

To Fire a message you can use the following method(s) in the Python-Tornado SDK:

pubnub.fire().channel(String).message(Object).meta(Object).use_post(Boolean)

Parameter	Type	Required	Defaults	Description
`channel`	String	Yes		Destination of `message`.
`message`	Object	Yes		The payload.
`use_post`	Boolean	Optional	false	Use POST to publish.
`meta`	Object	Optional	`None`	Meta data object which can be used with the filtering ability.

Basic Usage

Fire a message to a channel:

envelope = yield pubnub.fire().channel('my_channel').message('hello there').use_post(true).future()
print('fire timetoken: %d' % envelope.result.timetoken)

Signal

Description

The signal() function is used to send a signal to all subscribers of a channel.

By default, signals are limited to a message payload size of 30 bytes. This limit applies only to the payload, and not to the URI or headers. If you require a larger payload size, please contact support.

Method(s)

To Signal a message you can use the following method(s) in the Python-Tornado SDK:

```
pubnub.signal().message(Object).channel(String)
```
Parameter Type Required Description

message Object Yes The payload.

channel String Yes Destination of message.

Parameter	Type	Required	Description
`message`	Object	Yes	The payload.
`channel`	String	Yes	Destination of `message`.

Basic Usage

Signal a message to a channel:

envelope = yield pubnub.signal().channel('some_channel').message('foo').future()

Response

Field	Type	Description
timetoken	`int`	An `int` representation of the timetoken when Signal was sent.

Description

This function causes the client to create an open TCP socket to the PubNub Real-Time Network and begin listening for messages on a specified channel. To subscribe to a channel the client must send the appropriate subscribe_key at initialization.

By default a newly subscribed client will only receive messages published to the channel after the subscribe() call completes. If a client gets disconnected from a channel, it can automatically attempt to reconnect to that channel and retrieve any available messages that were missed during that period. This can be achieved by setting setReconnectionPolicy to PNReconnectionPolicy.LINEAR, when initializing the client.

Warning

Unsubscribing from all channels, and then subscribing to a new channel Y is not the same as subscribing to channel Y and then unsubscribing from the previously-subscribed channel(s). Unsubscribing from all channels resets the last-received timetoken and thus, there could be some gaps in the subscription that may lead to message loss.

Method(s)

To Subscribe to a channel you can use the following method(s) in the Python-Tornado SDK:

pubnub.subscribe().channels(String|List|Tuple).channel_groups(String|List|Tuple).with_timetoken(Int).with_presence().execute()

Parameter	Type	Required	Description
`channels`	String \| List \| Tuple	Optional	Subscribe to `channels`, Either `channel` or `channel_group` is required.
`channel_groups`	String \| List \| Tuple	Optional	Subscribe to `channel_groups`, Either `channel` or `channel_group` is required.
`timetoken`	Int	Optional	Pass a `timetoken`.
`with_presence`	Command	Optional	Also subscribe to related presence information.

Basic Usage

Subscribe to a channel:

pubnub.subscribe().channels("my_channel").execute()

Note

The response of the call is handled by adding a Listener. Please see the Listeners section for more details. Listeners should be added before calling the method.

Returns

Note

PNMessageResult is returned in the Listeners

The subscribe() operation returns a PNStatus for messages which contains the following fields:

Field	Type	Description
`category`	PNStatusCategory	Details of `StatusCategory` are here
`is_error`	Boolean	This is `true` if an error occurred in the execution of the operation.
`error_data`	PNErrorData	Error data of the exception (if `Error` is `true`).
`status_code`	int	Status code of the execution.

The subscribe() operation returns a PNMessageResult for messages which contains the following fields:

Field	Type	Description
`message`	Object	The `message` sent on `channel`.
`subscription`	String	The channel group or wildcard `subscription` match (if exists).
`channel`	String	The `channel` for which the message belongs.
`timetoken`	Int	`Timetoken` for the message.
`user_metadata`	Dict	User `metadata`.

The subscribe() operation returns a PNPresenceEventResult from presence which contains the following operations:

Field	Type	Description
`event`	String	Events like `join`, `leave`, `timeout`, `state-change`.
`uuid`	String	`uuid` for event.
`timestamp`	Int	`timestamp` for event.
`occupancy`	Int	Current `occupancy`.
`subscription`	String	The channel group or wildcard `subscription` match (if exists).
`channel`	String	The `channel` for which the message belongs.
`timetoken`	Int	`timetoken` of the message.
`user_metadata`	Dict	User `metadata`.

The subscribe() operation returns a PNSignalResult for signals which contains the following operations:

Field	Type	Description
`timetoken`	Int	An int representation of the `timetoken` when Signal was sent.
`channel`	String	The `channel` on which Signal occurred.
`publisher`	String	ID of the sender.
`message`	Object	The payload.

Other Examples

Basic subscribe with logging:

import logging
import pubnub

from pubnub.pnconfiguration import PNConfiguration
from pubnub.pubnub_tornado import PubNubTornado
from pubnub.pubnub_tornado import SubscribeListener

pubnub.set_stream_logger('pubnub', logging.DEBUG)

pnconfig = PNConfiguration()

pnconfig.subscribe_key = 'demo'
pnconfig.publish_key = 'demo'

pubnub = PubNubTornado(pnconfig)

pubnub.add_listener(SubscribeListener())
pubnub.subscribe().channels("my_channel").execute()

Subscribing to more than one channel: Requires Stream Controller add-onRequires that the Stream Controller add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-keys-

It is possible to subscribe to more than one channel over a single TCP socket by taking advantage of Multiplexing feature. See the Multiplexing section for more info on this feature as well as the examples below using a list or an array to specify channel name.
```
pubnub.subscribe().channels(["my_channel1", "my_channel2"]).execute()
```
Subscribing to a Presence channel: Requires Presence add-onRequires that the Presence add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-keys-

For any given channel there is an associated Presence channel. You can subscribe directly to the channel by appending -pnpres to the channel name. For example the channel named my_channel would have the presence channel named my_channel-pnpres.
```
pubnub.subscribe()\
    .channels("my_channel")\
    .with_presence()\
    .execute()
```
Sample Responses

Join Event
```
if envelope.event == 'join':
    envelope.uuid # 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    envelope.timestamp # 1345546797
    envelope.occupancy # 2
```
Leave Event
```
{
    "action" : "leave",
    "timestamp" : 1345549797,
    "uuid" : "175c2c67-b2a9-470d-8f4b-1db94f90e39e",
    "occupancy" : 1
}
```
Timeout Event
```
if envelope.event == 'timeout':
    envelope.uuid # 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    envelope.timestamp # 1345546797
    envelope.occupancy # 0
```
Custom Presence Event (State Change)
```
if envelope.event == 'state-change':
    envelope.uuid # 76c2c571-9a2b-d074-b4f8-e93e09f49bd
    envelope.timestamp # 1345546797
    envelope.user_metadata # {'is_typing': True}
```
Interval Event
```
{
    "action":"interval",
    "timestamp":1474396578,
    "occupancy":2
}
```
When a channel is in interval mode with presence_deltas pnconfig flag enabled, the interval message may also include the following fields which contain an array of changed UUIDs since the last interval message.
- joined
- left
- timedout
For example, this interval message indicates there were 2 new UUIDs that joined and 1 timed out UUID since the last interval:
```
{
    "action" : "interval",
    "occupancy" : <# users in channel>,
    "timestamp" : <unix timestamp>,
    "joined" : ["uuid2", "uuid3"],
    "timedout" : ["uuid1"]
}
```
If the full interval message is greater than 30KB (since the max publish payload is ∼32KB), none of the extra fields will be present. Instead there will be a here_now_refresh boolean field set to true. This indicates to the user that they should do a hereNow request to get the complete list of users present in the channel.
```
{
    "action" : "interval",
    "occupancy" : <# users in channel>,
    "timestamp" : <unix timestamp>,
    "here_now_refresh" : true
}
```
Wildcard subscribe to channels: Requires Stream Controller add-onRequires that the Stream Controller add-on is enabled with Enable Wildcard Subscribe checked for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-keys-

Wildcard subscribes allow the client to subscribe to multiple channels using wildcard. For example, if you subscribe to a.* you will get all messages for a.b, a.c, a.x. The wildcarded * portion refers to any portion of the channel string name after the dot (.).

Note

3 levels (2 dots) of wildcarding is supported, e.g.:
a.*

a.b.*
```
pubnub.subscribe().channels("foo.*").execute();
```

Subscribing with State:

Note

Always set the UUID to uniquely identify the user or device that connects to PubNub. This UUID should be persisted, and should remain unchanged for the lifetime of the user or the device. Not setting the UUID can significantly impact your billing if your account uses the Monthly Active Users (MAUs) based pricing model, and can also lead to unexpected behavior if you have Presence enabled.

from pubnub.pubnub_tornado import PubNubTornado
from pubnub.pubnub_tornado import SubscribeListener

class MySubscribeListener(SubscribeListener):
    def __init__(self):
        pass

    def status(self, pubnub, status):
        if status.category == PNStatusCategory.PNConnectedCategory:
            state = {
                'field_a': 'awesome',
                'field_b': 10
            }
            pubnub.ioloop.add_future(
                    pubnub.set_state().channels('my_channel').\
                        channel_groups('awesome_channel_groups').state(state).future()
                )
        else:
            pass

    def message(self, pubnub, message):
        pass

    def presence(self, pubnub, presence):
        pass

pubnub = PubNubTornado(pnconfig)

my_listener = MySubscribeListener()
pubnub.add_listener(my_listener)

pubnub.subscribe().channels("my_channel").execute()

Subscribe to a channel group: Requires Stream Controller add-onRequires that the Stream Controller add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-keys-
```
pubnub.subscribe().channel_groups("awesome_channel_group").execute()
```
Subscribe to the presence channel of a channel group: Requires Stream Controller and Presence add-onRequires that both Stream Controller and Presence add-ons are enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-keys-
```
pubnub.subscribe().channel_groups(["cg1", "cg2"]).with_presence().execute()
```

Unsubscribe

Description

When subscribed to a single channel, this function causes the client to issue a leave from the channel and close any open socket to the PubNub Network. For multiplexed channels, the specified channel(s) will be removed and the socket remains open until there are no more channels remaining in the list.

Warning

Method(s)

To Unsubscribe from a channel you can use the following method(s) in the Python-Tornado SDK:

pubnub.unsubscribe().channels(String|List|Tuple).channel_groups(String|List|Tuple).execute()

Parameter	Type	Required	Description
`channels`	String \| List \| Tuple	Optional	Subscribe to `channels`, Either `channel` or `channel_group` is required.
`channel_groups`	String \| List \| Tuple	Optional	Subscribe to `channel_groups`, Either `channel` or `channel_group` is required

Basic Usage

Unsubscribe from a channel:

pubnub.unsubscribe().channels("my_channel").execute()

Note

The response of the call is handled by adding a Listener. Please see the Listeners section for more details. Listeners should be added before calling the method.

Response

The output below demonstrates the response to a successful call:

if envelope.event == 'leave':
    envelope.uuid # 175c2c67-b2a9-470d-8f4b-1db94f90e39e
    envelope.timestamp # 1345546797
    envelope.occupancy # 2

Other Examples

Unsubscribing from multiple channels. Requires Stream Controller add-onRequires that the Stream Controller add-on is enabled for your key. See this page on enabling add-on features on your keys:
https://support.pubnub.com/hc/en-us/articles/360051974791-How-do-I-enable-add-on-features-for-my-keys-
```
pubnub.unsubscribe().channels(["my_channel1", "my_channel2"]).execute();
```
Example Response:
```
{
    "action" : "leave"
}
```

Unsubscribe from a channel group

pubnub.unsubscribe().channels_groups(["my_group1", "my_group2").execute()

Example Response:

{
    "action": "leave"
}

Unsubscribe All

Description

Unsubscribe from all channels and all channel groups

Method(s)

```
pubnub.unsubscribe_all()
```

Basic Usage

pubnub.unsubscribe_all();

Returns

None

Listeners

Description

You can be notified of connectivity status, message and presence notifications via the listeners.

Listeners should be added before calling the method.

Adding Listeners

from pubnub.callbacks import SubscribeCallback
from pubnub.enums import PNOperationType, PNStatusCategory

class MySubscribeCallback(SubscribeCallback):
    def status(self, pubnub, status):

        # The status object returned is always related to subscribe but could contain
        # information about subscribe, heartbeat, or errors
        # use the operationType to switch on different options
        if status.operation == PNOperationType.PNSubscribeOperation \
                or status.operation == PNOperationType.PNUnsubscribeOperation:
            if status.category == PNStatusCategory.PNConnectedCategory:
                pass
                # This is expected for a subscribe, this means there is no error or issue whatsoever
            elif status.category == PNStatusCategory.PNReconnectedCategory:
                pass
                # This usually occurs if subscribe temporarily fails but reconnects. This means
                # there was an error but there is no longer any issue
            elif status.category == PNStatusCategory.PNDisconnectedCategory:
                pass
                # This is the expected category for an unsubscribe. This means there
                # was no error in unsubscribing from everything
            elif status.category == PNStatusCategory.PNUnexpectedDisconnectCategory:
                pass
                # This is usually an issue with the internet connection, this is an error, handle
                # appropriately retry will be called automatically
            elif status.category == PNStatusCategory.PNAccessDeniedCategory:
                pass
                # This means that PAM does not allow this client to subscribe to this
                # channel and channel group configuration. This is another explicit error
            else:
                pass
                # This is usually an issue with the internet connection, this is an error, handle appropriately
                # retry will be called automatically
        elif status.operation == PNOperationType.PNSubscribeOperation:
            # Heartbeat operations can in fact have errors, so it is important to check first for an error.
            # For more information on how to configure heartbeat notifications through the status
            # PNObjectEventListener callback, consult http://www.pubnub.com/docs/sdks/python/tornado/api-reference/configuration#configuration
            if status.is_error():
                pass
                # There was an error with the heartbeat operation, handle here
            else:
                pass
                # Heartbeat operation was successful
        else:
            pass
            # Encountered unknown status type

    def presence(self, pubnub, presence):
        pass  # handle incoming presence data

    def message(self, pubnub, message):
        pass  # handle incoming messages

    def signal(self, pubnub, signal):
        pass # handle incoming signals

pubnub.add_listener(MySubscribeCallback())

Removing Listeners

my_listener = MySubscribeCallback()

pubnub.add_listener(my_listener)

# some time later
pubnub.remove_listener(my_listener)

Handling Disconnects

from pubnub.callbacks import SubscribeCallback
from pubnub.enums import PNStatusCategory

class HandleDisconnectsCallback(SubscribeCallback):
    def status(self, pubnub, status):
        if status.category == PNStatusCategory.PNUnexpectedDisconnectCategory:
            # internet got lost, do some magic and call reconnect when ready
            pubnub.reconnect()
        elif status.category == PNStatusCategory.PNTimeoutCategory:
            # do some magic and call reconnect when ready
            pubnub.reconnect()
        else:
            logger.debug(status)

    def presence(self, pubnub, presence):
        pass

    def message(self, pubnub, message):
        pass

    def signal(self, pubnub, signal):
        pass

disconnect_listener = HandleDisconnectsCallback()

pubnub.add_listener(disconnect_listener)

Listener status events

Category	Description
`PNTimeoutCategory`	Failure to establish a connection to PubNub due to a timeout.
`PNBadRequestCategory`	The server responded with a bad response error because the request is malformed.
`PNNetworkIssuesCategory`	A subscribe event experienced an exception when running. The SDK isn't able to reach the PubNub Data Stream Network. This may be due to many reasons, such as: the machine or device isn't connected to the internet; the internet connection has been lost; your internet service provider is having trouble; or, perhaps the SDK is behind a proxy.
`PNReconnectedCategory`	The SDK was able to reconnect to PubNub.
`PNConnectedCategory`	SDK subscribed with a new mix of channels. This is fired every time the `channel` or `channel group` mix changes.
`PNUnexpectedDisconnectCategory`	Previously started subscribe loop did fail and at this moment client disconnected from real-time data channels.
`PNUnknownCategory`	Returned when the subscriber gets a non-200 HTTP response code from the server.

Note

SubscribeListener should not be used with high-performance sections of your app.

Python version support

Publish

Description

Important

Publish Anytime

Message Data:

Don't JSON serialize!

Message Size:

Message Too Large Error

Message Publish Rate:

Publishing to Multiple Channels:

Publishing Messages Reliably:

Method(s)

Basic Usage

Publish a message to a channel:

Note

Returns

Other Examples

Fire

Description

Method(s)

Basic Usage

Fire a message to a channel:

Signal

Description

Method(s)

Basic Usage

Signal a message to a channel:

Response

Subscribe

Description

Warning

Method(s)

Basic Usage

Note

Returns

Note

Other Examples

Sample Responses

Timeout Event

Custom Presence Event (State Change)

Interval Event

Note

Note

Unsubscribe

Description

Warning

Method(s)

Basic Usage

Note

Response

Other Examples

Unsubscribe All

Description

Method(s)

Basic Usage

Returns

Listeners

Description

Adding Listeners

Removing Listeners

Handling Disconnects

Listener status events

Note