Publish/Subscribe API for PubNub Python-Twisted SDK

Deprecated

NOTICE: Based on current web trends and our own usage data, PubNub's Python Twisted SDK is deprecated as of May 1, 2019. Deprecation means we will no longer be updating the Python Twisted SDK but will continue to support users currently using it. Please feel free to use our other Python SDK offerings as they will continue to be supported and maintained. If you would like to use the Python Twisted SDK specifically, we would love to work with you on keeping this project alive!

Publish​

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-Twisted 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-Twisted SDK:

pubnub.publish().channel(String).message(Object).should_store(Boolean).meta(dict).use_post(Boolean)
ParameterTypeRequiredDefaultDescription
channelStringYesDestination of message.
messageObjectYesThe payload.
should_storeBooleanOptionalaccount defaultStore in history
metaObjectOptionalNoneMeta data object which can be used with the filtering ability.

Basic Usage​

Publish a message to a channel​

def callback(envelope):
    print("publish timetoken: %d" % envelope.result.timetoken)

d = pubnub.publish().channel("my_channel").message({
    'name': 'Alex',
    'online': True
}).future()
d.addCallback(callback)
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:

FieldTypeDescription
timetokenIntan int representation of the timetoken when the message was published

Other Examples​

Publish with metadata​

d = pubnub.publish()\
    .channel("my_channel")\
    .message(["hello", "there"])\
    .meta({'name': 'Alex'})\
    .deferred()
d.addCallback(callback)

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

Subscribe​

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-Twisted SDK:

pubnub.subscribe().channels(String|List|Tuple).channel_groups(String|List|Tuple).with_timetoken(Int).with_presence().execute()
ParameterTypeRequiredDescription
channelsString | List | TupleOptionalSubscribe to channels, Either channel or channel_group is required.
channel_groupsString | List | TupleOptionalSubscribe to channel_groups, Either channel or channel_group is required.
timetokenIntOptionalPass a timetoken.
with_presenceCommandOptionalAlso 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:

FieldTypeDescription
categoryPNStatusCategoryDetails of StatusCategory are here
is_errorBooleanThis is true if an error occurred in the execution of the operation.
error_dataPNErrorDataError data of the exception (if Error is true).
status_codeintStatus code of the execution.

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

FieldTypeDescription
messageObjectThe message sent on channel.
subscriptionStringThe channel group or wildcard subscription match (if exists).
channelStringThe channel for which the message belongs.
timetokenIntTimetoken for the message.
user_metadataDictUser metadata.

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

FieldTypeDescription
eventStringEvents like join, leave, timeout, state-change.
uuidStringuuid for event.
timestampInttimestamp for event.
occupancyIntCurrent occupancy.
subscriptionStringThe channel group or wildcard subscription match (if exists).
channelStringThe channel for which the message belongs.
timetokenInttimetoken of the message.
user_metadataDictUser metadata.

Other Examples​

Basic subscribe with logging​

import logging
import pubnub

from pubnub.pnconfiguration import PNConfiguration
from pubnub.pubnub_twisted import PubNubTwisted as PubNub
from pubnub.pubnub_twisted import SubscribeListener

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

pnconfig = PNConfiguration()

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

pubnub = PubNub(pnconfig)
show all 18 lines

Subscribing to multiple channels​

It's possible to subscribe to more than one channel using the Multiplexing feature. The example shows how to do that using an array to specify the channel names.

Alternative subscription methods

You can also use Wildcard Subscribe and Channel Groups to subscribe to multiple channels at a time. To use these features, the Stream Controller add-on must be enabled on your keyset in the Admin Portal.

pubnub.subscribe().channels(["my_channel1", "my_channel2"]).execute()

Subscribing to a Presence channel​

Requires Presence add-on

This method requires that the Presence add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your 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-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal (with Enable Wildcard Subscribe checked). Read the support page on enabling add-on features on your 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 (.).

pubnub.subscribe().channels("foo.*").execute();
Wildcard grants and revokes

Only one level (a.*) of wildcarding is supported. If you grant on * or a.b.*, the grant will treat * or a.b.* as a single channel named either * or a.b.*. You can also revoke permissions from multiple channels using wildcards but only if you previously granted permissions using the same wildcards. Wildcard revokes, similarly to grants, only work one level deep, like a.*.

Subscribing with State​

Requires Presence add-on

This method requires that the Presence add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

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. If you don't set the UUID, you won't be able to connect to PubNub.

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
            }
            d = pubnub.set_state().channels('awesome_channel').\
                channel_groups('awesome_channel_groups').state(state).deferred()
show all 31 lines

Subscribe to a channel group​

Requires Stream Controller add-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

pubnub.subscribe().channel_groups("awesome_channel_group").execute()

Subscribe to the presence channel of a channel group​

note
Requires Stream Controller and Presence add-ons

This method requires both the Stream Controller and Presence add-ons are enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your keys.

pubnub.subscribe().channel_groups(["cg1", "cg2"]).with_presence().execute()

Unsubscribe​

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

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

pubnub.unsubscribe().channels(String|List|Tuple).channel_groups(String|List|Tuple).execute()
ParameterTypeRequiredDescription
channelsString | List | TupleOptionalSubscribe to channels, Either channel or channel_group is required.
channel_groupsString | List | TupleOptionalSubscribe 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-on

This method requires that the Stream Controller add-on is enabled for your key in the Admin Portal. Read the support page on enabling add-on features on your 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​

Unsubscribe from all channels and all channel groups

Method(s)​

pubnub.unsubscribe_all()

Basic Usage​

pubnub.unsubscribe_all();

Returns​

None

Listeners​

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

Listeners should be added before calling the method.

Add Listeners​

from pubnub.callbacks import SubscribeCallback

class MySubscribeCallback(SubscribeCallback):
    def status(self, pubnub, status):
        pass
        # 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
show all 54 lines

Remove 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):
show all 26 lines

Listener status events​

CategoryDescription
PNTimeoutCategoryFailure to establish a connection to PubNub due to a timeout.
PNBadRequestCategoryThe server responded with a bad response error because the request is malformed.
PNNetworkIssuesCategoryA subscribe event experienced an exception when running. The SDK isn't able to reach PubNub servers. 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.
PNReconnectedCategoryThe SDK was able to reconnect to PubNub.
PNConnectedCategorySDK subscribed with a new mix of channels. This is fired every time the channel or channel group mix changes.
PNUnexpectedDisconnectCategoryPreviously started subscribe loop did fail and at this moment client disconnected from real-time data channels.
PNUnknownCategoryReturned 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.

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