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Pulsar Python client

You can use a Pulsar Python client to create producers, consumers, and readers.

All the methods in producer, consumer, and reader of a Python client are thread-safe. You can read the API docs for the Python client.

Installation​

Use pip to install the latest version:

pip install 'pulsar-client==2.10.1'

You can install optional components alongside the client library:

# avro serialization
pip install 'pulsar-client[avro]==2.10.1'

# functions runtime
pip install 'pulsar-client[functions]==2.10.1'

# all optional components
pip install 'pulsar-client[all]==2.10.1'

Installation via PyPi is available for the following Python versions:

PlatformSupported Python versions
macOS (>= 11.0)3.7, 3.8, 3.9 and 3.10
Linux (including Alpine Linux)3.7, 3.8, 3.9 and 3.10

Connection URLs​

To connect to Pulsar using client libraries, you need to specify a Pulsar protocol URL.

You can assign Pulsar protocol URLs to specific clusters and use the pulsar scheme. The following is an example of localhost with the default port 6650:

pulsar://localhost:6650

If you have multiple brokers, separate IP:port by commas:

pulsar://localhost:6550,localhost:6651,localhost:6652

If you use TLS authentication, add +ssl in the scheme:

pulsar+ssl://pulsar.us-west.example.com:6651

API Reference​

The complete Python API reference is available at api/python.

Examples​

You can find a variety of Python code examples for the pulsar-client library.

Producer example​

The following example creates a Python producer for the my-topic topic and sends 10 messages on that topic:

import pulsar

client = pulsar.Client('pulsar://localhost:6650')

producer = client.create_producer('my-topic')

for i in range(10):
    producer.send(('Hello-%d' % i).encode('utf-8'))

client.close()

Consumer example​

The following example creates a consumer with the my-subscription subscription name on the my-topic topic, receives incoming messages, prints the content and ID of messages that arrive, and acknowledges each message to the Pulsar broker.

import pulsar

client = pulsar.Client('pulsar://localhost:6650')

consumer = client.subscribe('my-topic', 'my-subscription')

while True:
    msg = consumer.receive()
    try:
        print("Received message '{}' id='{}'".format(msg.data(), msg.message_id()))
        # Acknowledge successful processing of the message
        consumer.acknowledge(msg)
    except Exception:
        # Message failed to be processed
        consumer.negative_acknowledge(msg)

client.close()

This example shows how to configure negative acknowledgment.

from pulsar import Client, schema
client = Client('pulsar://localhost:6650')
consumer = client.subscribe('negative_acks','test',schema=schema.StringSchema())
producer = client.create_producer('negative_acks',schema=schema.StringSchema())
for i in range(10):
    print('send msg "hello-%d"' % i)
    producer.send_async('hello-%d' % i, callback=None)
producer.flush()
for i in range(10):
    msg = consumer.receive()
    consumer.negative_acknowledge(msg)
    print('receive and nack msg "%s"' % msg.data())
for i in range(10):
    msg = consumer.receive()
    consumer.acknowledge(msg)
    print('receive and ack msg "%s"' % msg.data())
try:
    # No more messages expected
    msg = consumer.receive(100)
except:
    print("no more msg")
    pass

Reader interface example​

You can use the Pulsar Python API to use the Pulsar reader interface. Here's an example:

# MessageId taken from a previously fetched message
msg_id = msg.message_id()

reader = client.create_reader('my-topic', msg_id)

while True:
    msg = reader.read_next()
    print("Received message '{}' id='{}'".format(msg.data(), msg.message_id()))
    # No acknowledgment

Multi-topic subscriptions​

In addition to subscribing a consumer to a single Pulsar topic, you can also subscribe to multiple topics simultaneously. To use multi-topic subscriptions, you can supply a regular expression (regex) or a List of topics. If you select topics via regex, all topics must be within the same Pulsar namespace.

The following is an example:

import re
consumer = client.subscribe(re.compile('persistent://public/default/topic-*'), 'my-subscription')
while True:
    msg = consumer.receive()
    try:
        print("Received message '{}' id='{}'".format(msg.data(), msg.message_id()))
        # Acknowledge successful processing of the message
        consumer.acknowledge(msg)
    except Exception:
        # Message failed to be processed
        consumer.negative_acknowledge(msg)
client.close()

Create a Python client with multiple advertised listeners​

To ensure clients in both internal and external networks can connect to a Pulsar cluster, Pulsar introduces advertisedListeners.

The following example creates a Python client using multiple advertised listeners:

import pulsar

client = pulsar.Client('pulsar://localhost:6650', listener_name='external')

Schema​

Supported schema types​

You can use different built-in schema types in Pulsar. All the definitions are in the pulsar.schema package.

SchemaNotes
BytesSchemaGet the raw payload as a bytes object. No serialization/deserialization are performed. This is the default schema mode
StringSchemaEncode/decode payload as a UTF-8 string. Uses str objects
JsonSchemaRequire record definition. Serializes the record into standard JSON payload
AvroSchemaRequire record definition. Serializes in AVRO format

Schema definition reference​

The schema definition is done through a class that inherits from pulsar.schema.Record.

This class has a number of fields that can be of either pulsar.schema.Field type or another nested Record. All the fields are specified in the pulsar.schema package. The fields are matching the AVRO field types.

Field TypePython TypeNotes
Booleanbool
Integerint
Longint
Floatfloat
Doublefloat
Bytesbytes
Stringstr
ArraylistNeed to specify record type for items.
MapdictKey is always String. Need to specify value type.

Additionally, any Python Enum type can be used as a valid field type.

Fields parameters​

When adding a field, you can use these parameters in the constructor.

ArgumentDefaultNotes
defaultNoneSet a default value for the field, such as a = Integer(default=5).
requiredFalseMark the field as "required". It is set in the schema accordingly.

Schema definition examples​

Simple definition​
class Example(Record):
    a = String()
    b = Integer()
    c = Array(String())
    i = Map(String())
Using enums​
from enum import Enum

class Color(Enum):
    red = 1
    green = 2
    blue = 3

class Example(Record):
    name = String()
    color = Color
Complex types​
class MySubRecord(Record):
    x = Integer()
    y = Long()
    z = String()

class Example(Record):
    a = String()
    sub = MySubRecord()
Set namespace for Avro schema​

Set the namespace for the Avro Record schema using the special field _avro_namespace.

class NamespaceDemo(Record):
   _avro_namespace = 'xxx.xxx.xxx'
   x = String()
   y = Integer()

The schema definition is like this.

{
  "name": "NamespaceDemo", "namespace": "xxx.xxx.xxx", "type": "record", "fields": [
    {"name": "x", "type": ["null", "string"]},
    {"name": "y", "type": ["null", "int"]}
  ]
}

Declare and validate schema​

You can send messages using BytesSchema, StringSchema, AvroSchema, and JsonSchema.

Before the producer is created, the Pulsar broker validates that the existing topic schema is the correct type and that the format is compatible with the schema definition of a class. If the format of the topic schema is incompatible with the schema definition, an exception occurs in the producer creation.

Once a producer is created with a certain schema definition, it only accepts objects that are instances of the declared schema class.

Similarly, for a consumer or reader, the consumer returns an object (which is an instance of the schema record class) rather than raw bytes.

Example

consumer = client.subscribe(
                  topic='my-topic',
                  subscription_name='my-subscription',
                  schema=AvroSchema(Example) )

while True:
    msg = consumer.receive()
    ex = msg.value()
    try:
        print("Received message a={} b={} c={}".format(ex.a, ex.b, ex.c))
        # Acknowledge successful processing of the message
        consumer.acknowledge(msg)
    except Exception:
        # Message failed to be processed
        consumer.negative_acknowledge(msg)

You can send byte data using a BytesSchema.

Example

producer = client.create_producer(
                'bytes-schema-topic',
                schema=BytesSchema())
producer.send(b"Hello")

consumer = client.subscribe(
                'bytes-schema-topic',
                'sub',
                schema=BytesSchema())
msg = consumer.receive()
data = msg.value()

End-to-end encryption​

Pulsar encryption allows applications to encrypt messages at producers and decrypt messages at consumers. See Get started for more details.