Gufo Liftbridge Example: Publishing

The message queue has two fundamental operations: publishing and subscribing. Let's write the simple publisher.

Note

The stream and partition must be created before running the example, so refer to the Liftbridge Docs or pass the create example.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

Let's see the details.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

Gufo Liftbridge is an async library. In our case we should run the client from our synchronous script, so we need to import asyncio to use asyncio.run().

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

The client is implemented as a LiftbridgeClient class, which must be imported to be used.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

Liftbridge is the dynamic cluster, synchronized over Raft protocol. Cluster members may enter and leave and the client uses one or more cluster members as a bootstrap to recover an actual topology. These bootstrap members are called seeds and are defined as a list of the strings in the host:port format. For our example, we consider the Liftbridge is running locally at the 127.0.0.1:9292. Take note, ever we have one seed, we must define it as a list.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

All async code must be performed in the async functions, so our publish() function is async def.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

We need an instance of the client. The instance may be used directly or operated as an async context manager with the async with clause. When used as a context manager, the client automatically closes all connections on the exit of context, so its lifetime is defined explicitly. LiftbridgeClient requires a list of seeds to connect the cluster, so we passed the BROKERS list. The client is highly configurable, refer to the LiftbridgeClient reference for the detailed explanations.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

Let's publish 10 messages.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

The publish() function is used to publish one message immediately. The client does not enforce any specific data format and leaves it to the application. The only requirement is to pass the message value as the bytes type. In our example, we construct the string as the message and we have to encode it to the bytes manually. Then we must specify the stream and partition to publish, we use partition 0 of stream test in our example. publish() is the async function and must be awaited. The function may accept additional parameters, so refer to the publish() referece for the detailed explanations.

import asyncio
from gufo.liftbridge.client import LiftbridgeClient

BROKERS = ["127.0.0.1:9292"]


async def publish():
    async with LiftbridgeClient(BROKERS) as client:
        for i in range(10):
            await client.publish(
                f"msg{i}".encode("utf-8"), stream="test", partition=0
            )


asyncio.run(publish())

Use asyncio.run() function to start our async code.