Pub/Sub Lite: Qwik Start - GSP832

Overview

Complementing Pub/Sub, Pub/Sub Lite is a zonal service for messaging systems with predictable traffic patterns. If you publish 1 MiB-1 GiB of messages per second, Pub/Sub Lite is a low cost option for high-volume event ingestion.

Publishers send messages to Lite topics and subscribers receive messages from Lite subscriptions. Lite topics and Lite subscriptions are zonal resources that must be in the same Cloud project and zone. For a list of zones that Pub/Sub Lite supports, refer to Pub/Sub Lite locations.

In this lab you will learn how to:

• Create Lite topics and Lite subscriptions using the Cloud Console.

• Send and receive messages using the Pub/Sub Lite client library for Python.

Task 1. Create a Lite Topic

To create a Lite topic with the Cloud Console, follow these steps:

1. In the Cloud Console, go to Navigation menu > Pub/Sub > Lite Topics page.

2. Click Create Lite topic.

3. Select Regional Lite topic to choose the region and then select Zonal Lite topic to choose the zone (this lab uses us-west1), then click Continue.

4. In the Name section, enter my-lite-topic as the Lite topic ID. The Lite topic name includes the Lite topic ID, the zone, and the project number.

5. Click Continue.

6. Make sure to uncheck Attach to a reservation checkbox.

7. Click Create.

Click Check my progress to verify the objective.

Create a Lite Topic

Check my progress

Task 2. Create a Lite Subscription

To create a Lite subscription with Cloud Console, follow these steps:

1. Click on Lite Subscriptions in the left menu.

2. Click Create Lite subscription.

3. In the Lite subscription ID field, enter my-lite-subscription.

4. In Select a Lite resources select a Lite topic to receive messages, you created in the last step.

5. In the Delivery requirement section, select Deliver messages after stored.

6. Click Create.

The Lite subscription is in the same zone as the Lite topic.

Click Check my progress to verify the objective.

Create a Lite Subscription

Check my progress

Task 3. Send messages

Send messages to the Lite topic using the following publisher application. Using the Cloud Shell Editor or the editor of your choice, create a file called send_messages.py and add the following script, then:

1. Uncomment all steps in the TODO section.

2. Replace project_number with the project number you can see in the Lite topic and subscription name in the Console.

3. If you used a different cloud_region and zone_id, update with your information:

from google.cloud.pubsublite.cloudpubsub import PublisherClient
from google.cloud.pubsublite.types import (
    CloudRegion,
    CloudZone,
    MessageMetadata,
    TopicPath,
)

# TODO(developer):
# project_number = 1122334455
# cloud_region = "us-west1"
# zone_id = "a"
# topic_id = "my-lite-topic"
# num_messages = 100

location = CloudZone(CloudRegion(cloud_region), zone_id)
topic_path = TopicPath(project_number, location, topic_id)

# PublisherClient() must be used in a `with` block or have __enter__() called before use.
with PublisherClient() as publisher_client:
    data = "Hello world!"
    api_future = publisher_client.publish(topic_path, data.encode("utf-8"))
    # result() blocks. To resolve API futures asynchronously, use add_done_callback().
    message_id = api_future.result()
    publish_metadata = MessageMetadata.decode(message_id)
    print(
        f"Published a message to partition {publish_metadata.partition.value} and offset {publish_metadata.cursor.offset}."
    )

The publisher sends 100 messages to a Lite topic and prints the number of messages that the Pub/Sub Lite service receives.

Task 4. Receive messages

Receive messages from the Lite subscription using the following subscriber application. Using the Cloud Shell Editor or the editor of your choice, create a file called receive_messages.py and add the following script, then

1. Uncomment all steps in the TODO section.

2. Replace project_number with the Project number you can see in the Lite topic and subscription name in the Console.

3. If you used a different cloud_region and zone_id, update with your information:

from concurrent.futures._base import TimeoutError
from google.cloud.pubsublite.cloudpubsub import SubscriberClient
from google.cloud.pubsublite.types import (
    CloudRegion,
    CloudZone,
    FlowControlSettings,
    SubscriptionPath,
)

# TODO(developer):
# project_number = 1122334455
# cloud_region = "us-west1"
# zone_id = "a"
# subscription_id = "my-lite-subscription"
# timeout = 90

location = CloudZone(CloudRegion(cloud_region), zone_id)
subscription_path = SubscriptionPath(project_number, location, subscription_id)
# Configure when to pause the message stream for more incoming messages based on the
# maximum size or number of messages that a single-partition subscriber has received,
# whichever condition is met first.
per_partition_flow_control_settings = FlowControlSettings(
    # 1,000 outstanding messages. Must be >0.
    messages_outstanding=1000,
    # 10 MiB. Must be greater than the allowed size of the largest message (1 MiB).
    bytes_outstanding=10 * 1024 * 1024,
)

def callback(message):
    message_data = message.data.decode("utf-8")
    print(f"Received {message_data} of ordering key {message.ordering_key}.")
    message.ack()

# SubscriberClient() must be used in a `with` block or have __enter__() called before use.
with SubscriberClient() as subscriber_client:

    streaming_pull_future = subscriber_client.subscribe(
        subscription_path,
        callback=callback,
        per_partition_flow_control_settings=per_partition_flow_control_settings,
    )

    print(f"Listening for messages on {str(subscription_path)}...")

    try:
        streaming_pull_future.result(timeout=timeout)
    except TimeoutError or KeyboardInterrupt:
        streaming_pull_future.cancel()
        assert streaming_pull_future.done()

After the subscriber receives a message, the subscriber prints the message ID and the message data.

4. Now run both scripts:

python3 send_messages.py
python3 receive_messages.py

You will see output in Cloud Shell that looks like this:

Received Hello world! of ordering key .

You will also be able to monitor activity on the Lite Topics and Lite Subscriptions pages in the Cloud Console.

Task 5. Clean up

Although all resources will be destroyed when you end this lab, it's good practice to clean up resources you don't need to avoid charges.

1. In the Cloud Console, go to the Lite Topics page.

2. Click my-lite-topic.

3. On the Lite topic details page, click Delete.

4. In the field that appears, type delete to confirm that you want to delete the Lite topic.

5. Click Delete.

---

Answer of Lab

export REGION=

curl -LO raw.githubusercontent.com/quiccklabs/Labs_solutions/master/PubSub%20Lite%20Qwik%20Start/quicklabgsp832.sh
sudo chmod +x quicklabgsp832.sh
./quicklabgsp832.sh