Create subscription with filter

Create a Pub/Sub subscription with filtering enabled

Explore further

For detailed documentation that includes this code sample, see the following:

• Filter messages from a subscription

Code sample

C++

Before trying this sample, follow the C++ setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub C++ API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

namespace pubsub = ::google::cloud::pubsub;
namespace pubsub_admin = ::google::cloud::pubsub_admin;
[](pubsub_admin::SubscriptionAdminClient client,
   std::string const& project_id, std::string topic_id,
   std::string subscription_id) {
  google::pubsub::v1::Subscription request;
  request.set_name(
      pubsub::Subscription(project_id, std::move(subscription_id))
          .FullName());
  request.set_topic(
      pubsub::Topic(project_id, std::move(topic_id)).FullName());
  request.set_filter(R"""(attributes.is-even = "false")""");
  auto sub = client.CreateSubscription(request);
  if (sub.status().code() == google::cloud::StatusCode::kAlreadyExists) {
    std::cout << "The subscription already exists\n";
    return;
  }
  if (!sub) throw std::move(sub).status();

  std::cout << "The subscription was successfully created: "
            << sub->DebugString() << "\n";
}

C#

Before trying this sample, follow the C# setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub C# API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

using Google.Cloud.PubSub.V1;
using Grpc.Core;

public class CreateSubscriptionWithFilteringSample
{
    public Subscription CreateSubscriptionWithFiltering(string projectId, string topicId, string subscriptionId, string filter)
    {
        SubscriberServiceApiClient subscriber = SubscriberServiceApiClient.Create();
        TopicName topicName = TopicName.FromProjectTopic(projectId, topicId);
        SubscriptionName subscriptionName = SubscriptionName.FromProjectSubscription(projectId, subscriptionId);
        Subscription subscription = null;

        var subscriptionRequest = new Subscription
        {
            SubscriptionName = subscriptionName,
            TopicAsTopicName = topicName,
            Filter = filter
        };

        try
        {
            subscription = subscriber.CreateSubscription(subscriptionRequest);
        }
        catch (RpcException e) when (e.Status.StatusCode == StatusCode.AlreadyExists)
        {
            // Already exists.  That's fine.
        }
        return subscription;
    }
}

Go

Before trying this sample, follow the Go setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Go API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import (
	"context"
	"fmt"
	"io"

	"cloud.google.com/go/pubsub"
)

func createWithFilter(w io.Writer, projectID, subID, filter string, topic *pubsub.Topic) error {
	// Receive messages with attribute key "author" and value "unknown".
	// projectID := "my-project-id"
	// subID := "my-sub"
	// filter := "attributes.author=\"unknown\""
	// topic of type https://godoc.org/cloud.google.com/go/pubsub#Topic
	ctx := context.Background()
	client, err := pubsub.NewClient(ctx, projectID)
	if err != nil {
		return fmt.Errorf("pubsub.NewClient: %w", err)
	}
	defer client.Close()

	sub, err := client.CreateSubscription(ctx, subID, pubsub.SubscriptionConfig{
		Topic:  topic,
		Filter: filter,
	})
	if err != nil {
		return fmt.Errorf("CreateSubscription: %w", err)
	}
	fmt.Fprintf(w, "Created subscription with filter: %v\n", sub)
	return nil
}

Java

Before trying this sample, follow the Java setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Java API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.pubsub.v1.SubscriptionAdminClient;
import com.google.pubsub.v1.ProjectSubscriptionName;
import com.google.pubsub.v1.ProjectTopicName;
import com.google.pubsub.v1.Subscription;
import java.io.IOException;

public class CreateSubscriptionWithFiltering {
  public static void main(String... args) throws Exception {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-project-id";
    String topicId = "your-topic-id";
    String subscriptionId = "your-subscription-id";
    String filter = "attributes.author=\"unknown\"";

    createSubscriptionWithFilteringExample(projectId, topicId, subscriptionId, filter);
  }

  public static void createSubscriptionWithFilteringExample(
      String projectId, String topicId, String subscriptionId, String filter) throws IOException {
    try (SubscriptionAdminClient subscriptionAdminClient = SubscriptionAdminClient.create()) {

      ProjectTopicName topicName = ProjectTopicName.of(projectId, topicId);
      ProjectSubscriptionName subscriptionName =
          ProjectSubscriptionName.of(projectId, subscriptionId);

      Subscription subscription =
          subscriptionAdminClient.createSubscription(
              Subscription.newBuilder()
                  .setName(subscriptionName.toString())
                  .setTopic(topicName.toString())
                  // Receive messages with attribute key "author" and value "unknown".
                  .setFilter(filter)
                  .build());

      System.out.println(
          "Created a subscription with filtering enabled: " + subscription.getAllFields());
    }
  }
}

Node.js

/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const filterString = 'YOUR_FILTER_STRING';   // e.g. 'attributes.author="unknown"'

// Imports the Google Cloud client library
const {PubSub} = require('@google-cloud/pubsub');

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function createSubscriptionWithFilter(
  topicNameOrId,
  subscriptionNameOrId,
  filterString
) {
  // Creates a new subscription
  await pubSubClient
    .topic(topicNameOrId)
    .createSubscription(subscriptionNameOrId, {
      filter: filterString,
    });
  console.log(
    `Created subscription ${subscriptionNameOrId} with filter ${filterString}.`
  );
}

Node.js

/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const topicNameOrId = 'YOUR_TOPIC_NAME_OR_ID';
// const subscriptionNameOrId = 'YOUR_SUBSCRIPTION_NAME_OR_ID';
// const filterString = 'YOUR_FILTER_STRING';   // e.g. 'attributes.author="unknown"'

// Imports the Google Cloud client library
import {PubSub} from '@google-cloud/pubsub';

// Creates a client; cache this for further use
const pubSubClient = new PubSub();

async function createSubscriptionWithFilter(
  topicNameOrId: string,
  subscriptionNameOrId: string,
  filterString: string
) {
  // Creates a new subscription
  await pubSubClient
    .topic(topicNameOrId)
    .createSubscription(subscriptionNameOrId, {
      filter: filterString,
    });
  console.log(
    `Created subscription ${subscriptionNameOrId} with filter ${filterString}.`
  );
}

PHP

Before trying this sample, follow the PHP setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub PHP API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

use Google\Cloud\PubSub\PubSubClient;

/**
 * Creates a Pub/Sub subscription.
 *
 * @param string $projectId  The Google project ID.
 * @param string $topicName  The Pub/Sub topic name.
 * @param string $subscriptionName  The Pub/Sub subscription name.
 * @param string $filter  The Pub/Sub subscription filter.
 */
function create_subscription_with_filter(
    string $projectId,
    string $topicName,
    string $subscriptionName,
    string $filter
): void {
    $pubsub = new PubSubClient([
        'projectId' => $projectId,
    ]);
    $topic = $pubsub->topic($topicName);
    $subscription = $topic->subscription($subscriptionName);

    $subscription->create(['filter' => $filter]);

    printf('Subscription created: %s' . PHP_EOL, $subscription->name());
    printf('Subscription info: %s' . PHP_EOL, json_encode($subscription->info()));
}

Python

Before trying this sample, follow the Python setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Python API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

from google.cloud import pubsub_v1

# TODO(developer): Choose an existing topic.
# project_id = "your-project-id"
# topic_id = "your-topic-id"
# subscription_id = "your-subscription-id"
# filter = "attributes.author=\"unknown\""

publisher = pubsub_v1.PublisherClient()
subscriber = pubsub_v1.SubscriberClient()
topic_path = publisher.topic_path(project_id, topic_id)
subscription_path = subscriber.subscription_path(project_id, subscription_id)

with subscriber:
    subscription = subscriber.create_subscription(
        request={"name": subscription_path, "topic": topic_path, "filter": filter}
    )
    print(f"Created subscription with filtering enabled: {subscription}")

Ruby

Before trying this sample, follow the Ruby setup instructions in the Pub/Sub quickstart using client libraries. For more information, see the Pub/Sub Ruby API reference documentation.

To authenticate to Pub/Sub, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

require "google/cloud/pubsub"

# Shows how to create a new subscription with filter for a given topic
class PubsubCreateSubscriptionWithFilter
  def create_subscription_with_filter project_id:, topic_id:, subscription_id:, filter:
    pubsub = Google::Cloud::Pubsub.new project_id: project_id
    topic = pubsub.topic topic_id
    subscription = topic.subscribe subscription_id, filter: filter
    puts "Created subscription with filtering enabled: #{subscription_id}"
  end

  def self.run
    # TODO(developer): Replace these variables before running the sample.
    project_id = "your-project-id"
    topic_id = "your-topic-id"
    subscription_id = "id-for-new-subcription"
    filter = "attributes.author=\"unknown\""
    PubsubCreateSubscriptionWithFilter.new.create_subscription_with_filter project_id: project_id,
                                                                           topic_id: topic_id,
                                                                           subscription_id: subscription_id,
                                                                           filter: filter
  end
end

if $PROGRAM_NAME == __FILE__
  PubsubCreateSubscriptionWithFilter.run
end

What's next

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