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    Choose a subscription type

    This document helps you choose the appropriate type of Pub/Sub subscription suited to your business requirements.

    Pub/Sub offers the following types of subscriptions:

    • Pull subscriptionsuse a subscriber client to request messages from the Pub/Sub server.

    • Push subscriptionsuse the Pub/Sub server to initiate requests to your subscriber application to deliver messages.

    • Export subscriptionsexport your messages directly to a Google Cloud resource. These subscriptions include the following:

      • BigQuery subscriptionsexport data to a BigQuery table.

      • Cloud Storage subscriptionsexport data to a Cloud Storage bucket.

    Pub/Sub subscription comparison table

    The following table offers some guidance in choosing the appropriate delivery mechanism for your application:

    Features supported by Pub/Sub subscriptions
    Use case
    Pull subscription
    • Large volume of messages (GBs per second).
    • Efficiency and throughput of message processing is critical.
    • Environments where it's not feasible to set up a public HTTPS endpoint with a non-self-signed SSL certificate.
    Push subscription
    • Multiple topics that must be processed by the same webhook.
    • App Engine Standard or Cloud Run functions subscribers.
    • Environments where it's not feasible to set up Google Cloud dependencies such as credentials and the client library.
    Export subscription
    • Large volume of messages that can scale up to multiple millions of messages per second.
    • Sending messages directly to a Google Cloud resource without any additional processing.
    Endpoints
    Pull subscription
    Any device on the internet that has authorized credentials can call the Pub/Sub API.
    Push subscription

    An HTTPS server with non-self-signed certificate accessible on the public web.

    The receiving endpoint might be decoupled from the Pub/Sub subscription, so that messages from multiple subscriptions are sent to a single endpoint.

    Export subscription
    The subscription writes to a Google Cloud resource, such as a BigQuery table or Cloud Storage bucket.
    Load balancing
    Pull subscription
    Multiple subscribers can make pull calls to the same subscription. Each subscriber receives a subset of messages.
    Push subscription

    Push endpoints can be load balancers.

    Export subscription

    The Pub/Sub service automatically balances the load.

    Configuration
    Pull subscription

    No configuration is necessary.

    Push subscription
    • No configuration is necessary for App Engine apps in the same project as the subscriber.
    • Verification of push endpoints is not required in the Google Cloud console.
    • Endpoints must be reachable using DNS names and have SSL certificates installed.
    Export subscription
    The Google Cloud resource that the subscription exports to must exist and be configured with the appropriate permissions.
    Flow control
    Pull subscription
    The subscriber client controls the rate of delivery. The subscriber can dynamically modify the acknowledgment deadline, allowing message processing to take an arbitrarily long time.
    Push subscription
    The Pub/Sub server automatically implements flow control. Clients don't need to handle message flow. However, it's possible to indicate that the client can't handle the current message load, by passing back an HTTP error.
    Export subscription
    Pub/Sub automatically implements flow control to optimize writing messages to the destination Google Cloud resource.
    Efficiency and throughput
    Pull subscription
    Achieves high throughput at low CPU and bandwidth by allowing batched delivery, acknowledgments, and massively parallel consumption. Might be inefficient if frequent polling is used to minimize message delivery time.
    Push subscription
    Delivers one message per request and limits the maximum number of outstanding messages.
    Export subscription
    Pub/Sub dynamically handles scalability.

    When to use an export subscription

    Without an export subscription, you need a pull or push subscription and a subscriber (such as Dataflow) to read messages and write them to a Google Cloud resource. The overhead of running a Dataflow job is not necessary when messages don't require additional processing before being stored.

    Export subscriptions have the following advantages:

    • Simple deployment.You can set up an export subscription through a single workflow in the console, Google Cloud CLI, client library, or Pub/Sub API.

    • Low costs.Reduces the additional cost and latency of similar Pub/Sub pipelines that include Dataflow jobs. This cost optimization is useful for messaging systems that don't require additional processing before storage.

    • Minimal monitoring.Export subscriptions are part of the multi-tenant Pub/Sub service and don't require you to run separate monitoring jobs.

    • Flexibility. A BigQuery subscription can use the schema of the topic to which it is attached, which is not available with the basic Dataflow template for writing from Pub/Sub to BigQuery. Similarly, a Cloud Storage subscription offers configurable file batching options based on file size and elapsed time, which are not configurable in the basic Dataflow template for writing from Pub/Sub to Cloud Storage.

    However, a Dataflow pipeline is still recommended for Pub/Sub systems where some data transformation is required before the data is stored in a Google Cloud resource such as a BigQuery table or Cloud Storage bucket.

    To learn how to stream data from Pub/Sub to BigQuery with transformation by using Dataflow, see Stream from Pub/Sub to BigQuery .

    To learn how to stream data from Pub/Sub to Cloud Storage with transformation by using Dataflow, see Stream messages from Pub/Sub by using Dataflow .

    What's next

    Understand the workflow for each subscription type:
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