Cloud Computing, Google Cloud (GCP)

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Leveraging Pub/Sub for Triggering Cloud Functions: A Powerful Architecture Pattern

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In the modern era of cloud computing, event-driven architectures have become essential for building scalable and efficient applications. This blog will explore the combination of Google Cloud Pub/Sub and Cloud Functions and how leveraging Pub/Sub as a trigger for Cloud Functions can enable powerful architecture patterns. We will dive into the fundamental concepts of Pub/Sub and Cloud Functions and explain why this integration is a valuable approach for event-driven systems. Also, we will configure a simple trigger for the cloud function using Pub/Sub.

Pub/Sub and it's working

Pub/Sub, short for Publish/Subscribe, is a fully-managed messaging service provided by Google Cloud Platform (GCP).

It enables asynchronous communication and decouples the production and consumption of messages.

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Cloud Functions and its working

Cloud Functions is a serverless computing platform offered by GCP. It allows developers to write and deploy code that runs in response to various events.

Triggering Cloud Functions with Pub/Sub

Combining Pub/Sub and Cloud Functions offers several advantages and enables powerful architecture patterns. Following are some of the key points:

  • Seamless integration: Pub/Sub is natively integrated with Cloud Functions, simplifying the configuration and setup process.
  • Scalability and event-driven nature: Pub/Sub can handle high volumes of messages and trigger Cloud Functions in a distributed and scalable manner, enabling real-time processing of events.
  • Loose coupling and decoupling of systems: Pub/Sub allows for decoupling the producer and consumer of messages, facilitating flexibility and resilience in the overall system design.
  • Fault-tolerance and reliability: Pub/Sub ensures reliable delivery of messages even in the face of failures, guaranteeing the robustness of the event-driven architecture.

Steps to Configure Pub/Sub Trigger on Cloud Functions

  1. Creating a Pub/Sub topic:

Open the GCP console and go to Pub/Sub in the analytics section as below.


Next, Create a topic and ensure that create the default subscription box is unchecked as below.


2. Creating the Cloud Function:

Once the Topic is created, Open Cloud Functions in the serverless section of the GCP console as below.


Click on Create function, select the runtime of your choice (In this example, Python 3.9 is chosen), and select 1st Gen.


Next, in the Trigger section, select the Trigger type as Cloud Pub/Sub and choose the topic created in the first step.


Keep the rest of the configurations as default values and click on next.

3. Deploying the Cloud Function:

In the “Code” section, you will get a pre-written Python function that will print the message received from the Pub/Sub Topic triggering event. You can keep this code as it is and click on Deploy.


Once the Function gets deployed, Go back to the Pub/Sub console, and You can see a Subscription got created for the previously configured Topic as shown below.


4. Triggering the Cloud Function:

Next, click on the Pub/Sub Topic and go to the “Messages” section as below and click on Publish Message.


In the next section, Configure the number of messages and Message body per your requirement and click Publish.


5. Verifying the trigger in Cloud Function:

Next, Go back to the Cloud Function Console and click on the “Logs” section to verify that the Cloud Function has run and prints the message you have published in the Topic.



Triggering Cloud Functions with Pub/Sub presents an effective architecture pattern for building scalable and event-driven applications. By leveraging Pub/Sub’s publish/subscribe model and Cloud Functions’ serverless capabilities, developers can achieve loose coupling, scalability, and fault-tolerant event processing. This combination empowers developers to create powerful and efficient systems that respond to real-time events. By following the step-by-step process to configure Pub/Sub triggers on Cloud Functions, developers can unlock the potential of this architecture pattern and take advantage of the seamless integration between these two powerful GCP services.

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Drop a query if you have any questions regarding Pub/Sub, I will get back to you quickly.

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1. Can I use Pub/Sub to trigger multiple Cloud Functions?

ANS: – Yes, you can use Pub/Sub to trigger multiple Cloud Functions. By creating multiple subscriptions to the same Pub/Sub topic.

2. Is Pub/Sub the only trigger option for Cloud Functions?

ANS: – No, Pub/Sub is not the only trigger option for Cloud Functions. Cloud Functions supports various event sources for triggering, including HTTP requests, Cloud Storage changes, Firestore events, and more. Each trigger type is designed to handle different events, providing flexibility in choosing your application’s most suitable trigger mechanism.

3. Can I use Pub/Sub to trigger Cloud Functions across different projects or regions?

ANS: – Yes, Pub/Sub can be used to trigger Cloud Functions across different projects and regions. Pub/Sub is a global service within Google Cloud Platform (GCP), which means you can publish messages to a topic in one project or region and subscribe to that topic in another project or region. This flexibility allows you to build distributed systems and trigger Cloud Functions wherever deployed.


Vignesh K S works as a Research Associate at CloudThat. He is interested in learning the latest technologies and methodologies related to Cloud Services and Development in Cloud using serverless services.



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