How to use the command `gcloud app` (with examples)

The gcloud app command is part of the Google Cloud SDK and is designed for interacting with Google App Engine, a platform as a service (PaaS) that allows developers to deploy and scale applications seamlessly. This command enables developers to deploy, manage, and monitor their cloud-based applications with ease, leveraging Google’s infrastructure for serverless computing.

Use case 1: Deploy an app’s code and configuration to the App Engine server

Code:

gcloud app deploy deployables

Motivation:

Deploying an application to the Google App Engine is a critical task for developers who want to make their applications available to users. Using the gcloud app deploy command, developers can upload their code and configuration settings to the App Engine, ensuring their application is running on Google’s reliable infrastructure. This use case is particularly important during the initial launch or subsequent updates, as it provides a streamlined process for getting applications live with minimal operational overhead.

Explanation:

• gcloud: The Google Cloud command-line interface.
• app: Specifies that the command is related to App Engine operations.
• deploy: The action to take, which is to deploy an application.
• deployables: Refers to the set of files and configuration needed for deployment (typically your app’s directory or specific deployable files).

Example Output:

Services to deploy:

descriptor:      [/path/to/app.yaml]
source:          [/path/to/your/source/code]
target project:  [your-project-id]

Do you want to continue (Y/n)?  y
Beginning deployment of service [default]...

Use case 2: List all versions of all services deployed to the App Engine server

Code:

gcloud app versions list

Motivation:

Listing the versions of services deployed in App Engine is crucial for developers and system administrators who need to maintain and manage multiple iterations of applications. This command provides transparency into the deployment history, enabling users to track, validate, and roll back to a previous version if necessary. It simplifies the task of managing complex applications with multiple versions and ensures that teams can coordinate updates effectively.

Explanation:

• gcloud: The Google Cloud command-line tool.
• app: Indicates that you are working with App Engine.
• versions: Specifies the command pertains to different deployed versions.
• list: The action to perform, which is to list all versions.

Example Output:

SERVICE  VERSION  TRAFFIC_SPLIT  LAST_DEPLOYED           SERVING STATUS
default  20231001  1.00           2023-10-01T12:00:00Z  SERVING
default  20230901  0.00           2023-09-01T12:00:00Z  STOPPED

Use case 3: Open the current app in a web browser

Code:

gcloud app browse

Motivation:

Opening your app directly in a browser after deployment provides immediate feedback and assurance that the application has been successfully deployed and is accessible. This command is particularly useful during development and testing phases, enabling developers to quickly verify changes in real-time within a web browser, thus enhancing the agility of the development workflow.

Explanation:

• gcloud: The command-line interface for Google Cloud.
• app: Specifies actions related to App Engine.
• browse: The action to open the application in the default web browser.

Example Output:

Upon execution, your default web browser will open, displaying your application’s homepage, confirming that your app is live.

Use case 4: Create an App Engine app within the current project

Code:

gcloud app create

Motivation:

Creating an App Engine app is a foundational step for developers setting up their applications for cloud deployment. Before deploying code, it’s necessary to establish an App Engine within the Google Cloud project, which sets the environment and allocates resources. This command simplifies the setup process by initializing the App Engine environment, allowing developers to focus on building their applications without worrying about infrastructure nuances.

Explanation:

• gcloud: The Google Cloud command-line tool.
• app: Indicates you are performing an App Engine task.
• create: The action that initiates the creation of an App Engine app in your project.

Example Output:

Please enter an integer between 1 and 135: 
Creating App Engine application in project [your-project-id] and region [us-central].
Waiting for operation [operation-id] to complete...
Created app for project [your-project-id].

Use case 5: Display the latest App Engine app logs

Code:

gcloud app logs read

Motivation:

Accessing application logs is essential for monitoring, debugging, and understanding the behavior of an application in a production environment. By reading the latest App Engine logs, developers and system administrators can gain insights into application performance, detect anomalies, and troubleshoot issues efficiently. This use case is particularly important for maintaining the reliability and uptime of services hosted on Google App Engine.

Explanation:

• gcloud: The interface for interacting with Google Cloud.
• app: Specifies the task is related to App Engine.
• logs: Indicates that the command pertains to application logs.
• read: The action to fetch and display log entries.

Example Output:

2023-10-01 12:34:56 default[20231001]  This is a log message indicating successful execution.
2023-10-01 12:35:00 default[20231001]  Warning: Resource usage approaching limits.

Conclusion:

The gcloud app command is a versatile and powerful tool for managing applications on the Google App Engine platform. Each use case highlights different aspects of application management, from deployment to monitoring. By leveraging these command-line actions, developers and administrators can efficiently harness the capabilities of Google Cloud’s serverless infrastructure to build, deploy, and maintain robust, scalable applications.