This tutorial is a follow-up to TurboCharging your Android Gradle builds using build cache.

The key focus of this post is the remote build cache, a build speed acceleration technology that can be implemented for both local and CI builds. This is a technology worth knowing about because:

  • Without a cache system in place, every build is a new, clean build so the entire project builds from scratch, even for a small change.

Gradle provides a build cache node available as a Docker image. You can host this image in a number of ways. In this tutorial, I will lead you through the steps of setting up a build cache node on GCP (Google Cloud Platform), a free tool.

Prerequisites

To follow this tutorial, a few things are required:

  1. Basic understanding of the Gradle build tool
  2. Knowledge of how to set up an Android project on CircleCI
  3. Knowledge of the Android build process
  4. Basic knowledge of GCP virtual machine (VM) instances, firewalls, and how both work

Create and access your Google Console account

To get started, you will need to create or access your Google Cloud Platform account.

Note: If you are setting up your console for the first time, agree to terms of service, then click the Agree and Continue button.

Terms of Service

To access the free tier products on GCP, select the Getting Started option from the Navigation menu. Then click the Get Started For Free button.

Google Console Dashboard

Start by verifying your account information.

Account Information

Next, enter a valid phone number. Google will send you a confirmation text. After you complete the verification, click the Continue button.

Identity Verification

Although the next step requires you to enter you payment information, you will not be charged unless you turn on automatic billing.

Payment Information Verification

When you successfully complete the verification process, you will see a confirmation message. Click Got it to proceed.

Now that you have set up the console to use the free tier products, you can go on to the build cache node setup.

Setting up the build cache node

The build cache node setup is a 2 part process on the GCP instance:

  1. Creating a firewall rule under the VPC Network section
  2. Creating a VM instance under the Compute Engine section

By leveraging the Build Cache Node User Manual and adding some customized configurations for GCP, you can set up your build cache nodes.

Configuring a Virtual Private Cloud (VPC) network

A VPC network is a virtual version of a physical network, implemented inside of Google’s production network. It does a bunch of things but of importance is that it provides connectivity for your Compute Engine Virtual Machine (VM) instances. This is important because by default, incoming traffic from outside your network is blocked. That means we need to create a firewall rule to control incoming or outgoing traffic to our build cache node VM instance.

Creating the firewall rule

On the Google console dashboard, navigate to: Networking > VPC Network > Firewall. Click Enable to enable Compute Engine if you are prompted to do so. Then, click the Create Firewall Rule button.

Enter firewall rule details:

  • In the Name field, enter gradle-firewall-rule
  • In the Description field, enter Ingress firewall rule for the Gradle build cache node
  • Specify target tags as gradle-build-cache-node-tag
  • Enter 0.0.0.0/0 192.168.2.0/24 as source IP ranges
  • Specify protocols and ports as tcp: 5071

When the details are entered, click the Create button.

Fire Rule GIF

Setting up GCP to launch virtual machines

Google Compute Engine (GCE) is the Infrastructure as a Service (IaaS) component of Google Cloud Platform (GCP). GCP is built on the global infrastructure that runs Google’s search engine, Gmail, YouTube, and other services. Google Compute Engine enables users to launch virtual machines (VMs) on demand.

To create the VM instance, go to the Google Cloud Console dashboard, navigate to Compute > Compute Engine > VM instances, and click the Create Instance button.

Enter VM instance details:

  • In the Name field, enter gradle-build-cache-node.
  • Select Europe-north1 (Finland) as the region. Choose one that is close to you and your development team.
  • Select europe-north1-a as the Zone.
  • For Machine Configuration, enter N1 for Series.
  • Enter n1-standard-1 (1 vCPU, 3.75 GB memory) for Machine Type.

Create VM Instance

Next, select Deploy a container image to this VM instance. In the Container Image field, enter gradle/build-cache-node.

Container

We also need to set up a disk volume for our build cache to use. Expand Advanced container options and click Add Volume. Then add these parameters:

  • For Volume Type, add Directory.
  • For Mount path, add /data.
  • For Host path, add /home/build-cache.
  • Select Read/write mode.

Advanced Container Options

Complete the firewall configuration

Your next task is to add tags and firewall rules to allow specific network traffic from the Internet. Expand the Management, security, disks, networking, sole tenancy section and select the Networking tab. Then add the firewall rule we created earlier:

gradle-build-cache-node-tag

Firewall

Click Create and wait for your new VM to spin up.

Success VM Setup

Use the VM to access the cache node

To access the cache node via the VM instance’s external IP, append :5071 to the end of your external IP address. You can find the external IP address on the Google console.

Note: If you get a message that the site can’t provide a secure connection, access the IP via HTTP and not HTTPS.

Cache-Node

Configure access control for the build cache

This next step is important because we are implementing the UI Authorization security check. By default, the built-in cache node allows any user to store and retrieve entries from the cache. This is not ideal because unauthorized users can store, retrieve and delete cache entries. The only system allowed to make changes to the build cache node is your CI server, making it your single source of truth.

To change this, collapse the Settings section under Build Cache. Click Add user, and give the new user a username, password, and access level of Read & write. Read & write access allows storing artifacts. The (notes) field is not required, but it is helpful if there are multiple users for different scenarios.

Once a user has been added to the system, it is possible to restrict anonymous access to None for no access or Read for read-only access.

Click Save to store the credentials and permissions.

Cache-Access-Control

The recommended approach is to create a user with Read & write access, and restrict anonymous access to Read only. CI builds then authenticate as the user and write to the cache, while developers connect anonymously and only read from the cache.

Note: If you try to access the cache node and you aren’t authorized, you will get a response status 401: Unauthorized error.

Cache access control on an Android project

You can configure the credentials the HttpBuildCache uses to access the build cache server as shown in the settings.gradle file.

buildCache {
    remote(HttpBuildCache) {
        url = 'https://example.com:8123/cache/'
        credentials {
            username = 'build-cache-user'
            password = 'C0mplic@ted-pa$$worD'
        }
    }
}

Run CI build to verify the working cache node

Now, we need to make sure that the Gradle build cache is working as expected. Push the changes you made to your settings.gradle file to the GitHub repository. This push triggers the CI build.

Once the build successfully completes, there will be some artifacts stored in the build cache as shown on the UI dashboard.

Build-Cache-Artifacts

Conclusion

In this tutorial, you have learned how to create and run a Gradle build cache node using a GCP VM instance. You updated your app and pushed its cache to it. You now have experience using build speed acceleration technology that you can use for your local and CI builds. With a cache system in place, you no longer need to run the entire project from scratch. This saves your team time and resources, and lets you push smaller fixes and updates more often, so you can add features and fix bugs faster.


Taracha is a creator whose mission is to help companies solve complex problems in the simplest way possible. He cares about finding visions and causes that he is passionate about and using technology to help these companies solve their challenges.

He has over 6 years of native mobile application development experience and 4 years of web application development.

He is currently a Senior Software Engineer at Premise Data, where he champions the development and deployment of new product features and is particularly passionate about the Developer Productivity Engineering space.