Firebase App Hosting utilizesCloud Build to transform yourapplication source code into a containerized format suitable for deployment onCloud Run.

The build process operates through the following key stages:

1. Ingest: Gathers your application source code and configuration.

2. Build: Installs dependencies and builds your application.

3. Handoff: Finalizes the productionCloud Run container.

These three steps correspond directly to build steps 1, 2 and 3 as displayed inCloud Build in the Google Cloud Console:

Ingest stage

This stage is responsible for handling pre-build logic. It reads, sanitizes, andwrites user-defined environment variables. It also dereferences and pins anysecrets specified in theapphosting.yaml file.

Build stage

This is the core of the build process, responsible for generating a runnablecontainer image and abundle.yaml file defining your build configuration.It utilizesCloud Native Buildpacksto package theapplication efficiently. More information on thebundle.yamlfile can be foundongithub.

Buildpacks are responsible for transforming your application source code intoproduction ready container images.Firebase App Hosting chains togetherseveral buildpacks to complete the build process:

1. Runtime Buildpack: Ensures all necessary components for running a basicNode.js application are included and dependencies are installed.
2. Monorepo Buildpack: Configures subsequent buildpacks to handle differentmonorepo scenarios.

3. Framework Buildpack: Installs the correct framework adapter (likeAngular or Next.js) and prepares subsequent buildpacks.

   Framework adapters are in charge of running the productionized build command and mapping any relevant framework-specific config values to a standard format readable byApp Hosting.

4. Package Manager Buildpack: Executes the installation of dependencies andbuilds the app using npm, yarn, or pnpm.

5. Output Bundle Buildpack: Defines the run command and prepares the outputbundle for execution.

Handoff stage

This final stage packages all the information extracted from the applicationsource code plus the build container image and sends it to theApp Hostingbackend. TheApp Hosting backend then uses this information to set upCloud Run with the proper configurations.

Learn more

The entireApp Hosting build process is open source.

• The buildpack code is inthe Google Cloud buildpacks repo
• Code for framework adapters is in thefirebase-framework-tools repo
• Learn more aboutCloud Native buildpacks andCloud Build