Lifecycle
Understand the full journey of Serverless Functions in Juno, from setup and development to deployment and maintenance.
Initial Setup
If you didn’t use a template or skipped the language selection during setup, you can run juno functions eject at the root of your project. This command configures your project with the appropriate setup based on your language of choice. For Rust, it includes a Cargo.toml and a lib.rs file. For TypeScript, it sets up an index.ts file.
Developing Functions
Once your project is scaffolded, you can start writing your functions. Use the CLI to build them with:
juno functions build
If you start the emulator (see chapter below) in watch mode, your functions will be rebuilt automatically on save, so you don’t need to run this command manually.
Local Development
For local development and testing, a sandbox environment is essential. You can establish this environment by running the CLI command juno dev start.
Find more information about local development in the documentation.
The local sandbox environment supports hot reloading. This means that the container will automatically redeploy your local Satellite each time juno dev build is executed and a new version is produced.
If you start the emulator with the --watch flag, it will also rebuild your functions automatically when changes are detected.
Deploying
Juno offers two main ways to deploy your serverless functions, depending on whether you're working locally or integrating with a CI pipeline like GitHub Actions.
1. Direct Deploy
If you're developing locally or in another environment where the access key has admin privileges, you can deploy the latest build directly:
juno functions upgrade
- ✅ Skips the CDN.
- ✅ Immediate deployment.
- 🔐 Requires access key with upgrade permission.
- 📦 Uses the default path:
./target/deploy/satellite.wasm.gz.
Optional:
juno functions upgrade --src ./path/to/custom-build.wasm.gz
2. With CDN + Approval Workflow
If you're using CI (like GitHub Actions) or an environment where your access key has write privileges:
a) Publish to CDN
In your GitHub Action or script:
juno functions publish
With options:
juno functions publish --mode staging --src ./path/to/build.wasm.gz
- 📤 Uploads to the Satellite’s CDN release.
- 🔐 Requires access key with write role.
b) Upgrade from CDN
From your local CLI or in the Console UI, you can then upgrade.
juno functions upgrade --cdn
- 🔎 Interactively selects the WASM version from the published CDN.
- 🧾 Only deploys with a key that has upgrade rights.
- 🕵️ If your key is submit-only, the change will wait for approval in the Console UI or CLI.
3. Optional Approval Flow
If you're using CI (like GitHub Actions) or an environment where your access key has submit privileges — meaning it cannot directly modify or write data — you can follow a workflow that requires manual approval before deployment.
juno functions publish --no-apply
Then the published release:
- Becomes a pending change.
- Must be reviewed and applied manually.
Apply the change either in the Console UI or directly using the CLI.
📜 List submitted changes
juno changes list
✅ Apply a specific change
juno changes apply --id <change_id>
Once applied, the Satellite can then be upgraded in the CLI or respectively in the Console UI using:
juno functions upgrade --cdn-path <published_version_path>
Summary
A quick reference for the most common CLI commands and deployment workflows when working with serverless functions in Juno.
🛠️ Common CLI Commands
| Command(s) | Scenario |
|---|---|
juno functions eject | Initializes your project for writing serverless functions. |
juno dev start | Starts the emulator. |
juno functions build | Compiles your custom Satellite's code. Changes are automatically redeployed locally. |
🚀 Deployment Scenarios
| Command(s) | Scenario |
|---|---|
juno functions upgrade | Upgrades your serverless functions immediatly. |
juno functions upgrade --src ./path/to/custom-build.wasm.gz | Use a custom WASM path to upgrade. |
juno functions publish in CI → juno functions upgrade --cdn in CLI or Console UI | CI/CD with write access. |
juno functions publish --no-apply in CI → juno changes apply → juno functions upgrade --cdn-path ... | CI/CD with submit-only access. |
juno functions publish --mode staging | CI/CD using staging environment. |