GitHub Repository: gitpod-io/gitpod
Path: blob/main/memory-bank/components/local-app-api.md
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Local App API

Overview

The Local App API defines the gRPC interfaces for the Local App service, which facilitates communication between a user's local machine and Gitpod workspaces. This API enables port tunneling, SSH connection management, and other local-to-remote interactions.

Purpose

This API provides a standardized interface for:

Monitoring and managing port tunnels between local machines and remote workspaces
Enabling automatic port tunneling for seamless local-to-remote communication
Resolving SSH connection details for connecting to workspaces via SSH

Architecture

The Local App API is implemented as a gRPC service defined in Protocol Buffer files. These definitions are used to generate client and server code in Go for use by the local app and other components in the system.

Key Services

LocalApp

Provides methods for managing local-to-remote communication:

TunnelStatus: Streams the status of port tunnels for a workspace instance
AutoTunnel: Enables or disables automatic port tunneling for a workspace instance
ResolveSSHConnection: Resolves SSH connection details for connecting to a workspace

Key Data Structures

TunnelStatus

Represents the status of a port tunnel:

Remote port number
Local port number
Visibility setting (public, private, etc.)

ResolveSSHConnectionResponse

Contains SSH connection details:

Path to the SSH configuration file
Host identifier for the SSH connection

Communication Patterns

The API uses gRPC for efficient, typed communication
The TunnelStatus method uses server-side streaming to provide real-time updates on tunnel status
Requests include workspace instance identifiers to target specific workspaces

Dependencies

Depends on the Supervisor API for tunnel visibility definitions
Used by the local app client running on users' machines
Integrated with SSH configuration management

Usage Examples

Local development tools use this API to establish port forwarding to workspace services
IDE extensions use this API to enable SSH-based remote development
CLI tools use this API to connect to workspace resources

Version Compatibility

The API uses Protocol Buffers version 3 (proto3) syntax, which provides forward and backward compatibility features. The service is designed to allow for the addition of new tunneling and connection options without breaking existing clients.

Code Generation and Building

Regenerating Code from Protobuf Definitions

The Local App API uses Protocol Buffers and gRPC for defining interfaces. When changes are made to the .proto files, the corresponding code in various languages needs to be regenerated.

To regenerate the code:

Navigate to the local-app-api directory:
```
cd components/local-app-api
```
Run the generate script:
```
./generate.sh
```

This script performs the following actions:

Installs necessary dependencies (protoc plugins)
Generates Go code using protoc-gen-go and protoc-gen-go-grpc
Updates license headers

The Local App API has a dependency on the Supervisor API for tunnel visibility definitions, which is included in the protoc generation process.

Building After Code Generation

After regenerating the code, you may need to rebuild components that depend on the Local App API. This typically involves:

For Go components:

cd <component-directory>
go build ./...

Using Leeway (for CI/CD):

leeway build -D components/<component-name>:app

The Local App API is primarily used by the local-app component, which is a desktop application that runs on users' machines to facilitate communication with remote Gitpod workspaces.