Module Vine 

gRPC server and client for Cocoon extension host communication.

Vine gRPC Module

This module encapsulates all logic related to the gRPC-based Inter-Process Communication (IPC) system, codenamed “Vine”.

Architecture Overview

Vine implements a bidirectional gRPC communication protocol between:

• Mountain: The main VS Code extension host process
• Cocoon: The sidecar process handling web-based operations

The system uses two complementary gRPC services:

MountainService (Cocoon → Mountain)

• ProcessCocoonRequest: Request-response pattern for Cocoon to query Mountain
• SendCocoonNotification: Fire-and-forget notifications from Cocoon to Mountain
• CancelOperation: Request cancellation of long-running operations

CocoonService (Mountain → Cocoon)

• ProcessMountainRequest: Request-response pattern for Mountain to query Cocoon
• SendMountainNotification: Fire-and-forget notifications from Mountain to Cocoon
• CancelOperation: Request cancellation of long-running operations

Communication Protocol

All RPC messages use Protocol Buffers for serialization:

• GenericRequest: Contains request ID, method name, and JSON parameters
• GenericResponse: Contains request ID, JSON result, or optional error
• GenericNotification: Fire-and-forget message with method name and JSON parameters
• RpcError: JSON-RPC compliant error structure with code, message, and optional data

Data Flow

Cocoon (Sidecar)          Mountain (Extension Host)
      │                            │
      ├──────────────────────────►│ ProcessCocoonRequest
      │  Extension/Query           │ (returns GenericResponse)
      │                            │
      ├──────────────────────────►│ SendCocoonNotification
      │  Status Updates            │ (returns Empty)
      │                            │
      │◄───────────────────────────┤ ProcessMountainRequest
      │  Webview Operations         │ (returns GenericResponse)
      │                            │
      │◄───────────────────────────┤ SendMountainNotification
      │  Configuration Changes      │ (returns Empty)
      │                            │
      ◄═════════════════════════════╡ CancelOperation
                             Cancels either process

Key Features

• Thread-Safe Client: Connection pool with Arc<Mutex<>> for concurrent access
• Request Timeout: Configurable timeout per RPC call
• Error Handling: Comprehensive error types with gRPC status conversion
• Graceful Degradation: System continues when Cocoon is unavailable
• Health Checks: Connection validation before RPC calls
• Retry Logic: Automatic reconnection attempts for transient failures

Message Validation

• Maximum message size: 4MB (default tonic limit)
• JSON serialization validation on all parameters
• Request ID tracking for operation correlation
• Method whitelisting for security

Modules

• [Client]: gRPC client for connecting to Cocoon services
• Error: Comprehensive error types for Vine operations
• [Generated]: Auto-generated protobuf code from Vine.proto
• [Server]: gRPC server implementations for Mountain services

Modules

Client

Vine client - thread-safe gRPC client for a Cocoon sidecar process. Pool of CocoonClient connections keyed by identifier, automatic reconnect with exponential back-off, per-connection health metadata, per-call timeouts, message-size validation, and a broadcast fan-out of every observed notification.

Error

VineError

Generated

Vine Generated Code

Multiplexer

Bidirectional streaming multiplexer for the Vine gRPC bus.

Server

Vine gRPC Server Module