docs(handover): Add webnode docs

tizoc · tizoc · commit 3fb260a8dd02 · 2025-07-21T22:32:35.000-03:00
diff --git a/docs/handover/README.md b/docs/handover/README.md
@@ -22,6 +22,8 @@ structured onboarding experience for developers new to the project.
   routing and service patterns
 - **Testing framework**: [Testing Infrastructure](testing-infrastructure.md) -
   scenario-based testing with extensive examples
+- **Browser deployment**: [Webnode Implementation](webnode.md) - WebAssembly
+  build target for running OpenMina in browsers
 - **Ledger implementation overview**: [Ledger Crate](ledger-crate.md) - OCaml
   port with Rust adaptations
 - **Service integration**: [Services](services.md) - complete service inventory
@@ -55,6 +57,7 @@ structured onboarding experience for developers new to the project.
 - [Fuzzing Infrastructure](#fuzzing-infrastructure)
 - [Services Technical Debt](#services-technical-debt)
 - [State Machine Technical Debt](#state-machine-technical-debt)
+- [Webnode Implementation](#webnode-implementation)
 - [Circuits](#circuits)
 - [Debug Block Proof Generation](#debug-block-proof-generation)
 - [Persistence](#persistence)
@@ -193,6 +196,16 @@ Systemic architectural issues in state machine implementations:
 - Safety and linting improvements (including clippy lints)
 - Prioritized refactoring roadmap
 
+### [Webnode Implementation](webnode.md)
+
+WebAssembly build target for browser deployment:
+
+- WASM compilation with browser-specific threading adaptations
+- WebRTC-based P2P networking with pull-based protocol
+- JavaScript API for web application integration
+- Block production capabilities with browser-based SNARK proving
+- Technical constraints and workarounds for browser environment
+
 ### [Circuits](circuits.md)
 
 Circuit generation process and distribution:
diff --git a/docs/handover/webnode.md b/docs/handover/webnode.md
@@ -0,0 +1,185 @@
+# OpenMina Webnode Implementation
+
+This document covers the WebAssembly (WASM) build target of OpenMina located in
+`node/web/`.
+
+## Overview
+
+The webnode compiles the full OpenMina node to WebAssembly for browser
+execution. It includes block production, transaction processing, SNARK
+verification, and WebRTC-based P2P networking.
+
+### Design Goals
+
+- Run the full node stack in browsers without plugins
+- Maintain compatibility with the main OpenMina implementation
+- Support block production with browser-based proving
+- Provide JavaScript API for web applications
+
+## Architecture
+
+### WASM Target
+
+Builds as both `cdylib` and `rlib` crate types. Code is conditionally compiled
+with `#[cfg(target_family = "wasm")]` guards.
+
+#### Build Process
+
+```bash
+cd node/web
+cargo +nightly build --release --target wasm32-unknown-unknown
+wasm-bindgen --keep-debug --web --out-dir ../../frontend/src/assets/webnode/pkg ../../target/wasm32-unknown-unknown/release/openmina_node_web.wasm
+```
+
+Requires nightly toolchain and generates bindings for
+`frontend/src/assets/webnode/pkg/`.
+
+### Threading
+
+Browser threading constraints require specific adaptations:
+
+#### Rayon Setup
+
+`init_rayon()` in `rayon.rs` configures the thread pool using
+`num_cpus.max(2) - 1` threads. Must be called before SNARK verification.
+
+#### Task Spawning
+
+- `P2pTaskSpawner`: Uses `wasm_bindgen_futures::spawn_local()`
+- `P2pTaskRemoteSpawner`: Routes tasks to main thread via
+  `thread::start_task_in_main_thread()` because WebRTC APIs are main-thread only
+
+## Features
+
+Provides the same functionality as the native node:
+
+- Transaction validation and application
+- Ledger state management
+- SNARK verification using browser-compiled circuits
+- Consensus participation
+- RPC interface for web applications
+
+### Block Production
+
+Supports block production with:
+
+- Plain text or encrypted private keys (parsed in `parse_bp_key()`)
+- Custom coinbase receivers
+- Browser-based SNARK proving via `BlockProver::make()`
+
+### Networking
+
+#### WebRTC P2P Layer
+
+- **Transport**: WebRTC DataChannels for browser-to-browser communication
+- **Protocol**: Pull-based networking (see [P2P README](../p2p/readme.md))
+- **Default Peer**:
+  `/2bjYBqn45MmtismsAYP9rZ6Xns9snCcNsN1eDgQZB5s6AzY2CR2/https/webrtc3.webnode.openmina.com/443`
+- **Channels**: 8 distinct DataChannels for different protocol types (see
+  [P2P README](../p2p/readme.md#channels))
+
+#### Network Configuration
+
+```rust
+initial_peers: Vec<P2pConnectionOutgoingInitOpts>
+peer_discovery: !self.p2p_no_discovery
+max_peers: Some(100)
+```
+
+## Implementation Details
+
+### Key Files
+
+#### `lib.rs` - Main Entry Point
+
+- **`main()`**: Automatic WASM initialization
+- **`run()`**: Primary node startup function
+- **`build_env()`**: Build information export
+- **`parse_bp_key()`**: Block producer key parsing
+
+#### `node/builder.rs` - Node Construction
+
+- **`NodeBuilder`**: Node configuration
+- **Configuration Methods**: P2P setup, block production, verification
+- **Default Peers**: Single hardcoded WebRTC peer for bootstrap
+
+#### `node/mod.rs` - Type Definitions
+
+- **Type Aliases**: `Node = openmina_node_common::Node<NodeService>`
+- **Task Spawners**: P2P-specific spawning implementations for browser
+  constraints
+
+#### `rayon.rs` - Threading Setup
+
+- **`init_rayon()`**: Required initialization for multi-threading
+- **CPU Detection**: Automatic core count with minimum guarantees
+
+### JavaScript Interface
+
+#### Main Entry Point
+
+```javascript
+const rpcSender = await run(blockProducerKey, seedNodesUrl, genesisConfigUrl);
+```
+
+- `blockProducerKey`: Optional string or `[encrypted, password]` array
+- `seedNodesUrl`: Optional URL returning newline-separated peer addresses
+- `genesisConfigUrl`: Optional URL returning binary genesis config (defaults to
+  `DEVNET_CONFIG`)
+
+#### Setup
+
+- `console_error_panic_hook` enables panic traces in browser console
+- `keep_worker_alive_cursed_hack()` prevents worker termination (wasm-bindgen
+  issue #2945)
+
+### Performance
+
+- Parallel SNARK verification using `num_cpus.max(2) - 1` threads
+- Circuit reuse for verification operations
+- 100 peer connection limit configured in `P2pLimits`
+- Statistics collection via `gather_stats()` when enabled
+
+## Dependencies
+
+**WASM-specific**: `wasm-bindgen`, `wasm-bindgen-futures`, `js-sys`,
+`console_error_panic_hook`, `gloo-utils`
+
+**Core**: Standard OpenMina workspace crates plus `rayon` for threading
+
+## Known Issues
+
+- Worker lifecycle requires `keep_worker_alive_cursed_hack()` due to
+  wasm-bindgen issue #2945
+- WebRTC operations restricted to main thread
+- Careful initialization ordering required
+
+## Technical Debt
+
+- TODO in `setup_node()` for seed nodes refactoring
+- Single hardcoded default peer
+- Commented HTTP client and peer loading code in `builder.rs`
+
+## Usage
+
+```javascript
+// Basic startup
+const rpc = await run();
+
+// With block producer
+const rpc = await run("private-key");
+const rpc = await run([encryptedKey, "password"]);
+
+// With custom configuration
+const rpc = await run(key, peersUrl, genesisUrl);
+
+// RPC access
+const peers = await rpc.state().peers();
+const stats = await rpc.stats().sync();
+```
+
+## Future Work
+
+- Split prover to its own WASM heap
+  (https://github.com/openmina/openmina/issues/1128)
+- API for zkApp integration
