hakoniwa-pdu-python

Python PDU communication library for the Hakoniwa simulator. Provides a unified transport layer where RPC and Pub/Sub (topics) run seamlessly over WebSocket. For high-speed use cases, a Shared Memory (SHM) backend is also available. The architecture is extensible to Zenoh, enabling scalable and distributed systems. Binary ⇔ JSON ⇔ Python type conversion is built-in, reducing boilerplate to a minimum.

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✨ Features

• Unified layer: RPC and Pub/Sub integrated on top of WebSocket
• Automatic type conversion: safely convert between binary, JSON, and Python types with offset definitions
• Transport flexibility: choose between WebSocket, Shared Memory (SHM), and extensible backends such as Zenoh
• Explicit & secure connections: WebSocket URIs (ws://...) clearly define communication scope
• Event-driven & polling support: register handlers or poll buffers as needed
• Ready-to-run samples: minimal examples for Twist (topic) and AddTwoInts (RPC) included

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📦 Installation

pip install hakoniwa-pdu
pip show hakoniwa-pdu   # check version

Environment Variables

Specify the directory containing .offset files for PDU conversion:

export HAKO_BINARY_PATH=/your/path/to/offset

Default path if unset:

/usr/local/lib/hakoniwa/hako_binary/offset

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🚀 Quick Start (3 commands)

Example 1: WebSocket Topic (geometry_msgs/Twist publish → subscribe)

1. Publisher (server)

python examples/topic/websocket/remote_publisher.py \
  --uri ws://localhost:8080 \
  --pdu-config examples/pdu_config.json \
  --service-config examples/service.json

2. Subscriber (client)

python examples/topic/websocket/remote_subscriber.py \
  --uri ws://localhost:8080 \
  --pdu-config examples/pdu_config.json \
  --service-config examples/service.json

3. Output

[INFO] Received Twist: linear.x=0 angular.z=0
[INFO] Received Twist: linear.x=1 angular.z=1

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Example 2: WebSocket RPC (AddTwoInts service)

1. RPC Server

python examples/rpc/websocket/remote_rpc_server.py \
  --uri ws://localhost:8080 \
  --pdu-config examples/pdu_config.json \
  --service-config examples/service.json

2. RPC Client

python examples/rpc/websocket/remote_rpc_client.py \
  --uri ws://localhost:8080 \
  --pdu-config examples/pdu_config.json \
  --service-config examples/service.json

3. Output

Response: 3

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📡 Event-Driven PDU Handling

Server:

server_manager.register_handler_pdu_data(on_pdu)

def on_pdu(client_id, packet):
    ...

Client:

client_manager.register_handler_pdu_data(on_pdu)

def on_pdu(packet):
    ...

Polling via contains_buffer() / get_buffer() is also available.

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📁 Project Structure

hakoniwa_pdu/
├── pdu_manager.py
├── impl/
│   ├── icommunication_service.py
│   ├── websocket_communication_service.py
│   ├── websocket_server_communication_service.py
│   ├── shm_communication_service.py
│   ├── pdu_convertor.py
│   └── hako_binary/
├── rpc/
│   ├── ipdu_service_manager.py
│   ├── protocol_client.py
│   ├── protocol_server.py
│   ├── auto_wire.py
│   ├── remote/
│   └── shm/
├── resources/
│   └── offset/
└── examples/

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🧰 Hakoniwa Launcher

hako_launcher.py orchestrates multiple Hakoniwa assets described in a JSON file. The launcher handles environment preparation, process supervision, and optional notifications when an asset exits unexpectedly.

How to run

# Basic usage (immediate mode)
python -m hakoniwa_pdu.apps.launcher.hako_launcher path/to/launch.json

# Immediate mode with background exit (skip monitoring loop)
python -m hakoniwa_pdu.apps.launcher.hako_launcher path/to/launch.json --no-watch

# Interactive control (serve mode)
python -m hakoniwa_pdu.apps.launcher.hako_launcher path/to/launch.json --mode serve

• Immediate mode (default) performs activate → hako-cmd start → watch.
  • Assets whose activation_timing is "before_start" are spawned first.
  • After hako-cmd start completes successfully, assets with "after_start" are started.
  • Unless --no-watch is specified, the launcher keeps monitoring child processes. If any asset stops, every remaining asset is terminated.
• Serve mode keeps the process alive and accepts commands via STDIN. Available commands: activate, start, stop, reset, terminate, status, quit/exit.

Set HAKO_PDU_DEBUG=1 to enable debug logging from the launcher modules.

Launcher JSON format

The schema is provided at src/hakoniwa_pdu/apps/launcher/schemas/launcher.schema.json. A minimal configuration consists of a version header, optional defaults, and at least one asset definition.

{
  "version": "0.1",
  "defaults": {
    "cwd": ".",
    "stdout": "logs/${asset}.out",
    "stderr": "logs/${asset}.err",
    "start_grace_sec": 1,
    "delay_sec": 3,
    "env": {
      "prepend": {
        "PATH": ["/usr/bin"]
      }
    }
  },
  "assets": [
    {
      "name": "drone",
      "command": "linux-main_hako_aircraft_service_px4",
      "args": ["127.0.0.1", "4560"],
      "activation_timing": "before_start"
    }
  ]
}

Top level keys

Key	Description
version	Free-form version string for the specification.【F:src/hakoniwa_pdu/apps/launcher/model.py†L82-L90】
defaults	Shared defaults applied to every asset when the field is omitted at the asset level. Paths are resolved relative to the launch file.【F:src/hakoniwa_pdu/apps/launcher/loader.py†L47-L91】
assets	Array of process definitions. Launch order is automatically sorted by depends_on while preserving the original order when there is no dependency.【F:src/hakoniwa_pdu/apps/launcher/model.py†L112-L167】
notify	Optional notification that fires when an asset exits or the launcher aborts. Supports webhook and exec variants.【F:src/hakoniwa_pdu/apps/launcher/model.py†L58-L80】【F:src/hakoniwa_pdu/apps/launcher/hako_monitor.py†L83-L121】

Defaults block

• cwd, stdout, stderr: default working directory and log sinks for assets. These support ${asset}, ${timestamp}, and ${base_dir} placeholders. The loader resolves relative paths using the directory of the launch file.【F:src/hakoniwa_pdu/apps/launcher/loader.py†L30-L91】【F:src/hakoniwa_pdu/apps/launcher/hako_monitor.py†L19-L35】
• start_grace_sec: minimum time (seconds) an asset must stay alive after spawn to be considered healthy (default 5.0).【F:src/hakoniwa_pdu/apps/launcher/model.py†L40-L54】
• delay_sec: delay inserted before launching the next asset (default 3.0).【F:src/hakoniwa_pdu/apps/launcher/model.py†L40-L54】
• env: environment operations merged into the runtime environment in three stages: OS env → defaults.env → asset.env. Keys set, prepend, append, and unset are supported, and lib_path automatically maps to LD_LIBRARY_PATH/DYLD_LIBRARY_PATH/PATH depending on the platform.【F:src/hakoniwa_pdu/apps/launcher/model.py†L12-L37】【F:src/hakoniwa_pdu/apps/launcher/envmerge.py†L1-L103】

Environment variables written as ${VAR} or ${VAR:-default} inside the JSON are resolved when the file is loaded. Placeholders ${asset} and ${timestamp} are preserved for runtime expansion inside log paths and environment settings.【F:src/hakoniwa_pdu/apps/launcher/loader.py†L18-L67】

Asset entries

Field	Description
name	Asset identifier. Used for dependency checks and placeholders.【F:src/hakoniwa_pdu/apps/launcher/model.py†L56-L115】
command / args	Executable and argument vector passed to the process.【F:src/hakoniwa_pdu/apps/launcher/hako_monitor.py†L40-L77】
cwd	Working directory. Defaults to the launch file directory or defaults.cwd.【F:src/hakoniwa_pdu/apps/launcher/loader.py†L47-L91】
stdout / stderr	Optional log file destinations. Directories are created automatically and support placeholders. Leave null to inherit the parent stream.【F:src/hakoniwa_pdu/apps/launcher/hako_asset_runner.py†L60-L117】
delay_sec	Wait time before the next asset starts (overrides defaults.delay_sec).【F:src/hakoniwa_pdu/apps/launcher/model.py†L94-L107】
activation_timing	before_start launches prior to hako-cmd start; after_start launches only after a successful hako-cmd start.【F:src/hakoniwa_pdu/apps/launcher/model.py†L94-L107】【F:src/hakoniwa_pdu/apps/launcher/hako_launcher.py†L28-L70】
depends_on	List of other asset names that must start before this one. Cycles are rejected during load.【F:src/hakoniwa_pdu/apps/launcher/model.py†L112-L167】
start_grace_sec	Asset-specific stability grace period overriding defaults.start_grace_sec.【F:src/hakoniwa_pdu/apps/launcher/model.py†L94-L107】【F:src/hakoniwa_pdu/apps/launcher/hako_monitor.py†L40-L77】
env	Environment overrides merged on top of defaults.env. Supports ${asset}, ${timestamp}, and ${ENV:VAR} substitutions at runtime.【F:src/hakoniwa_pdu/apps/launcher/envmerge.py†L14-L103】

Notify section

• type: "exec" executes a local command when the launcher aborts (placeholders ${asset} and ${timestamp} are available).【F:src/hakoniwa_pdu/apps/launcher/model.py†L58-L80】【F:src/hakoniwa_pdu/apps/launcher/hako_monitor.py†L83-L121】
• type: "webhook" issues an HTTP POST with the event name, asset, and timestamp. Use for integrations such as Slack or monitoring dashboards.【F:src/hakoniwa_pdu/apps/launcher/model.py†L58-L80】【F:src/hakoniwa_pdu/apps/launcher/hako_monitor.py†L83-L121】

Refer to the sample JSON provided above for a real-world configuration that launches a drone asset together with supporting services.

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🧭 Class Overview

PduManager

• Orchestrates PDU buffers and delegates to a transport (ICommunicationService).
• Direct I/O: declare_pdu_for_read/write → flush_pdu_raw_data() / read_pdu_raw_data().
• For RPC: extended via rpc.IPduServiceManager (handles register_client, start_rpc_service, etc.).

Transport Implementations (impl/)

• ICommunicationService defines the transport API.
• WebSocketCommunicationService / WebSocketServerCommunicationService: WebSocket backend (explicit URI-based connection, simple & secure).
• ShmCommunicationService: high-speed shared memory backend.
• Pluggable design: additional transports (e.g., Zenoh) can be integrated without changing application code.

RPC Layer (rpc/)

• IPduServiceManager family provides RPC APIs (client/server).
• protocol_client.py / protocol_server.py: user-friendly helpers.
• auto_wire.py: auto-loads generated converters.
• remote/: WebSocket managers.
• shm/: SHM managers.

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🧩 Class Diagram (Mermaid)

classDiagram
    class PduManager
    PduManager --> ICommunicationService : uses
    PduManager --> CommunicationBuffer
    PduManager --> PduConvertor
    PduManager --> PduChannelConfig

    class ICommunicationService {
        <<interface>>
    }
    class WebSocketCommunicationService
    class WebSocketServerCommunicationService
    class ShmCommunicationService
    ICommunicationService <|.. WebSocketCommunicationService
    ICommunicationService <|.. WebSocketServerCommunicationService
    ICommunicationService <|.. ShmCommunicationService

    class IPduServiceManager {
        <<abstract>>
    }
    PduManager <|-- IPduServiceManager
    class IPduServiceClientManager
    class IPduServiceServerManager
    IPduServiceManager <|-- IPduServiceClientManager
    IPduServiceManager <|-- IPduServiceServerManager

    class RemotePduServiceBaseManager
    RemotePduServiceBaseManager <|-- RemotePduServiceClientManager
    RemotePduServiceBaseManager <|-- RemotePduServiceServerManager
    IPduServiceManager <|-- RemotePduServiceBaseManager

    class ShmPduServiceBaseManager
    ShmPduServiceBaseManager <|-- ShmPduServiceClientManager
    ShmPduServiceBaseManager <|-- ShmPduServiceServerManager
    IPduServiceManager <|-- ShmPduServiceBaseManager

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🔗 Links

• 📘 GitHub: https://github.com/hakoniwalab/hakoniwa-pdu-python
• 🌐 Hakoniwa Lab: https://hakoniwa-lab.net

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📚 Documentation

For detailed API usage: ➡️ API Reference (api-doc.md)

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📜 License

MIT License — see LICENSE