Now Playing Logger Plugin (Python)

A Python example plugin that demonstrates the Scheduler and SubsonicAPI host services by periodically logging what is currently playing in Navidrome.

Features

Uses scheduler_schedulerecurring host function to set up a recurring task
Uses subsonicapi_call host function to query the getNowPlaying API
Configurable cron expression and user via plugin config
Demonstrates Python host function imports using @extism.import_fn

Prerequisites

extism-py - Python PDK compiler

bash

curl -Ls https://raw.githubusercontent.com/extism/python-pdk/main/install.sh | bash

Note: extism-py requires Binaryen (wasm-merge, wasm-opt) to be installed.

Building

From the plugins/examples directory:

bash

make nowplaying-py.ndp

Or directly:

bash

extism-py plugin/__init__.py -o plugin.wasm
zip -j nowplaying-py.ndp manifest.json plugin.wasm

Installation

Copy nowplaying-py.ndp to your Navidrome plugins folder

Enable plugins in navidrome.toml:

toml

[Plugins]
Enabled = true
Folder = "/path/to/plugins"

Configure the plugin in the UI (Settings → Plugins → nowplaying-py)

Configuration

Key	Description	Default
`cron`	Cron expression for check frequency	`/1 * * *`
`user`	Navidrome user for SubsonicAPI	`admin`

Testing

Test the manifest:

bash

extism call nowplaying-py.wasm nd_manifest --wasi

Output

When running, the plugin logs messages like:

🎵 john is playing: Pink Floyd - Comfortably Numb (The Wall)
🎵 jane is playing: Radiohead - Paranoid Android (OK Computer)

Or when no one is playing:

🎵 No users currently playing music

How It Works

Initialization (nd_on_init): Reads the cron expression from config and schedules a recurring task using the Scheduler host service.
Callback (nd_scheduler_callback): When the scheduled task fires, calls the SubsonicAPI getNowPlaying endpoint and logs the results.

Host Function Usage (Python)

This plugin demonstrates how to call Navidrome host functions from Python:

python

import extism
import json

# Import the host function
@extism.import_fn("extism:host/user", "subsonicapi_call")
def _subsonicapi_call(offset: int) -> int:
    """Raw host function - returns memory offset."""
    ...

# Wrapper for JSON marshalling
def subsonicapi_call(uri: str) -> dict:
    request = {"uri": uri}
    request_bytes = json.dumps(request).encode('utf-8')
    request_mem = extism.memory.alloc(request_bytes)
    response_offset = _subsonicapi_call(request_mem.offset)
    response_mem = extism.memory.find(response_offset)
    response = json.loads(extism.memory.string(response_mem))
    
    if response.get("error"):
        raise Exception(response["error"])
    
    return json.loads(response.get("responseJSON", "{}"))