adk-plugin

Plugin system for ADK-Rust agents.

Overview

adk-plugin provides a plugin architecture for extending ADK agent behavior through callbacks at various lifecycle points.

Features

Run lifecycle hooks: Before/after the entire agent run
User message processing: Modify or inspect user input
Event processing: Modify or inspect agent events
Agent callbacks: Before/after agent execution
Model callbacks: Before/after LLM calls, error handling
Tool callbacks: Before/after tool execution, error handling

Installation

[dependencies]
adk-plugin = "0.3.1"

Quick Start

use adk_plugin::{Plugin, PluginConfig, PluginManager, PluginBuilder};

// Create a logging plugin using the builder
let logging_plugin = PluginBuilder::new("logging")
    .on_user_message(Box::new(|ctx, content| {
        Box::pin(async move {
            println!("User: {:?}", content);
            Ok(None) // Don't modify
        })
    }))
    .on_event(Box::new(|ctx, event| {
        Box::pin(async move {
            println!("Event: {}", event.id);
            Ok(None) // Don't modify
        })
    }))
    .build();

// Create a caching plugin
let cache_plugin = Plugin::new(PluginConfig {
    name: "cache".to_string(),
    before_model: Some(Box::new(|ctx, request| {
        Box::pin(async move {
            // Check cache...
            Ok(BeforeModelResult::Continue(request))
        })
    })),
    ..Default::default()
});

// Create plugin manager
let manager = PluginManager::new(vec![logging_plugin, cache_plugin]);

// Use with Runner

Callback Types

Run Lifecycle

Callback	Description
`on_user_message`	Called when user message received, can modify
`on_event`	Called for each event, can modify
`before_run`	Called before run starts, can skip run
`after_run`	Called after run completes (cleanup)

Agent Callbacks

Callback	Description
`before_agent`	Called before agent execution
`after_agent`	Called after agent execution

Model Callbacks

Callback	Description
`before_model`	Called before LLM call, can modify request or skip
`after_model`	Called after LLM call, can modify response
`on_model_error`	Called on LLM error, can provide fallback

Tool Callbacks

Callback	Description
`before_tool`	Called before tool execution
`after_tool`	Called after tool execution
`on_tool_error`	Called on tool error, can provide fallback

Example: Caching Plugin

use adk_plugin::{Plugin, PluginConfig};
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::RwLock;

// Simple in-memory cache
let cache = Arc::new(RwLock::new(HashMap::new()));
let cache_read = cache.clone();
let cache_write = cache.clone();

let caching_plugin = Plugin::new(PluginConfig {
    name: "response-cache".to_string(),
    before_model: Some(Box::new(move |ctx, request| {
        let cache = cache_read.clone();
        Box::pin(async move {
            let key = format!("{:?}", request.contents);
            let guard = cache.read().await;
            if let Some(cached) = guard.get(&key) {
                return Ok(BeforeModelResult::Skip(cached.clone()));
            }
            Ok(BeforeModelResult::Continue(request))
        })
    })),
    after_model: Some(Box::new(move |ctx, response| {
        let cache = cache_write.clone();
        Box::pin(async move {
            // Store in cache (simplified)
            Ok(None)
        })
    })),
    ..Default::default()
});

Example: Metrics Plugin

use adk_plugin::{Plugin, PluginConfig, collect_metrics};
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;

let run_count = Arc::new(AtomicU64::new(0));
let run_count_start = run_count.clone();
let run_count_end = run_count.clone();

let (before_run, after_run) = collect_metrics(
    move || { run_count_start.fetch_add(1, Ordering::SeqCst); },
    move || { println!("Runs: {}", run_count_end.load(Ordering::SeqCst)); },
);

let metrics_plugin = Plugin::new(PluginConfig {
    name: "metrics".to_string(),
    before_run: Some(before_run),
    after_run: Some(after_run),
    ..Default::default()
});

Related Crates

adk-rust - Meta-crate with all components
adk-core - Core traits and types
adk-agent - Agent implementations
adk-runner - Agent execution runtime

License

Apache-2.0

Part of ADK-Rust

This crate is part of the ADK-Rust framework for building AI agents in Rust.

adk-plugin 0.3.1