Trait WorkflowState

Source

pub trait WorkflowState:
    Clone
    + Send
    + Sync {
    type Checkpoint: Serialize + DeserializeOwned + Clone + Send;
    type Mutation: StateMutation<Self>;

    // Required methods
    fn snapshot(&self) -> Self::Checkpoint;
    fn restore(checkpoint: Self::Checkpoint) -> Self;

    // Provided methods
    fn apply_batch(
        &mut self,
        mutations: impl IntoIterator<Item = Self::Mutation>,
    ) { ... }
    fn initial() -> Self
       where Self: Default { ... }
}

Expand description

工作流状态 — 编译期类型安全的状态容器。

替代 HashMap<String, Value> 动态模型。每个工作流定义自己的 State struct 和 Mutation enum，实现此 trait 以声明关联类型。

State 只是数据。 状态变更逻辑在 StateMutation trait 中。 Merge 职责已从 WorkflowState 剥离到 MergeStrategy。 Checkpoint 采用 Projection 模式 — Runtime State 可包含不可序列化字段（如 Arc<dyn ...>, Sender, Cache），Checkpoint 只序列化必要字段。

§示例

// State 只是数据
pub struct AgentState {
    pub messages: Vec<Message>,
    pub iterations: usize,
    pub output_tokens: usize,
    pub cache: Arc<dyn ToolCatalog>,  // 不可序列化
}

// 可序列化的 Checkpoint 投影
#[derive(Serialize, Deserialize)]
pub struct AgentCheckpoint {
    pub messages: Vec<Message>,
    pub iterations: usize,
    pub output_tokens: usize,
    // 不包含 cache
}

// Mutation 自己知道怎么改 State
pub enum AgentMutation {
    AppendMessage(Message),
    IncrementIteration,
    RecordOutputTokens(usize),
}

impl StateMutation<AgentState> for AgentMutation {
    fn apply(self, state: &mut AgentState) {
        match self {
            AgentMutation::AppendMessage(msg) => state.messages.push(msg),
            AgentMutation::IncrementIteration => state.iterations += 1,
            AgentMutation::RecordOutputTokens(n) => state.output_tokens += n,
        }
    }
}

// WorkflowState 声明 Checkpoint 和 Mutation 关联类型
impl WorkflowState for AgentState {
    type Checkpoint = AgentCheckpoint;
    type Mutation = AgentMutation;

    fn snapshot(&self) -> AgentCheckpoint {
        AgentCheckpoint {
            messages: self.messages.clone(),
            iterations: self.iterations,
            output_tokens: self.output_tokens,
        }
    }

    fn restore(checkpoint: AgentCheckpoint) -> Self {
        AgentState {
            messages: checkpoint.messages,
            iterations: checkpoint.iterations,
            output_tokens: checkpoint.output_tokens,
            cache: Arc::new(ToolCatalog::default()),  // 重建
        }
    }
}