otel-arrow-dfe-engine 0.61.0

Async pipeline engine
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

//! Trait and types for local (!Send) extensions.

use crate::control::ExtensionControlMsg;
use crate::error::Error;
use crate::extension::EffectHandler;
use crate::local::message::LocalReceiver;
use crate::terminal_state::TerminalState;
use async_trait::async_trait;
use std::rc::Rc;

/// Local (!Send) control channel for extensions.
///
/// Wraps a [`LocalReceiver`] with shutdown-grace-period logic.
/// See [`crate::extension::ControlChannel`] for the implementation.
pub type ControlChannel = crate::extension::ControlChannel<LocalReceiver<ExtensionControlMsg>>;

/// A trait for extensions (!Send variant).
///
/// Extensions are long-lived components hosted alongside the data path --
/// today at pipeline scope, and in the future at engine, pipeline-group,
/// or node scope -- that expose functionality (e.g., authentication,
/// service discovery) to other components.
///
/// Unlike receivers, processors, and exporters, extensions are NOT generic
/// over PData -- they never process PData.
///
/// # Thread Safety
///
/// The local `Extension` trait does NOT require the `Send` bound, allowing
/// use of `Rc`, `RefCell`, and other !Send types within a single-threaded
/// `LocalSet`.
///
/// # Ownership
///
/// `start` takes `Rc<Self>` so the same instance can serve both the background
/// task and capability consumers without cloning internal state.
#[async_trait(?Send)]
pub trait Extension {
    /// Starts the extension.
    ///
    /// Extensions are started BEFORE receivers, processors, and exporters.
    ///
    /// # Errors
    ///
    /// Returns an [`Error`] if an unrecoverable error occurs.
    async fn start(
        self: Rc<Self>,
        ctrl_chan: ControlChannel,
        effect_handler: EffectHandler,
    ) -> Result<TerminalState, Error>;
}