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use crate::{ spawn::{spawn_task, task_name}, Bus, Lifeline, }; use log::{debug, error}; use std::future::Future; use std::{any::TypeId, fmt::Debug}; /// Takes channels from the [Bus](./trait.Bus.html), and spawns a tree of tasks. Returns one or more [Lifeline](./struct.Lifeline.html) values. /// When the [Lifeline](./struct.Lifeline.html) is dropped, the task tree is immediately cancelled. /// /// - Simple implementations can return the [Lifeline](./struct.Lifeline.html) value, a handle returned by [Task::task](./trait.Task.html#method.task). /// - Implementations which have fallible spawns can return `anyhow::Result<Lifeline>`. /// - Implementations which spawn multiple tasks can store lifelines for each task in self, and return `anyhow::Result<Self>`. /// /// ## Example /// ``` /// use lifeline::prelude::*; /// use tokio::sync::mpsc; /// /// lifeline_bus!(pub struct ExampleBus); /// /// #[derive(Debug, Clone)] /// struct ExampleMessage {} /// /// impl Message<ExampleBus> for ExampleMessage { /// type Channel = mpsc::Sender<Self>; /// } /// /// struct ExampleService { /// _run: Lifeline /// } /// /// impl Service for ExampleService { /// type Bus = ExampleBus; /// type Lifeline = anyhow::Result<Self>; /// /// fn spawn(bus: &ExampleBus) -> anyhow::Result<Self> { /// let mut rx = bus.rx::<ExampleMessage>()?; /// /// let _run = Self::task("run", async move { /// while let Some(msg) = rx.recv().await { /// log::info!("got message: {:?}", msg); /// } /// }); /// /// Ok(Self { _run }) /// } /// } /// /// async fn run() { /// let bus = ExampleBus::default(); /// let _service = ExampleService::spawn(&bus); /// } /// ``` pub trait Service: Task { /// The bus, which must be provided to spawn the task type Bus: Bus; /// The service lifeline. When dropped, all spawned tasks are immediately cancelled. type Lifeline; /// Spawns the service with all sub-tasks, and returns a lifeline value. When the lifeline is dropped, all spawned tasks are immediately cancelled. /// /// Implementations should synchronously take channels from the bus, and then use them asynchronously. This makes errors occur as early and predictably as possible. fn spawn(bus: &Self::Bus) -> Self::Lifeline; } /// Constructs the bus, spawns the service, and returns both. pub trait DefaultService: Service { fn spawn_default() -> (Self::Bus, Self::Lifeline); } impl<T> DefaultService for T where T: Service, { fn spawn_default() -> (Self::Bus, Self::Lifeline) { let bus = Self::Bus::default(); let lifeline = Self::spawn(&bus); (bus, lifeline) } } /// Carries messages between **two** bus instances. A variant of the [Service](./trait.Service.html). /// /// Bus types form a tree, with a 'root application' bus, and multiple busses focused on particular domains. This structure provides isolation, /// and predictable failures when [Services](./trait.Service.html) spawn. /// ```text /// - MainBus /// | ListenerBus /// | | ConnectionBus /// | DomainSpecificBus /// | | ... /// ``` /// /// This trait can be implemented to carry messages between the root and the leaf of the tree. /// /// ## Example /// ``` /// use lifeline::prelude::*; /// use tokio::sync::mpsc; /// lifeline_bus!(pub struct MainBus); /// lifeline_bus!(pub struct LeafBus); /// /// #[derive(Debug, Clone)] /// struct LeafShutdown {} /// /// #[derive(Debug, Clone)] /// struct MainShutdown {} /// /// impl Message<LeafBus> for LeafShutdown { /// type Channel = mpsc::Sender<Self>; /// } /// /// impl Message<MainBus> for MainShutdown { /// type Channel = mpsc::Sender<Self>; /// } /// /// pub struct LeafMainCarrier { /// _forward_shutdown: Lifeline /// } /// /// impl CarryFrom<MainBus> for LeafBus { /// type Lifeline = anyhow::Result<LeafMainCarrier>; /// fn carry_from(&self, from: &MainBus) -> Self::Lifeline { /// let mut rx = self.rx::<LeafShutdown>()?; /// let mut tx = from.tx::<MainShutdown>()?; /// /// let _forward_shutdown = Self::try_task("forward_shutdown", async move { /// if let Some(msg) = rx.recv().await { /// tx.send(MainShutdown{}).await?; /// } /// /// Ok(()) /// }); /// /// Ok(LeafMainCarrier { _forward_shutdown }) /// } /// } /// ``` pub trait CarryFrom<FromBus: Bus>: Bus + Task + Sized { /// The carrier lifeline. When dropped, all spawned tasks are immediately cancelled. type Lifeline; /// Spawns the carrier service, returning the lifeline value. fn carry_from(&self, from: &FromBus) -> Self::Lifeline; } /// The receprocial of the [CarryFrom](./trait.CarryFrom.html) trait. Implemented for all types on which [CarryFrom](./trait.CarryFrom.html) is implemented. pub trait CarryInto<IntoBus: Bus>: Bus + Task + Sized { /// The carrier lifeline. When dropped, all spawned tasks are immediately cancelled. type Lifeline; /// Spawns the carrier service, returning the lifeline value. fn carry_into(&self, into: &IntoBus) -> Self::Lifeline; } impl<F, I> CarryInto<I> for F where I: CarryFrom<F>, F: Bus, I: Bus, { type Lifeline = <I as CarryFrom<F>>::Lifeline; fn carry_into(&self, into: &I) -> Self::Lifeline { into.carry_from(self) } } /// Constructs two bus types, and spawns the carrier between them. /// Returns both busses, and the carrier's lifeline. pub trait DefaultCarrier<FromBus: Bus>: CarryFrom<FromBus> { fn carry_default() -> (Self, FromBus, Self::Lifeline) { let into = Self::default(); let from = FromBus::default(); let lifeline = into.carry_from(&from); (into, from, lifeline) } } /// Provides the [Self::task](./trait.Task.html#method.task) and [Self::try_task](./trait.Task.html#method.try_task) associated methods for all types. /// /// Lifeline supports the following task executors (using feature flags), and will use the first enabled flag: /// - `tokio-executor` /// - `async-std-executor` /// /// Fallible tasks can be invoked with [Self::try_task](./trait.Task.html#method.try_task). Lifeline will log OK/ERR status when the task finishes. /// /// # Example /// ``` /// use lifeline::prelude::*; /// use tokio::sync::mpsc; /// /// lifeline_bus!(pub struct ExampleBus); /// /// #[derive(Debug, Clone)] /// struct ExampleMessage {} /// /// impl Message<ExampleBus> for ExampleMessage { /// type Channel = mpsc::Sender<Self>; /// } /// /// struct ExampleService { /// _run: Lifeline /// } /// /// impl Service for ExampleService { /// type Bus = ExampleBus; /// type Lifeline = anyhow::Result<Self>; /// /// fn spawn(bus: &ExampleBus) -> anyhow::Result<Self> { /// let mut rx = bus.rx::<ExampleMessage>()?; /// /// let _run = Self::task("run", async move { /// while let Some(msg) = rx.recv().await { /// log::info!("got message: {:?}", msg); /// } /// }); /// /// Ok(Self { _run }) /// } /// } /// ``` pub trait Task { /// Spawns an infallible task using the provided executor, wrapping it in a [Lifeline](./struct.Lifeline.html) handle. /// The task will run until it finishes, or until the [Lifeline](./struct.Lifeline.html) is droped. fn task<Out>(name: &str, fut: impl Future<Output = Out> + Send + 'static) -> Lifeline where Out: Debug + Send + 'static, Self: Sized, { let service_name = task_name::<Self>(name); spawn_task(service_name, fut) } /// Spawns an fallible task using the provided executor, wrapping it in a [Lifeline](./struct.Lifeline.html) handle. /// The task will run until it finishes, or until the [Lifeline](./struct.Lifeline.html) is droped. /// /// If the task finishes, lifeline will log an 'OK' or 'ERR' message with the return value. fn try_task<Out>( name: &str, fut: impl Future<Output = anyhow::Result<Out>> + Send + 'static, ) -> Lifeline where Out: Debug + 'static, Self: Sized, { let service_name = task_name::<Self>(name); spawn_task(service_name.clone(), async move { match fut.await { Ok(val) => { if TypeId::of::<Out>() != TypeId::of::<()>() { debug!("OK {}: {:?}", service_name, val); } else { debug!("OK {}", service_name); } } Err(err) => { error!("ERR: {}: {}", service_name, err); } } }) } } impl<T> Task for T {}