apalis_core/task/
metadata.rs

1//! Task metadata extension trait and implementations
2//!
3//! The [`MetadataExt`] trait allows injecting and extracting metadata associated with tasks.
4//! It includes implementations for common metadata types.
5//!
6//! ## Overview
7//! - `MetadataExt<T>`: A trait for extracting and injecting metadata of type `T`.
8//!
9//! # Usage
10//! Implement the `MetadataExt` trait for your metadata types to enable easy extraction and injection
11//! from task contexts. This allows middleware and services to access and modify task metadata in a
12//! type-safe manner.
13use crate::task::Task;
14use crate::task_fn::FromRequest;
15
16/// Metadata wrapper for task contexts.
17#[derive(Debug, Clone)]
18pub struct Meta<T>(T);
19/// Task metadata extension trait and implementations.
20/// This trait allows for injecting and extracting metadata associated with tasks.
21pub trait MetadataExt<T> {
22    /// The error type that can occur during extraction or injection.
23    type Error;
24    /// Extract metadata of type `T`.
25    fn extract(&self) -> Result<T, Self::Error>;
26    /// Inject metadata of type `T`.
27    fn inject(&mut self, value: T) -> Result<(), Self::Error>;
28}
29
30impl<T, Args: Send + Sync, Ctx: MetadataExt<T> + Send + Sync, IdType: Send + Sync>
31    FromRequest<Task<Args, Ctx, IdType>> for Meta<T>
32{
33    type Error = Ctx::Error;
34
35    async fn from_request(task: &Task<Args, Ctx, IdType>) -> Result<Self, Self::Error> {
36        task.parts.ctx.extract().map(Meta)
37    }
38}
39
40#[cfg(test)]
41#[allow(unused)]
42mod tests {
43    use std::{convert::Infallible, fmt::Debug, task::Poll, time::Duration};
44
45    use crate::{
46        error::BoxDynError,
47        task::{
48            metadata::{Meta, MetadataExt},
49            Task,
50        },
51        task_fn::FromRequest,
52    };
53    use futures_core::future::BoxFuture;
54    use tower::Service;
55
56    #[derive(Debug, Clone)]
57    struct ExampleService<S> {
58        service: S,
59    }
60    #[derive(Debug, Clone, Default)]
61    struct ExampleConfig {
62        timeout: Duration,
63    }
64
65    struct SampleStore;
66
67    impl MetadataExt<ExampleConfig> for SampleStore {
68        type Error = Infallible;
69        fn extract(&self) -> Result<ExampleConfig, Self::Error> {
70            Ok(ExampleConfig {
71                timeout: Duration::from_secs(1),
72            })
73        }
74        fn inject(&mut self, _: ExampleConfig) -> Result<(), Self::Error> {
75            unreachable!()
76        }
77    }
78
79    #[cfg(feature = "json")]
80    impl<T: serde::de::DeserializeOwned> MetadataExt<T> for SampleStore {
81        type Error = Infallible;
82        fn extract(&self) -> Result<T, Self::Error> {
83            unimplemented!()
84        }
85        fn inject(&mut self, _: T) -> Result<(), Self::Error> {
86            unimplemented!()
87        }
88    }
89
90    impl<
91            S,
92            Args: Send + Sync + 'static,
93            Ctx: Send + Sync + 'static,
94            IdType: Send + Sync + 'static,
95        > Service<Task<Args, Ctx, IdType>> for ExampleService<S>
96    where
97        S: Service<Task<Args, Ctx, IdType>> + Clone + Send + 'static,
98        Ctx: MetadataExt<ExampleConfig> + Send,
99        Ctx::Error: Debug,
100        S::Future: Send + 'static,
101    {
102        type Response = S::Response;
103        type Error = S::Error;
104        type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;
105
106        fn poll_ready(&mut self, cx: &mut std::task::Context<'_>) -> Poll<Result<(), Self::Error>> {
107            self.service.poll_ready(cx)
108        }
109
110        fn call(&mut self, request: Task<Args, Ctx, IdType>) -> Self::Future {
111            let mut svc = self.service.clone();
112
113            // Do something with config
114            Box::pin(async move {
115                let _config: Meta<ExampleConfig> = request.extract().await.unwrap();
116                svc.call(request).await
117            })
118        }
119    }
120}
apalis_core/task/metadata.rs

apalis_core/task/
metadata.rs
