mirror of
https://github.com/Diggsey/sqlxmq.git
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5b04ca15f7
`#[warn(missing_docs)]` complains about the generated static as it misses documentation. This keeps the documentation both in front of the static and inside.
606 lines
18 KiB
Rust
606 lines
18 KiB
Rust
#![deny(missing_docs, unsafe_code)]
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//! # sqlxmq
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//!
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//! A job queue built on `sqlx` and `PostgreSQL`.
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//!
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//! This library allows a CRUD application to run background jobs without complicating its
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//! deployment. The only runtime dependency is `PostgreSQL`, so this is ideal for applications
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//! already using a `PostgreSQL` database.
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//!
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//! Although using a SQL database as a job queue means compromising on latency of
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//! delivered jobs, there are several show-stopping issues present in ordinary job
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//! queues which are avoided altogether.
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//!
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//! With most other job queues, in-flight jobs are state that is not covered by normal
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//! database backups. Even if jobs _are_ backed up, there is no way to restore both
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//! a database and a job queue to a consistent point-in-time without manually
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//! resolving conflicts.
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//!
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//! By storing jobs in the database, existing backup procedures will store a perfectly
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//! consistent state of both in-flight jobs and persistent data. Additionally, jobs can
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//! be spawned and completed as part of other transactions, making it easy to write correct
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//! application code.
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//!
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//! Leveraging the power of `PostgreSQL`, this job queue offers several features not
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//! present in other job queues.
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//!
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//! # Features
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//!
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//! - **Send/receive multiple jobs at once.**
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//!
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//! This reduces the number of queries to the database.
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//!
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//! - **Send jobs to be executed at a future date and time.**
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//!
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//! Avoids the need for a separate scheduling system.
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//!
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//! - **Reliable delivery of jobs.**
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//!
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//! - **Automatic retries with exponential backoff.**
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//!
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//! Number of retries and initial backoff parameters are configurable.
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//!
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//! - **Transactional sending of jobs.**
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//!
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//! Avoids sending spurious jobs if a transaction is rolled back.
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//!
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//! - **Transactional completion of jobs.**
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//!
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//! If all side-effects of a job are updates to the database, this provides
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//! true exactly-once execution of jobs.
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//!
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//! - **Transactional check-pointing of jobs.**
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//!
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//! Long-running jobs can check-point their state to avoid having to restart
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//! from the beginning if there is a failure: the next retry can continue
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//! from the last check-point.
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//!
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//! - **Opt-in strictly ordered job delivery.**
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//!
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//! Jobs within the same channel will be processed strictly in-order
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//! if this option is enabled for the job.
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//!
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//! - **Fair job delivery.**
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//!
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//! A channel with a lot of jobs ready to run will not starve a channel with fewer
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//! jobs.
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//!
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//! - **Opt-in two-phase commit.**
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//!
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//! This is particularly useful on an ordered channel where a position can be "reserved"
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//! in the job order, but not committed until later.
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//!
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//! - **JSON and/or binary payloads.**
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//!
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//! Jobs can use whichever is most convenient.
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//!
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//! - **Automatic keep-alive of jobs.**
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//!
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//! Long-running jobs will automatically be "kept alive" to prevent them being
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//! retried whilst they're still ongoing.
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//!
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//! - **Concurrency limits.**
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//!
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//! Specify the minimum and maximum number of concurrent jobs each runner should
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//! handle.
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//!
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//! - **Built-in job registry via an attribute macro.**
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//!
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//! Jobs can be easily registered with a runner, and default configuration specified
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//! on a per-job basis.
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//!
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//! - **Implicit channels.**
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//!
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//! Channels are implicitly created and destroyed when jobs are sent and processed,
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//! so no setup is required.
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//!
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//! - **Channel groups.**
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//!
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//! Easily subscribe to multiple channels at once, thanks to the separation of
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//! channel name and channel arguments.
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//!
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//! - **NOTIFY-based polling.**
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//!
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//! This saves resources when few jobs are being processed.
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//!
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//! # Getting started
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//!
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//! ## Database schema
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//!
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//! This crate expects certain database tables and stored procedures to exist.
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//! You can copy the migration files from this crate into your own migrations
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//! folder.
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//!
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//! All database items created by this crate are prefixed with `mq`, so as not
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//! to conflict with your own schema.
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//!
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//! ## Defining jobs
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//!
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//! The first step is to define a function to be run on the job queue.
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//!
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//! ```rust
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//! use std::error::Error;
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//!
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//! use sqlxmq::{job, CurrentJob};
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//!
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//! // Arguments to the `#[job]` attribute allow setting default job options.
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//! #[job(channel_name = "foo")]
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//! async fn example_job(
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//! // The first argument should always be the current job.
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//! mut current_job: CurrentJob,
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//! // Additional arguments are optional, but can be used to access context
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//! // provided via [`JobRegistry::set_context`].
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//! message: &'static str,
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//! ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
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//! // Decode a JSON payload
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//! let who: Option<String> = current_job.json()?;
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//!
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//! // Do some work
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//! println!("{}, {}!", message, who.as_deref().unwrap_or("world"));
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//!
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//! // Mark the job as complete
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//! current_job.complete().await?;
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//!
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//! Ok(())
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//! }
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//! ```
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//!
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//! ## Listening for jobs
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//!
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//! Next we need to create a job runner: this is what listens for new jobs
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//! and executes them.
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//!
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//! ```rust,no_run
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//! use std::error::Error;
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//!
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//! use sqlxmq::JobRegistry;
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//!
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//! # use sqlxmq::{job, CurrentJob};
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//! #
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//! # #[job]
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//! # async fn example_job(
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//! # current_job: CurrentJob,
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//! # ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> { Ok(()) }
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//! #
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//! # async fn connect_to_db() -> sqlx::Result<sqlx::Pool<sqlx::Postgres>> {
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//! # unimplemented!()
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//! # }
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//!
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//! #[tokio::main]
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//! async fn main() -> Result<(), Box<dyn Error>> {
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//! // You'll need to provide a Postgres connection pool.
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//! let pool = connect_to_db().await?;
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//!
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//! // Construct a job registry from our single job.
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//! let mut registry = JobRegistry::new(&[example_job]);
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//! // Here is where you can configure the registry
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//! // registry.set_error_handler(...)
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//!
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//! // And add context
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//! registry.set_context("Hello");
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//!
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//! let runner = registry
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//! // Create a job runner using the connection pool.
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//! .runner(&pool)
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//! // Here is where you can configure the job runner
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//! // Aim to keep 10-20 jobs running at a time.
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//! .set_concurrency(10, 20)
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//! // Start the job runner in the background.
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//! .run()
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//! .await?;
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//!
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//! // The job runner will continue listening and running
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//! // jobs until `runner` is dropped.
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//! Ok(())
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//! }
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//! ```
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//!
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//! ## Spawning a job
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//!
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//! The final step is to actually run a job.
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//!
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//! ```rust
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//! # use std::error::Error;
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//! # use sqlxmq::{job, CurrentJob};
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//! #
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//! # #[job]
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//! # async fn example_job(
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//! # current_job: CurrentJob,
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//! # ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> { Ok(()) }
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//! #
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//! # async fn example(
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//! # pool: sqlx::Pool<sqlx::Postgres>
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//! # ) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
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//! example_job.builder()
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//! // This is where we can override job configuration
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//! .set_channel_name("bar")
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//! .set_json("John")?
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//! .spawn(&pool)
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//! .await?;
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//! # Ok(())
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//! # }
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//! ```
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#[doc(hidden)]
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pub mod hidden;
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mod registry;
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mod runner;
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mod spawn;
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mod utils;
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pub use registry::*;
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pub use runner::*;
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pub use spawn::*;
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pub use sqlxmq_macros::job;
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pub use utils::OwnedHandle;
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/// Helper function to determine if a particular error condition is retryable.
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///
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/// For best results, database operations should be automatically retried if one
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/// of these errors is returned.
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pub fn should_retry(error: &sqlx::Error) -> bool {
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if let Some(db_error) = error.as_database_error() {
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// It's more readable as a match
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#[allow(clippy::match_like_matches_macro)]
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match (db_error.code().as_deref(), db_error.constraint()) {
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// Foreign key constraint violation on ordered channel
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(Some("23503"), Some("mq_msgs_after_message_id_fkey")) => true,
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// Unique constraint violation on ordered channel
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(Some("23505"), Some("mq_msgs_channel_name_channel_args_after_message_id_idx")) => true,
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// Serialization failure
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(Some("40001"), _) => true,
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// Deadlock detected
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(Some("40P01"), _) => true,
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// Other
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_ => false,
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}
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} else {
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false
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate as sqlxmq;
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use std::env;
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use std::error::Error;
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use std::future::Future;
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use std::ops::Deref;
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use std::sync::atomic::{AtomicUsize, Ordering};
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use std::sync::{Arc, Once};
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use std::time::Duration;
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use futures::channel::mpsc;
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use futures::StreamExt;
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use sqlx::{Pool, Postgres};
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use tokio::sync::{Mutex, MutexGuard};
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use tokio::task;
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struct TestGuard<T>(MutexGuard<'static, ()>, T);
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impl<T> Deref for TestGuard<T> {
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type Target = T;
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fn deref(&self) -> &T {
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&self.1
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}
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}
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async fn test_pool() -> TestGuard<Pool<Postgres>> {
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static INIT_LOGGER: Once = Once::new();
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static TEST_MUTEX: Mutex<()> = Mutex::const_new(());
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let guard = TEST_MUTEX.lock().await;
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let _ = dotenv::dotenv();
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INIT_LOGGER.call_once(pretty_env_logger::init);
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let pool = Pool::connect(&env::var("DATABASE_URL").unwrap())
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.await
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.unwrap();
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sqlx::query("TRUNCATE TABLE mq_payloads")
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.execute(&pool)
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.await
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.unwrap();
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sqlx::query("DELETE FROM mq_msgs WHERE id != uuid_nil()")
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.execute(&pool)
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.await
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.unwrap();
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TestGuard(guard, pool)
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}
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async fn test_job_runner<F: Future + Send + 'static>(
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pool: &Pool<Postgres>,
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f: impl (Fn(CurrentJob) -> F) + Send + Sync + 'static,
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) -> (OwnedHandle, Arc<AtomicUsize>)
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where
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F::Output: Send + 'static,
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{
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let counter = Arc::new(AtomicUsize::new(0));
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let counter2 = counter.clone();
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let runner = JobRunnerOptions::new(pool, move |job| {
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counter2.fetch_add(1, Ordering::SeqCst);
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task::spawn(f(job));
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})
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.run()
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.await
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.unwrap();
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(runner, counter)
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}
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fn job_proto<'a, 'b>(builder: &'a mut JobBuilder<'b>) -> &'a mut JobBuilder<'b> {
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builder.set_channel_name("bar")
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}
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#[job(channel_name = "foo", ordered, retries = 3, backoff_secs = 2.0)]
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async fn example_job1(
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mut current_job: CurrentJob,
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) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
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current_job.complete().await?;
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Ok(())
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}
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#[job(proto(job_proto))]
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async fn example_job2(
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mut current_job: CurrentJob,
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) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
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current_job.complete().await?;
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Ok(())
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}
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#[job]
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async fn example_job_with_ctx(
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mut current_job: CurrentJob,
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ctx1: i32,
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ctx2: &'static str,
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) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
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assert_eq!(ctx1, 42);
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assert_eq!(ctx2, "Hello, world!");
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current_job.complete().await?;
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Ok(())
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}
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async fn named_job_runner(pool: &Pool<Postgres>) -> OwnedHandle {
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let mut registry = JobRegistry::new(&[example_job1, example_job2, example_job_with_ctx]);
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registry.set_context(42).set_context("Hello, world!");
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registry.runner(pool).run().await.unwrap()
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}
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async fn pause() {
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pause_ms(200).await;
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}
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async fn pause_ms(ms: u64) {
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tokio::time::sleep(Duration::from_millis(ms)).await;
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}
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#[tokio::test]
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async fn it_can_spawn_job() {
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{
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let pool = &*test_pool().await;
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let (_runner, counter) =
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test_job_runner(pool, |mut job| async move { job.complete().await }).await;
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assert_eq!(counter.load(Ordering::SeqCst), 0);
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JobBuilder::new("foo").spawn(pool).await.unwrap();
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pause().await;
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assert_eq!(counter.load(Ordering::SeqCst), 1);
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}
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pause().await;
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}
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#[tokio::test]
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async fn it_can_clear_jobs() {
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{
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let pool = &*test_pool().await;
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JobBuilder::new("foo")
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.set_channel_name("foo")
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.spawn(pool)
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.await
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.unwrap();
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JobBuilder::new("foo")
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.set_channel_name("foo")
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.spawn(pool)
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.await
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.unwrap();
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JobBuilder::new("foo")
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.set_channel_name("bar")
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.spawn(pool)
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.await
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.unwrap();
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JobBuilder::new("foo")
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.set_channel_name("bar")
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.spawn(pool)
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.await
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.unwrap();
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JobBuilder::new("foo")
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.set_channel_name("baz")
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.spawn(pool)
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.await
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.unwrap();
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JobBuilder::new("foo")
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.set_channel_name("baz")
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.spawn(pool)
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.await
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.unwrap();
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sqlxmq::clear(pool, &["foo", "baz"]).await.unwrap();
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let (_runner, counter) =
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test_job_runner(pool, |mut job| async move { job.complete().await }).await;
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pause().await;
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assert_eq!(counter.load(Ordering::SeqCst), 2);
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}
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pause().await;
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}
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#[tokio::test]
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async fn it_runs_jobs_in_order() {
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{
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let pool = &*test_pool().await;
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let (tx, mut rx) = mpsc::unbounded();
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let (_runner, counter) = test_job_runner(pool, move |job| {
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let tx = tx.clone();
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async move {
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tx.unbounded_send(job).unwrap();
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}
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})
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.await;
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assert_eq!(counter.load(Ordering::SeqCst), 0);
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JobBuilder::new("foo")
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.set_ordered(true)
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.spawn(pool)
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.await
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.unwrap();
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JobBuilder::new("bar")
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.set_ordered(true)
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.spawn(pool)
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.await
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.unwrap();
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pause().await;
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assert_eq!(counter.load(Ordering::SeqCst), 1);
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let mut job = rx.next().await.unwrap();
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job.complete().await.unwrap();
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pause().await;
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assert_eq!(counter.load(Ordering::SeqCst), 2);
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}
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pause().await;
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}
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#[tokio::test]
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async fn it_runs_jobs_in_parallel() {
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{
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let pool = &*test_pool().await;
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let (tx, mut rx) = mpsc::unbounded();
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let (_runner, counter) = test_job_runner(pool, move |job| {
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let tx = tx.clone();
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async move {
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tx.unbounded_send(job).unwrap();
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}
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})
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.await;
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assert_eq!(counter.load(Ordering::SeqCst), 0);
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JobBuilder::new("foo").spawn(pool).await.unwrap();
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JobBuilder::new("bar").spawn(pool).await.unwrap();
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pause().await;
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assert_eq!(counter.load(Ordering::SeqCst), 2);
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for _ in 0..2 {
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let mut job = rx.next().await.unwrap();
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job.complete().await.unwrap();
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}
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}
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pause().await;
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}
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#[tokio::test]
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async fn it_retries_failed_jobs() {
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{
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let pool = &*test_pool().await;
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let (_runner, counter) = test_job_runner(pool, move |_| async {}).await;
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let backoff = 500;
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assert_eq!(counter.load(Ordering::SeqCst), 0);
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JobBuilder::new("foo")
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.set_retry_backoff(Duration::from_millis(backoff))
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.set_retries(2)
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.spawn(pool)
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.await
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.unwrap();
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// First attempt
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pause().await;
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assert_eq!(counter.load(Ordering::SeqCst), 1);
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// Second attempt
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pause_ms(backoff).await;
|
|
pause().await;
|
|
assert_eq!(counter.load(Ordering::SeqCst), 2);
|
|
|
|
// Third attempt
|
|
pause_ms(backoff * 2).await;
|
|
pause().await;
|
|
assert_eq!(counter.load(Ordering::SeqCst), 3);
|
|
|
|
// No more attempts
|
|
pause_ms(backoff * 5).await;
|
|
assert_eq!(counter.load(Ordering::SeqCst), 3);
|
|
}
|
|
pause().await;
|
|
}
|
|
|
|
#[tokio::test]
|
|
async fn it_can_checkpoint_jobs() {
|
|
{
|
|
let pool = &*test_pool().await;
|
|
let (_runner, counter) = test_job_runner(pool, move |mut current_job| async move {
|
|
let state: bool = current_job.json().unwrap().unwrap();
|
|
if state {
|
|
current_job.complete().await.unwrap();
|
|
} else {
|
|
current_job
|
|
.checkpoint(Checkpoint::new().set_json(&true).unwrap())
|
|
.await
|
|
.unwrap();
|
|
}
|
|
})
|
|
.await;
|
|
|
|
let backoff = 200;
|
|
|
|
assert_eq!(counter.load(Ordering::SeqCst), 0);
|
|
JobBuilder::new("foo")
|
|
.set_retry_backoff(Duration::from_millis(backoff))
|
|
.set_retries(5)
|
|
.set_json(&false)
|
|
.unwrap()
|
|
.spawn(pool)
|
|
.await
|
|
.unwrap();
|
|
|
|
// First attempt
|
|
pause().await;
|
|
assert_eq!(counter.load(Ordering::SeqCst), 1);
|
|
|
|
// Second attempt
|
|
pause_ms(backoff).await;
|
|
pause().await;
|
|
assert_eq!(counter.load(Ordering::SeqCst), 2);
|
|
|
|
// No more attempts
|
|
pause_ms(backoff * 3).await;
|
|
assert_eq!(counter.load(Ordering::SeqCst), 2);
|
|
}
|
|
pause().await;
|
|
}
|
|
|
|
#[tokio::test]
|
|
async fn it_can_use_registry() {
|
|
{
|
|
let pool = &*test_pool().await;
|
|
let _runner = named_job_runner(pool).await;
|
|
|
|
example_job1.builder().spawn(pool).await.unwrap();
|
|
example_job2.builder().spawn(pool).await.unwrap();
|
|
example_job_with_ctx.builder().spawn(pool).await.unwrap();
|
|
pause().await;
|
|
}
|
|
pause().await;
|
|
}
|
|
}
|