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Diggory Blake 2021-03-29 03:05:20 +01:00
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4
Cargo.toml
View file

@ -4,6 +4,9 @@ version = "0.1.0"
authors = ["Diggory Blake <diggsey@googlemail.com>"]
edition = "2018"
[workspace]
members = ["sqlxmq_macros"]
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[dependencies]
@ -21,6 +24,7 @@ uuid = { version = "0.8.2", features = ["v4"] }
log = "0.4.14"
serde_json = "1.0.64"
serde = "1.0.124"
sqlxmq_macros = { version = "0.1", path = "sqlxmq_macros" }
[dev-dependencies]
dotenv = "0.15.0"

176
README.md Normal file
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@ -0,0 +1,176 @@
# sqlxmq
A task queue built on `sqlx` and `PostgreSQL`.
This library allows a CRUD application to run background tasks without complicating its
deployment. The only runtime dependency is `PostgreSQL`, so this is ideal for applications
already using a `PostgreSQL` database.
Although using a SQL database as a task queue means compromising on latency of
delivered tasks, there are several show-stopping issues present in ordinary task
queues which are avoided altogether.
With any other task queue, in-flight tasks are state that is not covered by normal
database backups. Even if tasks _are_ backed up, there is no way to restore both
a database and a task queue to a consistent point-in-time without manually
resolving conflicts.
By storing tasks in the database, existing backup procedures will store a perfectly
consistent state of both in-flight tasks and persistent data. Additionally, tasks can
be spawned and completed as part of other transactions, making it easy to write correct
application code.
Leveraging the power of `PostgreSQL`, this task queue offers several features not
present in other task queues.
# Features
- **Send/receive multiple tasks at once.**
This reduces the number of queries to the database.
- **Send tasks to be executed at a future date and time.**
Avoids the need for a separate scheduling system.
- **Reliable delivery of tasks.**
- **Automatic retries with exponential backoff.**
Number of retries and initial backoff parameters are configurable.
- **Transactional sending of tasks.**
Avoids sending spurious tasks if a transaction is rolled back.
- **Transactional completion of tasks.**
If all side-effects of a task are updates to the database, this provides
true exactly-once execution of tasks.
- **Transactional check-pointing of tasks.**
Long-running tasks can check-point their state to avoid having to restart
from the beginning if there is a failure: the next retry can continue
from the last check-point.
- **Opt-in strictly ordered task delivery.**
Tasks within the same channel will be processed strictly in-order
if this option is enabled for the task.
- **Fair task delivery.**
A channel with a lot of tasks ready to run will not starve a channel with fewer
tasks.
- **Opt-in two-phase commit.**
This is particularly useful on an ordered channel where a position can be "reserved"
in the task order, but not committed until later.
- **JSON and/or binary payloads.**
Tasks can use whichever is most convenient.
- **Automatic keep-alive of tasks.**
Long-running tasks will automatically be "kept alive" to prevent them being
retried whilst they're still ongoing.
- **Concurrency limits.**
Specify the minimum and maximum number of concurrent tasks each runner should
handle.
- **Built-in task registry via an attribute macro.**
Tasks can be easily registered with a runner, and default configuration specified
on a per-task basis.
- **Implicit channels.**
Channels are implicitly created and destroyed when tasks are sent and processed,
so no setup is required.
- **Channel groups.**
Easily subscribe to multiple channels at once, thanks to the separation of
channel name and channel arguments.
- **NOTIFY-based polling.**
This saves resources when few tasks are being processed.
# Getting started
## Defining tasks
The first step is to define a function to be run on the task queue.
```rust
use sqlxmq::{task, CurrentTask};
// Arguments to the `#[task]` attribute allow setting default task options.
#[task(channel_name = "foo")]
async fn example_task(
mut current_task: CurrentTask,
) -> sqlx::Result<()> {
// Decode a JSON payload
let who: Option<String> = current_task.json()?;
// Do some work
println!("Hello, {}!", who.as_deref().unwrap_or("world"));
// Mark the task as complete
current_task.complete().await?;
Ok(())
}
```
## Listening for tasks
Next we need to create a task runner: this is what listens for new tasks
and executes them.
```rust
use sqlxmq::TaskRegistry;
#[tokio::main]
async fn main() -> Result<(), Box<dyn Error>> {
// You'll need to provide a Postgres connection pool.
let pool = connect_to_db().await?;
// Construct a task registry from our single task.
let mut registry = TaskRegistry::new(&[example_task]);
// Here is where you can configure the registry
// registry.set_error_handler(...)
let runner = registry
// Create a task runner using the connection pool.
.runner(&pool)
// Here is where you can configure the task runner
// Aim to keep 10-20 tasks running at a time.
.set_concurrency(10, 20)
// Start the task runner in the background.
.run()
.await?;
// The task runner will continue listening and running
// tasks until `runner` is dropped.
}
```
## Spawning a task
The final step is to actually run a task.
```rust
example_task.new()
// This is where we override task configuration
.set_channel_name("bar")
.set_json("John")
.spawn(&pool)
.await?;
```

13
sqlxmq_macros/Cargo.toml Normal file
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@ -0,0 +1,13 @@
[package]
name = "sqlxmq_macros"
version = "0.1.0"
authors = ["Diggory Blake <diggsey@googlemail.com>"]
edition = "2018"
# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[lib]
proc-macro = true
[dependencies]
syn = { version = "1.0.64", features = ["derive"] }
quote = "1.0.9"

244
sqlxmq_macros/src/lib.rs Normal file
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@ -0,0 +1,244 @@
#![deny(missing_docs, unsafe_code)]
//! # sqlxmq_macros
//!
//! Provides procedural macros for the `sqlxmq` crate.
use std::mem;
use proc_macro::TokenStream;
use quote::quote;
use syn::{
parse_macro_input, parse_quote, AttributeArgs, Error, ItemFn, Lit, Meta, NestedMeta, Path,
Result, Visibility,
};
#[derive(Default)]
struct TaskOptions {
proto: Option<Path>,
name: Option<String>,
channel_name: Option<String>,
retries: Option<u32>,
backoff_secs: Option<f64>,
ordered: Option<bool>,
}
enum OptionValue<'a> {
None,
Lit(&'a Lit),
Path(&'a Path),
}
fn interpret_task_arg(options: &mut TaskOptions, arg: NestedMeta) -> Result<()> {
fn error(arg: NestedMeta) -> Result<()> {
Err(Error::new_spanned(arg, "Unexpected attribute argument"))
}
match &arg {
NestedMeta::Lit(Lit::Str(s)) if options.name.is_none() => {
options.name = Some(s.value());
}
NestedMeta::Meta(m) => {
if let Some(ident) = m.path().get_ident() {
let name = ident.to_string();
let value = match &m {
Meta::List(l) => {
if let NestedMeta::Meta(Meta::Path(p)) = &l.nested[0] {
OptionValue::Path(p)
} else {
return error(arg);
}
}
Meta::Path(_) => OptionValue::None,
Meta::NameValue(nvp) => OptionValue::Lit(&nvp.lit),
};
match (name.as_str(), value) {
("proto", OptionValue::Path(p)) if options.proto.is_none() => {
options.proto = Some(p.clone());
}
("name", OptionValue::Lit(Lit::Str(s))) if options.name.is_none() => {
options.name = Some(s.value());
}
("channel_name", OptionValue::Lit(Lit::Str(s)))
if options.channel_name.is_none() =>
{
options.channel_name = Some(s.value());
}
("retries", OptionValue::Lit(Lit::Int(n))) if options.retries.is_none() => {
options.name = Some(n.base10_parse()?);
}
("backoff_secs", OptionValue::Lit(Lit::Float(n)))
if options.backoff_secs.is_none() =>
{
options.backoff_secs = Some(n.base10_parse()?);
}
("backoff_secs", OptionValue::Lit(Lit::Int(n)))
if options.backoff_secs.is_none() =>
{
options.backoff_secs = Some(n.base10_parse()?);
}
("ordered", OptionValue::None) if options.ordered.is_none() => {
options.ordered = Some(true);
}
("ordered", OptionValue::Lit(Lit::Bool(b))) if options.ordered.is_none() => {
options.ordered = Some(b.value);
}
_ => return error(arg),
}
}
}
_ => return error(arg),
}
Ok(())
}
/// Marks a function as being a background task.
///
/// The function must take a single `CurrentTask` argument, and should
/// be async or return a future.
///
/// The async result must be a `Result<(), E>` type, where `E` is convertible
/// to a `Box<dyn Error + Send + Sync + 'static>`, which is the case for most
/// error types.
///
/// Several options can be provided to the `#[task]` attribute:
///
/// # Name
///
/// ```
/// #[task("example")]
/// #[task(name="example")]
/// ```
///
/// This overrides the name for this task. If unspecified, the fully-qualified
/// name of the function is used. If you move a task to a new module or rename
/// the function, you may which to override the task name to prevent it from
/// changing.
///
/// # Channel name
///
/// ```
/// #[task(channel_name="foo")]
/// ```
///
/// This sets the default channel name on which the task will be spawned.
///
/// # Retries
///
/// ```
/// #[task(retries = 3)]
/// ```
///
/// This sets the default number of retries for the task.
///
/// # Retry backoff
///
/// ```
/// #[task(backoff_secs=1.5)]
/// #[task(backoff_secs=2)]
/// ```
///
/// This sets the default initial retry backoff for the task in seconds.
///
/// # Ordered
///
/// ```
/// #[task(ordered)]
/// #[task(ordered=true)]
/// #[task(ordered=false)]
/// ```
///
/// This sets whether the task will be strictly ordered by default.
///
/// # Prototype
///
/// ```
/// fn my_proto<'a, 'b>(
/// builder: &'a mut TaskBuilder<'b>
/// ) -> &'a mut TaskBuilder<'b> {
/// builder.set_channel_name("bar")
/// }
///
/// #[task(proto(my_proto))]
/// ```
///
/// This allows setting several task options at once using the specified function,
/// and can be convient if you have several tasks which should have similar
/// defaults.
///
/// # Combinations
///
/// Multiple task options can be combined. The order is not important, but the
/// prototype will always be applied first so that explicit options can override it.
/// Each option can only be provided once in the attribute.
///
/// ```
/// #[task("my_task", proto(my_proto), retries=0, ordered)]
/// ```
///
#[proc_macro_attribute]
pub fn task(attr: TokenStream, item: TokenStream) -> TokenStream {
let args = parse_macro_input!(attr as AttributeArgs);
let mut inner_fn = parse_macro_input!(item as ItemFn);
let mut options = TaskOptions::default();
let mut errors = Vec::new();
for arg in args {
if let Err(e) = interpret_task_arg(&mut options, arg) {
errors.push(e.into_compile_error());
}
}
let vis = mem::replace(&mut inner_fn.vis, Visibility::Inherited);
let name = mem::replace(&mut inner_fn.sig.ident, parse_quote! {inner});
let fq_name = if let Some(name) = options.name {
quote! { #name }
} else {
let name_str = name.to_string();
quote! { concat!(module_path!(), "::", #name_str) }
};
let mut chain = Vec::new();
if let Some(proto) = &options.proto {
chain.push(quote! {
.set_proto(#proto)
});
}
if let Some(channel_name) = &options.channel_name {
chain.push(quote! {
.set_channel_name(#channel_name)
});
}
if let Some(retries) = &options.retries {
chain.push(quote! {
.set_retries(#retries)
});
}
if let Some(backoff_secs) = &options.backoff_secs {
chain.push(quote! {
.set_retry_backoff(::std::time::Duration::from_secs_f64(#backoff_secs))
});
}
if let Some(ordered) = options.ordered {
chain.push(quote! {
.set_ordered(#ordered)
});
}
let expanded = quote! {
#(#errors)*
#[allow(non_upper_case_globals)]
#vis static #name: &'static sqlxmq::NamedTask = &{
#inner_fn
sqlxmq::NamedTask::new_internal(
#fq_name,
sqlxmq::hidden::BuildFn(|builder| {
builder #(#chain)*
}),
sqlxmq::hidden::RunFn(|registry, current_task| {
registry.spawn_internal(#fq_name, inner(current_task));
}),
)
};
};
// Hand the output tokens back to the compiler.
TokenStream::from(expanded)
}

6
src/hidden.rs Normal file
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@ -0,0 +1,6 @@
use crate::{CurrentTask, TaskBuilder, TaskRegistry};
#[doc(hidden)]
pub struct BuildFn(pub for<'a> fn(&'a mut TaskBuilder<'static>) -> &'a mut TaskBuilder<'static>);
#[doc(hidden)]
pub struct RunFn(pub fn(&TaskRegistry, CurrentTask));

269
src/lib.rs
View file

@ -1,16 +1,201 @@
#![deny(missing_docs, unsafe_code)]
//! # sqlxmq
//!
//! A task queue built on `sqlx` and `PostgreSQL`.
//!
//! This library allows a CRUD application to run background tasks without complicating its
//! deployment. The only runtime dependency is `PostgreSQL`, so this is ideal for applications
//! already using a `PostgreSQL` database.
//!
//! Although using a SQL database as a task queue means compromising on latency of
//! delivered tasks, there are several show-stopping issues present in ordinary task
//! queues which are avoided altogether.
//!
//! With any other task queue, in-flight tasks are state that is not covered by normal
//! database backups. Even if tasks _are_ backed up, there is no way to restore both
//! a database and a task queue to a consistent point-in-time without manually
//! resolving conflicts.
//!
//! By storing tasks in the database, existing backup procedures will store a perfectly
//! consistent state of both in-flight tasks and persistent data. Additionally, tasks can
//! be spawned and completed as part of other transactions, making it easy to write correct
//! application code.
//!
//! Leveraging the power of `PostgreSQL`, this task queue offers several features not
//! present in other task queues.
//!
//! # Features
//!
//! - **Send/receive multiple tasks at once.**
//!
//! This reduces the number of queries to the database.
//!
//! - **Send tasks to be executed at a future date and time.**
//!
//! Avoids the need for a separate scheduling system.
//!
//! - **Reliable delivery of tasks.**
//!
//! - **Automatic retries with exponential backoff.**
//!
//! Number of retries and initial backoff parameters are configurable.
//!
//! - **Transactional sending of tasks.**
//!
//! Avoids sending spurious tasks if a transaction is rolled back.
//!
//! - **Transactional completion of tasks.**
//!
//! If all side-effects of a task are updates to the database, this provides
//! true exactly-once execution of tasks.
//!
//! - **Transactional check-pointing of tasks.**
//!
//! Long-running tasks can check-point their state to avoid having to restart
//! from the beginning if there is a failure: the next retry can continue
//! from the last check-point.
//!
//! - **Opt-in strictly ordered task delivery.**
//!
//! Tasks within the same channel will be processed strictly in-order
//! if this option is enabled for the task.
//!
//! - **Fair task delivery.**
//!
//! A channel with a lot of tasks ready to run will not starve a channel with fewer
//! tasks.
//!
//! - **Opt-in two-phase commit.**
//!
//! This is particularly useful on an ordered channel where a position can be "reserved"
//! in the task order, but not committed until later.
//!
//! - **JSON and/or binary payloads.**
//!
//! Tasks can use whichever is most convenient.
//!
//! - **Automatic keep-alive of tasks.**
//!
//! Long-running tasks will automatically be "kept alive" to prevent them being
//! retried whilst they're still ongoing.
//!
//! - **Concurrency limits.**
//!
//! Specify the minimum and maximum number of concurrent tasks each runner should
//! handle.
//!
//! - **Built-in task registry via an attribute macro.**
//!
//! Tasks can be easily registered with a runner, and default configuration specified
//! on a per-task basis.
//!
//! - **Implicit channels.**
//!
//! Channels are implicitly created and destroyed when tasks are sent and processed,
//! so no setup is required.
//!
//! - **Channel groups.**
//!
//! Easily subscribe to multiple channels at once, thanks to the separation of
//! channel name and channel arguments.
//!
//! - **NOTIFY-based polling.**
//!
//! This saves resources when few tasks are being processed.
//!
//! # Getting started
//!
//! ## Defining tasks
//!
//! The first step is to define a function to be run on the task queue.
//!
//! ```rust
//! use sqlxmq::{task, CurrentTask};
//!
//! // Arguments to the `#[task]` attribute allow setting default task options.
//! #[task(channel_name = "foo")]
//! async fn example_task(
//! mut current_task: CurrentTask,
//! ) -> sqlx::Result<()> {
//! // Decode a JSON payload
//! let who: Option<String> = current_task.json()?;
//!
//! // Do some work
//! println!("Hello, {}!", who.as_deref().unwrap_or("world"));
//!
//! // Mark the task as complete
//! current_task.complete().await?;
//!
//! Ok(())
//! }
//! ```
//!
//! ## Listening for tasks
//!
//! Next we need to create a task runner: this is what listens for new tasks
//! and executes them.
//!
//! ```rust
//! use sqlxmq::TaskRegistry;
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Box<dyn Error>> {
//! // You'll need to provide a Postgres connection pool.
//! let pool = connect_to_db().await?;
//!
//! // Construct a task registry from our single task.
//! let mut registry = TaskRegistry::new(&[example_task]);
//! // Here is where you can configure the registry
//! // registry.set_error_handler(...)
//!
//! let runner = registry
//! // Create a task runner using the connection pool.
//! .runner(&pool)
//! // Here is where you can configure the task runner
//! // Aim to keep 10-20 tasks running at a time.
//! .set_concurrency(10, 20)
//! // Start the task runner in the background.
//! .run()
//! .await?;
//!
//! // The task runner will continue listening and running
//! // tasks until `runner` is dropped.
//! }
//! ```
//!
//! ## Spawning a task
//!
//! The final step is to actually run a task.
//!
//! ```rust
//! example_task.new()
//! // This is where we override task configuration
//! .set_channel_name("bar")
//! .set_json("John")
//! .spawn(&pool)
//! .await?;
//! ```
#[doc(hidden)]
pub mod hidden;
mod registry;
mod runner;
mod spawn;
mod utils;
pub use registry::*;
pub use runner::*;
pub use spawn::*;
pub use sqlxmq_macros::task;
pub use utils::OwnedTask;
#[cfg(test)]
mod tests {
use super::*;
use crate as sqlxmq;
use std::env;
use std::error::Error;
use std::future::Future;
use std::ops::Deref;
use std::sync::atomic::{AtomicUsize, Ordering};
@ -78,8 +263,36 @@ mod tests {
(runner, counter)
}
fn task_proto<'a, 'b>(builder: &'a mut TaskBuilder<'b>) -> &'a mut TaskBuilder<'b> {
builder.set_channel_name("bar")
}
#[task(channel_name = "foo", ordered, retries = 3, backoff_secs = 2.0)]
async fn example_task1(
mut current_task: CurrentTask,
) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
current_task.complete().await?;
Ok(())
}
#[task(proto(task_proto))]
async fn example_task2(
mut current_task: CurrentTask,
) -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
current_task.complete().await?;
Ok(())
}
async fn named_task_runner(pool: &Pool<Postgres>) -> OwnedTask {
TaskRegistry::new(&[example_task1, example_task2])
.runner(pool)
.run()
.await
.unwrap()
}
async fn pause() {
pause_ms(50).await;
pause_ms(100).await;
}
async fn pause_ms(ms: u64) {
@ -164,7 +377,7 @@ mod tests {
let pool = &*test_pool().await;
let (_runner, counter) = test_task_runner(&pool, move |_| async {}).await;
let backoff = 100;
let backoff = 200;
assert_eq!(counter.load(Ordering::SeqCst), 0);
TaskBuilder::new("foo")
@ -192,4 +405,56 @@ mod tests {
pause_ms(backoff * 5).await;
assert_eq!(counter.load(Ordering::SeqCst), 3);
}
#[tokio::test]
async fn it_can_checkpoint_tasks() {
let pool = &*test_pool().await;
let (_runner, counter) = test_task_runner(&pool, move |mut current_task| async move {
let state: bool = current_task.json().unwrap().unwrap();
if state {
current_task.complete().await.unwrap();
} else {
current_task
.checkpoint(Checkpoint::new().set_json(&true).unwrap())
.await
.unwrap();
}
})
.await;
let backoff = 200;
assert_eq!(counter.load(Ordering::SeqCst), 0);
TaskBuilder::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);
}
#[tokio::test]
async fn it_can_use_registry() {
let pool = &*test_pool().await;
let _runner = named_task_runner(pool).await;
example_task1.new().spawn(pool).await.unwrap();
example_task2.new().spawn(pool).await.unwrap();
pause().await;
}
}

129
src/registry.rs Normal file
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@ -0,0 +1,129 @@
use std::collections::HashMap;
use std::error::Error;
use std::fmt::Display;
use std::future::Future;
use std::sync::Arc;
use sqlx::{Pool, Postgres};
use uuid::Uuid;
use crate::hidden::{BuildFn, RunFn};
use crate::utils::Opaque;
use crate::{TaskBuilder, TaskRunnerOptions};
/// Stores a mapping from task name to task. Can be used to construct
/// a task runner.
pub struct TaskRegistry {
error_handler: Arc<dyn Fn(&str, Box<dyn Error + Send + 'static>) + Send + Sync>,
task_map: HashMap<&'static str, &'static NamedTask>,
}
/// Error returned when a task is received whose name is not in the registry.
#[derive(Debug)]
pub struct UnknownTaskError;
impl Error for UnknownTaskError {}
impl Display for UnknownTaskError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str("Unknown task")
}
}
impl TaskRegistry {
/// Construct a new task registry from the provided task list.
pub fn new(tasks: &[&'static NamedTask]) -> Self {
let mut task_map = HashMap::new();
for &task in tasks {
if task_map.insert(task.name(), task).is_some() {
panic!("Duplicate task registered: {}", task.name());
}
}
Self {
error_handler: Arc::new(Self::default_error_handler),
task_map,
}
}
/// Set a function to be called whenever a task returns an error.
pub fn set_error_handler(
&mut self,
error_handler: impl Fn(&str, Box<dyn Error + Send + 'static>) + Send + Sync + 'static,
) -> &mut Self {
self.error_handler = Arc::new(error_handler);
self
}
/// Look-up a task by name.
pub fn resolve_task(&self, name: &str) -> Option<&'static NamedTask> {
self.task_map.get(name).copied()
}
/// The default error handler implementation, which simply logs the error.
pub fn default_error_handler(name: &str, error: Box<dyn Error + Send + 'static>) {
log::error!("Task {} failed: {}", name, error);
}
#[doc(hidden)]
pub fn spawn_internal<E: Into<Box<dyn Error + Send + Sync + 'static>>>(
&self,
name: &'static str,
f: impl Future<Output = Result<(), E>> + Send + 'static,
) {
let error_handler = self.error_handler.clone();
tokio::spawn(async move {
if let Err(e) = f.await {
error_handler(name, e.into());
}
});
}
/// Construct a task runner from this registry and the provided connection
/// pool.
pub fn runner(self, pool: &Pool<Postgres>) -> TaskRunnerOptions {
TaskRunnerOptions::new(pool, move |current_task| {
if let Some(task) = self.resolve_task(current_task.name()) {
(task.run_fn.0 .0)(&self, current_task);
} else {
(self.error_handler)(current_task.name(), Box::new(UnknownTaskError))
}
})
}
}
/// Type for a named task. Functions annotated with `#[task]` are
/// transformed into static variables whose type is `&'static NamedTask`.
#[derive(Debug)]
pub struct NamedTask {
name: &'static str,
build_fn: Opaque<BuildFn>,
run_fn: Opaque<RunFn>,
}
impl NamedTask {
#[doc(hidden)]
pub const fn new_internal(name: &'static str, build_fn: BuildFn, run_fn: RunFn) -> Self {
Self {
name,
build_fn: Opaque(build_fn),
run_fn: Opaque(run_fn),
}
}
/// Initialize a task builder with the name and defaults of this task.
pub fn new(&self) -> TaskBuilder<'static> {
let mut builder = TaskBuilder::new(self.name);
(self.build_fn.0 .0)(&mut builder);
builder
}
/// Initialize a task builder with the name and defaults of this task,
/// using the provided task ID.
pub fn new_with_id(&self, id: Uuid) -> TaskBuilder<'static> {
let mut builder = TaskBuilder::new_with_id(id, self.name);
(self.build_fn.0 .0)(&mut builder);
builder
}
/// Returns the name of this task.
pub const fn name(&self) -> &'static str {
self.name
}
}

71
src/runner.rs
View file

@ -14,12 +14,13 @@ use uuid::Uuid;
use crate::utils::{Opaque, OwnedTask};
/// Type used to build a task runner.
#[derive(Debug, Clone)]
pub struct TaskRunnerOptions {
min_concurrency: usize,
max_concurrency: usize,
channel_names: Option<Vec<String>>,
runner: Opaque<Arc<dyn Fn(CurrentTask) + Send + Sync + 'static>>,
dispatch: Opaque<Arc<dyn Fn(CurrentTask) + Send + Sync + 'static>>,
pool: Pool<Postgres>,
keep_alive: bool,
}
@ -31,6 +32,7 @@ struct TaskRunner {
notify: Notify,
}
/// Type used to checkpoint a running task.
#[derive(Debug, Clone)]
pub struct Checkpoint<'a> {
duration: Duration,
@ -40,7 +42,9 @@ pub struct Checkpoint<'a> {
}
impl<'a> Checkpoint<'a> {
pub fn new(duration: Duration) -> Self {
/// Construct a new checkpoint which also keeps the task alive
/// for the specified interval.
pub fn new_keep_alive(duration: Duration) -> Self {
Self {
duration,
extra_retries: 0,
@ -48,18 +52,26 @@ impl<'a> Checkpoint<'a> {
payload_bytes: None,
}
}
/// Construct a new checkpoint.
pub fn new() -> Self {
Self::new_keep_alive(Duration::from_secs(0))
}
/// Add extra retries to the current task.
pub fn set_extra_retries(&mut self, extra_retries: usize) -> &mut Self {
self.extra_retries = extra_retries;
self
}
/// Specify a new raw JSON payload.
pub fn set_raw_json(&mut self, raw_json: &'a str) -> &mut Self {
self.payload_json = Some(Cow::Borrowed(raw_json));
self
}
/// Specify a new raw binary payload.
pub fn set_raw_bytes(&mut self, raw_bytes: &'a [u8]) -> &mut Self {
self.payload_bytes = Some(raw_bytes);
self
}
/// Specify a new JSON payload.
pub fn set_json<T: Serialize>(&mut self, value: &T) -> Result<&mut Self, serde_json::Error> {
let value = serde_json::to_string(value)?;
self.payload_json = Some(Cow::Owned(value));
@ -82,6 +94,10 @@ impl<'a> Checkpoint<'a> {
}
}
/// Handle to the currently executing task.
/// When dropped, the task is assumed to no longer be running.
/// To prevent the task being retried, it must be explicitly completed using
/// one of the `.complete_` methods.
#[derive(Debug)]
pub struct CurrentTask {
id: Uuid,
@ -93,6 +109,7 @@ pub struct CurrentTask {
}
impl CurrentTask {
/// Returns the database pool used to receive this task.
pub fn pool(&self) -> &Pool<Postgres> {
&self.task_runner.options.pool
}
@ -106,6 +123,8 @@ impl CurrentTask {
.await?;
Ok(())
}
/// Complete this task and commit the provided transaction at the same time.
/// If the transaction cannot be committed, the task will not be completed.
pub async fn complete_with_transaction(
&mut self,
mut tx: sqlx::Transaction<'_, Postgres>,
@ -115,11 +134,15 @@ impl CurrentTask {
self.keep_alive = None;
Ok(())
}
/// Complete this task.
pub async fn complete(&mut self) -> Result<(), sqlx::Error> {
self.delete(self.pool()).await?;
self.keep_alive = None;
Ok(())
}
/// Checkpoint this task and commit the provided transaction at the same time.
/// If the transaction cannot be committed, the task will not be checkpointed.
/// Checkpointing allows the task payload to be replaced for the next retry.
pub async fn checkpoint_with_transaction(
&mut self,
mut tx: sqlx::Transaction<'_, Postgres>,
@ -129,10 +152,12 @@ impl CurrentTask {
tx.commit().await?;
Ok(())
}
/// Checkpointing allows the task payload to be replaced for the next retry.
pub async fn checkpoint(&mut self, checkpoint: &Checkpoint<'_>) -> Result<(), sqlx::Error> {
checkpoint.execute(self.id, self.pool()).await?;
Ok(())
}
/// Prevent this task from being retried for the specified interval.
pub async fn keep_alive(&mut self, duration: Duration) -> Result<(), sqlx::Error> {
sqlx::query("SELECT mq_keep_alive(ARRAY[$1], $2)")
.bind(self.id)
@ -141,12 +166,15 @@ impl CurrentTask {
.await?;
Ok(())
}
/// Returns the ID of this task.
pub fn id(&self) -> Uuid {
self.id
}
/// Returns the name of this task.
pub fn name(&self) -> &str {
&self.name
}
/// Extracts the JSON payload belonging to this task (if present).
pub fn json<'a, T: Deserialize<'a>>(&'a self) -> Result<Option<T>, serde_json::Error> {
if let Some(payload_json) = &self.payload_json {
serde_json::from_str(payload_json).map(Some)
@ -154,9 +182,11 @@ impl CurrentTask {
Ok(None)
}
}
/// Returns the raw JSON payload for this task.
pub fn raw_json(&self) -> Option<&str> {
self.payload_json.as_deref()
}
/// Returns the raw binary payload for this task.
pub fn raw_bytes(&self) -> Option<&[u8]> {
self.payload_bytes.as_deref()
}
@ -176,16 +206,49 @@ impl Drop for CurrentTask {
}
impl TaskRunnerOptions {
/// Begin constructing a new task runner using the specified connection pool,
/// and the provided execution function.
pub fn new<F: Fn(CurrentTask) + Send + Sync + 'static>(pool: &Pool<Postgres>, f: F) -> Self {
Self {
min_concurrency: 16,
max_concurrency: 32,
channel_names: None,
keep_alive: true,
runner: Opaque(Arc::new(f)),
dispatch: Opaque(Arc::new(f)),
pool: pool.clone(),
}
}
/// Set the concurrency limits for this task runner. When the number of active
/// tasks falls below the minimum, the runner will poll for more, up to the maximum.
///
/// The difference between the min and max will dictate the maximum batch size which
/// can be received: larger batch sizes are more efficient.
pub fn set_concurrency(&mut self, min_concurrency: usize, max_concurrency: usize) -> &mut Self {
self.min_concurrency = min_concurrency;
self.max_concurrency = max_concurrency;
self
}
/// Set the channel names which this task runner will subscribe to. If unspecified,
/// the task runner will subscribe to all channels.
pub fn set_channel_names<'a>(&'a mut self, channel_names: &[&str]) -> &'a mut Self {
self.channel_names = Some(
channel_names
.iter()
.copied()
.map(ToOwned::to_owned)
.collect(),
);
self
}
/// Choose whether to automatically keep tasks alive whilst they're still
/// running. Defaults to `true`.
pub fn set_keep_alive(&mut self, keep_alive: bool) -> &mut Self {
self.keep_alive = keep_alive;
self
}
/// Start the task runner in the background. The task runner will stop when the
/// returned handle is dropped.
pub async fn run(&self) -> Result<OwnedTask, sqlx::Error> {
let options = self.clone();
let task_runner = Arc::new(TaskRunner {
@ -304,7 +367,7 @@ async fn poll_and_dispatch(
keep_alive,
};
task_runner.running_tasks.fetch_add(1, Ordering::SeqCst);
(options.runner)(current_task);
(options.dispatch)(current_task);
}
}

51
src/spawn.rs
View file

@ -6,13 +6,14 @@ use serde::Serialize;
use sqlx::Postgres;
use uuid::Uuid;
/// Type for building a task to send.
#[derive(Debug, Clone)]
pub struct TaskBuilder<'a> {
id: Uuid,
delay: Duration,
channel_name: &'a str,
channel_args: &'a str,
retries: usize,
retries: u32,
retry_backoff: Duration,
commit_interval: Option<Duration>,
ordered: bool,
@ -22,9 +23,11 @@ pub struct TaskBuilder<'a> {
}
impl<'a> TaskBuilder<'a> {
/// Prepare to send a task with the specified name.
pub fn new(name: &'a str) -> Self {
Self::new_with_id(Uuid::new_v4(), name)
}
/// Prepare to send a task with the specified name and ID.
pub fn new_with_id(id: Uuid, name: &'a str) -> Self {
Self {
id,
@ -40,47 +43,76 @@ impl<'a> TaskBuilder<'a> {
payload_bytes: None,
}
}
/// Use the provided function to set any number of configuration
/// options at once.
pub fn set_proto<'b>(
&'b mut self,
proto: impl FnOnce(&'b mut Self) -> &'b mut Self,
) -> &'b mut Self {
proto(self)
}
/// Set the channel name (default "").
pub fn set_channel_name(&mut self, channel_name: &'a str) -> &mut Self {
self.channel_name = channel_name;
self
}
/// Set the channel arguments (default "").
pub fn set_channel_args(&mut self, channel_args: &'a str) -> &mut Self {
self.channel_args = channel_args;
self
}
pub fn set_retries(&mut self, retries: usize) -> &mut Self {
/// Set the number of retries after the initial attempt (default 4).
pub fn set_retries(&mut self, retries: u32) -> &mut Self {
self.retries = retries;
self
}
/// Set the initial backoff for retries (default 1s).
pub fn set_retry_backoff(&mut self, retry_backoff: Duration) -> &mut Self {
self.retry_backoff = retry_backoff;
self
}
/// Set the commit interval for two-phase commit (default disabled).
pub fn set_commit_interval(&mut self, commit_interval: Option<Duration>) -> &mut Self {
self.commit_interval = commit_interval;
self
}
/// Set whether this task is strictly ordered with respect to other ordered
/// task in the same channel (default false).
pub fn set_ordered(&mut self, ordered: bool) -> &mut Self {
self.ordered = ordered;
self
}
/// Set a delay before this task is executed (default none).
pub fn set_delay(&mut self, delay: Duration) -> &mut Self {
self.delay = delay;
self
}
/// Set a raw JSON payload for the task.
pub fn set_raw_json(&mut self, raw_json: &'a str) -> &mut Self {
self.payload_json = Some(Cow::Borrowed(raw_json));
self
}
/// Set a raw binary payload for the task.
pub fn set_raw_bytes(&mut self, raw_bytes: &'a [u8]) -> &mut Self {
self.payload_bytes = Some(raw_bytes);
self
}
pub fn set_json<T: Serialize>(&mut self, value: &T) -> Result<&mut Self, serde_json::Error> {
/// Set a JSON payload for the task.
pub fn set_json<T: ?Sized + Serialize>(
&mut self,
value: &T,
) -> Result<&mut Self, serde_json::Error> {
let value = serde_json::to_string(value)?;
self.payload_json = Some(Cow::Owned(value));
Ok(self)
}
/// Spawn the task using the given executor. This might be a connection
/// pool, a connection, or a transaction.
pub async fn spawn<'b, E: sqlx::Executor<'b, Database = Postgres>>(
&self,
executor: E,
@ -104,3 +136,16 @@ impl<'a> TaskBuilder<'a> {
Ok(self.id)
}
}
/// Commit the specified tasks. The tasks should have been previously spawned
/// with the two-phase commit option enabled.
pub async fn commit<'b, E: sqlx::Executor<'b, Database = Postgres>>(
executor: E,
task_ids: &[Uuid],
) -> Result<(), sqlx::Error> {
sqlx::query("SELECT mq_commit($1)")
.bind(task_ids)
.execute(executor)
.await?;
Ok(())
}

3
src/utils.rs
View file

@ -27,6 +27,9 @@ impl<T: Any> DerefMut for Opaque<T> {
}
}
/// A handle to a background task which will be automatically cancelled if
/// the handle is dropped. Extract the inner join handle to prevent this
/// behaviour.
#[derive(Debug)]
pub struct OwnedTask(pub JoinHandle<()>);