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# Fang
Background task processing library for Rust. It uses Postgres DB as a task queue.
## Key Features
Here are some of the fang's key features:
- Async and threaded workers.
Workers can be started in threads (threaded workers) or `tokio` tasks (async workers)
- Scheduled tasks.
Tasks can be scheduled at any time in the future
- Periodic (CRON) tasks.
Tasks can be scheduled using cron expressions
- Unique tasks.
Tasks are not duplicated in the queue if they are unique
- Single-purpose workers.
Tasks are stored in a single table but workers can execute only tasks of the specific type
- Retries.
Tasks can be retried with a custom backoff mode
## Installation
1. Add this to your Cargo.toml
#### the Blocking feature
```toml
[dependencies]
fang = { version = "0.10.4" , features = ["blocking"], default-features = false }
```
#### the Asynk feature
```toml
[dependencies]
fang = { version = "0.10.4" , features = ["asynk"], default-features = false }
```
#### the Asynk feature with derive macro
```toml
[dependencies]
fang = { version = "0.10.4" , features = ["asynk", "derive-error" ], default-features = false }
```
#### All features
```toml
fang = { version = "0.10.4" }
```
*Supports rustc 1.62+*
2. Create the `fang_tasks` table in the Postgres database. The migration can be found in [the migrations directory](https://github.com/ayrat555/fang/blob/master/migrations/2022-08-20-151615_create_fang_tasks/up.sql).
## Usage
### Defining a task
#### Blocking feature
Every task should implement the `fang::Runnable` trait which is used by `fang` to execute it.
If you have a `CustomError`, it is recommended to implement `From<FangError>`. So this way you can use [? operator](https://stackoverflow.com/questions/42917566/what-is-this-question-mark-operator-about#42921174) inside the `run` function available in `fang::Runnable` trait.
You can easily implement it with the macro `ToFangError`. This macro is only available in the feature `derive-error`.
```rust
use fang::FangError;
use fang::Runnable;
use fang::typetag;
use fang::PgConnection;
use fang::serde::{Deserialize, Serialize};
use fang::ToFangError;
use std::fmt::Debug;
#[derive(Debug, ToFangError)]
enum CustomError {
ErrorOne(String),
ErrorTwo(u32),
}
fn my_func(num : u16) -> Result<(), CustomError> {
if num == 0 {
Err(CustomError::ErrorOne("is zero".to_string()))
}
if num > 500 {
Err(CustomError::ErrorTwo(num))
}
Ok(())
}
#[derive(Serialize, Deserialize)]
#[serde(crate = "fang::serde")]
struct MyTask {
pub number: u16,
}
#[typetag::serde]
impl Runnable for MyTask {
fn run(&self, _queue: &dyn Queueable) -> Result<(), FangError> {
println!("the number is {}", self.number);
my_func(self.number)?;
// You can use ? operator because
// From<FangError> is implemented thanks to ToFangError derive macro.
Ok(())
}
// If `uniq` is set to true and the task is already in the storage, it won't be inserted again
// The existing record will be returned for for any insertions operaiton
fn uniq(&self) -> bool {
true
}
// This will be useful if you want to filter tasks.
// the default value is `common`
fn task_type(&self) -> String {
"my_task".to_string()
}
// This will be useful if you would like to schedule tasks.
// default value is None (the task is not scheduled, it's just executed as soon as it's inserted)
fn cron(&self) -> Option<Scheduled> {
let expression = "0/20 * * * Aug-Sep * 2022/1";
Some(Scheduled::CronPattern(expression.to_string()))
}
// the maximum number of retries. Set it to 0 to make it not retriable
// the default value is 20
fn max_retries(&self) -> i32 {
20
}
// backoff mode for retries
fn backoff(&self, attempt: u32) -> u32 {
u32::pow(2, attempt)
}
}
```
As you can see from the example above, the trait implementation has `#[typetag::serde]` attribute which is used to deserialize the task.
The second parameter of the `run` function is a struct that implements `fang::Queueable`. You can re-use it to manipulate the task queue, for example, to add a new job during the current job's execution. If you don't need it, just ignore it.
#### Asynk feature
Every task should implement `fang::AsyncRunnable` trait which is used by `fang` to execute it.
Be careful not to call two implementations of the AsyncRunnable trait with the same name, because it will cause a failure in the `typetag` crate.
```rust
use fang::AsyncRunnable;
use fang::asynk::async_queue::AsyncQueueable;
use fang::serde::{Deserialize, Serialize};
use fang::async_trait;
#[derive(Serialize, Deserialize)]
#[serde(crate = "fang::serde")]
struct AsyncTask {
pub number: u16,
}
#[typetag::serde]
#[async_trait]
impl AsyncRunnable for AsyncTask {
async fn run(&self, _queueable: &mut dyn AsyncQueueable) -> Result<(), Error> {
Ok(())
}
// this func is optional
// Default task_type is common
fn task_type(&self) -> String {
"my-task-type".to_string()
}
// If `uniq` is set to true and the task is already in the storage, it won't be inserted again
// The existing record will be returned for for any insertions operaiton
fn uniq(&self) -> bool {
true
}
// This will be useful if you would like to schedule tasks.
// default value is None (the task is not scheduled, it's just executed as soon as it's inserted)
fn cron(&self) -> Option<Scheduled> {
let expression = "0/20 * * * Aug-Sep * 2022/1";
Some(Scheduled::CronPattern(expression.to_string()))
}
// the maximum number of retries. Set it to 0 to make it not retriable
// the default value is 20
fn max_retries(&self) -> i32 {
20
}
// backoff mode for retries
fn backoff(&self, attempt: u32) -> u32 {
u32::pow(2, attempt)
}
}
```
In both modules, tasks can be scheduled to be executed once. Use `Scheduled::ScheduleOnce` enum variant.
Datetimes and cron patterns are interpreted in the UTC timezone. So you should introduce the offset to schedule in a different timezone.
Example:
If your timezone is UTC + 2 and you want to schedule at 11:00:
```rust
let expression = "0 0 9 * * * *";
```
### Enqueuing a task
#### the Blocking feature
To enqueue a task use `Queue::enqueue_task`
```rust
use fang::Queue;
// create a r2d2 pool
// create a fang queue
let queue = Queue::builder().connection_pool(pool).build();
let task_inserted = queue.insert_task(&MyTask::new(1)).unwrap();
```
#### the Asynk feature
To enqueue a task use `AsyncQueueable::insert_task`.
For Postgres backend.
```rust
use fang::asynk::async_queue::AsyncQueue;
use fang::NoTls;
use fang::AsyncRunnable;
// Create an AsyncQueue
let max_pool_size: u32 = 2;
let mut queue = AsyncQueue::builder()
// Postgres database url
.uri("postgres://postgres:postgres@localhost/fang")
// Max number of connections that are allowed
.max_pool_size(max_pool_size)
.build();
// Always connect first in order to perform any operation
queue.connect(NoTls).await.unwrap();
```
As an easy example, we are using NoTls type. If for some reason you would like to encrypt Postgres requests, you can use [openssl](https://docs.rs/postgres-openssl/latest/postgres_openssl/) or [native-tls](https://docs.rs/postgres-native-tls/latest/postgres_native_tls/).
```rust
// AsyncTask from the first example
let task = AsyncTask { 8 };
let task_returned = queue
.insert_task(&task as &dyn AsyncRunnable)
.await
.unwrap();
```
### Starting workers
#### the Blocking feature
Every worker runs in a separate thread. In case of panic, they are always restarted.
Use `WorkerPool` to start workers. Use `WorkerPool::builder` to create your worker pool and run tasks.
```rust
use fang::WorkerPool;
use fang::Queue;
// create a Queue
let mut worker_pool = WorkerPool::<Queue>::builder()
.queue(queue)
.number_of_workers(3_u32)
// if you want to run tasks of the specific kind
.task_type("my_task_type")
.build();
worker_pool.start();
```
#### the Asynk feature
Every worker runs in a separate `tokio` task. In case of panic, they are always restarted.
Use `AsyncWorkerPool` to start workers.
```rust
use fang::asynk::async_worker_pool::AsyncWorkerPool;
// Need to create a queue
// Also insert some tasks
let mut pool: AsyncWorkerPool<AsyncQueue<NoTls>> = AsyncWorkerPool::builder()
.number_of_workers(max_pool_size)
.queue(queue.clone())
// if you want to run tasks of the specific kind
.task_type("my_task_type")
.build();
pool.start().await;
```
Check out:
- [Simple Worker Example](https://github.com/ayrat555/fang/tree/master/fang_examples/blocking/simple_worker) - simple worker example
- [Simple Cron Worker Example](https://github.com/ayrat555/fang/tree/master/fang_examples/blocking/simple_cron_worker) - simple worker example
- [Simple Async Worker Example](https://github.com/ayrat555/fang/tree/master/fang_examples/asynk/simple_async_worker) - simple async worker example
- [Simple Cron Async Worker Example](https://github.com/ayrat555/fang/tree/master/fang_examples/asynk/simple_cron_async_worker) - simple async worker example
- [El Monitorro](https://github.com/ayrat555/el_monitorro) - telegram feed reader. It uses the Fang's blocking module to synchronize feeds and deliver updates to users.
- [weather_bot_rust](https://github.com/pxp9/weather_bot_rust) - A bot that provides weather info. It uses the Fang's asynk module to process updates from Telegram users and schedule weather info.
### Configuration
#### Blocking feature
Just use `TypeBuilder` for `WorkerPool`.
#### Asynk feature
Just use `TypeBuilder` for `AsyncWorkerPool`.
### Configuring the type of workers
### Configuring retention mode
By default, all successfully finished tasks are removed from the DB, failed tasks aren't.
There are three retention modes you can use:
```rust
pub enum RetentionMode {
KeepAll, // doesn't remove tasks
RemoveAll, // removes all tasks
RemoveFinished, // default value
}
```
Set retention mode with worker pools `TypeBuilder` in both modules.
### Configuring sleep values
#### Blocking feature
You can use use `SleepParams` to configure sleep values:
```rust
pub struct SleepParams {
pub sleep_period: Duration, // default value is 5 seconds
pub max_sleep_period: Duration, // default value is 15 seconds
pub min_sleep_period: Duration, // default value is 5 seconds
pub sleep_step: Duration, // default value is 5 seconds
}
```
If there are no tasks in the DB, a worker sleeps for `sleep_period` and each time this value increases by `sleep_step` until it reaches `max_sleep_period`. `min_sleep_period` is the initial value for `sleep_period`. All values are in seconds.
Use `set_sleep_params` to set it:
```rust
let sleep_params = SleepParams {
sleep_period: Duration::from_secs(2),
max_sleep_period: Duration::from_secs(6),
min_sleep_period: Duration::from_secs(2),
sleep_step: Duration::from_secs(1),
};
```
Set sleep params with worker pools `TypeBuilder` in both modules.
## Contributing
1. [Fork it!](https://github.com/ayrat555/fang/fork)
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request
### Running tests locally
- Install diesel_cli.
```
cargo install diesel_cli
```
- Install docker on your machine.
- Run a Postgres docker container. (See in Makefile.)
```
make db
```
- Run the migrations
```
make diesel
```
- Run tests
```
make tests
```
- Run dirty//long tests, DB must be recreated afterwards.
```
make ignored
```
- Kill the docker container
```
make stop
```
## Authors
- Ayrat Badykov (@ayrat555)
- Pepe Márquez (@pxp9)
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[docs]: https://docs.rs/fang/
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