[−][src]Crate background_jobs

Background Jobs

This crate provides tooling required to run some processes asynchronously from a usually synchronous application. The standard example of this is Web Services, where certain things need to be processed, but processing them while a user is waiting for their browser to respond might not be the best experience.

Usage

Add Background Jobs to your project

[dependencies]
actix = "0.8"
background-jobs = "0.6.0"
failure = "0.1"
futures = "0.1"
serde = "1.0"
serde_drive = "1.0"
sled = "0.28"

To get started with Background Jobs, first you should define a job.

Jobs are a combination of the data required to perform an operation, and the logic of that operation. They implment the Job, serde::Serialize, and serde::DeserializeOwned.

use background_jobs::Job;
use serde_derive::{Deserialize, Serialize};
use failure::Error;

#[derive(Clone, Debug, Deserialize, Serialize)]
pub struct MyJob {
    some_usize: usize,
    other_usize: usize,
}

impl MyJob {
    pub fn new(some_usize: usize, other_usize: usize) -> Self {
        MyJob {
            some_usize,
            other_usize,
        }
    }
}

impl Job for MyJob {
    type Processor = MyProcessor; // We'll define this later
    type State = ();
    type Future = Result<(), Error>;

    fn run(self, _: Self::State) -> Self::Future {
        println!("args: {:?}", self);

        Ok(())
    }
}

The run method for a job takes an additional argument, which is the state the job expects to use. The state for all jobs defined in an application must be the same. By default, the state is an empty tuple, but it's likely you'll want to pass in some Actix address, or something else.

Let's re-define the job to care about some application state.

#[derive(Clone, Debug)]
pub struct MyState {
    pub app_name: String,
}

impl MyState {
    pub fn new(app_name: &str) -> Self {
        MyState {
            app_name: app_name.to_owned(),
        }
    }
}

impl Job for MyJob {
    type Processor = MyProcessor;
    type State = MyState;
    type Future = Result<(), Error>;

    fn run(self, state: Self::State) -> Self::Future {
        info!("{}: args, {:?}", state.app_name, self);

        Ok(())
    }
}

Next, define a Processor.

Processors are types that define default attributes for jobs, as well as containing some logic used internally to perform the job. Processors must implement Proccessor and Clone.

use background_jobs::{Backoff, MaxRetries, Processor};

const DEFAULT_QUEUE: &'static str = "default";

#[derive(Clone, Debug)]
pub struct MyProcessor;

impl Processor for MyProcessor {
    // The kind of job this processor should execute
    type Job = MyJob;

    // The name of the processor. It is super important that each processor has a unique name,
    // because otherwise one processor will overwrite another processor when they're being
    // registered.
    const NAME: &'static str = "MyProcessor";

    // The queue that this processor belongs to
    //
    // Workers have the option to subscribe to specific queues, so this is important to
    // determine which worker will call the processor
    //
    // Jobs can optionally override the queue they're spawned on
    const QUEUE: &'static str = DEFAULT_QUEUE;

    // The number of times background-jobs should try to retry a job before giving up
    //
    // Jobs can optionally override this value
    const MAX_RETRIES: MaxRetries = MaxRetries::Count(1);

    // The logic to determine how often to retry this job if it fails
    //
    // Jobs can optionally override this value
    const BACKOFF_STRATEGY: Backoff = Backoff::Exponential(2);
}

Running jobs

By default, this crate ships with the background-jobs-actix feature enabled. This uses the background-jobs-actix crate to spin up a Server and Workers, and provides a mechanism for spawning new jobs.

background-jobs-actix on it's own doesn't have a mechanism for storing worker state. This can be implemented manually by implementing the Storage trait from background-jobs-core, or the background-jobs-sled-storage crate can be used to provide a Sled-backed jobs store.

With that out of the way, back to the examples:

Main

use actix::System;
use background_jobs::{ServerConfig, sled_storage::Storage, WorkerConfig};
use failure::Error;
use sled::Db;

fn main() -> Result<(), Error> {
    // First set up the Actix System to ensure we have a runtime to spawn jobs on.
    let sys = System::new("my-actix-system");

    // Set up our Storage
    let db = Db::start_default("my-sled-db")?;
    let storage = Storage::new(db)?;

    // Start the application server. This guards access to to the jobs store
    let queue_handle = ServerConfig::new(storage).start();

    // Configure and start our workers
    WorkerConfig::new(move || MyState::new("My App"))
        .register(MyProcessor)
        .set_processor_count(DEFAULT_QUEUE, 16)
        .start(queue_handle.clone());

    // Queue our jobs
    queue_handle.queue::<MyProcessor>(MyJob::new(1, 2))?;
    queue_handle.queue::<MyProcessor>(MyJob::new(3, 4))?;
    queue_handle.queue::<MyProcessor>(MyJob::new(5, 6))?;

    // Block on Actix
    sys.run()?;
    Ok(())
}

memory_storage	A default, in-memory implementation of a storage mechanism
sled_storage

Structs

Every	A type used to schedule recurring jobs.
JobStat	A time-based overview of job completion and failures
QueueHandle	A handle to the job server, used for queuing new jobs
ServerConfig	The configuration for a jobs server
Stats	Statistics about the jobs processor
WorkerConfig	Worker Configuration

Enums

Backoff	Different styles for retrying jobs
MaxRetries	How many times a job should be retried before giving up

Traits

Job	The Job trait defines parameters pertaining to an instance of background job
Processor	The Processor trait