apalis-workflow

This crate provides a flexible and composable workflow engine for apalis. Can be used for building general workflows or advanced LLM workflows.

Overview

The workflow engine allows you to define a sequence or DAG chain of steps in a workflow. Workflows are built by composing steps/nodes, and can be executed using supported backends

Features

• Extensible, durable and resumable workflows.
• Workflows are processed in a distributed manner.
• Parallel and concurrent execution of single steps.
• Full integration with apalis backends, workers and middleware.
• Macro free with compile-time guarantees.

Example

Currently apalis-workflow supports sequential and directed acyclic graph based workflows

Sequential Workflow

use apalis::prelude::*;
use apalis_workflow::*;
use apalis_file_storage::JsonStorage;;

#[tokio::main]
async fn main() {
   let workflow = Workflow::new("odd-numbers-workflow")
       .and_then(|a: usize| async move { Ok::<_, BoxDynError>((0..a).collect::<Vec<_>>()) })
       .filter_map(|x| async move { if x % 2 != 0 { Some(x) } else { None } })
       .and_then(|a: Vec<usize>| async move {
           println!("Sum: {}", a.iter().sum::<usize>());
           Ok::<_, BoxDynError>(())
        });

   let mut in_memory = JsonStorage::new_temp().unwrap();

   in_memory.push_start(10).await.unwrap();

   let worker = WorkerBuilder::new("rango-tango")
       .backend(in_memory)
       .on_event(|ctx, ev| {
           println!("On Event = {:?}", ev);
       })
       .build(workflow);
   worker.run().await.unwrap();
}

Directed Acyclic Graph

use apalis::prelude::*;
use apalis_file_storage::JsonStorage;
use apalis_workflow::{DagFlow, WorkflowSink};
use serde_json::Value;

async fn get_name(user_id: u32) -> Result<String, BoxDynError> {
    Ok(user_id.to_string())
}

async fn get_age(user_id: u32) -> Result<usize, BoxDynError> {
    Ok(user_id as usize + 20)
}

async fn get_address(user_id: u32) -> Result<usize, BoxDynError> {
    Ok(user_id as usize + 100)
}

async fn collector(
    (name, age, address): (String, usize, usize),
    wrk: WorkerContext,
) -> Result<usize, BoxDynError> {
    let result = name.parse::<usize>()? + age + address;
    wrk.stop().unwrap();
    Ok(result)
}


#[tokio::main]
async fn main() -> Result<(), BoxDynError> {
    let mut backend = JsonStorage::new_temp().unwrap();

    backend
        .push_start(vec![42, 43, 44])
        .await
        .unwrap();

    let dag_flow = DagFlow::new("user-etl-workflow");
    let get_name = dag_flow.node(get_name);
    let get_age = dag_flow.node(get_age);
    let get_address = dag_flow.node(get_address);
    dag_flow
        .node(collector)
        .depends_on((&get_name, &get_age, &get_address)); // Order and types matters here

    dag_flow.validate()?; // Ensure DAG is valid

    info!("Executing workflow:\n{}", dag_flow); // Print the DAG structure in dot format

    WorkerBuilder::new("tasty-banana")
        .backend(backend)
        .enable_tracing()
        .on_event(|_c, e| info!("{e}"))
        .build(dag_flow)
        .run()
        .await?;
    Ok(())
}

Observability

You can track your workflows using apalis-board.

Backend Support

• JSONStorage
• SqliteStorage
• RedisStorage
• PostgresStorage
• MysqlStorage
• RsMq

Roadmap

• AndThen: Sequential execution on success
• Delay: Delay execution
• FilterMap: MapReduce
• Fold
• Repeater
• Subflow
• DAG

Inspirations:

• Underway: Postgres-only stepped solution
• dagx: blazing fast in-memory dag solution

License

Licensed under MIT or Apache-2.0.