apalis-workflow 0.1.0-rc.7

A flexible and composable task workflow engine for rust
Documentation 
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use std::{
    collections::{HashMap, VecDeque},
    fmt::Debug,
    pin::Pin,
    task::{Context, Poll},
};

use apalis_core::{
    backend::{BackendExt, codec::RawDataBackend},
    error::BoxDynError,
    task::{
        Task,
        metadata::{Meta, MetadataExt},
    },
    worker::builder::{IntoWorkerService, WorkerService},
};
use petgraph::graph::{DiGraph, NodeIndex};
use tower::Service;

use crate::{
    DagFlow, DagService,
    dag::{
        DagFlowContext, RootDagService,
        error::{DagFlowError, DagServiceError},
    },
    id_generator::GenerateId,
};

/// Executor for DAG workflows
#[derive(Debug)]
pub struct DagExecutor<B>
where
    B: BackendExt,
{
    pub(super) graph: DiGraph<DagService<B::Compact, B::Context, B::IdType>, ()>,
    pub(super) node_mapping: HashMap<String, NodeIndex>,
    pub(super) topological_order: Vec<NodeIndex>,
    pub(super) start_nodes: Vec<NodeIndex>,
    pub(super) end_nodes: Vec<NodeIndex>,
    pub(super) not_ready: VecDeque<NodeIndex>,
}

impl<B> Clone for DagExecutor<B>
where
    B: BackendExt,
{
    fn clone(&self) -> Self {
        Self {
            graph: self.graph.clone(),
            node_mapping: self.node_mapping.clone(),
            topological_order: self.topological_order.clone(),
            start_nodes: self.start_nodes.clone(),
            end_nodes: self.end_nodes.clone(),
            not_ready: self.not_ready.clone(),
        }
    }
}

impl<B> DagExecutor<B>
where
    B: BackendExt,
{
    /// Get a node by name
    pub fn get_node_by_name_mut(
        &mut self,
        name: &str,
    ) -> Option<&mut DagService<B::Compact, B::Context, B::IdType>> {
        self.node_mapping
            .get(name)
            .and_then(|&idx| self.graph.node_weight_mut(idx))
    }
}

impl<B, MetaError> Service<Task<B::Compact, B::Context, B::IdType>> for DagExecutor<B>
where
    B: BackendExt,
    B::Context:
        Send + Sync + 'static + MetadataExt<DagFlowContext<B::IdType>, Error = MetaError> + Default,
    B::IdType: Clone + Send + Sync + 'static + GenerateId + Debug,
    B::Compact: Send + Sync + 'static,
    MetaError: Into<BoxDynError>,
{
    type Response = B::Compact;
    type Error = DagFlowError;
    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        loop {
            // must wait for *all* services to be ready.
            // this will cause head-of-line blocking unless the underlying services are always ready.
            if self.not_ready.is_empty() {
                return Poll::Ready(Ok(()));
            } else {
                if self
                    .graph
                    .node_weight_mut(self.not_ready[0])
                    .ok_or(DagFlowError::MissingService(self.not_ready[0]))?
                    .poll_ready(cx)
                    .map_err(DagServiceError::PollError)
                    .map_err(DagFlowError::Service)?
                    .is_pending()
                {
                    return Poll::Pending;
                }

                self.not_ready.pop_front();
            }
        }
    }

    fn call(&mut self, req: Task<B::Compact, B::Context, B::IdType>) -> Self::Future {
        let mut graph = self.graph.clone();

        Box::pin(async move {
            let context = req
                .extract::<Meta<DagFlowContext<B::IdType>>>()
                .await
                .map_err(|e| DagFlowError::Metadata(e.into()))?
                .0;
            // Get the service for this node
            let service = graph
                .node_weight_mut(context.current_node)
                .ok_or_else(|| DagFlowError::MissingService(context.current_node))?;

            let result = service
                .call(req)
                .await
                .map_err(DagFlowError::NodeExecutionError)?;

            Ok(result)
        })
    }
}

impl<B, Compact, Err> IntoWorkerService<B, RootDagService<B>, B::Compact, B::Context> for DagFlow<B>
where
    B: BackendExt<Compact = Compact, Args = Compact, Error = Err> + Clone,
    Err: std::error::Error + Send + Sync + 'static,
    B::Context: MetadataExt<DagFlowContext<B::IdType>> + Send + Sync + 'static,
    B::IdType: Send + Sync + 'static + Default + GenerateId + PartialEq + Debug,
    B::Compact: Send + Sync + 'static + Clone,
    RootDagService<B>: Service<Task<Compact, B::Context, B::IdType>>,
{
    type Backend = RawDataBackend<B>;
    fn into_service(self, b: B) -> WorkerService<RawDataBackend<B>, RootDagService<B>> {
        let executor = self.build().expect("Execution should be valid");
        WorkerService {
            backend: RawDataBackend::new(b.clone()),
            service: RootDagService::new(executor, b),
        }
    }
}