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// Copyright 2017-2020 Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! Utility module for subsystems
//!
//! Many subsystems have common interests such as canceling a bunch of spawned jobs,
//! or determining what their validator ID is. These common interests are factored into
//! this module.
use crate::{
messages::{AllMessages, RuntimeApiMessage, RuntimeApiRequest, SchedulerRoster},
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FromOverseer, SpawnedSubsystem, Subsystem, SubsystemContext, SubsystemError, SubsystemResult,
};
use futures::{
channel::{mpsc, oneshot},
future::Either,
prelude::*,
select,
stream::Stream,
};
use futures_timer::Delay;
use keystore::KeyStorePtr;
use parity_scale_codec::Encode;
use pin_project::{pin_project, pinned_drop};
use polkadot_primitives::v1::{
EncodeAs, Hash, HeadData, Id as ParaId, Signed, SigningContext,
ValidatorId, ValidatorIndex, ValidatorPair,
};
use sp_core::{
Pair,
traits::SpawnNamed,
};
use std::{
collections::HashMap,
convert::{TryFrom, TryInto},
marker::Unpin,
pin::Pin,
time::Duration,
};
use streamunordered::{StreamUnordered, StreamYield};
/// Duration a job will wait after sending a stop signal before hard-aborting.
pub const JOB_GRACEFUL_STOP_DURATION: Duration = Duration::from_secs(1);
/// Capacity of channels to and from individual jobs
pub const JOB_CHANNEL_CAPACITY: usize = 64;
/// Utility errors
#[derive(Debug, derive_more::From)]
pub enum Error {
/// Attempted to send or receive on a oneshot channel which had been canceled
#[from]
Oneshot(oneshot::Canceled),
/// Attempted to send on a MPSC channel which has been canceled
#[from]
Mpsc(mpsc::SendError),
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/// A subsystem error
#[from]
Subsystem(SubsystemError),
/// The type system wants this even though it doesn't make sense
#[from]
Infallible(std::convert::Infallible),
/// Attempted to convert from an AllMessages to a FromJob, and failed.
SenderConversion(String),
/// The local node is not a validator.
NotAValidator,
/// The desired job is not present in the jobs list.
JobNotFound(Hash),
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/// Already forwarding errors to another sender
AlreadyForwarding,
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}
/// Request some data from the `RuntimeApi`.
pub async fn request_from_runtime<RequestBuilder, Response, FromJob>(
parent: Hash,
sender: &mut mpsc::Sender<FromJob>,
request_builder: RequestBuilder,
) -> Result<oneshot::Receiver<Response>, Error>
where
RequestBuilder: FnOnce(oneshot::Sender<Response>) -> RuntimeApiRequest,
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
let (tx, rx) = oneshot::channel();
sender
.send(
AllMessages::RuntimeApi(RuntimeApiMessage::Request(parent, request_builder(tx)))
.try_into()
.map_err(|err| Error::SenderConversion(format!("{:?}", err)))?,
)
.await?;
Ok(rx)
}
/// Request a validator set from the `RuntimeApi`.
pub async fn request_validators<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
) -> Result<oneshot::Receiver<Vec<ValidatorId>>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| RuntimeApiRequest::Validators(tx)).await
}
/// Request the scheduler roster from `RuntimeApi`.
pub async fn request_validator_groups<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
) -> Result<oneshot::Receiver<SchedulerRoster>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| RuntimeApiRequest::ValidatorGroups(tx)).await
}
/// Request a `SigningContext` from the `RuntimeApi`.
pub async fn request_signing_context<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
) -> Result<oneshot::Receiver<SigningContext>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| RuntimeApiRequest::SigningContext(tx)).await
}
/// Request `HeadData` for some `ParaId` from `RuntimeApi`.
pub async fn request_head_data<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
id: ParaId,
) -> Result<oneshot::Receiver<HeadData>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| RuntimeApiRequest::HeadData(id, tx)).await
}
/// From the given set of validators, find the first key we can sign with, if any.
pub fn signing_key(validators: &[ValidatorId], keystore: &KeyStorePtr) -> Option<ValidatorPair> {
let keystore = keystore.read();
validators
.iter()
.find_map(|v| keystore.key_pair::<ValidatorPair>(&v).ok())
}
/// Local validator information
///
/// It can be created if the local node is a validator in the context of a particular
/// relay chain block.
pub struct Validator {
signing_context: SigningContext,
key: ValidatorPair,
index: ValidatorIndex,
}
impl Validator {
/// Get a struct representing this node's validator if this node is in fact a validator in the context of the given block.
pub async fn new<FromJob>(
parent: Hash,
keystore: KeyStorePtr,
mut sender: mpsc::Sender<FromJob>,
) -> Result<Self, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
// Note: request_validators and request_signing_context do not and cannot run concurrently: they both
// have a mutable handle to the same sender.
// However, each of them returns a oneshot::Receiver, and those are resolved concurrently.
let (validators, signing_context) = futures::try_join!(
request_validators(parent, &mut sender).await?,
request_signing_context(parent, &mut sender).await?,
)?;
Self::construct(&validators, signing_context, keystore)
}
/// Construct a validator instance without performing runtime fetches.
///
/// This can be useful if external code also needs the same data.
pub fn construct(
validators: &[ValidatorId],
signing_context: SigningContext,
keystore: KeyStorePtr,
) -> Result<Self, Error> {
let key = signing_key(validators, &keystore).ok_or(Error::NotAValidator)?;
let index = validators
.iter()
.enumerate()
.find(|(_, k)| k == &&key.public())
.map(|(idx, _)| idx as ValidatorIndex)
.expect("signing_key would have already returned NotAValidator if the item we're searching for isn't in this list; qed");
Ok(Validator {
signing_context,
key,
index,
})
}
/// Get this validator's id.
pub fn id(&self) -> ValidatorId {
self.key.public()
}
/// Get this validator's local index.
pub fn index(&self) -> ValidatorIndex {
self.index
}
/// Get the current signing context.
pub fn signing_context(&self) -> &SigningContext {
&self.signing_context
}
/// Sign a payload with this validator
pub fn sign<Payload: EncodeAs<RealPayload>, RealPayload: Encode>(
&self,
payload: Payload,
) -> Signed<Payload, RealPayload> {
Signed::sign(payload, &self.signing_context, self.index, &self.key)
}
/// Validate the payload with this validator
///
/// Validation can only succeed if `signed.validator_index() == self.index()`.
/// Normally, this will always be the case for a properly operating program,
/// but it's double-checked here anyway.
pub fn check_payload<Payload: EncodeAs<RealPayload>, RealPayload: Encode>(
&self,
signed: Signed<Payload, RealPayload>,
) -> Result<(), ()> {
if signed.validator_index() != self.index {
return Err(());
}
signed.check_signature(&self.signing_context, &self.id())
}
}
/// ToJob is expected to be an enum declaring the set of messages of interest to a particular job.
///
/// Normally, this will be some subset of `Allmessages`, and a `Stop` variant.
pub trait ToJobTrait: TryFrom<AllMessages> {
/// The `Stop` variant of the ToJob enum.
const STOP: Self;
/// If the message variant contains its relay parent, return it here
fn relay_parent(&self) -> Option<Hash>;
}
/// A JobHandle manages a particular job for a subsystem.
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struct JobHandle<ToJob> {
abort_handle: future::AbortHandle,
to_job: mpsc::Sender<ToJob>,
finished: oneshot::Receiver<()>,
outgoing_msgs_handle: usize,
}
impl<ToJob> JobHandle<ToJob> {
/// Send a message to the job.
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async fn send_msg(&mut self, msg: ToJob) -> Result<(), Error> {
self.to_job.send(msg).await.map_err(Into::into)
}
}
impl<ToJob: ToJobTrait> JobHandle<ToJob> {
/// Stop this job gracefully.
///
/// If it hasn't shut itself down after `JOB_GRACEFUL_STOP_DURATION`, abort it.
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async fn stop(mut self) {
// we don't actually care if the message couldn't be sent
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if let Err(_) = self.to_job.send(ToJob::STOP).await {
// no need to wait further here: the job is either stalled or
// disconnected, and in either case, we can just abort it immediately
self.abort_handle.abort();
return;
}
let stop_timer = Delay::new(JOB_GRACEFUL_STOP_DURATION);
match future::select(stop_timer, self.finished).await {
Either::Left((_, _)) => {}
Either::Right((_, _)) => {
self.abort_handle.abort();
}
}
}
}
/// This trait governs jobs.
///
/// Jobs are instantiated and killed automatically on appropriate overseer messages.
/// Other messages are passed along to and from the job via the overseer to other
/// subsystems.
pub trait JobTrait: Unpin {
/// Message type to the job. Typically a subset of AllMessages.
type ToJob: 'static + ToJobTrait + Send;
/// Message type from the job. Typically a subset of AllMessages.
type FromJob: 'static + Into<AllMessages> + Send;
/// Job runtime error.
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type Error: 'static + std::fmt::Debug + Send;
/// Extra arguments this job needs to run properly.
///
/// If no extra information is needed, it is perfectly acceptable to set it to `()`.
type RunArgs: 'static + Send;
/// Name of the job, i.e. `CandidateBackingJob`
const NAME: &'static str;
/// Run a job for the parent block indicated
fn run(
parent: Hash,
run_args: Self::RunArgs,
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receiver: mpsc::Receiver<Self::ToJob>,
sender: mpsc::Sender<Self::FromJob>,
) -> Pin<Box<dyn Future<Output = Result<(), Self::Error>> + Send>>;
/// Handle a message which has no relay parent, and therefore can't be dispatched to a particular job
///
/// By default, this is implemented with a NOP function. However, if
/// ToJob occasionally has messages which do not correspond to a particular
/// parent relay hash, then this function will be spawned as a one-off
/// task to handle those messages.
// TODO: the API here is likely not precisely what we want; figure it out more
// once we're implementing a subsystem which actually needs this feature.
// In particular, we're quite likely to want this to return a future instead of
// interrupting the active thread for the duration of the handler.
fn handle_unanchored_msg(_msg: Self::ToJob) -> Result<(), Self::Error> {
Ok(())
}
}
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/// Error which can be returned by the jobs manager
///
/// Wraps the utility error type and the job-specific error
#[derive(Debug, derive_more::From)]
pub enum JobsError<JobError> {
/// utility error
#[from]
Utility(Error),
/// internal job error
Job(JobError),
}
/// Jobs manager for a subsystem
///
/// - Spawns new jobs for a given relay-parent on demand.
/// - Closes old jobs for a given relay-parent on demand.
/// - Dispatches messages to the appropriate job for a given relay-parent.
/// - When dropped, aborts all remaining jobs.
/// - implements `Stream<Item=Job::FromJob>`, collecting all messages from subordinate jobs.
#[pin_project(PinnedDrop)]
pub struct Jobs<Spawner, Job: JobTrait> {
spawner: Spawner,
running: HashMap<Hash, JobHandle<Job::ToJob>>,
#[pin]
outgoing_msgs: StreamUnordered<mpsc::Receiver<Job::FromJob>>,
job: std::marker::PhantomData<Job>,
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errors: Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>,
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impl<Spawner: SpawnNamed, Job: 'static + JobTrait> Jobs<Spawner, Job> {
/// Create a new Jobs manager which handles spawning appropriate jobs.
pub fn new(spawner: Spawner) -> Self {
Self {
spawner,
running: HashMap::new(),
outgoing_msgs: StreamUnordered::new(),
job: std::marker::PhantomData,
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errors: None,
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/// Monitor errors which may occur during handling of a spawned job.
///
/// By default, an error in a job is simply logged. Once this is called,
/// the error is forwarded onto the provided channel.
///
/// Errors if the error channel already exists.
pub fn forward_errors(&mut self, tx: mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>) -> Result<(), Error> {
if self.errors.is_some() { return Err(Error::AlreadyForwarding) }
self.errors = Some(tx);
Ok(())
}
/// Spawn a new job for this `parent_hash`, with whatever args are appropriate.
fn spawn_job(&mut self, parent_hash: Hash, run_args: Job::RunArgs) -> Result<(), Error> {
let (to_job_tx, to_job_rx) = mpsc::channel(JOB_CHANNEL_CAPACITY);
let (from_job_tx, from_job_rx) = mpsc::channel(JOB_CHANNEL_CAPACITY);
let (finished_tx, finished) = oneshot::channel();
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// clone the error transmitter to move into the future
let err_tx = self.errors.clone();
let (future, abort_handle) = future::abortable(async move {
if let Err(e) = Job::run(parent_hash, run_args, to_job_rx, from_job_tx).await {
log::error!(
"{}({}) finished with an error {:?}",
Job::NAME,
parent_hash,
e,
);
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if let Some(mut err_tx) = err_tx {
// if we can't send the notification of error on the error channel, then
// there's no point trying to propagate this error onto the channel too
// all we can do is warn that error propagatio has failed
if let Err(e) = err_tx.send((Some(parent_hash), JobsError::Job(e))).await {
log::warn!("failed to forward error: {:?}", e);
}
}
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// the spawn mechanism requires that the spawned future has no output
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// job errors are already handled within the future, meaning
// that any errors here are due to the abortable mechanism.
// failure to abort isn't of interest.
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// transmission failure here is only possible if the receiver is closed,
// which means the handle is dropped, which means we don't care anymore
let _ = finished_tx.send(());
};
self.spawner.spawn(Job::NAME, future.boxed());
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// this handle lets us remove the appropriate receiver from self.outgoing_msgs
// when it's time to stop the job.
let outgoing_msgs_handle = self.outgoing_msgs.push(from_job_rx);
let handle = JobHandle {
abort_handle,
to_job: to_job_tx,
finished,
outgoing_msgs_handle,
};
self.running.insert(parent_hash, handle);
Ok(())
}
/// Stop the job associated with this `parent_hash`.
pub async fn stop_job(&mut self, parent_hash: Hash) -> Result<(), Error> {
match self.running.remove(&parent_hash) {
Some(handle) => {
Pin::new(&mut self.outgoing_msgs).remove(handle.outgoing_msgs_handle);
handle.stop().await;
Ok(())
}
None => Err(Error::JobNotFound(parent_hash)),
}
}
/// Send a message to the appropriate job for this `parent_hash`.
async fn send_msg(&mut self, parent_hash: Hash, msg: Job::ToJob) -> Result<(), Error> {
match self.running.get_mut(&parent_hash) {
Some(job) => job.send_msg(msg).await?,
None => return Err(Error::JobNotFound(parent_hash)),
}
Ok(())
}
}
// Note that on drop, we don't have the chance to gracefully spin down each of the remaining handles;
// we just abort them all. Still better than letting them dangle.
#[pinned_drop]
impl<Spawner, Job: JobTrait> PinnedDrop for Jobs<Spawner, Job> {
fn drop(self: Pin<&mut Self>) {
for job_handle in self.running.values() {
job_handle.abort_handle.abort();
}
}
}
impl<Spawner, Job> Stream for Jobs<Spawner, Job>
where
Spawner: SpawnNamed,
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Job: JobTrait,
{
type Item = Job::FromJob;
fn poll_next(self: Pin<&mut Self>, cx: &mut task::Context) -> task::Poll<Option<Self::Item>> {
// pin-project the outgoing messages
self.project()
.outgoing_msgs
.poll_next(cx)
.map(|opt| opt.and_then(|(stream_yield, _)| match stream_yield {
StreamYield::Item(msg) => Some(msg),
StreamYield::Finished(_) => None,
}))
}
}
/// A basic implementation of a subsystem.
///
/// This struct is responsible for handling message traffic between
/// this subsystem and the overseer. It spawns and kills jobs on the
/// appropriate Overseer messages, and dispatches standard traffic to
/// the appropriate job the rest of the time.
pub struct JobManager<Spawner, Context, Job: JobTrait> {
spawner: Spawner,
run_args: Job::RunArgs,
context: std::marker::PhantomData<Context>,
job: std::marker::PhantomData<Job>,
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errors: Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>,
}
impl<Spawner, Context, Job> JobManager<Spawner, Context, Job>
where
Spawner: SpawnNamed + Clone + Send + Unpin,
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Job: 'static + JobTrait,
Job::RunArgs: Clone,
Job::ToJob: TryFrom<AllMessages> + TryFrom<<Context as SubsystemContext>::Message> + Sync,
{
/// Creates a new `Subsystem`.
pub fn new(spawner: Spawner, run_args: Job::RunArgs) -> Self {
Self {
spawner,
run_args,
context: std::marker::PhantomData,
job: std::marker::PhantomData,
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errors: None,
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/// Monitor errors which may occur during handling of a spawned job.
///
/// By default, an error in a job is simply logged. Once this is called,
/// the error is forwarded onto the provided channel.
///
/// Errors if the error channel already exists.
pub fn forward_errors(&mut self, tx: mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>) -> Result<(), Error> {
if self.errors.is_some() { return Err(Error::AlreadyForwarding) }
self.errors = Some(tx);
Ok(())
}
/// Run this subsystem
///
/// Conceptually, this is very simple: it just loops forever.
///
/// - On incoming overseer messages, it starts or stops jobs as appropriate.
/// - On other incoming messages, if they can be converted into Job::ToJob and
/// include a hash, then they're forwarded to the appropriate individual job.
/// - On outgoing messages from the jobs, it forwards them to the overseer.
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///
/// If `err_tx` is not `None`, errors are forwarded onto that channel as they occur.
/// Otherwise, most are logged and then discarded.
pub async fn run(mut ctx: Context, run_args: Job::RunArgs, spawner: Spawner, mut err_tx: Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>) {
let mut jobs = Jobs::new(spawner.clone());
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if let Some(ref err_tx) = err_tx {
jobs.forward_errors(err_tx.clone()).expect("we never call this twice in this context; qed");
}
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incoming = ctx.recv().fuse() => if Self::handle_incoming(incoming, &mut jobs, &run_args, &mut err_tx).await { break },
outgoing = jobs.next().fuse() => if Self::handle_outgoing(outgoing, &mut ctx, &mut err_tx).await { break },
complete => break,
}
}
}
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// if we have a channel on which to forward errors, do so
async fn fwd_err(hash: Option<Hash>, err: JobsError<Job::Error>, err_tx: &mut Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>) {
if let Some(err_tx) = err_tx {
// if we can't send on the error transmission channel, we can't do anything useful about it
// still, we can at least log the failure
if let Err(e) = err_tx.send((hash, err)).await {
log::warn!("failed to forward error: {:?}", e);
}
}
}
// handle an incoming message. return true if we should break afterwards.
async fn handle_incoming(
incoming: SubsystemResult<FromOverseer<Context::Message>>,
jobs: &mut Jobs<Spawner, Job>,
run_args: &Job::RunArgs,
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err_tx: &mut Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>
) -> bool {
use crate::FromOverseer::{Communication, Signal};
use crate::OverseerSignal::{Conclude, StartWork, StopWork};
match incoming {
Ok(Signal(StartWork(hash))) => {
if let Err(e) = jobs.spawn_job(hash, run_args.clone()) {
log::error!("Failed to spawn a job: {:?}", e);
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Self::fwd_err(Some(hash), e.into(), err_tx).await;
return true;
}
}
Ok(Signal(StopWork(hash))) => {
if let Err(e) = jobs.stop_job(hash).await {
log::error!("Failed to stop a job: {:?}", e);
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Self::fwd_err(Some(hash), e.into(), err_tx).await;
return true;
}
}
Ok(Signal(Conclude)) => {
// Breaking the loop ends fn run, which drops `jobs`, which immediately drops all ongoing work.
// We can afford to wait a little while to shut them all down properly before doing that.
//
// Forwarding the stream to a drain means we wait until all of the items in the stream
// have completed. Contrast with `into_future`, which turns it into a future of `(head, rest_stream)`.
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use futures::sink::drain;
use futures::stream::StreamExt;
use futures::stream::FuturesUnordered;
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if let Err(e) = jobs.running
.drain()
.map(|(_, handle)| handle.stop())
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.collect::<FuturesUnordered<_>>()
.map(Ok)
.forward(drain())
.await
{
log::error!("failed to stop all jobs on conclude signal: {:?}", e);
Self::fwd_err(None, Error::from(e).into(), err_tx).await;
}
return true;
}
Ok(Communication { msg }) => {
if let Ok(to_job) = <Job::ToJob>::try_from(msg) {
match to_job.relay_parent() {
Some(hash) => {
if let Err(err) = jobs.send_msg(hash, to_job).await {
log::error!("Failed to send a message to a job: {:?}", err);
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Self::fwd_err(Some(hash), err.into(), err_tx).await;
return true;
}
}
None => {
if let Err(err) = Job::handle_unanchored_msg(to_job) {
log::error!("Failed to handle unhashed message: {:?}", err);
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Self::fwd_err(None, JobsError::Job(err), err_tx).await;
return true;
}
}
}
}
}
Err(err) => {
log::error!("error receiving message from subsystem context: {:?}", err);
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Self::fwd_err(None, Error::from(err).into(), err_tx).await;
return true;
}
}
false
}
// handle an outgoing message. return true if we should break afterwards.
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async fn handle_outgoing(outgoing: Option<Job::FromJob>, ctx: &mut Context, err_tx: &mut Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>) -> bool {
match outgoing {
Some(msg) => {
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if let Err(e) = ctx.send_message(msg.into()).await {
Self::fwd_err(None, Error::from(e).into(), err_tx).await;
}
}
None => return true,
}
false
}
}
impl<Spawner, Context, Job> Subsystem<Context> for JobManager<Spawner, Context, Job>
where
Spawner: SpawnNamed + Send + Clone + Unpin + 'static,
Context: SubsystemContext,
<Context as SubsystemContext>::Message: Into<Job::ToJob>,
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Job: 'static + JobTrait + Send,
Job::RunArgs: Clone + Sync,
Job::ToJob: TryFrom<AllMessages> + Sync,
{
fn start(self, ctx: Context) -> SpawnedSubsystem {
let spawner = self.spawner.clone();
let run_args = self.run_args.clone();
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let errors = self.errors;
let future = Box::pin(async move {
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Self::run(ctx, run_args, spawner, errors).await;
});
SpawnedSubsystem {
name: "JobManager",
future,
}
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#[cfg(test)]
mod tests {
use assert_matches::assert_matches;
use crate::{
messages::{AllMessages, CandidateSelectionMessage},
test_helpers::{self, make_subsystem_context},
util::{
self,
JobsError,
JobManager,
JobTrait,
ToJobTrait,
},
FromOverseer,
OverseerSignal,
};
use futures::{
channel::mpsc,
executor,
Future,
FutureExt,
stream::{self, StreamExt},
SinkExt,
};
use futures_timer::Delay;
use polkadot_primitives::v1::Hash;
use std::{
collections::HashMap,
convert::TryFrom,
pin::Pin,
time::Duration,
};
// basic usage: in a nutshell, when you want to define a subsystem, just focus on what its jobs do;
// you can leave the subsystem itself to the job manager.
// for purposes of demonstration, we're going to whip up a fake subsystem.
// this will 'select' candidates which are pre-loaded in the job
// job structs are constructed within JobTrait::run
// most will want to retain the sender and receiver, as well as whatever other data they like
struct FakeCandidateSelectionJob {
receiver: mpsc::Receiver<ToJob>,
}
// ToJob implementations require the following properties:
//
// - have a Stop variant (to impl ToJobTrait)
// - impl ToJobTrait
// - impl TryFrom<AllMessages>
// - impl From<CandidateSelectionMessage> (from SubsystemContext::Message)
//
// Mostly, they are just a type-safe subset of AllMessages that this job is prepared to receive
enum ToJob {
CandidateSelection(CandidateSelectionMessage),
Stop,
}
impl ToJobTrait for ToJob {
const STOP: Self = ToJob::Stop;
fn relay_parent(&self) -> Option<Hash> {
match self {
Self::CandidateSelection(csm) => csm.relay_parent(),
Self::Stop => None,
}
}
}
impl TryFrom<AllMessages> for ToJob {
type Error = ();
fn try_from(msg: AllMessages) -> Result<Self, Self::Error> {
match msg {
AllMessages::CandidateSelection(csm) => Ok(ToJob::CandidateSelection(csm)),
_ => Err(())
}
}
}
impl From<CandidateSelectionMessage> for ToJob {
fn from(csm: CandidateSelectionMessage) -> ToJob {
ToJob::CandidateSelection(csm)
}
}
// FromJob must be infallibly convertable into AllMessages.
//
// It exists to be a type-safe subset of AllMessages that this job is specified to send.
//
// Note: the Clone impl here is not generally required; it's just ueful for this test context because
// we include it in the RunArgs
#[derive(Clone)]
enum FromJob {
Test(String),
}
impl From<FromJob> for AllMessages {
fn from(from_job: FromJob) -> AllMessages {
match from_job {
FromJob::Test(s) => AllMessages::Test(s),
}
}
}
// Error will mostly be a wrapper to make the try operator more convenient;
// deriving From implementations for most variants is recommended.
// It must implement Debug for logging.
#[derive(Debug, derive_more::From)]
enum Error {
#[from]
Sending(mpsc::SendError)
}
impl JobTrait for FakeCandidateSelectionJob {
type ToJob = ToJob;
type FromJob = FromJob;
type Error = Error;
// RunArgs can be anything that a particular job needs supplied from its external context
// in order to create the Job. In this case, they're a hashmap of parents to the mock outputs
// expected from that job.
//
// Note that it's not recommended to use something as heavy as a hashmap in production: the
// RunArgs get cloned so that each job gets its own owned copy. If you need that, wrap it in
// an Arc. Within a testing context, that efficiency is less important.
type RunArgs = HashMap<Hash, Vec<FromJob>>;
const NAME: &'static str = "FakeCandidateSelectionJob";
/// Run a job for the parent block indicated
//
// this function is in charge of creating and executing the job's main loop
fn run(
parent: Hash,
mut run_args: Self::RunArgs,
receiver: mpsc::Receiver<ToJob>,
mut sender: mpsc::Sender<FromJob>,
) -> Pin<Box<dyn Future<Output = Result<(), Self::Error>> + Send>> {
async move {
let job = FakeCandidateSelectionJob {
receiver,
};
// most jobs will have a request-response cycle at the heart of their run loop.
// however, in this case, we never receive valid messages, so we may as well
// just send all of our (mock) output messages now
let mock_output = run_args.remove(&parent).unwrap_or_default();
let mut stream = stream::iter(mock_output.into_iter().map(Ok));
sender.send_all(&mut stream).await?;
// it isn't necessary to break run_loop into its own function,
// but it's convenient to separate the concerns in this way
job.run_loop().await
}.boxed()
}
}
impl FakeCandidateSelectionJob {
async fn run_loop(mut self) -> Result<(), Error> {
while let Some(msg) = self.receiver.next().await {
match msg {
ToJob::CandidateSelection(_csm) => {
unimplemented!("we'd report the collator to the peer set manager here, but that's not implemented yet");
}
ToJob::Stop => break,
}
}
Ok(())
}
}
// with the job defined, it's straightforward to get a subsystem implementation.
type FakeCandidateSelectionSubsystem<Spawner, Context> = JobManager<Spawner, Context, FakeCandidateSelectionJob>;
// this type lets us pretend to be the overseer
type OverseerHandle = test_helpers::TestSubsystemContextHandle<CandidateSelectionMessage>;
fn test_harness<T: Future<Output=()>>(run_args: HashMap<Hash, Vec<FromJob>>, test: impl FnOnce(OverseerHandle, mpsc::Receiver<(Option<Hash>, JobsError<Error>)>) -> T) {
let pool = sp_core::testing::TaskExecutor::new();
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let (context, overseer_handle) = make_subsystem_context(pool.clone());
let (err_tx, err_rx) = mpsc::channel(16);
let subsystem = FakeCandidateSelectionSubsystem::run(context, run_args, pool, Some(err_tx));
let test_future = test(overseer_handle, err_rx);
let timeout = Delay::new(Duration::from_secs(2));
futures::pin_mut!(test_future);
futures::pin_mut!(subsystem);
futures::pin_mut!(timeout);
executor::block_on(async move {
futures::select! {
_ = test_future.fuse() => (),
_ = subsystem.fuse() => (),
_ = timeout.fuse() => panic!("test timed out instead of completing"),
}
});
}
#[test]
fn starting_and_stopping_job_works() {
let relay_parent: Hash = [0; 32].into();
let mut run_args = HashMap::new();
let test_message = format!("greetings from {}", relay_parent);
run_args.insert(relay_parent.clone(), vec![FromJob::Test(test_message.clone())]);
test_harness(run_args, |mut overseer_handle, err_rx| async move {
overseer_handle.send(FromOverseer::Signal(OverseerSignal::StartWork(relay_parent))).await;
assert_matches!(
overseer_handle.recv().await,
AllMessages::Test(msg) if msg == test_message
);
overseer_handle.send(FromOverseer::Signal(OverseerSignal::StopWork(relay_parent))).await;
let errs: Vec<_> = err_rx.collect().await;
assert_eq!(errs.len(), 0);
});
}
#[test]
fn stopping_non_running_job_fails() {
let relay_parent: Hash = [0; 32].into();
let run_args = HashMap::new();
test_harness(run_args, |mut overseer_handle, err_rx| async move {
overseer_handle.send(FromOverseer::Signal(OverseerSignal::StopWork(relay_parent))).await;
let errs: Vec<_> = err_rx.collect().await;
assert_eq!(errs.len(), 1);
assert_eq!(errs[0].0, Some(relay_parent));
assert_matches!(
errs[0].1,
JobsError::Utility(util::Error::JobNotFound(match_relay_parent)) if relay_parent == match_relay_parent
);
});
}
}