Newer
Older
// 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::{
asynchronous rob
committed
messages::{
AllMessages, RuntimeApiMessage, RuntimeApiRequest, RuntimeApiSender,
asynchronous rob
committed
},
Peter Goodspeed-Niklaus
committed
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::{
CoreState, EncodeAs, Hash, Signed, SigningContext, SessionIndex,
asynchronous rob
committed
ValidatorId, ValidatorIndex, ValidatorPair, GroupRotationInfo,
use sp_core::Pair;
use std::{
collections::HashMap,
convert::{TryFrom, TryInto},
marker::Unpin,
pin::Pin,
time::Duration,
};
use streamunordered::{StreamUnordered, StreamYield};
/// This reexport is required so that external crates can use the `delegated_subsystem` macro properly.
///
/// Otherwise, downstream crates might have to modify their `Cargo.toml` to ensure `sp-core` appeared there.
pub use sp_core::traits::SpawnNamed;
/// 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),
Peter Goodspeed-Niklaus
committed
/// A subsystem error
#[from]
Subsystem(SubsystemError),
/// An error in the Chain API.
#[from]
ChainApi(ChainApiError),
/// An error in the Runtime API.
asynchronous rob
committed
#[from]
RuntimeApi(RuntimeApiError),
Peter Goodspeed-Niklaus
committed
/// 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),
Peter Goodspeed-Niklaus
committed
/// Already forwarding errors to another sender
AlreadyForwarding,
asynchronous rob
committed
/// A type alias for Runtime API receivers.
pub type RuntimeApiReceiver<T> = oneshot::Receiver<Result<T, RuntimeApiError>>;
/// 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,
asynchronous rob
committed
) -> Result<RuntimeApiReceiver<Response>, Error>
asynchronous rob
committed
RequestBuilder: FnOnce(RuntimeApiSender<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>,
asynchronous rob
committed
) -> Result<RuntimeApiReceiver<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
}
asynchronous rob
committed
/// Request the validator groups.
pub async fn request_validator_groups<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
asynchronous rob
committed
) -> Result<RuntimeApiReceiver<(Vec<Vec<ValidatorIndex>>, GroupRotationInfo)>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| RuntimeApiRequest::ValidatorGroups(tx)).await
}
asynchronous rob
committed
/// Request the session index of the child block.
pub async fn request_session_index_for_child<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
asynchronous rob
committed
) -> Result<RuntimeApiReceiver<SessionIndex>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
asynchronous rob
committed
request_from_runtime(parent, s, |tx| {
RuntimeApiRequest::SessionIndexForChild(tx)
}).await
/// Request all availability cores
pub async fn request_availability_cores<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
) -> Result<RuntimeApiReceiver<Vec<CoreState>>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| {
RuntimeApiRequest::AvailabilityCores(tx)
}).await
}
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
/// Request global validation data.
pub async fn request_global_validation_data<FromJob>(
parent: Hash,
s: &mut mpsc::Sender<FromJob>,
) -> Result<RuntimeApiReceiver<GlobalValidationData>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| {
RuntimeApiRequest::GlobalValidationData(tx)
}).await
}
/// Request local validation data.
pub async fn request_local_validation_Data<FromJob>(
parent: Hash,
para_id: ParaId,
assumption: OccupiedCoreAssumption,
s: &mut mpsc::Sender<FromJob>,
) -> Result<RuntimeApiReceiver<LocalValidationData>, Error>
where
FromJob: TryFrom<AllMessages>,
<FromJob as TryFrom<AllMessages>>::Error: std::fmt::Debug,
{
request_from_runtime(parent, s, |tx| {
RuntimeApiRequest::LocalValidationData(para_id, assumption, tx)
}).await
}
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
/// 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,
{
asynchronous rob
committed
// Note: request_validators and request_session_index_for_child 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.
asynchronous rob
committed
let (validators, session_index) = futures::try_join!(
request_validators(parent, &mut sender).await?,
asynchronous rob
committed
request_session_index_for_child(parent, &mut sender).await?,
asynchronous rob
committed
let signing_context = SigningContext {
session_index: session_index?,
parent_hash: parent,
};
let validators = validators?;
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
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.
Peter Goodspeed-Niklaus
committed
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.
Peter Goodspeed-Niklaus
committed
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.
Peter Goodspeed-Niklaus
committed
async fn stop(mut self) {
// we don't actually care if the message couldn't be sent
Peter Goodspeed-Niklaus
committed
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.
Peter Goodspeed-Niklaus
committed
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,
Peter Goodspeed-Niklaus
committed
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(())
}
}
Peter Goodspeed-Niklaus
committed
/// 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>,
Peter Goodspeed-Niklaus
committed
errors: Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>,
Peter Goodspeed-Niklaus
committed
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,
Peter Goodspeed-Niklaus
committed
errors: None,
Peter Goodspeed-Niklaus
committed
/// 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();
Peter Goodspeed-Niklaus
committed
// 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,
);
Peter Goodspeed-Niklaus
committed
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);
}
}
Peter Goodspeed-Niklaus
committed
// the spawn mechanism requires that the spawned future has no output
Peter Goodspeed-Niklaus
committed
// 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.
Peter Goodspeed-Niklaus
committed
// 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());
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
// 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,
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
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>,
Peter Goodspeed-Niklaus
committed
errors: Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>,
}
impl<Spawner, Context, Job> JobManager<Spawner, Context, Job>
where
Spawner: SpawnNamed + Clone + Send + Unpin,
Peter Goodspeed-Niklaus
committed
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,
Peter Goodspeed-Niklaus
committed
errors: None,
Peter Goodspeed-Niklaus
committed
/// 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.
Peter Goodspeed-Niklaus
committed
///
/// 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());
Peter Goodspeed-Niklaus
committed
if let Some(ref err_tx) = err_tx {
jobs.forward_errors(err_tx.clone()).expect("we never call this twice in this context; qed");
}
Peter Goodspeed-Niklaus
committed
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,
}
}
}
Peter Goodspeed-Niklaus
committed
// 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,
Peter Goodspeed-Niklaus
committed
err_tx: &mut Option<mpsc::Sender<(Option<Hash>, JobsError<Job::Error>)>>
) -> bool {
use crate::FromOverseer::{Communication, Signal};
use crate::ActiveLeavesUpdate;
use crate::OverseerSignal::{BlockFinalized, Conclude, ActiveLeaves};
Ok(Signal(ActiveLeaves(ActiveLeavesUpdate { activated, deactivated }))) => {
for hash in activated {
if let Err(e) = jobs.spawn_job(hash, run_args.clone()) {
log::error!("Failed to spawn a job: {:?}", e);
Self::fwd_err(Some(hash), e.into(), err_tx).await;
return true;
}
for hash in deactivated {
if let Err(e) = jobs.stop_job(hash).await {
log::error!("Failed to stop a job: {:?}", e);
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)`.
Peter Goodspeed-Niklaus
committed
use futures::sink::drain;
use futures::stream::StreamExt;
use futures::stream::FuturesUnordered;
Peter Goodspeed-Niklaus
committed
if let Err(e) = jobs.running
.drain()
.map(|(_, handle)| handle.stop())
Peter Goodspeed-Niklaus
committed
.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);
Peter Goodspeed-Niklaus
committed
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);
Peter Goodspeed-Niklaus
committed
Self::fwd_err(None, JobsError::Job(err), err_tx).await;
return true;
}
}
}
}
}
Ok(Signal(BlockFinalized(_))) => {}
Err(err) => {
log::error!("error receiving message from subsystem context: {:?}", err);
Peter Goodspeed-Niklaus
committed
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.
Peter Goodspeed-Niklaus
committed
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) => {
Peter Goodspeed-Niklaus
committed
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>,
Peter Goodspeed-Niklaus
committed
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();
Peter Goodspeed-Niklaus
committed
let errors = self.errors;
let future = Box::pin(async move {
Peter Goodspeed-Niklaus
committed
Self::run(ctx, run_args, spawner, errors).await;
});
SpawnedSubsystem {
Peter Goodspeed-Niklaus
committed
name: Job::NAME.strip_suffix("Job").unwrap_or(Job::NAME),
Peter Goodspeed-Niklaus
committed
/// Create a delegated subsystem
///
/// It is possible to create a type which implements `Subsystem` by simply doing:
///
/// ```ignore
/// pub type ExampleSubsystem<Spawner, Context> = util::JobManager<Spawner, Context, ExampleJob>;
/// ```
///
/// However, doing this requires that job itself and all types which comprise it (i.e. `ToJob`, `FromJob`, `Error`, `RunArgs`)
/// are public, to avoid exposing private types in public interfaces. It's possible to delegate instead, which
/// can reduce the total number of public types exposed, i.e.
///
/// ```ignore
/// type Manager<Spawner, Context> = util::JobManager<Spawner, Context, ExampleJob>;
/// pub struct ExampleSubsystem {
/// manager: Manager<Spawner, Context>,
/// }
///
/// impl<Spawner, Context> Subsystem<Context> for ExampleSubsystem<Spawner, Context> { ... }
/// ```
///
/// This dramatically reduces the number of public types in the crate; the only things which must be public are now
///
/// - `struct ExampleSubsystem` (defined by this macro)
/// - `type ToJob` (because it appears in a trait bound)
/// - `type RunArgs` (because it appears in a function signature)
///
/// Implementing this all manually is of course possible, but it's tedious; why bother? This macro exists for
/// the purpose of doing it automatically:
///
/// ```ignore
/// delegated_subsystem!(ExampleJob(ExampleRunArgs) <- ExampleToJob as ExampleSubsystem);
/// ```
#[macro_export]
macro_rules! delegated_subsystem {
($job:ident($run_args:ty) <- $to_job:ty as $subsystem:ident) => {
delegated_subsystem!($job($run_args) <- $to_job as $subsystem; stringify!($subsystem));
};
($job:ident($run_args:ty) <- $to_job:ty as $subsystem:ident; $subsystem_name:expr) => {
#[doc = "Manager type for the "]
#[doc = $subsystem_name]
type Manager<Spawner, Context> = $crate::util::JobManager<Spawner, Context, $job>;
#[doc = "An implementation of the "]
#[doc = $subsystem_name]
pub struct $subsystem<Spawner, Context> {
manager: Manager<Spawner, Context>,
}
impl<Spawner, Context> $subsystem<Spawner, Context>
where
Spawner: Clone + $crate::util::SpawnNamed + Send + Unpin,
Context: $crate::SubsystemContext,
<Context as $crate::SubsystemContext>::Message: Into<$to_job>,
{
#[doc = "Creates a new "]
#[doc = $subsystem_name]
pub fn new(spawner: Spawner, run_args: $run_args) -> Self {
$subsystem {
manager: $crate::util::JobManager::new(spawner, run_args)
}
}
/// Run this subsystem
pub async fn run(ctx: Context, run_args: $run_args, spawner: Spawner) {
<Manager<Spawner, Context>>::run(ctx, run_args, spawner, None).await
}
}
impl<Spawner, Context> $crate::Subsystem<Context> for $subsystem<Spawner, Context>
where
Spawner: $crate::util::SpawnNamed + Send + Clone + Unpin + 'static,
Context: $crate::SubsystemContext,
<Context as $crate::SubsystemContext>::Message: Into<$to_job>,
{
fn start(self, ctx: Context) -> $crate::SpawnedSubsystem {
self.manager.start(ctx)
}
}
};
}
Peter Goodspeed-Niklaus
committed
#[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,
},
ActiveLeavesUpdate,
Peter Goodspeed-Niklaus
committed
FromOverseer,
OverseerSignal,
Peter Goodspeed-Niklaus
committed
SpawnedSubsystem,
Subsystem,
Peter Goodspeed-Niklaus
committed
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
};
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,