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::{
messages::{AllMessages, RuntimeApiMessage, RuntimeApiRequest, SchedulerRoster},
FromOverseer, SpawnedSubsystem, Subsystem, SubsystemContext, SubsystemResult,
};
use futures::{
channel::{mpsc, oneshot},
prelude::*,
stream::Stream,
task::{self, Spawn, SpawnError, SpawnExt},
};
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;
use std::{
collections::HashMap,
convert::{TryFrom, TryInto},
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;
#[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),
/// Attempted to spawn a new task, and failed
#[from]
Spawn(SpawnError),
/// 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),
}
/// 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.
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)?;
200
201
202
203
204
205
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
235
236
237
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>;
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
}
/// A JobHandle manages a particular job for a subsystem.
pub 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.
pub async fn send_msg(&mut self, msg: ToJob) -> Result<(), Error> {
self.to_job.send(msg).await.map_err(Into::into)
}
/// Abort the job without waiting for a graceful shutdown
pub fn abort(self) {
self.abort_handle.abort();
}
}
impl<ToJob: ToJobTrait> JobHandle<ToJob> {
/// Stop this job gracefully.
///
/// If it hasn't shut itself down after `JOB_GRACEFUL_STOP_DURATION`, abort it.
pub async fn stop(mut self) {
// we don't actually care if the message couldn't be sent
let _ = self.to_job.send(ToJob::STOP).await;
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.
type Error: std::fmt::Debug;
/// 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,
rx_to: mpsc::Receiver<Self::ToJob>,
tx_from: 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_orphan_msg(_msg: Self::ToJob) -> Result<(), Self::Error> {
}
/// 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>,
}
impl<Spawner: Spawn, Job: 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,
}
}
/// 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();
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,
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
parent_hash,
e,
);
}
});
// discard output
let future = async move {
let _ = future.await;
let _ = finished_tx.send(());
};
self.spawner.spawn(future)?;
// 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: Spawn,
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>,
}
impl<Spawner, Context, Job> JobManager<Spawner, Context, Job>
where
Spawner: Spawn + Clone + Send + Unpin,
Context: SubsystemContext,
Job: JobTrait,
Job::RunArgs: Clone,
Job::ToJob: TryFrom<AllMessages> + TryFrom<<Context as SubsystemContext>::Message> + Sync,
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
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
{
/// 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,
}
}
/// 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.
pub async fn run(mut ctx: Context, run_args: Job::RunArgs, spawner: Spawner) {
let mut jobs = Jobs::new(spawner.clone());
loop {
select! {
incoming = ctx.recv().fuse() => if Self::handle_incoming(incoming, &mut jobs, &run_args).await { break },
outgoing = jobs.next().fuse() => if Self::handle_outgoing(outgoing, &mut ctx).await { break },
complete => break,
}
}
}
// 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,
) -> 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);
return true;
}
}
Ok(Signal(StopWork(hash))) => {
if let Err(e) = jobs.stop_job(hash).await {
log::error!("Failed to stop a job: {:?}", e);
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.
future::join_all(jobs.running.drain().map(|(_, handle)| handle.stop())).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);
return true;
}
}
if let Err(err) = Job::handle_orphan_msg(to_job) {
log::error!("Failed to handle unhashed message: {:?}", err);
return true;
}
}
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
}
}
}
Err(err) => {
log::error!("error receiving message from subsystem context: {:?}", err);
return true;
}
}
false
}
// handle an outgoing message. return true if we should break afterwards.
async fn handle_outgoing(outgoing: Option<Job::FromJob>, ctx: &mut Context) -> bool {
match outgoing {
Some(msg) => {
// discard errors when sending the message upstream
let _ = ctx.send_message(msg.into()).await;
}
None => return true,
}
false
}
}
impl<Spawner, Context, Job> Subsystem<Context> for JobManager<Spawner, Context, Job>
where
Spawner: Spawn + Send + Clone + Unpin + 'static,
Context: SubsystemContext,
<Context as SubsystemContext>::Message: Into<Job::ToJob>,
Job: 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();
SpawnedSubsystem(Box::pin(async move {
Self::run(ctx, run_args, spawner).await;
}))
}
}