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Distribute a PoV after seconding it (#1924)

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We need to distribute the PoV after we have seconded it. Other nodes
that will receive our `Secondded` statement and want to validate the
candidate another time will request this PoV from us.
This commit is contained in:
Bastian Köcher
2020-11-06 09:38:44 +01:00
committed by GitHub
parent 2cdc1c0409
commit 8a2911b85d
9 changed files with 63 additions and 43 deletions
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polkadot/roadmap/implementers-guide/src/node/backing/candidate-backing.md
+15 -9
View File
@@ -39,7 +39,7 @@ The subsystem should maintain a set of handles to Candidate Backing Jobs that ar
### On Receiving `CandidateBackingMessage`
* If the message is a [`CandidateBackingMessage`][CBM]`::GetBackedCandidates`, get all backable candidates from the statement table and send them back.
* If the message is a [`CandidateBackingMessage`][CBM]`::Second`, sign and dispatch a `Seconded` statement only if we have not seconded any other candidate and have not signed a `Valid` statement for the requested candidate. Signing both a `Seconded` and `Valid` message is a double-voting misbehavior with a heavy penalty, and this could occur if another validator has seconded the same candidate and we've received their message before the internal seconding request.
* If the message is a [`CandidateBackingMessage`][CBM]`::Second`, sign and dispatch a `Seconded` statement only if we have not seconded any other candidate and have not signed a `Valid` statement for the requested candidate. Signing both a `Seconded` and `Valid` message is a double-voting misbehavior with a heavy penalty, and this could occur if another validator has seconded the same candidate and we've received their message before the internal seconding request. After successfully dispatching the `Seconded` statement we have to distribute the PoV.
* If the message is a [`CandidateBackingMessage`][CBM]`::Statement`, count the statement to the quorum. If the statement in the message is `Seconded` and it contains a candidate that belongs to our assignment, request the corresponding `PoV` from the `PoVDistribution` and launch validation. Issue our own `Valid` or `Invalid` statement as a result.
> big TODO: "contextual execution"
@@ -72,16 +72,18 @@ match msg {
}
CandidateBackingMessage::Second(hash, candidate) => {
if candidate is unknown and in local assignment {
spawn_validation_work(candidate, parachain head, validation function)
if spawn_validation_work(candidate, parachain head, validation function).await == Valid {
send(DistributePoV(pov))
}
}
}
CandidateBackingMessage::Statement(hash, statement) => {
// count to the votes on this candidate
if let Statement::Seconded(candidate) = statement {
if candidate.parachain_id == our_assignment {
spawn_validation_work(candidate, parachain head, validation function)
}
}
if let Statement::Seconded(candidate) = statement {
if candidate.parachain_id == our_assignment {
spawn_validation_work(candidate, parachain head, validation function)
}
}
}
}
```
@@ -110,14 +112,18 @@ fn spawn_validation_work(candidate, parachain head, validation function) {
### Fetch Pov Block
Create a `(sender, receiver)` pair.
Dispatch a [`PoVDistributionMessage`][PDM]`::FecthPoV(relay_parent, candidate_hash, sender)` and listen on the receiver for a response.
Dispatch a [`PoVDistributionMessage`][PDM]`::FetchPoV(relay_parent, candidate_hash, sender)` and listen on the receiver for a response.
### Distribute Pov Block
Dispatch a [`PoVDistributionMessage`][PDM]`::DistributePoV(relay_parent, candidate_descriptor, pov)`.
### Validate PoV Block
Create a `(sender, receiver)` pair.
Dispatch a `CandidateValidationMessage::Validate(validation function, candidate, pov, sender)` and listen on the receiver for a response.
### Distribute Signed Statemnet
### Distribute Signed Statement
Dispatch a [`StatementDistributionMessage`][PDM]`::Share(relay_parent, SignedFullStatement)`.