Enum polkadot_node_core_pvf::InvalidCandidate

pub enum InvalidCandidate {
    PrepareError(String),
    WorkerReportedError(String),
    AmbiguousWorkerDeath,
    HardTimeout,
    Panic(String),
}

A description of an error raised during executing a PVF and can be attributed to the combination of the candidate polkadot_parachain_primitives::primitives::ValidationParams and the PVF.

Variants

PrepareError(String)

PVF preparation ended up with a deterministic error.

WorkerReportedError(String)

The failure is reported by the execution worker. The string contains the error message.

AmbiguousWorkerDeath

The worker has died during validation of a candidate. That may fall in one of the following categories, which we cannot distinguish programmatically:

(a) Some sort of transient glitch caused the worker process to abort. An example would be that the host machine ran out of free memory and the OOM killer started killing the processes, and in order to save the parent it will “sacrifice child” first.

(b) The candidate triggered a code path that has lead to the process death. For example, the PVF found a way to consume unbounded amount of resources and then it either exceeded an rlimit (if set) or, again, invited OOM killer. Another possibility is a bug in wasmtime allowed the PVF to gain control over the execution worker.

We attribute such an event to an invalid candidate in either case.

The rationale for this is that a glitch may lead to unfair rejecting candidate by a single validator. If the glitch is somewhat more persistent the validator will reject all candidate thrown at it and hopefully the operator notices it by decreased reward performance of the validator. On the other hand, if the worker died because of (b) we would have better chances to stop the attack.

HardTimeout

PVF execution (compilation is not included) took more time than was allotted.

Panic(String)

A panic occurred and we can’t be sure whether the candidate is really invalid or some internal glitch occurred. Whenever we are unsure, we can never treat an error as internal as we would abstain from voting. This is bad because if the issue was due to the candidate, then all validators would abstain, stalling finality on the chain. So we will first retry the candidate, and if the issue persists we are forced to vote invalid.

Trait Implementations

impl Clone for InvalidCandidate

fn clone(&self) -> InvalidCandidate

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for InvalidCandidate

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.