Enum JournalError 

pub enum JournalError {
    CasConflict(String),
    Integrity(String),
    Io {
        message: String,
        source: Error,
    },
}

Why a journal operation failed, split into the three classes a caller must treat differently.

variant	journal state	response
JournalError::CasConflict	known: someone else won	retryable — abort(token) → re-read head → rebuild → replay the input (spec §8.3)
JournalError::Integrity	known: contradictory	never retryable — retrying replays the same contradiction
JournalError::Io	unknown	neither; the append may or may not have landed

No variant permits publishing kernel effects (§9.1, “journal failure 不发布 kernel effects”).

Variants

CasConflict(String)

The CAS precondition did not hold: the journal head (or checkpoint pointer) moved.

Integrity(String)

The journal contents contradict themselves or the caller’s claim: a broken digest chain, a step_seq that does not follow its predecessor, a checkpoint whose covered_head does not match the record at its through_step_seq.

Io

The storage layer failed (disk full, permission denied, hard links unsupported). Distinct from both of the above: the journal state is unknown, not known-conflicting and not known-corrupt.

Fields

message: String

source: Error

Implementations

impl JournalError

pub fn conflict(message: impl Into<String>) -> Self

pub fn integrity(message: impl Into<String>) -> Self

pub fn io(message: impl Into<String>, source: Error) -> Self

pub fn is_retryable(&self) -> bool

A CAS conflict is the only class the durable-step protocol may retry. Integrity is a permanent contradiction; Io leaves the journal in an unknown state, so a retry could double-append rather than resolve anything — the caller must re-read the head first.

Trait Implementations

impl Debug for JournalError

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

Formats the value using the given formatter.

impl Display for JournalError

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

Formats the value using the given formatter.

impl Error for JournalError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl From<JournalError> for HostTransitionError

fn from(source: JournalError) -> Self

Converts to this type from the input type.

impl From<JournalError> for Error

fn from(err: JournalError) -> Self

Io keeps its ErrorKind (so callers that already match on crate::Error::Io keep working); the two journal-semantic classes become crate::Error::Other carrying their full message — the SDK-level error has no variant that could preserve the distinction, and silently mapping a CAS conflict onto Io would tell a caller to retry storage instead of rebuilding.