Enum ServerError 

pub enum ServerError {
    Backend(BackendError),
    BackendContext {
        source: BackendError,
        context: String,
    },
    Config(ConfigError),
    LibraryLoad(LoadError),
    PartitionMismatch(String),
    NotFound(String),
    InvalidInput(String),
    OperationFailed(String),
    Script(String),
    ConcurrencyLimitExceeded(&'static str, u32),
    ValkeyVersionTooLow {
        detected: String,
        required: String,
    },
    BackendNotReady {
        backend: &'static str,
        stage: &'static str,
    },
    Engine(Box<EngineError>),
}

Server error type.

Variants

Backend(BackendError)

Backend transport error. Previously wrapped ferriskey::Error directly (#88); now carries a backend-agnostic ff_core::BackendError so consumers match on ff_core::BackendErrorKind instead of ferriskey’s native taxonomy. The ferriskey → ff_core::BackendError mapping lives in ff_backend_valkey::backend_error_from_ferriskey.

BackendContext

Backend error with additional context. Previously ValkeyContext { source: ferriskey::Error } (#88).

Fields

source: BackendError

context: String

Config(ConfigError)

LibraryLoad(LoadError)

PartitionMismatch(String)

NotFound(String)

InvalidInput(String)

OperationFailed(String)

Script(String)

ConcurrencyLimitExceeded(&'static str, u32)

Server-wide concurrency limit reached on a labelled pool. Surfaces as HTTP 429 at the REST boundary so load balancers and clients can retry with backoff. The source label (“stream_ops”, “admin_rotate”, etc.) identifies WHICH pool is exhausted so operators aren’t misled by a single “tail unavailable” string when the real fault is rotation contention.

Fields: (source_label, max_permits).

ValkeyVersionTooLow

Detected Valkey version is below the RFC-011 §13 minimum. The engine depends on Valkey Functions (stabilized in 7.2), RESP3 (7.2+), and hash-tag routing; older versions do not implement the required primitives. Operator action: upgrade Valkey.

Fields

detected: String

required: String

BackendNotReady

RFC-017 §9.0 hard-gate: selected backend is not yet permitted to boot in this ff-server binary. Operator action is to either (a) select FF_BACKEND=valkey, or (b) upgrade to a Stage E binary once v0.8.0 ships.

stage names the current stage (“A”/“B”/“C”/“D”) so operator tooling can correlate the refusal with the migration plan.

Fields

backend: &'static str

stage: &'static str

Engine(Box<EngineError>)

RFC-017 Stage A: an EngineBackend trait method returned a typed error that is not one of the specific business outcomes existing ServerError variants model. Includes transport faults, validation/corruption, and Unavailable for methods the backend has not implemented yet.

Stage B/C migrations may refine individual arms into richer ServerError variants as more handlers route through the trait; Stage A keeps this catch-all so the migration lands additively. Boxed to keep ServerError small (clippy result_large_err — EngineError is ~200 bytes).

Implementations

impl ServerError

pub fn backend_kind(&self) -> Option<BackendErrorKind>

Returns the classified ff_core::BackendErrorKind if this error carries a backend transport fault. Covers direct Backend variants and library-load failures.

Renamed from valkey_kind in #88 — the previous return type Option<ferriskey::ErrorKind> leaked ferriskey into every consumer doing retry/error classification.

pub fn is_retryable(&self) -> bool

Whether this error is safely retryable by a caller. For backend transport variants, delegates to ff_core::BackendErrorKind::is_retryable. Business-logic rejections (NotFound, InvalidInput, OperationFailed, Script, Config, PartitionMismatch) return false — those won’t change on retry.

Trait Implementations

impl Debug for ServerError

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

Formats the value using the given formatter.

impl Display for ServerError

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

Formats the value using the given formatter.

impl Error for ServerError

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<BackendError> for ServerError

fn from(source: BackendError) -> Self

Converts to this type from the input type.

impl From<Box<EngineError>> for ServerError

fn from(source: Box<EngineError>) -> Self

Converts to this type from the input type.

impl From<ConfigError> for ServerError

fn from(source: ConfigError) -> Self

Converts to this type from the input type.

impl From<EngineError> for ServerError

Lift an unboxed EngineError into ServerError::Engine. The variant stores a Box<EngineError> to keep ServerError small (clippy result_large_err); this From restores ?-propagation from trait-dispatched handler paths.

fn from(err: EngineError) -> Self

Converts to this type from the input type.

impl From<Error> for ServerError

Lift a native ferriskey::Error into ServerError::Backend via ff_backend_valkey::backend_error_from_ferriskey (#88). Keeps ?-propagation ergonomic at ferriskey call sites while the public variant stays backend-agnostic.

fn from(err: Error) -> Self

Converts to this type from the input type.

impl From<LoadError> for ServerError

fn from(source: LoadError) -> Self

Converts to this type from the input type.