Enum Error 

pub enum Error {
    SerializationError(String),
    DeserializationError(String),
    ValidationError(String),
    CacheMiss,
    BackendError(String),
    RepositoryError(String),
    Timeout(String),
    ConfigError(String),
    NotImplemented(String),
    InvalidCacheEntry(String),
    VersionMismatch {
        expected: u32,
        found: u32,
    },
    Other(String),
}

Error types for cache framework.

All cache operations return Result<T> where Result is defined as std::result::Result<T, Error>. Different error variants represent different failure modes:

Variants

SerializationError(String)

Serialization failed when converting entity to cache bytes.

This occurs when the entity’s Serde implementation fails. Common causes:

• Entity contains non-serializable types
• Serde serialization panic/error
• Postcard codec error

DeserializationError(String)

Deserialization failed when converting cache bytes to entity.

This indicates corrupted or malformed data in cache. Common causes:

• Cache was corrupted during transport or storage
• Invalid Postcard encoding
• Incomplete data read from backend

Recovery: Cache entry should be evicted and recomputed.

ValidationError(String)

Validation failed in feeder or entity.

This is raised when:

• CacheFeed::validate() returns an error
• CacheEntity::validate() returns an error after deserialization

Implement these methods to add custom validation logic.

CacheMiss

Cache miss: key not found in cache.

Not necessarily an error condition, but indicates cache entry was absent. Only returned with CacheStrategy::Fresh when cache lookup fails.

BackendError(String)

Backend storage error (Redis, Memcached, etc).

This indicates the cache backend is unavailable or returned an error. Common causes:

• Redis/Memcached connection lost
• Network timeout
• Backend storage full
• Backend protocol error

Recovery: Retry the operation or fallback to database.

RepositoryError(String)

Data repository error (database, etc).

This indicates the source repository (database) failed to fetch data. Common causes:

• Database connection lost
• Query syntax error
• Database server error
• Row/record not found

Recovery: Retry after connection recovery.

Timeout(String)

Operation exceeded configured timeout threshold.

This occurs when cache or repository operations take too long. Common causes:

• Network latency
• Slow database query
• Backend overload

Recovery: Retry with exponential backoff.

ConfigError(String)

Configuration error during crate initialization.

This occurs when creating backends or policies with invalid config. Common causes:

• Invalid connection string
• Missing required configuration
• Invalid TTL policy

Recovery: Fix configuration and restart.

NotImplemented(String)

Feature not implemented or not enabled.

This indicates a requested feature is not available. Common causes:

• Cargo feature not enabled (e.g., “redis” for RedisBackend)
• Backend-specific operation called on wrong backend type

Recovery: Enable the required Cargo feature.

InvalidCacheEntry(String)

Invalid cache entry: corrupted envelope or bad magic.

This indicates the cache entry header is invalid. Returned when:

• Magic header is not b"CKIT"
• Envelope deserialization fails
• Non-cache-kit data in cache key

Recovery: Evict the cache entry and recompute.

VersionMismatch

Schema version mismatch between code and cached data.

This indicates the cache entry was created with a different schema version. Raised when:

• CURRENT_SCHEMA_VERSION changed
• Struct fields were added/removed/reordered
• Enum variants changed

Recovery: Cache entry is automatically evicted and recomputed on next access. No action needed - this is expected during deployments.

Fields

expected: u32

Expected schema version (from compiled code)

found: u32

Found schema version (from cached entry)

Other(String)

Generic error with custom message.

Used for errors that don’t fit into other variants.

Trait Implementations

impl Clone for Error

fn clone(&self) -> Error

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Error

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

Formats the value using the given formatter.

impl Display for Error

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

Formats the value using the given formatter.

impl Error for Error

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<&str> for Error

fn from(e: &str) -> Self

Converts to this type from the input type.

impl From<Error> for Error

fn from(e: Error) -> Self

Converts to this type from the input type.

impl From<Error> for Error

fn from(e: Error) -> Self

Converts to this type from the input type.

impl From<String> for Error

fn from(e: String) -> Self

Converts to this type from the input type.