Struct Persistent

pub struct Persistent<Context, Value, Routine>(PhantomData<(Value, Context, Routine)>)
where
    Context: Config,
    Value: Portable,
    Routine: Routines<BlockNumberFor<Context>>;

Marker type for persistent offchain storage, providing fork-independent, non-reverting state with routine-defined error and logging semantics.

Intended for Substrate FRAME-based runtimes only.

Persistent offchain storage is not fork-aware:

• Values persist across block re-organizations.
• Values are shared across all forks.
• Values are not reverted if the current fork is abandoned.

This marker is used to specialize KeyValueStore implementations backed by [StorageValueRef::persistent].

Error policy requirement

When KeyValueStore is used for this type, the corresponding Routine must also implement OffchainStorageError for the same specialized Persistent<Context, Value, Routine> type.

This ensures that:

• storage-level failures are surfaced as caller-defined errors,
• errors are attributed to the routine’s domain rather than the storage layer,
• and each failure is logged exactly once.

Timestamp semantics

This storage backend is explicitly bound to block numbers as its timestamp source. It does not accept a generic timestamp parameter.

All logging and routine behavior associated with this backend uses [BlockNumberFor], reflecting its intended use inside FRAME-based runtimes.

Type parameters

• Context: The active runtime type (i.e. a type implementing [frame_system::Config]). This binds the storage to a specific runtime configuration.
• Value: The value type stored in persistent offchain storage.
• Routine: A routine type implementing Routines parameterized by [BlockNumberFor], ensuring logging, error handling, and behavior are specialized to block-based execution.

This type is a marker only and carries no runtime data.

Tuple Fields

0: PhantomData<(Value, Context, Routine)>

Trait Implementations

impl<Context, Value, Routine> Clone for Persistent<Context, Value, Routine>

where Context: Config + Clone, Value: Portable + Clone, Routine: Routines<BlockNumberFor<Context>> + Clone,

fn clone(&self) -> Persistent<Context, Value, Routine>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<Context, Value, Routine> Debug for Persistent<Context, Value, Routine>

where Context: Config + Debug, Value: Portable + Debug, Routine: Routines<BlockNumberFor<Context>> + Debug,

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

Formats the value using the given formatter.

impl<Context, Value, Routine> Default for Persistent<Context, Value, Routine>

where Context: Config + Default, Value: Portable + Default, Routine: Routines<BlockNumberFor<Context>> + Default,

fn default() -> Persistent<Context, Value, Routine>

Returns the “default value” for a type.

impl<T, Value, Routine> KeyValueStore<Value, <<<T as Config>::Block as HeaderProvider>::HeaderT as Header>::Number> for Persistent<T, Value, Routine>

where T: Config, Value: Portable, Routine: OffchainStorageError<Self> + Routines<BlockNumberFor<T>>,

Peristent Offchain Storage Kind/Backend Default KeyValueStore Implementation.

Intended for Substrate FRAME-based runtimes only.

The timestamp type is the runtime’s block number ([BlockNumberFor]), ensuring that all logs are tagged with the block context in which the operation occurred.

type Key = [u8]

Keys are raw byte slices; allows flexible usage for any encoded identifier.

type Value = Value

Value type implementing [Encode] and [Decode]

fn insert( key: &Self::Key, value: &Value, _target: Option<&str>, _fmt: Option<LogFormatter<BlockNumberFor<T>, Self::Level>>, ) -> Result<(), Self::Logger>

This writes directly to persistent offchain storage and is therefore not reverted on chain re-orgs.

fn get( key: &Self::Key, target: Option<&str>, fmt: Option<LogFormatter<BlockNumberFor<T>, Self::Level>>, ) -> Result<Option<Value>, Self::Logger>

Reads from persistent offchain storage, which is shared across forks and survives re-orgs.

fn remove( key: &Self::Key, target: Option<&str>, fmt: Option<LogFormatter<BlockNumberFor<T>, Self::Level>>, ) -> Result<Option<Value>, Self::Logger>

Removes the value from persistent offchain storage.

Since persistent storage is not fork-aware, removals are permanent and are not reverted on chain re-orgs.

fn mutate<F>( key: &Self::Key, f: F, target: Option<&str>, fmt: Option<LogFormatter<BlockNumberFor<T>, Self::Level>>, ) -> Result<(), Self::Logger>

where F: FnOnce(Result<Option<Value>, Self::Logger>) -> Result<Value, Self::Logger>,

Mutates the value associated with the given key in persistent offchain storage.

The closure is invoked with the current value, if any, and must return the new value to store. Removal is not supported by this method.

Persistent storage is not fork-aware: mutations persist across re-orgs and are visible on all forks.

impl<Context, Value, Routine> Copy for Persistent<Context, Value, Routine>

where Context: Config + Copy, Value: Portable + Copy, Routine: Routines<BlockNumberFor<Context>> + Copy,

impl<Context, Value, Routine> SubstrateOffchainStorage for Persistent<Context, Value, Routine>

where Context: Config, Value: Portable, Routine: Routines<BlockNumberFor<Context>>,

Default backend marker implementation for all valid Persistent specializations.

This blanket implementation marks every well-formed Persistent<Context, Value, Routine> type as a supported Substrate offchain storage backend.