Trait ContextReadState

pub trait ContextReadState<'ctx>: SealedContext<'ctx> {
    // Provided methods
    fn get<T: Deserialize + 'static>(
        &self,
        key: &str,
    ) -> impl Future<Output = Result<Option<T>, TerminalError>> + 'ctx { ... }
    fn get_keys(
        &self,
    ) -> impl Future<Output = Result<Vec<String>, TerminalError>> + 'ctx { ... }
}

Reading state

You can store key-value state in Restate. Restate makes sure the state is consistent with the processing of the code execution.

This feature is only available for Virtual Objects and Workflows:

• For Virtual Objects, the state is isolated per Virtual Object and lives forever (across invocations for that object).
• For Workflows, you can think of it as if every workflow execution is a new object. So the state is isolated to a single workflow execution. The state can only be mutated by the run handler of the workflow. The other handlers can only read the state.

    /// 1. Listing state keys
    /// List all the state keys that have entries in the state store for this object, via:
    let keys = ctx.get_keys().await?;

    /// 2. Getting a state value
    let my_string = ctx
        .get::<String>("my-key")
        .await?
        .unwrap_or(String::from("my-default"));
    let my_number = ctx.get::<f64>("my-number-key").await?.unwrap_or_default();

    /// 3. Setting a state value
    ctx.set("my-key", String::from("my-value"));

    /// 4. Clearing a state value
    ctx.clear("my-key");

    /// 5. Clearing all state values
    /// Deletes all the state in Restate for the object
    ctx.clear_all();

For more info about serialization, see crate::serde

Command-line introspection

You can inspect and edit the K/V state stored in Restate via psql and the CLI. Have a look at the introspection docs for more information.

Provided Methods

fn get<T: Deserialize + 'static>( &self, key: &str, ) -> impl Future<Output = Result<Option<T>, TerminalError>> + 'ctx

Get state

fn get_keys( &self, ) -> impl Future<Output = Result<Vec<String>, TerminalError>> + 'ctx

Get state keys

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<'ctx, CTX: SealedContext<'ctx> + SealedCanReadState> ContextReadState<'ctx> for CTX