Package dev.restate.sdk

Interface Context

All Known Subinterfaces:
ObjectContext, SharedObjectContext, SharedWorkflowContext, WorkflowContext
public interface Context
This interface exposes the Restate functionalities to Restate services. It can be used to interact with other Restate services, record non-deterministic closures, execute timers and synchronize with external systems.

All methods of this interface, and related interfaces, throws either TerminalException or AbortedExecutionException, where the former can be caught and acted upon, while the latter MUST NOT be caught, but simply propagated for clean up purposes.

NOTE: This interface MUST NOT be accessed concurrently since it can lead to different orderings of user actions, corrupting the execution of the invocation.

  • Method Details

    • request

      Request request()

    • call

      <T, R> Awaitable<R> call(Target target, Serde<T> inputSerde, Serde<R> outputSerde, T parameter)
      Invoke another Restate service method.
      Parameters:
      target - the address of the callee
      inputSerde - Input serde
      outputSerde - Output serde
      parameter - the invocation request parameter.
      Returns:
      an Awaitable that wraps the Restate service method result.

    • call

      default Awaitable<byte[]> call(Target target, byte[] parameter)
      Like call(Target, Serde, Serde, Object) with raw input/output.

    • send

      <T> void send(Target target, Serde<T> inputSerde, T parameter)
      Invoke another Restate service without waiting for the response.
      Parameters:
      target - the address of the callee
      inputSerde - Input serde
      parameter - the invocation request parameter.

    • send

      default void send(Target target, byte[] parameter)
      Like send(Target, Serde, Object) with bytes input.

    • send

      <T> void send(Target target, Serde<T> inputSerde, T parameter, Duration delay)
      Invoke another Restate service without waiting for the response after the provided delay has elapsed.

      This method returns immediately, as the timer is executed and awaited on Restate.

      Parameters:
      target - the address of the callee
      inputSerde - Input serde
      parameter - the invocation request parameter.
      delay - time to wait before executing the call.

    • send

      default void send(Target target, byte[] parameter, Duration delay)
      Like send(Target, Serde, Object, Duration) with bytes input.

    • sleep

      default void sleep(Duration duration)
      Causes the current execution of the function invocation to sleep for the given duration.
      Parameters:
      duration - for which to sleep.

    • timer

      Awaitable<Void> timer(Duration duration)
      Causes the start of a timer for the given duration. You can await on the timer end by invoking Awaitable.await().
      Parameters:
      duration - for which to sleep.

    • run

      <T> T run(String name, Serde<T> serde, ThrowingSupplier<T> action) throws TerminalException
      Execute a non-deterministic closure, recording the result value in the journal. The result value will be re-played in case of re-invocation (e.g. because of failure recovery or suspension point) without re-executing the closure. Use this feature if you want to perform non-deterministic operations.

      You can name this closure using the name parameter. This name will be available in the observability tools.

      The closure should tolerate retries, that is Restate might re-execute the closure multiple times until it records a result.

      Error handling: Errors occurring within this closure won't be propagated to the caller, unless they are TerminalException. Consider the following code: 

      
 // Bad usage of try-catch outside the run
 try {
     ctx.run(() -> {
         throw new IllegalStateException();
     });
 } catch (IllegalStateException e) {
     // This will never be executed,
     // but the error will be retried by Restate,
     // following the invocation retry policy.
 }

 // Good usage of try-catch outside the run
 try {
     ctx.run(() -> {
         throw new TerminalException("my error");
     });
 } catch (TerminalException e) {
     // This is invoked
 }
      To propagate run failures to the call-site, make sure to wrap them in TerminalException.
      Type Parameters:
      T - type of the return value.
      Parameters:
      name - name of the side effect.
      serde - the type tag of the return value, used to serialize/deserialize it.
      action - closure to execute.
      Returns:
      value of the run operation.
      Throws:
      TerminalException

    • run

      default void run(String name, ThrowingRunnable runnable) throws TerminalException
      Like run(String, Serde, ThrowingSupplier), but without returning a value.
      Throws:
      TerminalException

    • run

      default <T> T run(Serde<T> serde, ThrowingSupplier<T> action) throws TerminalException
      Like run(String, Serde, ThrowingSupplier), but without a name.
      Throws:
      TerminalException

    • run

      default void run(ThrowingRunnable runnable) throws TerminalException
      Like run(String, ThrowingRunnable), but without a name.
      Throws:
      TerminalException

    • awakeable

      <T> Awakeable<T> awakeable(Serde<T> serde)
      Create an Awakeable, addressable through Awakeable.id().

      You can use this feature to implement external asynchronous systems interactions, for example you can send a Kafka record including the Awakeable.id(), and then let another service consume from Kafka the responses of given external system interaction by using awakeableHandle(String).

      Parameters:
      serde - the response type tag to use for deserializing the Awakeable result.
      Returns:
      the Awakeable to await on.
      See Also:

    • awakeableHandle

      AwakeableHandle awakeableHandle(String id)
      Create a new AwakeableHandle for the provided identifier. You can use it to AwakeableHandle.resolve(Serde, Object) or AwakeableHandle.reject(String) the linked Awakeable.
      See Also:

    • random

      RestateRandom random()
      See Also: