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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. State is isolated per Virtual Object.

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.

You can do the following operations on the state:

Listing state keys​

For a single Virtual Object, you can list all the state keys that have entries in the state store via:


Collection<String> keys = ctx.stateKeys();

Retrieving state​


// Getting String value
StateKey<String> STRING_STATE_KEY = StateKey.of("my-key", CoreSerdes.JSON_STRING);
String stringState = ctx.get(STRING_STATE_KEY).orElse("my-default");
// Getting integer value
StateKey<Integer> INT_STATE_KEY = StateKey.of("my-key", CoreSerdes.JSON_INT);
int intState = ctx.get(INT_STATE_KEY).orElse(0);

  1. Define the state key (key name and (de)serializer) at the top of the Virtual Object class.
  2. Use ctx.get to retrieve the state for a specific key.

Setting state​


StateKey<String> STRING_STATE_KEY = StateKey.of("my-key", CoreSerdes.JSON_STRING);
ctx.set(STRING_STATE_KEY, "my-new-value");

  1. Define the state key (key name and (de)serializer) at the top of the Virtual Object class.
  2. Use ctx.set to set the state for a specific key. The type of value needs to line up with the type that was defined in the StateKey.

Clearing state​


StateKey<String> STRING_STATE_KEY = StateKey.of("my-key", CoreSerdes.JSON_STRING);
ctx.clear(STRING_STATE_KEY);

  1. Define the state key (key name and (de)serializer) at the top of the Virtual Object class.
  2. Use ctx.clear to delete the state for a specific key.

Clearing all state​


ctx.clearAll();

This will delete all the state stored in Restate for the Virtual Object.