Services

​

Prerequisites

• NodeJS >= v20 or Bun or Deno
• npm CLI >= 9.6.7

​

Getting started

​

Basic Services

import * as restate from "@restatedev/restate-sdk";

export const myService = restate.service({
  name: "MyService",
  handlers: {
    myHandler: async (ctx: restate.Context, greeting: string) => {
      return `${greeting}!`;
    },
  },
});

restate.serve({ services: [myService] });

• Define a service using restate.service.
• The service has a name and a list of handlers.
• Each handler has a name and can be called at <RESTATE_INGRESS>/myService/myHandler
• Handlers take the Context as the first argument.
• Handlers can take one optional JSON-serializable input and must return a JSON-serializable output (see custom serialization for advanced types).
• Serve the service over HTTP (port 9080 by default).

​

Virtual Objects

import * as restate from "@restatedev/restate-sdk";

export const myObject = restate.object({
  name: "MyObject",
  handlers: {
    myHandler: async (ctx: restate.ObjectContext, greeting: string) => {
      return `${greeting} ${ctx.key}!`;
    },
    myConcurrentHandler: restate.handlers.object.shared(
      async (ctx: restate.ObjectSharedContext, greeting: string) => {
        return `${greeting} ${ctx.key}!`;
      }
    ),
  },
});

restate.serve({ services: [myObject] });

• Define a Virtual Object using restate.object(...)
• Each instance is identified by a key (accessible via ctx.key).
• Virtual Objects can have exclusive and shared handlers.
• Exclusive handlers receive an ObjectContext, allowing read/write access to object state.
• Shared handlers are wrapped in handlers.object.shared(...) and use the ObjectSharedContext
• Serve the Virtual Object over HTTP (port 9080 by default).

​

Workflows

import * as restate from "@restatedev/restate-sdk";

export const myWorkflow = restate.workflow({
  name: "MyWorkflow",
  handlers: {
    run: async (ctx: restate.WorkflowContext, req: string) => {
      // implement workflow logic here

      return "success";
    },

    interactWithWorkflow: async (ctx: restate.WorkflowSharedContext) => {
      // implement interaction logic here
      // e.g. resolve a promise that the workflow is waiting on
    },
  },
});

restate.serve({ services: [myWorkflow] });

• Define a workflow with restate.workflow(...)
• Every workflow must include a run handler:
  • This is the main orchestration entry point
  • It runs exactly once per workflow execution and uses the WorkflowContext
  • Resubmission of the same workflow will fail with “Previously accepted”. The invocation ID can be found in the request header x-restate-id.
  • Use ctx.key to access the workflow’s unique ID
• Additional handlers must use the WorkflowSharedContext and can signal or query the workflow. They can run concurrently with the run handler and until the retention time expires.
• Serve the Workflow over HTTP (port 9080 by default).

​

Configuring services