Scheduling is used to trigger events in the future. The actor scheduler is like setTimeout, except the timeout will persist even if the actor restarts, upgrades, or crashes.

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Use Cases

Scheduling is helpful for long-running timeouts like month-long billing periods or account trials.

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Scheduling

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c.schedule.after(duration, fn, ...args)

Schedules a function to be executed after a specified duration. This function persists across actor restarts, upgrades, or crashes.

Parameters:

  • duration (number): The delay in milliseconds.
  • fn (string): The name of the action to be executed.
  • ...args (unknown[]): Additional arguments to pass to the function.

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c.schedule.at(timestamp, fn, ...args)

Schedules a function to be executed at a specific timestamp. This function persists across actor restarts, upgrades, or crashes.

Parameters:

  • timestamp (number): The exact time in milliseconds since the Unix epoch when the function should be executed.
  • fn (string): The name of the action to be executed.
  • ...args (unknown[]): Additional arguments to pass to the function.

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Scheduling Private Actions

Currently, scheduling can only trigger public actions. If the scheduled action is private, it needs to be secured with something like a token.

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Full Example

import { actor } from "actor-core";

const reminderService = actor({
  state: {
    reminders: {}
  },
  
  actions: {
    setReminder: (c, userId, message, delayMs) => {
      const reminderId = crypto.randomUUID();
      
      // Store the reminder in state
      c.state.reminders[reminderId] = {
        userId,
        message,
        scheduledFor: Date.now() + delayMs
      };
      
      // Schedule the sendReminder action to run after the delay
      c.after(delayMs, "sendReminder", reminderId);
      
      return { reminderId };
    },
    
    sendReminder: (c, reminderId) => {
      const reminder = c.state.reminders[reminderId];
      if (!reminder) return;
      
      // Find the user's connection if they're online
      const userConn = c.conns.find(
        conn => conn.state.userId === reminder.userId
      );
      
      if (userConn) {
        // Send the reminder to the user
        userConn.send("reminder", {
          message: reminder.message,
          scheduledAt: reminder.scheduledFor
        });
      } else {
        // If user is offline, store reminder for later delivery
        // ...
      }
      
      // Clean up the processed reminder
      delete c.state.reminders[reminderId];
    }
  }
});