Tasks

A task is created by using the schedule() or spawn() builder followed by a call to a method.

important

When to use schedule() vs spawn()?

From within a writer or transaction method, i.e., using a WriterContext or TransactionContext, you use schedule(). This is because the creation of a task is an effect, and effects only occur after the method completes. In other words, if the methods's execution fails at any point, its scheduled tasks will not be run.

From within a workflow, i.e., using a WorkflowContext, as well as any code external to a Reboot application, i.e., using an ExternalContext, you use spawn(). A spawn()ed task is guaranteed to run as soon as the spawn() call returns, even if subsequent calls fail.

schedule()

Using schedule() from a writer or a transaction returns a task ID for a task that hasn't started yet (or even: the intent to run the task hasn't been persisted yet). Here's an example:

Python

task_id = await self.ref().schedule().WelcomeEmail(context)

TypeScript

const taskId = await this.ref().schedule().welcomeEmail(context);

spawn()

Using spawn() from a workflow or with an ExternalContext returns a [MethodName]Task for a running task, which you can await to get the response.

Python

task = await self.ref().spawn().WelcomeEmail(context)
response = await task

TypeScript

const { task } = await this.ref().spawn().welcomeEmail(context);
const response = await task;

Running a task at a specific time in the future

If no arguments are passed to schedule() or spawn(), the task will be started as soon as possible in the background.

You can alternatively pass the when argument to delay the task's execution until a specific time in the future.

info

Similar to a browser's setTimeout, work isn't guaranteed to start exactly when time has elapsed but sometime shortly thereafter, when resources are available to handle the request.

Python

await self.ref().schedule(
    when=timedelta(seconds=request.quote_expiration_seconds),
).ExpireQuote(
    context,
    quote=quote,
)

TypeScript

await this.ref().schedule({
  when: new Date(Date.now() + request.quoteExpirationSeconds * 1000)
}).expireQuoteTask(context, { quote })

tip

In Python you can pass either a timedate for a specific point in time or a timedelta for some amount of time in the future.

Retrieving a task from a task ID

If all you have is a TaskId you can retrieve a [MethodName]Task and await it to get the response.

Python

response = await Account.WelcomeEmailTask.retrieve(
    context,
    task_id=welcome_email_task_id,
)

TypeScript

const response = await Account.WelcomeEmailTask.retrieve(context, { taskId });

Unexpected task errors and hotfixing

If a task encounters an unexpected error, it will be retried until it eventually runs to completion. Learn more about expected and unexpected errors.

Tasks that are failing to complete due to errors can be "hotfixed" by deploying a new version of the app. The next time the task runs, it will use the fixed code.

tip

Hotfix code in development with ⌘s. Saving a new version rebuilds your app automatically. Learn more about rbt dev watch.

Learn how to hotfix an app in production by deploying a new version.

rbt task

Task administration, such as listing and cancelling tasks, can be done through the Reboot CLI.

list

To get a list of all tasks currently executing, run e.g. rbt task list --application-url=http://localhost:9991. Note, your application-url may be different.

To see tasks in production, you will need to pass a few additional flags; see rbt task list -h for more details.

cancel

To cancel a specific task, use rbt task cancel. To cancel a task, in addition to the --application-url, you must pass flags to identify the task by its --state-type, --state-id, and --task-uuid. These values can be found by first running rbt task list.