Tasks

A task is a function type that can be invoked directly from other functions or executed on a specified interval. This allows for cron jobs, which are great for re-occurring tasks. A cron job is a task automated using cron, a scheduler tool on a Unix-like operating system. Common cron jobs are clearing caches and monitoring servers.

To see example expressions and read a detailed description of cron syntax, see the Cron documentation.

8base.yml Declaration

A task can be specified to run on a schedule or when called by another custom function. The schedule parameter accepts minute, hourly, or daily intervals. Here is a task that will execute every 7 days:

functions:
  #
  # Declare tasks like so.
  sendEmail:
    handler:
      code: src/sendEmail.ts
    type: task
  #
  # Declare tasks (scheduled tasks) like so.
  sendWeeklyReport:
    handler:
      code: src/sendWeeklyReport.ts
    type: task
    schedule: 'rate(7 days)'

Non-scheduled function calls

Functions like resolvers, triggers, and webhooks usually run in response to user actions. Normally, you want to return a response to the user as soon as possible, while offloading any longer-running processes to background tasks. To do this, use the invokeFunction(taskName, args, options) method found on the context argument to invoke a background task.

// Context (ctx) argument maintains the invokeFunction method for
// invoking tasks from other functions.
module.exports = async (event, ctx) => {
  const args = { data: { param: 'value' } };

  await ctx.invokeFunction('myTask', args, {
    waitForResponse: false,
  });
};

// The "myTask" handler may looks like that
module.exports = async (event, ctx) => {
  const { param } = event.data;
  // ...
};

The options.waitForResponse (default: false) property tells the platform to resolve the promise immediately, without waiting for the task to complete. If you want to delay task result, you can set waitForResponse to true.

note

The value of args is passed as an event argument to the invoked task.

Scheduled Tasks

You can configure tasks to run on schedule using the schedule option in the 8base.yml declaration. The schedule parameter accepts two types of expressions: Rate and Cron. Both specify a scheduled invocation on a re-occuring schedule.

Rate Expressions

rate(Value Unit)

Expression	Instruction
rate(5 minutes)	Invoke task every 5 minutes
rate(1 hour)	Invoke task every hour
rate(7 days)	Invoke task every seven days

Singular vs Plural

For a singular value (1) the unit must be written as singular, otherwise it needs to be plural. For example:

• rate(1 day)
• rate(5 days)

Cron Expressions

cron(Minutes Hours Day-of-month Month Day-of-week Year)

Expression	Instruction
cron(0 10 * * ? *)	Invoke task at 10:00am (UTC) everyday
cron(15 12 * * ? *)	Invoke task at 12:15pm (UTC) everyday
cron(0 18 ? * MON-FRI *)	Invoke task at 06:00pm (UTC) every Mon-Fri
cron(0/10 * ? * MON-FRI *)	Invoke task every 10 min Mon-Fri
cron(0/5 8-17 ? * MON-FRI *)	Invoke task every 5 minutes Mon-Fri between 8:00am and 5:55pm (UTC)
cron(0 9 ? * 2#1 *)	Invoke task at 9 a.m. (UTC) the first Monday of each month

Cron expressions that lead to rates faster than one invocation per minute are not supported. Additionally, one of the day-of-month or day-of-week values must be a question mark ?.

Task Arguments

To learn about the arguments that are passed to tasks, see custom function arguments.