Workflow futures - Ruby SDK

Workflow Futures

Temporalio::Workflow::Future can be used for running things in the background or concurrently. Temporal provides Workflow-safe wrappers around some core language features in cases like these. Temporalio::Workflow::Future is a safe wrapper around Fiber.schedule for running multiple Activities at once. The Ruby SDK also provides Workflow.wait_condition for awaiting a result.

Futures are never used implicitly, but they work with all Workflow code and constructs. For instance, to run 3 activities and wait for them all to complete, something like this can be written:

# Start 3 activities in background
fut1 = Temporalio::Workflow::Future.new do
  Temporalio::Workflow.execute_activity(MyActivity1, schedule_to_close_timeout: 300)
end
fut2 = Temporalio::Workflow::Future.new do
  Temporalio::Workflow.execute_activity(MyActivity2, schedule_to_close_timeout: 300)
end
fut3 = Temporalio::Workflow::Future.new do
  Temporalio::Workflow.execute_activity(MyActivity3, schedule_to_close_timeout: 300)
end

# Wait for them all to complete
Temporalio::Workflow::Future.all_of(fut1, fut2, fut3).wait

Temporalio::Workflow.logger.info("Got: #{fut1.result}, #{fut2.result}, #{fut3.result}")

Or, say, to wait on the first of 5 activities or a timeout to complete:

# Start 5 activities
act_futs = 5.times.map do |i|
  Temporalio::Workflow::Future.new do
    Temporalio::Workflow.execute_activity(MyActivity, "my-arg-#{i}", schedule_to_close_timeout: 300)
  end
end
# Start a timer
sleep_fut = Temporalio::Workflow::Future.new { Temporalio::Workflow.sleep(30) }

# Wait for first act result or sleep fut
act_result = Temporalio::Workflow::Future.any_of(sleep_fut, *act_futs).wait
# Fail if timer done first
raise Temporalio::Error::ApplicationError, 'Timer expired' if sleep_fut.done?
# Print act result otherwise
Temporalio::Workflow.logger.info("Act result: #{act_result}")

There are several other details not covered here about futures, such as how exceptions are handled, how to use a setter proc instead of a block, etc. See the API documentation for details.