Module: Aws::ECS::Waiters
- Defined in:
- gems/aws-sdk-ecs/lib/aws-sdk-ecs/waiters.rb
Overview
Waiters are utility methods that poll for a particular state to occur on a client. Waiters can fail after a number of attempts at a polling interval defined for the service client.
For a list of operations that can be waited for and the client methods called for each operation, see the table below or the Client#wait_until field documentation for the Client.
Invoking a Waiter
To invoke a waiter, call #wait_until on a Client. The first parameter is the waiter name, which is specific to the service client and indicates which operation is being waited for. The second parameter is a hash of parameters that are passed to the client method called by the waiter, which varies according to the waiter name.
Wait Failures
To catch errors in a waiter, use WaiterFailed, as shown in the following example.
rescue rescue Aws::Waiters::Errors::WaiterFailed => error
puts "failed waiting for instance running: #{error.message}
end
Configuring a Waiter
Each waiter has a default polling interval and a maximum number of
attempts it will make before returning control to your program.
To set these values, use the max_attempts
and delay
parameters
in your #wait_until
call.
The following example waits for up to 25 seconds, polling every five seconds.
client.wait_until(...) do |w|
w.max_attempts = 5
w.delay = 5
end
To disable wait failures, set the value of either of these parameters
to nil
.
Extending a Waiter
To modify the behavior of waiters, you can register callbacks that are triggered before each polling attempt and before waiting.
The following example implements an exponential backoff in a waiter by doubling the amount of time to wait on every attempt.
client.wait_until(...) do |w|
w.interval = 0 # disable normal sleep
w.before_wait do |n, resp|
sleep(n ** 2)
end
end
Available Waiters
The following table lists the valid waiter names, the operations they call,
and the default :delay
and :max_attempts
values.
waiter_name | params | :delay | :max_attempts |
---|---|---|---|
services_inactive | Client#describe_services | 15 | 40 |
services_stable | Client#describe_services | 15 | 40 |
tasks_running | Client#describe_tasks | 6 | 100 |
tasks_stopped | Client#describe_tasks | 6 | 100 |
Defined Under Namespace
Classes: ServicesInactive, ServicesStable, TasksRunning, TasksStopped