You can set retry rules for a task exec function by using the maxRetries parameter. For example, to have your task exec retry 3 times due to any unhandled exception:

exec -maxRetries 3

You can also optionally specify a task exec to be retried only when a certain error message occurs using the retryTriggerErrorPattern parameter in conjunction with maxRetries:

exec -maxRetries 3 -retryTriggerErrorPattern "Service is not currently available."

Notes

1. psake will wait 1 second between retries.
2. The default for the maxRetries parameter if not specified is 0, i.e. the task will not be retried.