Retry Strategy Configuration

Tornado allows the configuration of a global retry strategy to be applied when the execution of an Action fails.

A retry strategy is composed by:

• retry policy: the policy that defines whether an action execution should be retried after an execution failure;

• backoff policy: the policy that defines the sleep time between retries.

Valid values for the retry policy are:

• {type = "MaxRetries", retries = 5} => A predefined maximum amount of retry attempts. This is the default value with a retries set to 20.

• {type = "None"} => No retries are performed.

• {type = "Infinite"} => The operation will be retried an infinite number of times. This setting must be used with extreme caution as it could fill the entire memory buffer preventing Tornado from processing incoming events.

Valid values for the backoff policy are:

• {type = "Exponential", ms = 1000, multiplier = 2 }: It increases the back off period for each retry attempt in a given set using the exponential function. The period to sleep on the first backoff is the ms; the multiplier is instead used to calculate the next backoff interval from the last. This is the default configuration.

• {type = "None"}: No sleep time between retries. This is the default value.

• {type = "Fixed", ms = 1000 }: A fixed amount of milliseconds to sleep between each retry attempt.

• {type = "Variable", ms = [1000, 5000, 10000]}: The amount of milliseconds between two consecutive retry attempts.

  The time to wait after ‘i’ retries is specified in the vector at position ‘i’.

  If the number of retries is bigger than the vector length, then the last value in the vector is used. For example:

  ms = [111,222,333] -> It waits 111 ms after the first failure, 222 ms after the second failure and then 333 ms for all following failures.

Example of a complete Retry Strategy configuration

[tornado.daemon]
retry_strategy.retry_policy = {type = "Infinite"}
retry_strategy.backoff_policy = {type = "Variable", ms = [1000, 5000, 10000]}

When not provided explicitly, the following default Retry Strategy is used:

[tornado.daemon]
retry_strategy.retry_policy = {type = "MaxRetries", retries = 20}
retry_strategy.backoff_policy = {type = "Exponential", ms = 1000, multiplier = 2 }