Backoff strategies

A subscriber backoff strategy specifies after what delay should a failed message delivery (one that ended with a result other than subscriber target responding with HTTP 2XX code) be retried. A total of 6 backoff strategies are supported.

Constant backoff strategy (constant)

Delivery of each message will be retried after a constant timeout specified as retryDelay.

Linear backoff strategy (linear)

The n-th message delivery attempt will be performed after n * retryDelay milliseconds.

Exponential backoff strategy (exponential)

The n-th message delivery attempt will be performed after 2^n-1 * retryDelay milliseconds.

Randomized backoff strategy variants (*-random)

Backoff strategies, names of which are suffixed with -random will for each n-th retry draw a random delay value that is between the value of n-1 attempt of the underlying backoff strategy and n+1 attempt of the underlying backoff strategy.

Note

One exception to the rule described above is the constant-random backoff strategy, which upon each retry produces a random value between 50% and 150% of retryDelay.

Example:

A linear backoff strategy with a base delay of 1000ms will produce a delay of 3000ms before the 3rd delivery attempt, 4000ms before the 4th delivery attempt and 5000ms before the 5th delivery attempt. Consequently, a randomized linear backoff strategy will during the 4th delivery attempt produce a random value between that of the 3rd attempt and 5th attempt of the linear backoff strategy, that is between 3000ms and 5000ms.