mantono/tardigrade

Retry and back off handling for actions that may fail

tardigrade

Simple retry and back off handling of requests or actions that may fail for some reason.

Example

Blocking

This code would make 5 attempts to requested URL. The returned value is the Kotlin Result type

val result: Result<String> = attempt {
    // Request that may fail (as in throwing an exception)
    Unirest.get("https://github.com/mantono").asString
}

More advanced example, here we create a BlockingGuard object which allows us to configure the back-off algorithm used (how much the delay should be after each attempt).

val guard: BlockingGuard<String> = BlockingGuard(
    /**
     * Give up after 20 attempts, and return the last exception that was caught
     */
    maxAttempts = 20,
    /**
     * Custom back-off algorithm;
     * Attempt ---> Wait time (ms)
     *       1 ---> 1_000
     *       2 ---> 4_000
     *       3 ---> 9_000
     *       4 ---> 16_000
     */
    backOff = { it * it * 1_000L }
)

val result: Result<String> = guard {
    Unirest.get("https://github.com/mantono").asString
}

Async/Suspending

Equivalent functionality of the blocking function and guard can be done with Kotlin coroutines and suspend functions.

• Instead of attempt we have attemptAsync
• Instead of BlockingGuard we have AsyncGuard

val result: Deferred<Result<String>> = attemptAsync(maxAttempts = 10) {
    // Suspending function that may fail
}

With AsyncGuard

val guard = AsyncGuard<String>()
val result: Deferred<Result<String>> = guard {
    // Suspending function that may fail
}

Both of these will return Deferred<Result<T>> instead of just Result<T>. See Kotlin documentation on Deferred for more information.