Package ratpack.exec.util.retry

Class IndexedDelay

  • All Implemented Interfaces:
    Delay
    public class IndexedDelay
extends Object
implements Delay
    A index based implementation of Delay. By being configurable through an injected function, callers can implement customs backoff algorithms. 
    
 import ratpack.exec.ExecResult;
 import ratpack.exec.Promise;
 import ratpack.exec.util.retry.AttemptRetryPolicy;
 import ratpack.exec.util.retry.RetryPolicy;
 import ratpack.exec.util.retry.IndexedDelay;
 import ratpack.test.exec.ExecHarness;

 import java.time.Duration;
 import java.util.Arrays;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;

 import static org.junit.jupiter.api.Assertions.assertEquals;

 public class Example {
   private static final List<String> LOG = new LinkedList<>();

   public static void main(String... args) throws Exception {
     AtomicInteger source = new AtomicInteger();

     RetryPolicy retryPolicy = AttemptRetryPolicy.of(b -> b
       .delay(IndexedDelay.of(i -> Duration.ofMillis(500).multipliedBy(i)))
       .maxAttempts(3));

     ExecResult<Integer> result = ExecHarness.yieldSingle(exec ->
       Promise.sync(source::incrementAndGet)
         .mapIf(i -> i < 3, i -> { throw new IllegalStateException(); })
         .retry(retryPolicy, (i, t) -> LOG.add("retry attempt: " + i))
     );

     assertEquals(Integer.valueOf(3), result.getValue());
     assertEquals(Arrays.asList("retry attempt: 1", "retry attempt: 2"), LOG);
   }
 }
    Since:
    1.7

    • Method Detail

      • of

        public static IndexedDelay of​(Function<? super Integer,​Duration> indexedDelay)
        Builds an index based delay.
        Parameters:
        indexedDelay - a function expecting a retry attempt and returning the delay duration
        Returns:
        an indexed delay

      • delay

        public Promise<Duration> delay​(Integer attempt)
        Builds a promise wrapping a duration that will instruct the caller how long to wait between retries.
        Specified by:
        delay in interface Delay
        Parameters:
        attempt - current retry attempt to provide sophisticated delay strategies
        Returns:
        a promise wrapping a duration that will instruct the caller how long to wait between retries.