Renames backoff-jitter to a broader name: design-pattern-cloud.

patterns/design-patterns-cloud/src/test/java/com/baeldung/backoff/jitter/BackoffWithJitterTest.java

@@ -0,0 +1,103 @@
+package com.baeldung.backoff.jitter;
+
+import io.github.resilience4j.retry.IntervalFunction;
+import io.github.resilience4j.retry.Retry;
+import io.github.resilience4j.retry.RetryConfig;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.function.Function;
+
+import static com.baeldung.backoff.jitter.BackoffWithJitterTest.RetryProperties.*;
+import static io.github.resilience4j.retry.IntervalFunction.ofExponentialBackoff;
+import static io.github.resilience4j.retry.IntervalFunction.ofExponentialRandomBackoff;
+import static java.util.Collections.nCopies;
+import static java.util.concurrent.Executors.newFixedThreadPool;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.*;
+
+public class BackoffWithJitterTest {
+
+    static Logger log = LoggerFactory.getLogger(BackoffWithJitterTest.class);
+
+    interface PingPongService {
+
+        String call(String ping) throws PingPongServiceException;
+    }
+
+    class PingPongServiceException extends RuntimeException {
+
+        public PingPongServiceException(String reason) {
+            super(reason);
+        }
+    }
+
+    private PingPongService service;
+    private static final int NUM_CONCURRENT_CLIENTS = 8;
+
+    @Before
+    public void setUp() {
+        service = mock(PingPongService.class);
+    }
+
+    @Test
+    public void whenRetryExponentialBackoff_thenRetriedConfiguredNoOfTimes() {
+        IntervalFunction intervalFn = ofExponentialBackoff(INITIAL_INTERVAL, MULTIPLIER);
+        Function<String, String> pingPongFn = getRetryablePingPongFn(intervalFn);
+
+        when(service.call(anyString())).thenThrow(PingPongServiceException.class);
+        try {
+            pingPongFn.apply("Hello");
+        } catch (PingPongServiceException e) {
+            verify(service, times(MAX_RETRIES)).call(anyString());
+        }
+    }
+
+    @Test
+    public void whenRetryExponentialBackoffWithoutJitter_thenThunderingHerdProblemOccurs() throws InterruptedException {
+        IntervalFunction intervalFn = ofExponentialBackoff(INITIAL_INTERVAL, MULTIPLIER);
+        test(intervalFn);
+    }
+
+    @Test
+    public void whenRetryExponentialBackoffWithJitter_thenRetriesAreSpread() throws InterruptedException {
+        IntervalFunction intervalFn = ofExponentialRandomBackoff(INITIAL_INTERVAL, MULTIPLIER, RANDOMIZATION_FACTOR);
+        test(intervalFn);
+    }
+
+    private void test(IntervalFunction intervalFn) throws InterruptedException {
+        Function<String, String> pingPongFn = getRetryablePingPongFn(intervalFn);
+        ExecutorService executors = newFixedThreadPool(NUM_CONCURRENT_CLIENTS);
+        List<Callable<String>> tasks = nCopies(NUM_CONCURRENT_CLIENTS, () -> pingPongFn.apply("Hello"));
+
+        when(service.call(anyString())).thenThrow(PingPongServiceException.class);
+
+        executors.invokeAll(tasks);
+    }
+
+    private Function<String, String> getRetryablePingPongFn(IntervalFunction intervalFn) {
+        RetryConfig retryConfig = RetryConfig.custom()
+                .maxAttempts(MAX_RETRIES)
+                .intervalFunction(intervalFn)
+                .retryExceptions(PingPongServiceException.class)
+                .build();
+        Retry retry = Retry.of("pingpong", retryConfig);
+        return Retry.decorateFunction(retry, ping -> {
+            log.info("Invoked at {}", LocalDateTime.now());
+            return service.call(ping);
+        });
+    }
+
+    static class RetryProperties {
+        static final Long INITIAL_INTERVAL = 1000L;
+        static final Double MULTIPLIER = 2.0D;
+        static final Double RANDOMIZATION_FACTOR = 0.6D;
+        static final Integer MAX_RETRIES = 4;
+    }
+}