first commit - basic test

patterns/backoff-jitter/pom.xml

@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>backoff-jitter</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+    <packaging>pom</packaging>
+
+    <!--<parent>-->
+    <!--<artifactId>patterns</artifactId>-->
+    <!--<groupId>com.baeldung</groupId>-->
+    <!--<version>1.0.0-SNAPSHOT</version>-->
+    <!--<relativePath>..</relativePath>-->
+    <!--</parent>-->
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>${mockito-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.github.resilience4j</groupId>
+            <artifactId>resilience4j-retry</artifactId>
+            <version>${resilience4j.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>${slf4j.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <version>${slf4j.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <junit.version>4.12</junit.version>
+        <mockito-core.version>2.27.0</mockito-core.version>
+        <slf4j.version>1.7.26</slf4j.version>
+        <resilience4j.version>0.16.0</resilience4j.version>
+    </properties>
+
+</project>

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

@@ -0,0 +1,81 @@
+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_TASKS = 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_TRIES)).call(anyString());
+        }
+    }
+
+    private Function<String, String> getRetryablePingPongFn(IntervalFunction intervalFn) {
+        RetryConfig retryConfig = RetryConfig.custom()
+                .maxAttempts(MAX_TRIES)
+                .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_TRIES = 4;
+    }
+}

patterns/pom.xml

@@ -19,7 +19,8 @@
         <module>design-patterns</module>
         <module>design-patterns-2</module>
         <module>solid</module>
-        <module>dip</module>     
+        <module>dip</module>
+        <module>backoff-jitter</module>
     </modules>
 
     <dependencyManagement>