Adding new circuitbreaker-failsafe with naive implementation

- Started working on spring-cloud-incubator/spring-cloud-circuitbreaker/spring-cloud#30

pom.xml

@@ -75,6 +75,7 @@
         <module>spring-cloud-circuitbreaker-commons</module>
         <module>spring-cloud-starter-circuitbreaker</module>
         <module>spring-cloud-circuitbreaker-hystrix</module>
+        <module>spring-cloud-circuitbreaker-failsafe</module>
         <module>spring-cloud-circuitbreaker-sentinel</module>
         <module>docs</module>
 		<module>spring-cloud-circuitbreaker-spring-retry</module>

spring-cloud-circuitbreaker-dependencies/pom.xml

@@ -19,6 +19,7 @@
 
     <properties>
         <resilience4j.version>0.13.1</resilience4j.version>
+        <failsafe.version>2.0.1</failsafe.version>
         <sentinel.version>1.5.1</sentinel.version>
     </properties>
 
@@ -39,6 +40,11 @@
                 <artifactId>resilience4j-reactor</artifactId>
                 <version>${resilience4j.version}</version>
             </dependency>
+			<dependency>
+				<groupId>net.jodah</groupId>
+				<artifactId>failsafe</artifactId>
+				<version>${failsafe.version}</version>
+			</dependency>
             <dependency>
                 <groupId>com.alibaba.csp</groupId>
                 <artifactId>sentinel-core</artifactId>

spring-cloud-circuitbreaker-failsafe/pom.xml

@@ -0,0 +1,40 @@
+<?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">
+	<parent>
+		<artifactId>spring-cloud-circuitbreaker</artifactId>
+		<groupId>org.springframework.cloud</groupId>
+		<version>0.0.1.BUILD-SNAPSHOT</version>
+	</parent>
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>spring-cloud-circuitbreaker-failsafe</artifactId>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-circuitbreaker-commons</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>net.jodah</groupId>
+			<artifactId>failsafe</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+
+</project>

spring-cloud-circuitbreaker-failsafe/src/main/java/org/springframework/cloud/circuitbreaker/failsafe/FailsafeAutoConfiguration.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2013-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.circuitbreaker.failsafe;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.annotation.PostConstruct;
+
+import net.jodah.failsafe.Failsafe;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.cloud.circuitbreaker.commons.CircuitBreakerFactory;
+import org.springframework.cloud.circuitbreaker.commons.Customizer;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+/**
+ * @author Jakub Marchwicki
+ */
+@Configuration
+@ConditionalOnClass(Failsafe.class)
+public class FailsafeAutoConfiguration {
+
+	@Bean
+	@ConditionalOnMissingBean(CircuitBreakerFactory.class)
+	public CircuitBreakerFactory failsafeCircuitBreakerFactory() {
+		return new FailsafeCircuitBreakerFactory();
+	}
+
+	@Configuration
+	public static class FailsafeCustomizerConfiguration {
+
+		@Autowired(required = false)
+		private List<Customizer<FailsafeCircuitBreakerFactory>> customizers = new ArrayList<>();
+
+		@Autowired(required = false)
+		private FailsafeCircuitBreakerFactory factory;
+
+		@PostConstruct
+		public void init() {
+			customizers.forEach(customizer -> customizer.customize(factory));
+		}
+
+	}
+
+}

spring-cloud-circuitbreaker-failsafe/src/main/java/org/springframework/cloud/circuitbreaker/failsafe/FailsafeCircuitBreaker.java

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2013-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.circuitbreaker.failsafe;
+
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+import net.jodah.failsafe.Failsafe;
+import net.jodah.failsafe.Fallback;
+import net.jodah.failsafe.event.ExecutionAttemptedEvent;
+import net.jodah.failsafe.function.CheckedFunction;
+
+import org.springframework.cloud.circuitbreaker.commons.CircuitBreaker;
+
+/**
+ * @author Jakub Marchwicki
+ */
+public class FailsafeCircuitBreaker implements CircuitBreaker {
+
+	private String id;
+
+	private FailsafeConfigBuilder.FailsafeConfig config;
+
+	// private Optional<Customizer<RetryTemplate>> retryTemplateCustomizer;
+	//
+	// private RetryTemplate retryTemplate;
+
+	public FailsafeCircuitBreaker(String id,
+			FailsafeConfigBuilder.FailsafeConfig config) {
+		// ,
+		// Optional<Customizer<RetryTemplate>> retryTemplateCustomizer) {
+		this.id = id;
+		this.config = config;
+		// this.retryTemplateCustomizer = retryTemplateCustomizer;
+		// this.retryTemplate = new RetryTemplate();
+	}
+
+	@Override
+	public <T> T run(Supplier<T> toRun, Function<Throwable, T> fallback) {
+
+		// retryTemplate.setBackOffPolicy(config.getBackOffPolicy());
+		// retryTemplate.setRetryPolicy(config.getRetryPolicy());
+		//
+		// retryTemplateCustomizer
+		// .ifPresent(customizer -> customizer.customize(retryTemplate));
+
+		Fallback<T> f = Fallback.of(extract(fallback));
+		return Failsafe.with(f).get(ex -> toRun.get());
+		// return retryTemplate.execute(context -> toRun.get(),
+		// context -> fallback.apply(context.getLastThrowable()),
+		// new DefaultRetryState(id, config.isForceRefreshState(),
+		// config.getStateClassifier()));
+	}
+
+	private <T> CheckedFunction<ExecutionAttemptedEvent<? extends T>, ? extends T> extract(
+			Function<Throwable, T> fallback) {
+		return execution -> fallback.apply(execution.getLastFailure());
+	}
+
+}

spring-cloud-circuitbreaker-failsafe/src/main/java/org/springframework/cloud/circuitbreaker/failsafe/FailsafeCircuitBreakerFactory.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2013-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.circuitbreaker.failsafe;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Function;
+
+import net.jodah.failsafe.Policy;
+
+import org.springframework.cloud.circuitbreaker.commons.CircuitBreaker;
+import org.springframework.cloud.circuitbreaker.commons.CircuitBreakerFactory;
+import org.springframework.cloud.circuitbreaker.commons.Customizer;
+import org.springframework.util.Assert;
+
+/**
+ * @author Jakub Marchwicki
+ */
+public class FailsafeCircuitBreakerFactory extends
+		CircuitBreakerFactory<FailsafeConfigBuilder.FailsafeConfig, FailsafeConfigBuilder> {
+
+	private Function<String, FailsafeConfigBuilder.FailsafeConfig> defaultConfig = id -> new FailsafeConfigBuilder(
+			id).build();
+
+	private Map<String, Customizer<Policy>> failsafeCustomizers = new HashMap<>();
+
+	@Override
+	protected FailsafeConfigBuilder configBuilder(String id) {
+		return new FailsafeConfigBuilder(id);
+	}
+
+	@Override
+	public void configureDefault(
+			Function<String, FailsafeConfigBuilder.FailsafeConfig> defaultConfiguration) {
+		this.defaultConfig = defaultConfiguration;
+	}
+
+	@Override
+	public CircuitBreaker create(String id) {
+		Assert.hasText(id, "A circuit breaker must have an id");
+		FailsafeConfigBuilder.FailsafeConfig config = getConfigurations()
+				.computeIfAbsent(id, defaultConfig);
+		return new FailsafeCircuitBreaker(id, config);
+	}
+
+	public void addRetryTemplateCustomizers(Customizer<Policy> customizer,
+			String... ids) {
+		for (String id : ids) {
+			this.failsafeCustomizers.put(id, customizer);
+		}
+	}
+
+}