从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

时间:2023-11-26 13:14:14

API 网关

API 网关出现的原因是微服务架构的出现,不同的微服务一般会有不同的网络地址,而外部客户端可能需要调用多个服务的接口才能完成一个业务需求,如果让客户端直接与各个微服务通信,会有以下的问题:

  1. 客户端会多次请求不同的微服务,增加了客户端的复杂性。
  2. 存在跨域请求,在一定场景下处理相对复杂。
  3. 认证复杂,每个服务都需要独立认证。
  4. 难以重构,随着项目的迭代,可能需要重新划分微服务。例如,可能将多个服务合并成一个或者将一个服务拆分成多个。如果客户端直接与微服务通信,那么重构将会很难实施。
  5. 某些微服务可能使用了防火墙 / 浏览器不友好的协议,直接访问会有一定的困难。

以上这些问题可以借助 API 网关解决。API 网关是介于客户端和服务器端之间的中间层,所有的外部请求都会先经过 API 网关这一层。也就是说,API 的实现方面更多的考虑业务逻辑,而安全、性能、监控可以交由 API 网关来做,这样既提高业务灵活性又不缺安全性,典型的架构图如图所示:

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

使用 API 网关后的优点如下:

  • 易于监控。可以在网关收集监控数据并将其推送到外部系统进行分析。
  • 易于认证。可以在网关上进行认证,然后再将请求转发到后端的微服务,而无须在每个微服务中进行认证。
  • 减少了客户端与各个微服务之间的交互次数。

API 网关选型

业界的情况:

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

我前面的文章<Netflix网关zuul(1.x和2.x)全解析>已经介绍了zuul1 和zuul2,现在就尝试从实例入手介绍一下spring cloud gateway

首先我们一步步实现一个最简单的网关例子

步骤1:在http://start.spring.io网站上创建一个spring-cloud-gateway-example项目,依赖spring-cloud-gateway,如下图所示

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

此时生产了一个spring-cloud-gateway-example的空项目包,pom.xml文件如下

<?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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.3.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>spring-cloud-gateway-example</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>spring-cloud-gateway-example</name>
<description>Demo project for Spring Boot</description> <properties>
<java.version>1.8</java.version>
<spring-cloud.version>Greenwich.RELEASE</spring-cloud.version>
</properties> <dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-gateway</artifactId>
</dependency> <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies> <dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement> <build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build> <repositories>
<repository>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
</repository>
</repositories> </project>

2.创建一个Route实例的配置类GatewayRoutes

package com.example.springcloudgatewayexample;

import org.springframework.cloud.gateway.route.RouteLocator;
import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class GatewayRoutes {
@Bean
public RouteLocator routeLocator(RouteLocatorBuilder builder) {
return builder.routes()
.route(r ->
r.path("/java/**")
.filters(
f -> f.stripPrefix(1)
)
.uri("http://localhost:8090/helloWorld")
)
.build();
}
}

当然,也可以不适用配置类,使用配置文件,如下图所示

spring:
cloud:
gateway:
routes:
- predicates:
- Path=/java/**
filters:
- StripPrefix=1
uri: "http://localhost:8090/helloWorld"

不过,为了调试方便,我们使用配置类方式。

此时项目已经完成,足够简单吧。

3.启动此项目

>>因api网关需要转发到一个服务上,本文为http://localhost:8090/helloWorld,那需要先启动我上文<spring boot整合spring5-webflux从0开始的实战及源码解析>,你也可以创建一个普通的web项目,启动端口设置为8090,然后启动。

. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.3.RELEASE) 2019-02-21 09:29:07.450 INFO 11704 --- [ main] c.e.demo.Spring5WebfluxApplication : Starting Spring5WebfluxApplication on DESKTOP-405G2C8 with PID 11704 (E:\workspaceForCloud\spring5-webflux\target\classes started by dell in E:\workspaceForCloud\spring5-webflux)
2019-02-21 09:29:07.455 INFO 11704 --- [ main] c.e.demo.Spring5WebfluxApplication : No active profile set, falling back to default profiles: default
2019-02-21 09:29:09.409 INFO 11704 --- [ main] o.s.b.web.embedded.netty.NettyWebServer : Netty started on port(s): 8090
2019-02-21 09:29:09.413 INFO 11704 --- [ main] c.e.demo.Spring5WebfluxApplication : Started Spring5WebfluxApplication in 2.304 seconds (JVM running for 7.311)

>>以spring boot方式启动spring-cloud-gateway-example项目,日志如下

2019-02-21 10:34:33.435  INFO 8580 --- [           main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$1e059320] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)

  .   ____          _            __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.1.3.RELEASE) 2019-02-21 10:34:33.767 INFO 8580 --- [ main] e.s.SpringCloudGatewayExampleApplication : No active profile set, falling back to default profiles: default
2019-02-21 10:34:34.219 INFO 8580 --- [ main] o.s.cloud.context.scope.GenericScope : BeanFactory id=d98183ec-3e46-38ba-ba4c-e976a1017dce
2019-02-21 10:34:34.243 INFO 8580 --- [ main] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration' of type [org.springframework.cloud.autoconfigure.ConfigurationPropertiesRebinderAutoConfiguration$$EnhancerBySpringCGLIB$$1e059320] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2019-02-21 10:34:44.367 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [After]
2019-02-21 10:34:44.367 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Before]
2019-02-21 10:34:44.367 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Between]
2019-02-21 10:34:44.367 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Cookie]
2019-02-21 10:34:44.367 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Header]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Host]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Method]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Path]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Query]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [ReadBodyPredicateFactory]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [RemoteAddr]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [Weight]
2019-02-21 10:34:44.368 INFO 8580 --- [ main] o.s.c.g.r.RouteDefinitionRouteLocator : Loaded RoutePredicateFactory [CloudFoundryRouteService]
2019-02-21 10:34:44.920 INFO 8580 --- [ main] o.s.b.web.embedded.netty.NettyWebServer : Netty started on port(s): 8080
2019-02-21 10:34:44.923 INFO 8580 --- [ main] e.s.SpringCloudGatewayExampleApplication : Started SpringCloudGatewayExampleApplication in 12.329 seconds (JVM running for 13.126)

4.测试,浏览器访问http://localhost:8080/java/helloWorld

返回hello world !

5.从上面的代码和配置及实例中,我们可以看出spring cloud gateway处理request请求的流程如下所示:

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

即在最前端,启动一个netty server(默认端口为8080)接受请求,然后通过Routes(每个Route由Predicate(等同于HandlerMapping)和Filter(等同于HandlerAdapter))处理后通过Netty Client发给响应的微服务。

那么在gateway本身最重要的应该是Route(Netty Server和Client已经封装好了),它由RouteLocatorBuilder构建,内部包含Predicate和Filter,

    private Route(String id, URI uri, int order, AsyncPredicate<ServerWebExchange> predicate, List<GatewayFilter> gatewayFilters) {
this.id = id;
this.uri = uri;
this.order = order;
this.predicate = predicate;
this.gatewayFilters = gatewayFilters;
}

那么我们就来探讨一下这两个组件吧

5.1.Predicate

Predicte由PredicateSpec来构建,主要实现有:

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

以path为例

    /**
* A predicate that checks if the path of the request matches the given pattern
* @param patterns the pattern to check the path against.
* The pattern is a {@link org.springframework.util.PathMatcher} pattern
* @return a {@link BooleanSpec} to be used to add logical operators
*/
public BooleanSpec path(String... patterns) {
return asyncPredicate(getBean(PathRoutePredicateFactory.class)
.applyAsync(c -> c.setPatterns(Arrays.asList(patterns))));
}

PathRoutePredicateFactory中执行

    @Override
public Predicate<ServerWebExchange> apply(Config config) {
final ArrayList<PathPattern> pathPatterns = new ArrayList<>();
synchronized (this.pathPatternParser) {
pathPatternParser.setMatchOptionalTrailingSeparator(
config.isMatchOptionalTrailingSeparator());
config.getPatterns().forEach(pattern -> {
PathPattern pathPattern = this.pathPatternParser.parse(pattern);
pathPatterns.add(pathPattern);
});
}
return exchange -> {
PathContainer path = parsePath(exchange.getRequest().getURI().getPath()); Optional<PathPattern> optionalPathPattern = pathPatterns.stream()
.filter(pattern -> pattern.matches(path)).findFirst(); if (optionalPathPattern.isPresent()) {
PathPattern pathPattern = optionalPathPattern.get();
traceMatch("Pattern", pathPattern.getPatternString(), path, true);
PathMatchInfo pathMatchInfo = pathPattern.matchAndExtract(path);
putUriTemplateVariables(exchange, pathMatchInfo.getUriVariables());
return true;
}
else {
traceMatch("Pattern", config.getPatterns(), path, false);
return false;
}
};
}

5.2.Filter

Filter分两种,一种GatewayFilter,一种GlobalFilter

5.2.1 GatewayFilter

GatewayFilter由GatewayFilterSpec构建,GatewayFilter的构建器

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

5.2.2 GlobalFilter

从0开始构建你的api网关--Spring Cloud Gateway网关实战及原理解析

5.3 GlobalFilter和GatewayFilter的联系

FilteringWebHandler.GatewayFilterAdapter代理了GlobalFilter

6.总结

本文从一个spring-cloud-gateway实例入手,深入浅出的介绍了spring-cloud-gateway的组件,并从源码角度给出了实现的原理。

spring-cloud-gateway在最前端,启动一个netty server(默认端口为8080)接受请求,然后通过Routes(每个Route由Predicate(等同于HandlerMapping)和Filter(等同于HandlerAdapter))处理后通过Netty Client发给响应的微服务。

Predicate和Filter的各个实现定义了spring-cloud-gateway拥有的功能。

参考资料:

【1】https://www.infoq.cn/article/comparing-api-gateway-performances

【2】https://dzone.com/articles/spring-cloud-gateway-configuring-a-simple-route