背景
Sentinel 官网文档:introduction
springmvc项目中集成sentinel,通过sentinel提供的控制台配置限流、熔断等规则,
项目实现UrlBlockHandler,实现在catch到blockexception时进行自定义返回值处理
sentinel的官网文档非常详细的介绍了如何下载部署控制台、以及如何接入各类型的项目框架,本文以mvc项目为例,集成sentinel。
sentinel 控制台jar下载地址:Releases · alibaba/Sentinel · GitHub
启动控制台
java -Dserver.port=8080 -Dcsp.sentinel.dashboard.server=localhost:8080 -Dproject.name=sentinel-dashboard -jar sentinel-dashboard-1.8.5.jar
集成
maven配置
项目maven依赖,sentinel-web-servlet是web项目与sentinel客户端的适配器项目,又引用了sentinel-core核心依赖,web-servlet主要提供一个filter,用来集成sentinel功能
sentinel-transport-simple-http实现与控制台通讯
<dependency>
<groupId>com.alibaba.csp</groupId>
<artifactId>sentinel-web-servlet</artifactId>
<version>1.8.5</version>
</dependency>
<dependency>
<groupId>com.alibaba.csp</groupId>
<artifactId>sentinel-transport-simple-http</artifactId>
<version>1.8.5</version>
</dependency>
web.xml配置
通过配置web.xml 的filter开启sentinel支持
<filter>
<filter-name>SentinelCommonFilter</filter-name>
<filter-class>com.alibaba.csp.sentinel.adapter.servlet.CommonFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>SentinelCommonFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
Sentinel配置
SentinelConfiguration配置类主要自定义一个UrlBlockHandler,用来处理异常,要确保这个配置类会被框架扫描到
import java.io.IOException;
import java.io.PrintWriter;
import javax.annotation.PostConstruct;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.context.annotation.Configuration;
import com.alibaba.csp.sentinel.adapter.servlet.callback.UrlBlockHandler;
import com.alibaba.csp.sentinel.adapter.servlet.callback.WebCallbackManager;
import com.alibaba.csp.sentinel.adapter.servlet.config.WebServletConfig;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.slots.block.authority.AuthorityException;
import com.alibaba.csp.sentinel.slots.block.degrade.DegradeException;
import com.alibaba.csp.sentinel.slots.block.flow.FlowException;
import com.alibaba.csp.sentinel.slots.system.SystemBlockException;
import com.alibaba.csp.sentinel.util.StringUtil;
@Configuration
public class SentinelConfiguration {
public UrlBlockHandler urlBlockHandler() {
return new UrlBlockHandler() {
@Override
public void blocked(HttpServletRequest request, HttpServletResponse response, BlockException ex) throws IOException {
if (ex instanceof FlowException) {
// 触发接口限流
} else if (ex instanceof DegradeException) {
// 触发熔断降级
} else if (ex instanceof SystemBlockException) {
// 触发系统保护
} else if (ex instanceof AuthorityException) {
// 触发授权规则
}
String errMsg = "Blocked by Sentinel (flow limiting)!" + ex.getRule().getResource();
StringBuffer url = request.getRequestURL();
if ("GET".equals(request.getMethod()) && StringUtil.isNotBlank(request.getQueryString())) {
url.append("?").append(request.getQueryString());
}
if (StringUtil.isBlank(WebServletConfig.getBlockPage())) {
response.setStatus(WebServletConfig.getBlockPageHttpStatus());
PrintWriter out = response.getWriter();
out.print("{\"code\":0,\"message\":\"" + errMsg + "\"}");
out.flush();
out.close();
} else {
String redirectUrl = WebServletConfig.getBlockPage() + "?http_referer=" + url.toString();
// Redirect to the customized block page.
response.sendRedirect(redirectUrl);
}
}
};
}
@PostConstruct
public void init() {
WebCallbackManager.setUrlBlockHandler(urlBlockHandler());
}
}
启动
项目启动时加入 JVM 参数 -Dcsp.sentinel.dashboard.server=localhost:8080
指定控制台地址和端口
更多启动参数配置参考startup-configuration