这是坚持技术写作计划(含翻译)的第8篇,定个小目标999,每周最少2篇。
前段时间的文章多是运维方面的,最近放出一波后端相关的。
背景
最近开始使用Sentinel进行流量保护,但是默认的web servlet filter是拦截全部http请求。在传统的项目中问题不大。但是如果项目中用了Spring MVC,并且用了@PathVariable就尴尬了。
比如 uri pattern是 /foo/{id}
,而从Sentinel监控看 /foo/1
和 /foo/2
就是两个资源了,并且Sentinel最大支持6000个资源,再多就不生效了。
解决办法
官方给的方案是:UrlCleaner
WebCallbackManager.setUrlCleaner(new UrlCleaner() {
@Override
public String clean(String originUrl) {
if (originUrl.startsWith(fooPrefix)) {
return "/foo/*";
}
return originUrl;
}
});
复制代码
但是想想就吐, /v1/{foo}/{bar}/qux/{baz}
这种的来个20来个,截一个我看看。
AOP
换种思路,uri pattern难搞,用笨办法 aop总行吧?答案是可以的。
@Aspect
public class SentinelResourceAspect {
@Pointcut("within(com.anjia.*.web.rest..*)")
public void sentinelResourcePackagePointcut() {
// Method is empty as this is just a Pointcut, the implementations are
// in the advices.
}
@Around("sentinelResourcePackagePointcut()")
public Object sentinelResourceAround(ProceedingJoinPoint joinPoint) throws Throwable {
Entry entry = null;
// 务必保证finally会被执行
try {
// 资源名可使用任意有业务语义的字符串
// 注意此处只是类名#方法名,方法重载是合并的,如果需要进行区分,
// 可以获取参数类型加入到资源名称上
entry = SphU.entry(joinPoint.getSignature().getDeclaringTypeName()+
"#"+joinPoint.getSignature().getName());
// 被保护的业务逻辑
// do something...
} catch (BlockException ex) {
// 资源访问阻止,被限流或被降级
// 进行相应的处理操作
} finally {
if (entry != null) {
entry.exit();
}
}
return result;
}
}
复制代码
拦截器
温习一下 Spring mvc的执行流程 doFilter -> doService -> dispatcher -> preHandle -> controller -> postHandle -> afterCompletion -> filterAfter
核心的是 String pattern = (String) request.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
但是是在dispatcher阶段才赋值的,所以在CommFilter是取不到的,所以导致使用官方的Filter是不行的。只能用拦截器
import com.alibaba.csp.sentinel.EntryType;
import com.alibaba.csp.sentinel.SphU;
import com.alibaba.csp.sentinel.adapter.servlet.callback.RequestOriginParser;
import com.alibaba.csp.sentinel.adapter.servlet.callback.UrlCleaner;
import com.alibaba.csp.sentinel.adapter.servlet.callback.WebCallbackManager;
import com.alibaba.csp.sentinel.adapter.servlet.util.FilterUtil;
import com.alibaba.csp.sentinel.context.ContextUtil;
import com.alibaba.csp.sentinel.log.RecordLog;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import com.alibaba.csp.sentinel.util.StringUtil;
import org.apache.commons.lang3.StringUtils;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.HandlerMapping;
import org.springframework.web.servlet.ModelAndView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class SentinelHandlerInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
String origin = parseOrigin(request);
String pattern = (String) request.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
String uriTarget = StringUtils.defaultString(pattern,FilterUtil.filterTarget(request));
try {
// Clean and unify the URL.
// For REST APIs, you have to clean the URL (e.g. `/foo/1` and `/foo/2` -> `/foo/:id`), or
// the amount of context and resources will exceed the threshold.
UrlCleaner urlCleaner = WebCallbackManager.getUrlCleaner();
if (urlCleaner != null) {
uriTarget = urlCleaner.clean(uriTarget);
}
RecordLog.info(String.format("[Sentinel Pre Filter] Origin: %s enter Uri Path: %s", origin, uriTarget));
SphU.entry(uriTarget, EntryType.IN);
return true;
} catch (BlockException ex) {
RecordLog.warn(String.format("[Sentinel Pre Filter] Block Exception when Origin: %s enter fall back uri: %s", origin, uriTarget), ex);
return false;
}
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
while (ContextUtil.getContext() != null && ContextUtil.getContext().getCurEntry() != null) {
ContextUtil.getContext().getCurEntry().exit();
}
ContextUtil.exit();
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
}
private String parseOrigin(HttpServletRequest request) {
RequestOriginParser originParser = WebCallbackManager.getRequestOriginParser();
String origin = EMPTY_ORIGIN;
if (originParser != null) {
origin = originParser.parseOrigin(request);
if (StringUtil.isEmpty(origin)) {
return EMPTY_ORIGIN;
}
}
return origin;
}
private static final String EMPTY_ORIGIN = "";
}
复制代码
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
@Configuration
public class WebConfig extends WebMvcConfigurationSupport {
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new SentinelHandlerInterceptor());
}
}
复制代码
参考资料
招聘小广告
山东济南的小伙伴欢迎投简历啊 加入我们 , 一起搞事情。
长期招聘,Java程序员,大数据工程师,运维工程师,前端工程师。