常見限流方案
1.計數器法
- 原理:在單位時間段內,對請求數進行計數,如果數量超過了單位時間的限制,則執行限流策略,當單位時間結束後,計數器清零,這個過程週而復始,就是計數器法。
- 缺點:不能均衡限流,在一個單位時間的末尾和下一個單位時間的開始,很可能會有兩個訪問的峯值,導致系統崩潰。
- 改進方式:可以通過減小單位時間來提高精度。
2.漏桶算法
- 原理:假設有一個水桶,水桶有一定的容量,所有請求不論速度都會注入到水桶中,然後水桶以一個恆定的速度向外將請求放出,當水桶滿了的時候,新的請求被丟棄。
- 優點:可以平滑請求,削減峯值。
- 缺點:瓶頸會在漏出的速度,可能會拖慢整個系統,且不能有效地利用系統的資源。
3.令牌桶算法(推薦)
- 原理:有一個令牌桶,單位時間內令牌會以恆定的數量(即令牌的加入速度)加入到令牌桶中,所有請求都需要獲取令牌纔可正常訪問。當令牌桶中沒有令牌可取的時候,則拒絕請求。
- 優點:相比漏桶算法,令牌桶算法允許一定的突發流量,但是又不會讓突發流量超過我們給定的限制(單位時間窗口內的令牌數)。即限制了我們所說的 QPS(每秒查詢率)。
實現
1.依賴
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>27.1-jre</version>
</dependency>
2.註解類
import java.lang.annotation.*;
import java.util.concurrent.TimeUnit;
/**
* @author EDZ
* @Classname RequestLimiter
* @Description TODO
* @Date 2020/6/29 17:46
* @Created zzf
*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestLimiter {
/**
* 每秒創建令牌個數,默認:10
*/
double QPS() default 10D;
/**
* 獲取令牌等待超時時間 默認:500
*/
long timeout() default 500;
/**
* 超時時間單位 默認:毫秒
*/
TimeUnit timeunit() default TimeUnit.MILLISECONDS;
/**
* 無法獲取令牌返回提示信息
*/
String msg() default "服務器繁忙,請稍後重試!";
}
3.定義一個枚舉類用於狀態返回
/**
* @Classname ResponseEnum
* @Description TODO
* @Date 2020/6/29 17:52
* @Created zzf
*/
public enum ResponseEnum {
SUCCESS("200", "000000", "請求成功"),
FAIL("200", "100000", "請求失敗"),
FAIL_BY_PARAMS("200", "200000", "請求參數異常"),
FAIL_IN_SERVER("200", "300000", "服務器內部異常"),
RATE_LIMIT("200", "400000", "限流中");
public String status;
public String code;
public String message;
ResponseEnum(String s, String s1, String s2) {
this.status = s;
this.code = s1;
this.message = s2;
}
}
4.自定義攔截器,並在攔截器中實現限流
import com.alibaba.fastjson.JSON;
import com.ils.intelab.common.result.CommonResult;
import com.ils.intelab.openapi.client.enums.ResponseEnum;
import com.ils.intelab.openapi.client.result.OpenApiResultCode;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.MediaType;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;
/**
* 抽象攔截器
*/
public abstract class AbstractInterceptor extends HandlerInterceptorAdapter {
private Logger logger = LoggerFactory.getLogger(AbstractInterceptor.class);
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
ResponseEnum result;
try {
result = preFilter(request, response, handler);
} catch (Exception e) {
logger.error("preHandle catch a exception:" + e.getMessage());
result = ResponseEnum.FAIL;
}
if (ResponseEnum.SUCCESS.code.equals(result.code)) {
return true;
}
handlerResponse(result, response);
return false;
}
/**
* 自定義pre處理
*
* @param request
* @return
*/
protected abstract ResponseEnum preFilter(HttpServletRequest request, HttpServletResponse response, Object handler);
/**
* 錯誤處理事件
*
* @param result
* @param response
*/
private void handlerResponse(ResponseEnum result, HttpServletResponse response) {
CommonResult commonResult = new CommonResult();
commonResult.setData(null);
CommonResult<Object> errorInfo = new CommonResult<>();
errorInfo.setCodes(OpenApiResultCode.ERROR_DEFAULT_NOT_CATCH.getCode());
errorInfo.setSuccess(false);
errorInfo.setMessage(OpenApiResultCode.errorMessageByLanguage.get("zh").get(OpenApiResultCode.ERROR_DEFAULT_NOT_CATCH.getMessage()));
errorInfo.setData(null);
response.setStatus(HttpServletResponse.SC_OK);
response.setContentType(MediaType.APPLICATION_JSON_UTF8_VALUE);
PrintWriter printWriter = null;
try {
printWriter = response.getWriter();
printWriter.write(JSON.toJSONString(errorInfo));
} catch (Exception e) {
logger.error("handlerResponse catch a exception:" + e.getMessage());
} finally {
if (printWriter != null) {
printWriter.close();
}
}
}
}
實現
import com.google.common.util.concurrent.RateLimiter;
import com.ils.intelab.openapi.annotation.RequestLimiter;
import com.ils.intelab.openapi.client.enums.ResponseEnum;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import org.springframework.web.method.HandlerMethod;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* 請求限流器
* @Classname RequestLimiterInterceptor
* @Description TODO
* @Date 2020/6/29 17:47
* @Created zzf
*/
@Slf4j
@Component
public class RequestLimiterInterceptor extends AbstractInterceptor {
/**
* 不同的方法存放不同的令牌桶
*/
private final Map<String, RateLimiter> rateLimiterMap = new ConcurrentHashMap<>();
@Override
protected ResponseEnum preFilter(HttpServletRequest request, HttpServletResponse response, Object handler) {
try {
if (handler instanceof HandlerMethod) {
HandlerMethod handlerMethod = (HandlerMethod) handler;
RequestLimiter rateLimit = handlerMethod.getMethodAnnotation(RequestLimiter.class);
//判斷是否有註解
if (rateLimit != null) {
// 獲取請求url
String key = request.getMethod() + request.getRequestURI();
RateLimiter rateLimiter;
// 判斷map集合中是否有創建好的令牌桶
if (!rateLimiterMap.containsKey(key)) {
// 創建令牌桶,以n r/s往桶中放入令牌
rateLimiter = RateLimiter.create(rateLimit.QPS());
rateLimiterMap.put(key, rateLimiter);
}
rateLimiter = rateLimiterMap.get(key);
// 獲取令牌
boolean acquire = rateLimiter.tryAcquire(rateLimit.timeout(), rateLimit.timeunit());
if (acquire) {
//獲取令牌成功
return ResponseEnum.SUCCESS;
} else {
log.warn("請求被限流,url:{}", request.getServletPath());
return ResponseEnum.RATE_LIMIT;
}
}
}
return ResponseEnum.SUCCESS;
} catch (Exception var6) {
var6.printStackTrace();
return ResponseEnum.RATE_LIMIT;
}
}
}
5.繼承WebMvcConfigurerAdapter來添加自定義攔截器
import com.ils.intelab.openapi.aspect.RequestLimiterInterceptor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
/**
* 註冊攔截器
*/
@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
/**
* 請求限流攔截器
*/
@Autowired
protected RequestLimiterInterceptor requestLimiterInterceptor;
public WebMvcConfig() {
}
@Override
public void addInterceptors(InterceptorRegistry registry) {
// 請求限流
registry.addInterceptor(requestLimiterInterceptor).addPathPatterns("/**");
}
}
6.測試
import com.ils.intelab.common.result.CommonResult;
import com.ils.intelab.openapi.annotation.RequestLimiter;
import io.swagger.annotations.*;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import java.util.concurrent.TimeUnit;
/**
* @Classname TestController
* @Description TODO
* @Date 2020/5/27 9:50
* @Created zzf
*/
@RestController
@RequestMapping("/api/v3/")
@Api(value = "open_api", description = "open_api基礎接口", tags = {"open_api"})
public class TestController {
@ApiOperation(value = "測試", notes = "測試")
@ApiResponses({
@ApiResponse(code = 400, message = "參數非法"),
@ApiResponse(code = 500, message = "服務器錯誤"),
@ApiResponse(code = 200, message = "成功")
})
@ApiImplicitParams({
})
@RequestLimiter(QPS = 1, timeout = 200, timeunit = TimeUnit.MILLISECONDS, msg = "服務器繁忙,請稍後再試")
@RequestMapping(value = "/test", method = RequestMethod.GET)
public CommonResult<String> getUserInfo() {
return new CommonResult<>("999");
}
}