---

背景

公司有個(gè)渠道系統(tǒng)，專門對(duì)接三方渠道使用，沒(méi)有什么業(yè)務(wù)邏輯，主要是轉(zhuǎn)換報(bào)文和參數(shù)校驗(yàn)之類的工作，起著一個(gè)承上啟下的作用。

最近在優(yōu)化接口的響應(yīng)時(shí)間，優(yōu)化了代碼之后，但是時(shí)間還是達(dá)不到要求；有一個(gè)詭異的100ms左右的耗時(shí)問(wèn)題，在接口中打印了請(qǐng)求處理時(shí)間后，和調(diào)用方的響應(yīng)時(shí)間還有差了100ms左右。比如程序里記錄150ms，但是調(diào)用方等待時(shí)間卻為250ms左右。

下面記錄下當(dāng)時(shí)詳細(xì)的定位&解決流程（其實(shí)解決很簡(jiǎn)單，關(guān)鍵在于怎么定位并找到解決問(wèn)題的方法）

基于 Spring Boot + MyBatis Plus + Vue & Element 實(shí)現(xiàn)的后臺(tái)管理系統(tǒng) + 用戶小程序，支持 RBAC 動(dòng)態(tài)權(quán)限、多租戶、數(shù)據(jù)權(quán)限、工作流、三方登錄、支付、短信、商城等功能

• 項(xiàng)目地址：https://gitee.com/zhijiantianya/ruoyi-vue-pro
• 視頻教程：https://doc.iocoder.cn/video/

定位過(guò)程

分析代碼

渠道系統(tǒng)是一個(gè)常見(jiàn)的spring-boot web工程，使用了集成的tomcat。分析了代碼之后，發(fā)現(xiàn)并沒(méi)有特殊的地方，沒(méi)有特殊的過(guò)濾器或者攔截器，所以初步排除是業(yè)務(wù)代碼問(wèn)題

分析調(diào)用流程

出現(xiàn)這個(gè)問(wèn)題之后，首先確認(rèn)了下接口的調(diào)用流程。由于是內(nèi)部測(cè)試，所以調(diào)用流程較少。

Nginx-反向代理->渠道系統(tǒng)

公司是云服務(wù)器，網(wǎng)絡(luò)走的也是云的內(nèi)網(wǎng)。由于不明確問(wèn)題的原因，所以用排除法，首先確認(rèn)服務(wù)器網(wǎng)絡(luò)是否有問(wèn)題。

先確認(rèn)發(fā)送端到Nginx Host是否有問(wèn)題：

[jboss@VM_0_139_centos~]$ping10.0.0.139
PING10.0.0.139(10.0.0.139)56(84)bytesofdata.
64bytesfrom10.0.0.139:icmp_seq=1ttl=64time=0.029ms
64bytesfrom10.0.0.139:icmp_seq=2ttl=64time=0.041ms
64bytesfrom10.0.0.139:icmp_seq=3ttl=64time=0.040ms
64bytesfrom10.0.0.139:icmp_seq=4ttl=64time=0.040ms

從ping結(jié)果上看，發(fā)送端到Nginx主機(jī)的延遲是無(wú)問(wèn)題的，接下來(lái)查看Nginx到渠道系統(tǒng)的網(wǎng)絡(luò)。

>基于SpringCloudAlibaba+Gateway+Nacos+RocketMQ+Vue&Element實(shí)現(xiàn)的后臺(tái)管理系統(tǒng)+用戶小程序，支持RBAC動(dòng)態(tài)權(quán)限、多租戶、數(shù)據(jù)權(quán)限、工作流、三方登錄、支付、短信、商城等功能
>
>*項(xiàng)目地址：//gitee.com/zhijiantianya/yudao-cloud>
>*視頻教程：//doc.iocoder.cn/video/>

#由于日志是沒(méi)問(wèn)題的，這里直接復(fù)制上面日志了
[jboss@VM_0_139_centos~]$ping10.0.0.139
PING10.0.0.139(10.0.0.139)56(84)bytesofdata.
64bytesfrom10.0.0.139:icmp_seq=1ttl=64time=0.029ms
64bytesfrom10.0.0.139:icmp_seq=2ttl=64time=0.041ms
64bytesfrom10.0.0.139:icmp_seq=3ttl=64time=0.040ms
64bytesfrom10.0.0.139:icmp_seq=4ttl=64time=0.040ms

從ping結(jié)果上看，Nginx到渠道系統(tǒng)服務(wù)器網(wǎng)絡(luò)延遲也是沒(méi)問(wèn)題的

既然網(wǎng)絡(luò)看似沒(méi)問(wèn)題，那么可以繼續(xù)排除法，砍掉Nginx，客戶端直接再渠道系統(tǒng)的服務(wù)器上，通過(guò)回環(huán)地址（localhost）直連，避免經(jīng)過(guò)網(wǎng)卡/dns，縮小問(wèn)題范圍看看能否復(fù)現(xiàn)（這個(gè)應(yīng)用和地址是我后期模擬的，測(cè)試的是一個(gè)空接口）：

[jboss@VM_10_91_centostmp]$curl-w"@curl-time.txt"http://127.0.0.1:7744/send
success
http:200
dns:0.001s
redirect:0.000s
time_connect:0.001s
time_appconnect:0.000s
time_pretransfer:0.001s
time_starttransfer:0.073s
size_download:7bytes
speed_download:95.000B/s
----------
time_total:0.073s請(qǐng)求總耗時(shí)

從curl日志上看，通過(guò)回環(huán)地址調(diào)用一個(gè)空接口耗時(shí)也有73ms。這就奇怪了，跳過(guò)了中間所有調(diào)用節(jié)點(diǎn)（包括過(guò)濾器&攔截器之類），直接請(qǐng)求應(yīng)用一個(gè)空接口，都有73ms的耗時(shí)，再請(qǐng)求一次看看：

[jboss@VM_10_91_centostmp]$curl-w"@curl-time.txt"http://127.0.0.1:7744/send
success
http:200
dns:0.001s
redirect:0.000s
time_connect:0.001s
time_appconnect:0.000s
time_pretransfer:0.001s
time_starttransfer:0.003s
size_download:7bytes
speed_download:2611.000B/s
----------
time_total:0.003s

更奇怪的是，第二次請(qǐng)求耗時(shí)就正常了，變成了3ms。經(jīng)查閱資料，linux curl是默認(rèn)開啟http keep-alive的。就算不開啟keep-alive，每次重新handshake，也不至于需要70ms。

經(jīng)過(guò)不斷分析測(cè)試發(fā)現(xiàn)，連續(xù)請(qǐng)求的話時(shí)間就會(huì)很短，每次請(qǐng)求只需要幾毫秒，但是如果隔一段時(shí)間再請(qǐng)求，就會(huì)花費(fèi)70ms以上。

從這個(gè)現(xiàn)象猜想，可能是某些緩存機(jī)制導(dǎo)致的，連續(xù)請(qǐng)求因?yàn)橛芯彺妫运俣瓤欤瑫r(shí)間長(zhǎng)緩存失效后導(dǎo)致時(shí)間長(zhǎng)。

那么這個(gè)問(wèn)題點(diǎn)到底在哪一層呢？tomcat層還是spring-webmvc呢？

光猜想定位不了問(wèn)題，還是得實(shí)際測(cè)試一下，把渠道系統(tǒng)的代碼放到本地ide里啟動(dòng)測(cè)試能否復(fù)現(xiàn)

但是導(dǎo)入本地Ide后，在Ide中啟動(dòng)后并不能復(fù)現(xiàn)問(wèn)題，并沒(méi)有70+ms的延遲問(wèn)題。這下頭疼了，本地?zé)o法復(fù)現(xiàn)，不能Debug，由于問(wèn)題點(diǎn)不在業(yè)務(wù)代碼，也不能通過(guò)加日志的方式來(lái)Debug

這時(shí)候可以祭出神器Arthas了

Arthas分析問(wèn)題

Arthas 是Alibaba開源的Java診斷工具，深受開發(fā)者喜愛(ài)。當(dāng)你遇到以下類似問(wèn)題而束手無(wú)策時(shí)，Arthas可以幫助你解決：

• 這個(gè)類從哪個(gè) jar 包加載的？為什么會(huì)報(bào)各種類相關(guān)的 Exception？
• 我改的代碼為什么沒(méi)有執(zhí)行到？難道是我沒(méi) commit？分支搞錯(cuò)了？
• 遇到問(wèn)題無(wú)法在線上 debug，難道只能通過(guò)加日志再重新發(fā)布嗎？
• 線上遇到某個(gè)用戶的數(shù)據(jù)處理有問(wèn)題，但線上同樣無(wú)法 debug，線下無(wú)法重現(xiàn)！
• 是否有一個(gè)全局視角來(lái)查看系統(tǒng)的運(yùn)行狀況？
• 有什么辦法可以監(jiān)控到JVM的實(shí)時(shí)運(yùn)行狀態(tài)？

上面是Arthas的官方簡(jiǎn)介，這次我只需要用他的一個(gè)小功能trace。動(dòng)態(tài)計(jì)算方法調(diào)用路徑和時(shí)間，這樣我就可以定位時(shí)間在哪個(gè)地方被消耗了。

• trace 方法內(nèi)部調(diào)用路徑，并輸出方法路徑上的每個(gè)節(jié)點(diǎn)上耗時(shí)
• trace 命令能主動(dòng)搜索 class-pattern／method-pattern
• 對(duì)應(yīng)的方法調(diào)用路徑，渲染和統(tǒng)計(jì)整個(gè)調(diào)用鏈路上的所有性能開銷和追蹤調(diào)用鏈路。

有了神器，那么該追蹤什么方法呢？由于我對(duì)Tomcat源碼不是很熟，所以只能從spring mvc下手，先來(lái)trace一下spring mvc的入口：

[arthas@24851]$traceorg.springframework.web.servlet.DispatcherServlet*
PressQorCtrl+Ctoabort.
Affect(class-cnt:1,method-cnt:44)costin508ms.
`---ts=2019-09-1421:07:44;thread_name=http-nio-7744-exec-2;id=11;is_daemon=true;priority=5;TCCL=org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader@7c136917
`---[2.952142ms]org.springframework.web.servlet.DispatcherServlet:buildLocaleContext()

`---ts=2019-09-1421:07:44;thread_name=http-nio-7744-exec-2;id=11;is_daemon=true;priority=5;TCCL=org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader@7c136917
`---[18.08903ms]org.springframework.web.servlet.DispatcherServlet:doService()
+---[0.041346ms]org.apache.commons.logging.Log:isDebugEnabled()#889
+---[0.022398ms]org.springframework.web.util.WebUtils:isIncludeRequest()#898
+---[0.014904ms]org.springframework.web.servlet.DispatcherServlet:getWebApplicationContext()#910
+---[1.071879ms]javax.servlet.http.HttpServletRequest:setAttribute()#910
+---[0.020977ms]javax.servlet.http.HttpServletRequest:setAttribute()#911
+---[0.017073ms]javax.servlet.http.HttpServletRequest:setAttribute()#912
+---[0.218277ms]org.springframework.web.servlet.DispatcherServlet:getThemeSource()#913
|`---[0.137568ms]org.springframework.web.servlet.DispatcherServlet:getThemeSource()
|`---[min=0.00783ms,max=0.014251ms,total=0.022081ms,count=2]org.springframework.web.servlet.DispatcherServlet:getWebApplicationContext()#782
+---[0.019363ms]javax.servlet.http.HttpServletRequest:setAttribute()#913
+---[0.070694ms]org.springframework.web.servlet.FlashMapManager:retrieveAndUpdate()#916
+---[0.01839ms]org.springframework.web.servlet.FlashMap:()#920
+---[0.016943ms]javax.servlet.http.HttpServletRequest:setAttribute()#920
+---[0.015268ms]javax.servlet.http.HttpServletRequest:setAttribute()#921
+---[15.050124ms]org.springframework.web.servlet.DispatcherServlet:doDispatch()#925
|`---[14.943477ms]org.springframework.web.servlet.DispatcherServlet:doDispatch()
|+---[0.019135ms]org.springframework.web.context.request.async.WebAsyncUtils:getAsyncManager()#953
|+---[2.108373ms]org.springframework.web.servlet.DispatcherServlet:checkMultipart()#960
||`---[2.004436ms]org.springframework.web.servlet.DispatcherServlet:checkMultipart()
||`---[1.890845ms]org.springframework.web.multipart.MultipartResolver:isMultipart()#1117
|+---[2.054361ms]org.springframework.web.servlet.DispatcherServlet:getHandler()#964
||`---[1.961963ms]org.springframework.web.servlet.DispatcherServlet:getHandler()
||+---[0.02051ms]java.util.List:iterator()#1183
||+---[min=0.003805ms,max=0.009641ms,total=0.013446ms,count=2]java.util.Iterator:hasNext()#1183
||+---[min=0.003181ms,max=0.009751ms,total=0.012932ms,count=2]java.util.Iterator:next()#1183
||+---[min=0.005841ms,max=0.015308ms,total=0.021149ms,count=2]org.apache.commons.logging.Log:isTraceEnabled()#1184
||`---[min=0.474739ms,max=1.19145ms,total=1.666189ms,count=2]org.springframework.web.servlet.HandlerMapping:getHandler()#1188
|+---[0.013071ms]org.springframework.web.servlet.HandlerExecutionChain:getHandler()#971
|+---[0.372236ms]org.springframework.web.servlet.DispatcherServlet:getHandlerAdapter()#971
||`---[0.280073ms]org.springframework.web.servlet.DispatcherServlet:getHandlerAdapter()
||+---[0.004804ms]java.util.List:iterator()#1224
||+---[0.003668ms]java.util.Iterator:hasNext()#1224
||+---[0.003038ms]java.util.Iterator:next()#1224
||+---[0.006451ms]org.apache.commons.logging.Log:isTraceEnabled()#1225
||`---[0.012683ms]org.springframework.web.servlet.HandlerAdapter:supports()#1228
|+---[0.012848ms]javax.servlet.http.HttpServletRequest:getMethod()#974
|+---[0.013132ms]java.lang.String:equals()#975
|+---[0.003025ms]org.springframework.web.servlet.HandlerExecutionChain:getHandler()#977
|+---[0.008095ms]org.springframework.web.servlet.HandlerAdapter:getLastModified()#977
|+---[0.006596ms]org.apache.commons.logging.Log:isDebugEnabled()#978
|+---[0.018024ms]org.springframework.web.context.request.ServletWebRequest:()#981
|+---[0.017869ms]org.springframework.web.context.request.ServletWebRequest:checkNotModified()#981
|+---[0.038542ms]org.springframework.web.servlet.HandlerExecutionChain:applyPreHandle()#986
|+---[0.00431ms]org.springframework.web.servlet.HandlerExecutionChain:getHandler()#991
|+---[4.248493ms]org.springframework.web.servlet.HandlerAdapter:handle()#991
|+---[0.014805ms]org.springframework.web.context.request.async.WebAsyncManager:isConcurrentHandlingStarted()#993
|+---[1.444994ms]org.springframework.web.servlet.DispatcherServlet:applyDefaultViewName()#997
||`---[0.067631ms]org.springframework.web.servlet.DispatcherServlet:applyDefaultViewName()
|+---[0.012027ms]org.springframework.web.servlet.HandlerExecutionChain:applyPostHandle()#998
|+---[0.373997ms]org.springframework.web.servlet.DispatcherServlet:processDispatchResult()#1008
||`---[0.197004ms]org.springframework.web.servlet.DispatcherServlet:processDispatchResult()
||+---[0.007074ms]org.apache.commons.logging.Log:isDebugEnabled()#1075
||+---[0.005467ms]org.springframework.web.context.request.async.WebAsyncUtils:getAsyncManager()#1081
||+---[0.004054ms]org.springframework.web.context.request.async.WebAsyncManager:isConcurrentHandlingStarted()#1081
||`---[0.011988ms]org.springframework.web.servlet.HandlerExecutionChain:triggerAfterCompletion()#1087
|`---[0.004015ms]org.springframework.web.context.request.async.WebAsyncManager:isConcurrentHandlingStarted()#1018
+---[0.005055ms]org.springframework.web.context.request.async.WebAsyncUtils:getAsyncManager()#928
`---[0.003422ms]org.springframework.web.context.request.async.WebAsyncManager:isConcurrentHandlingStarted()#928

~

[jboss@VM_10_91_centostmp]$curl-w"@curl-time.txt"http://127.0.0.1:7744/send
success
http:200
dns:0.001s
redirect:0.000s
time_connect:0.001s
time_appconnect:0.000s
time_pretransfer:0.001s
time_starttransfer:0.115s
size_download:7bytes
speed_download:60.000B/s
----------
time_total:0.115s

本次調(diào)用，調(diào)用端時(shí)間花費(fèi)115ms，但是從arthas trace上看，spring mvc只消耗了18ms，那么剩下的97ms去哪了呢？

本地測(cè)試后已經(jīng)可以排除spring mvc的問(wèn)題了，最后也是唯一可能出問(wèn)題的點(diǎn)就是tomcat

可是本人并不熟悉tomcat中的源碼，就連請(qǐng)求入口都不清楚，tomcat里需要trace的類都不好找。。。

不過(guò)沒(méi)關(guān)系，有神器Arthas，可以通過(guò)stack命令來(lái)反向查找調(diào)用路徑，以org.springframework.web.servlet.DispatcherServlet作為參數(shù)：

stack 輸出當(dāng)前方法被調(diào)用的調(diào)用路徑

很多時(shí)候我們都知道一個(gè)方法被執(zhí)行，但這個(gè)方法被執(zhí)行的路徑非常多，或者你根本就不知道這個(gè)方法是從那里被執(zhí)行了，此時(shí)你需要的是 stack 命令。

[arthas@24851]$stackorg.springframework.web.servlet.DispatcherServlet*
PressQorCtrl+Ctoabort.
Affect(class-cnt:1,method-cnt:44)costin495ms.
ts=2019-09-1421:15:19;thread_name=http-nio-7744-exec-5;id=14;is_daemon=true;priority=5;TCCL=org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader@7c136917
@org.springframework.web.servlet.FrameworkServlet.processRequest()
atorg.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
atjavax.servlet.http.HttpServlet.service(HttpServlet.java:635)
atorg.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
atjavax.servlet.http.HttpServlet.service(HttpServlet.java:742)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
atorg.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
atorg.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
atorg.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
atorg.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
atorg.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
atorg.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
atorg.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
atorg.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
atorg.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
atorg.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468)
atorg.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
atorg.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
atjava.lang.Thread.run(Thread.java:748)

ts=2019-09-1421:15:19;thread_name=http-nio-7744-exec-5;id=14;is_daemon=true;priority=5;TCCL=org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader@7c136917
@org.springframework.web.servlet.DispatcherServlet.doService()
atorg.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
atorg.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
atjavax.servlet.http.HttpServlet.service(HttpServlet.java:635)
atorg.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
atjavax.servlet.http.HttpServlet.service(HttpServlet.java:742)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
atorg.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
atorg.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
atorg.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
atorg.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
atorg.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
atorg.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
atorg.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
atorg.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
atorg.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
atorg.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
atorg.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
atorg.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
atorg.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
atorg.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468)
atorg.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
atorg.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
atjava.lang.Thread.run(Thread.java:748)

從stack日志上可以很直觀的看出DispatchServlet的調(diào)用棧，那么這么長(zhǎng)的路徑，該trace哪個(gè)類呢（這里跳過(guò)spring mvc中的過(guò)濾器的trace過(guò)程，實(shí)際排查的時(shí)候也trace了一遍，但這詭異的時(shí)間消耗不是由這里過(guò)濾器產(chǎn)生的）？

有一定經(jīng)驗(yàn)的老司機(jī)從名字上大概也能猜出來(lái)從哪里下手比較好，那就是org.apache.coyote.http11.Http11Processor.service，從名字上看，http1.1處理器，這可能是一個(gè)比較好的切入點(diǎn)。下面來(lái)trace一下：

[arthas@24851]$traceorg.apache.coyote.http11.Http11Processorservice
PressQorCtrl+Ctoabort.
Affect(class-cnt:1,method-cnt:1)costin269ms.
`---ts=2019-09-1421:22:51;thread_name=http-nio-7744-exec-8;id=17;is_daemon=true;priority=5;TCCL=org.springframework.boot.loader.LaunchedURLClassLoader@20ad9418
`---[131.650285ms]org.apache.coyote.http11.Http11Processor:service()
+---[0.036851ms]org.apache.coyote.Request:getRequestProcessor()#667
+---[0.009986ms]org.apache.coyote.RequestInfo:setStage()#668
+---[0.008928ms]org.apache.coyote.http11.Http11Processor:setSocketWrapper()#671
+---[0.013236ms]org.apache.coyote.http11.Http11InputBuffer:init()#672
+---[0.00981ms]org.apache.coyote.http11.Http11OutputBuffer:init()#673
+---[min=0.00213ms,max=0.007317ms,total=0.009447ms,count=2]org.apache.coyote.http11.Http11Processor:getErrorState()#683
+---[min=0.002098ms,max=0.008888ms,total=0.010986ms,count=2]org.apache.coyote.ErrorState:isError()#683
+---[min=0.002448ms,max=0.007149ms,total=0.009597ms,count=2]org.apache.coyote.http11.Http11Processor:isAsync()#683
+---[min=0.002399ms,max=0.00852ms,total=0.010919ms,count=2]org.apache.tomcat.util.net.AbstractEndpoint:isPaused()#683
+---[min=0.033587ms,max=0.11832ms,total=0.151907ms,count=2]org.apache.coyote.http11.Http11InputBuffer:parseRequestLine()#687
+---[0.005384ms]org.apache.tomcat.util.net.AbstractEndpoint:isPaused()#695
+---[0.007924ms]org.apache.coyote.Request:getMimeHeaders()#702
+---[0.006744ms]org.apache.tomcat.util.net.AbstractEndpoint:getMaxHeaderCount()#702
+---[0.012574ms]org.apache.tomcat.util.http.MimeHeaders:setLimit()#702
+---[0.14319ms]org.apache.coyote.http11.Http11InputBuffer:parseHeaders()#703
+---[0.003997ms]org.apache.coyote.Request:getMimeHeaders()#743
+---[0.026561ms]org.apache.tomcat.util.http.MimeHeaders:values()#743
+---[min=0.002869ms,max=0.01203ms,total=0.014899ms,count=2]java.util.Enumeration:hasMoreElements()#745
+---[0.070114ms]java.util.Enumeration:nextElement()#746
+---[0.010921ms]java.lang.String:toLowerCase()#746
+---[0.008453ms]java.lang.String:contains()#746
+---[0.002698ms]org.apache.coyote.http11.Http11Processor:getErrorState()#775
+---[0.00307ms]org.apache.coyote.ErrorState:isError()#775
+---[0.002708ms]org.apache.coyote.RequestInfo:setStage()#777
+---[0.171139ms]org.apache.coyote.http11.Http11Processor:prepareRequest()#779
+---[0.009349ms]org.apache.tomcat.util.net.SocketWrapperBase:decrementKeepAlive()#794
+---[0.002574ms]org.apache.coyote.http11.Http11Processor:getErrorState()#800
+---[0.002696ms]org.apache.coyote.ErrorState:isError()#800
+---[0.002499ms]org.apache.coyote.RequestInfo:setStage()#802
+---[0.005641ms]org.apache.coyote.http11.Http11Processor:getAdapter()#803
+---[129.868916ms]org.apache.coyote.Adapter:service()#803
+---[0.003859ms]org.apache.coyote.http11.Http11Processor:getErrorState()#809
+---[0.002365ms]org.apache.coyote.ErrorState:isError()#809
+---[0.003844ms]org.apache.coyote.http11.Http11Processor:isAsync()#809
+---[0.002382ms]org.apache.coyote.Response:getStatus()#809
+---[0.002476ms]org.apache.coyote.http11.Http11Processor:statusDropsConnection()#809
+---[0.002284ms]org.apache.coyote.RequestInfo:setStage()#838
+---[0.00222ms]org.apache.coyote.http11.Http11Processor:isAsync()#839
+---[0.037873ms]org.apache.coyote.http11.Http11Processor:endRequest()#843
+---[0.002188ms]org.apache.coyote.RequestInfo:setStage()#845
+---[0.002112ms]org.apache.coyote.http11.Http11Processor:getErrorState()#849
+---[0.002063ms]org.apache.coyote.ErrorState:isError()#849
+---[0.002504ms]org.apache.coyote.http11.Http11Processor:isAsync()#853
+---[0.009808ms]org.apache.coyote.Request:updateCounters()#854
+---[0.002008ms]org.apache.coyote.http11.Http11Processor:getErrorState()#855
+---[0.002192ms]org.apache.coyote.ErrorState:isIoAllowed()#855
+---[0.01968ms]org.apache.coyote.http11.Http11InputBuffer:nextRequest()#856
+---[0.010065ms]org.apache.coyote.http11.Http11OutputBuffer:nextRequest()#857
+---[0.002576ms]org.apache.coyote.RequestInfo:setStage()#870
+---[0.016599ms]org.apache.coyote.http11.Http11Processor:processSendfile()#872
+---[0.008182ms]org.apache.coyote.http11.Http11InputBuffer:getParsingRequestLinePhase()#688
+---[0.0075ms]org.apache.coyote.http11.Http11Processor:handleIncompleteRequestLineRead()#690
+---[0.001979ms]org.apache.coyote.RequestInfo:setStage()#875
+---[0.001981ms]org.apache.coyote.http11.Http11Processor:getErrorState()#877
+---[0.001934ms]org.apache.coyote.ErrorState:isError()#877
+---[0.001995ms]org.apache.tomcat.util.net.AbstractEndpoint:isPaused()#877
+---[0.002403ms]org.apache.coyote.http11.Http11Processor:isAsync()#879
`---[0.006176ms]org.apache.coyote.http11.Http11Processor:isUpgrade()#881

日志里有一個(gè)129ms的耗時(shí)點(diǎn)（時(shí)間比沒(méi)開arthas的時(shí)候更長(zhǎng)是因?yàn)閍rthas本身帶來(lái)的性能消耗，所以生產(chǎn)環(huán)境小心使用），這個(gè)就是要找的問(wèn)題點(diǎn)。

打問(wèn)題點(diǎn)找到了，那怎么定位是什么導(dǎo)致的問(wèn)題呢，又如何解決呢？

繼續(xù)trace吧，細(xì)化到具體的代碼塊或者內(nèi)容。trace由于性能考慮，不會(huì)展示所有的調(diào)用路徑，如果調(diào)用路徑過(guò)深，只有手動(dòng)深入trace，原則就是trace耗時(shí)長(zhǎng)的那個(gè)方法：

[arthas@24851]$traceorg.apache.coyote.Adapterservice
PressQorCtrl+Ctoabort.
Affect(class-cnt:1,method-cnt:1)costin608ms.
`---ts=2019-09-1421:34:33;thread_name=http-nio-7744-exec-1;id=10;is_daemon=true;priority=5;TCCL=org.springframework.boot.loader.LaunchedURLClassLoader@20ad9418
`---[81.70999ms]org.apache.catalina.connector.CoyoteAdapter:service()
+---[0.032546ms]org.apache.coyote.Request:getNote()#302
+---[0.007148ms]org.apache.coyote.Response:getNote()#303
+---[0.007475ms]org.apache.catalina.connector.Connector:getXpoweredBy()#324
+---[0.00447ms]org.apache.coyote.Request:getRequestProcessor()#331
+---[0.007902ms]java.lang.ThreadLocal:get()#331
+---[0.006522ms]org.apache.coyote.RequestInfo:setWorkerThreadName()#331
+---[73.793798ms]org.apache.catalina.connector.CoyoteAdapter:postParseRequest()#336
+---[0.001536ms]org.apache.catalina.connector.Connector:getService()#339
+---[0.004469ms]org.apache.catalina.Service:getContainer()#339
+---[0.007074ms]org.apache.catalina.Engine:getPipeline()#339
+---[0.004334ms]org.apache.catalina.Pipeline:isAsyncSupported()#339
+---[0.002466ms]org.apache.catalina.connector.Request:setAsyncSupported()#339
+---[6.01E-4ms]org.apache.catalina.connector.Connector:getService()#342
+---[0.001859ms]org.apache.catalina.Service:getContainer()#342
+---[9.65E-4ms]org.apache.catalina.Engine:getPipeline()#342
+---[0.005231ms]org.apache.catalina.Pipeline:getFirst()#342
+---[7.239154ms]org.apache.catalina.Valve:invoke()#342
+---[0.006904ms]org.apache.catalina.connector.Request:isAsync()#345
+---[0.00509ms]org.apache.catalina.connector.Request:finishRequest()#372
+---[0.051461ms]org.apache.catalina.connector.Response:finishResponse()#373
+---[0.007244ms]java.util.concurrent.atomic.AtomicBoolean:()#379
+---[0.007314ms]org.apache.coyote.Response:action()#380
+---[0.004518ms]org.apache.catalina.connector.Request:isAsyncCompleting()#382
+---[0.001072ms]org.apache.catalina.connector.Request:getContext()#394
+---[0.007166ms]java.lang.System:currentTimeMillis()#401
+---[0.004367ms]org.apache.coyote.Request:getStartTime()#401
+---[0.011483ms]org.apache.catalina.Context:logAccess()#401
+---[0.0014ms]org.apache.coyote.Request:getRequestProcessor()#406
+---[min=8.0E-4ms,max=9.22E-4ms,total=0.001722ms,count=2]java.lang.Integer:()#406
+---[0.001082ms]java.lang.reflect.Method:invoke()#406
+---[0.001851ms]org.apache.coyote.RequestInfo:setWorkerThreadName()#406
+---[0.035805ms]org.apache.catalina.connector.Request:recycle()#410
`---[0.007849ms]org.apache.catalina.connector.Response:recycle()#411

一段無(wú)聊的手動(dòng)深入trace之后………………

[arthas@24851]$traceorg.apache.catalina.webresources.AbstractArchiveResourceSetgetArchiveEntries
PressQorCtrl+Ctoabort.
Affect(class-cnt:4,method-cnt:2)costin150ms.
`---ts=2019-09-1421:36:26;thread_name=http-nio-7744-exec-3;id=12;is_daemon=true;priority=5;TCCL=org.springframework.boot.loader.LaunchedURLClassLoader@20ad9418
`---[75.743681ms]org.apache.catalina.webresources.JarWarResourceSet:getArchiveEntries()
+---[0.025731ms]java.util.HashMap:()#106
+---[0.097729ms]org.apache.catalina.webresources.JarWarResourceSet:openJarFile()#109
+---[0.091037ms]java.util.jar.JarFile:getJarEntry()#110
+---[0.096325ms]java.util.jar.JarFile:getInputStream()#111
+---[0.451916ms]org.apache.catalina.webresources.TomcatJarInputStream:()#113
+---[min=0.001175ms,max=0.001176ms,total=0.002351ms,count=2]java.lang.Integer:()#114
+---[0.00104ms]java.lang.reflect.Method:invoke()#114
+---[0.045105ms]org.apache.catalina.webresources.TomcatJarInputStream:getNextJarEntry()#114
+---[min=5.02E-4ms,max=0.008531ms,total=0.028864ms,count=31]java.util.jar.JarEntry:getName()#116
+---[min=5.39E-4ms,max=0.022805ms,total=0.054647ms,count=31]java.util.HashMap:put()#116
+---[min=0.004452ms,max=34.479307ms,total=74.206249ms,count=31]org.apache.catalina.webresources.TomcatJarInputStream:getNextJarEntry()#117
+---[0.018358ms]org.apache.catalina.webresources.TomcatJarInputStream:getManifest()#119
+---[0.006429ms]org.apache.catalina.webresources.JarWarResourceSet:setManifest()#120
+---[0.010904ms]org.apache.tomcat.util.compat.JreCompat:isJre9Available()#121
+---[0.003307ms]org.apache.catalina.webresources.TomcatJarInputStream:getMetaInfEntry()#133
+---[5.5E-4ms]java.util.jar.JarEntry:getName()#135
+---[6.42E-4ms]java.util.HashMap:put()#135
+---[0.001981ms]org.apache.catalina.webresources.TomcatJarInputStream:getManifestEntry()#137
+---[0.064484ms]org.apache.catalina.webresources.TomcatJarInputStream:close()#141
+---[0.007961ms]org.apache.catalina.webresources.JarWarResourceSet:closeJarFile()#151
`---[0.004643ms]java.io.InputStream:close()#155

發(fā)現(xiàn)了一個(gè)值得暫停思考的點(diǎn)：

+---[min=0.004452ms,max=34.479307ms,total=74.206249ms,count=31]org.apache.catalina.webresources.TomcatJarInputStream:getNextJarEntry()#117

這行代碼加載了31次，一共耗時(shí)74ms；從名字上看，應(yīng)該是tomcat加載jar包時(shí)的耗時(shí)，那么是加載了31個(gè)jar包的耗時(shí)，還是加載了jar包內(nèi)的某些資源31次耗時(shí)呢？

TomcatJarInputStream這個(gè)類源碼的注釋寫到：

Thepurposeofthissub-classistoobtainreferencestotheJarEntryobjectsforMETA-INF/andMETA-INF/MANIFEST.MFthatareotherwiseswallowedbytheJarInputStreamimplementation.

大概意思也就是，獲取jar包內(nèi)META-INF/，META-INF/MANIFEST的資源，這是一個(gè)子類，更多的功能在父類JarInputStream里。

其實(shí)看到這里大概也能猜到問(wèn)題了，tomcat加載jar包內(nèi)META-INF/，META-INF/MANIFEST的資源導(dǎo)致的耗時(shí)，至于為什么連續(xù)請(qǐng)求不會(huì)耗時(shí)，應(yīng)該是tomcat的緩存機(jī)制（下面介紹源碼分析）

不著急定位問(wèn)題，試著通過(guò)Arthas最終定位問(wèn)題細(xì)節(jié)，繼續(xù)手動(dòng)深入trace

[arthas@24851]$traceorg.apache.catalina.webresources.TomcatJarInputStream*
PressQorCtrl+Ctoabort.
Affect(class-cnt:1,method-cnt:4)costin44ms.
`---ts=2019-09-1421:37:47;thread_name=http-nio-7744-exec-5;id=14;is_daemon=true;priority=5;TCCL=org.springframework.boot.loader.LaunchedURLClassLoader@20ad9418
`---[0.234952ms]org.apache.catalina.webresources.TomcatJarInputStream:createZipEntry()
+---[0.039455ms]java.util.jar.JarInputStream:createZipEntry()#43
`---[0.007827ms]java.lang.String:equals()#44

`---ts=2019-09-1421:37:47;thread_name=http-nio-7744-exec-5;id=14;is_daemon=true;priority=5;TCCL=org.springframework.boot.loader.LaunchedURLClassLoader@20ad9418
`---[0.050222ms]org.apache.catalina.webresources.TomcatJarInputStream:createZipEntry()
+---[0.001889ms]java.util.jar.JarInputStream:createZipEntry()#43
`---[0.001643ms]java.lang.String:equals()#46
#這里一共31個(gè)trace日志，刪減了剩下的

從方法名上看，還是加載資源之類的意思。都已經(jīng)到j(luò)dk源碼了，這時(shí)候來(lái)看一下TomcatJarInputStream這個(gè)類的源碼:

/**
*CreatesanewJarEntry(ZipEntry)forthe
*specifiedJARfileentryname.Themanifestattributesof
*thespecifiedJARfileentrynamewillbecopiedtothenew
*JarEntry.
*
*@paramnamethenameoftheJAR/ZIPfileentry
*@returntheJarEntryobjectjustcreated
*/
protectedZipEntrycreateZipEntry(Stringname){
JarEntrye=newJarEntry(name);
if(man!=null){
e.attr=man.getAttributes(name);
}
returne;
}

這個(gè)createZipEntry有個(gè)name參數(shù)，從注釋上看，是jar/zip文件名，如果能得到文件名這種關(guān)鍵信息，就可以直接定位問(wèn)題了；還是通過(guò)Arthas，使用watch命令，動(dòng)態(tài)監(jiān)測(cè)方法調(diào)用數(shù)據(jù)

watch方法執(zhí)行數(shù)據(jù)觀測(cè)

讓你能方便的觀察到指定方法的調(diào)用情況。能觀察到的范圍為：返回值、拋出異常、入?yún)ⅲㄟ^(guò)編寫 OGNL 表達(dá)式進(jìn)行對(duì)應(yīng)變量的查看。

watch 該方法的入?yún)?/p>

[arthas@24851]$watchorg.apache.catalina.webresources.TomcatJarInputStreamcreateZipEntry"{params[0]}"
PressQorCtrl+Ctoabort.
Affect(class-cnt:1,method-cnt:1)costin27ms.
ts=2019-09-1421:51:14;[cost=0.14547ms]result=@ArrayList[
@String[META-INF/],
]
ts=2019-09-1421:51:14;[cost=0.048028ms]result=@ArrayList[
@String[META-INF/MANIFEST.MF],
]
ts=2019-09-1421:51:14;[cost=0.046071ms]result=@ArrayList[
@String[META-INF/resources/],
]
ts=2019-09-1421:51:14;[cost=0.033855ms]result=@ArrayList[
@String[META-INF/resources/swagger-ui.html],
]
ts=2019-09-1421:51:14;[cost=0.039138ms]result=@ArrayList[
@String[META-INF/resources/webjars/],
]
ts=2019-09-1421:51:14;[cost=0.033701ms]result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/],
]
ts=2019-09-1421:51:14;[cost=0.033644ms]result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/favicon-16x16.png],
]
ts=2019-09-1421:51:14;[cost=0.033976ms]result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/springfox.css],
]
ts=2019-09-1421:51:14;[cost=0.032818ms]result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/swagger-ui-standalone-preset.js.map],
]
ts=2019-09-1421:51:14;[cost=0.04651ms]result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/swagger-ui.css],
]
ts=2019-09-1421:51:14;[cost=0.034793ms]result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/swagger-ui.js.map],

這下直接看到了具體加載的資源名，這么熟悉的名字：swagger-ui，一個(gè)國(guó)外的rest接口文檔工具，又有國(guó)內(nèi)開發(fā)者基于swagger-ui做了一套spring mvc的集成工具，通過(guò)注解就可以自動(dòng)生成swagger-ui需要的接口定義json文件，用起來(lái)還比較方便，就是侵入性較強(qiáng)。

刪除swagger的jar包后問(wèn)題，詭異的70+ms就消失了

<dependency>
<groupId>io.springfoxgroupId>
<artifactId>springfox-swagger2artifactId>
<version>2.9.2version>
dependency>
<dependency>
<groupId>io.springfoxgroupId>
<artifactId>springfox-swagger-uiartifactId>
<version>2.9.2version>
dependency>

那么為什么swagger會(huì)導(dǎo)致請(qǐng)求耗時(shí)呢，為什么每次請(qǐng)求偶讀會(huì)加載swagger內(nèi)部的靜態(tài)資源呢？

其實(shí)這是tomcat-embed的一個(gè)bug吧，下面詳細(xì)介紹一下該Bug

Tomcat embed Bug分析&解決

源碼分析過(guò)程實(shí)在太漫長(zhǎng)，而且也不是本文的重點(diǎn)，所以就不介紹了， 下面直接介紹下分析結(jié)果

順便貼一張tomcat處理請(qǐng)求的核心類圖

為什么每次請(qǐng)求會(huì)加載Jar包內(nèi)的靜態(tài)資源

關(guān)鍵在于org.apache.catalina.mapper.Mapper#internalMapWrapper這個(gè)方法，該版本下處理請(qǐng)求的方式有問(wèn)題，導(dǎo)致每次都校驗(yàn)靜態(tài)資源。

為什么連續(xù)請(qǐng)求不會(huì)出現(xiàn)問(wèn)題

因?yàn)門omcat對(duì)于這種靜態(tài)資源的解析是有緩存的，優(yōu)先從緩存查找，緩存過(guò)期后再重新解析。具體參考org.apache.catalina.webresources.Cache，默認(rèn)過(guò)期時(shí)間ttl是5000ms。

為什么本地不會(huì)復(fù)現(xiàn)

其實(shí)確切的說(shuō)，是通過(guò)spring-boot打包插件后不能復(fù)現(xiàn)。由于啟動(dòng)方式的不同，tomcat使用了不同的類去處理靜態(tài)資源，所以沒(méi)問(wèn)題

如何解決

升級(jí)tomcat-embed版本即可

當(dāng)前出現(xiàn)Bug的版本為：

spring-boot:2.0.2.RELEASE，內(nèi)置的tomcat embed版本為8.5.31

升級(jí)tomcat embed版本至8.5.40+即可解決此問(wèn)題，新版本已經(jīng)修復(fù)了

通過(guò)替換springboot pom properties方式

如果項(xiàng)目是maven是繼承的springboot，即parent配置為springboot的，或者dependencyManagement中import spring boot包的

<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.0.2.RELEASEversion>
<relativePath/>
parent>

pom中直接覆蓋properties即可：

<properties>
<tomcat.version>8.5.40tomcat.version>
properties>

升級(jí)spring boot版本

springboot 2.1.0.RELEASE中的tomcat embed版本已經(jīng)大于8.5.31了，所以直接將springboot升級(jí)至該版本及以上版本就可以解決此問(wèn)題

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審核編輯 ：李倩