記一次經過Arthas定位解決spring-boot中內嵌tomcat的Bug問題
背景
公司有個渠道系統，專門對接三方渠道使用，沒有什麼業務邏輯，主要是轉換報文和參數校驗之類的工做，起着一個承上啓下的做用。css
最近在優化接口的響應時間，優化了代碼以後，可是時間仍是達不到要求；有一個詭異的100ms左右的耗時問題，在接口中打印了請求處理時間後，和調用方的響應時間還有差了100ms左右。好比程序裏記錄150ms，可是調用方等待時間卻爲250ms左右。html
下面記錄下當時詳細的定位&解決流程（其實解決很簡單，關鍵在於怎麼定位並找到解決問題的方法）java
定位過程
分析代碼
渠道系統是一個常見的spring-boot web工程，使用了集成的tomcat。分析了代碼以後，發現並無特殊的地方，沒有特殊的過濾器或者攔截器，因此初步排除是業務代碼問題linux
分析調用流程
出現這個問題以後，首先確認了下接口的調用流程。因爲是內部測試，因此調用流程較少。git
Nginx -反向代理-> 渠道系統github
公司是雲服務器，網絡走的也是雲的內網。因爲不明確問題的緣由，因此用排除法，首先確認服務器網絡是否有問題。web
先確認發送端到Nginx Host是否有問題：spring
[jboss@VM_0_139_centos ~]$ ping 10.0.0.139 PING 10.0.0.139 (10.0.0.139) 56(84) bytes of data. 64 bytes from 10.0.0.139: icmp_seq=1 ttl=64 time=0.029 ms 64 bytes from 10.0.0.139: icmp_seq=2 ttl=64 time=0.041 ms 64 bytes from 10.0.0.139: icmp_seq=3 ttl=64 time=0.040 ms 64 bytes from 10.0.0.139: icmp_seq=4 ttl=64 time=0.040 ms
從ping結果上看，發送端到Nginx主機的延遲是無問題的，接下來查看Nginx到渠道系統的網絡。apache
# 因爲日誌是沒問題的，這裏直接複製上面日誌了 [jboss@VM_0_139_centos ~]$ ping 10.0.0.139 PING 10.0.0.139 (10.0.0.139) 56(84) bytes of data. 64 bytes from 10.0.0.139: icmp_seq=1 ttl=64 time=0.029 ms 64 bytes from 10.0.0.139: icmp_seq=2 ttl=64 time=0.041 ms 64 bytes from 10.0.0.139: icmp_seq=3 ttl=64 time=0.040 ms 64 bytes from 10.0.0.139: icmp_seq=4 ttl=64 time=0.040 ms
從ping結果上看，Nginx到渠道系統服務器網絡延遲也是沒問題的json
既然網絡看似沒問題，那麼能夠繼續排除法，砍掉Nginx，客戶端直接再渠道系統的服務器上，經過迴環地址（localhost）直連，避免通過網卡/dns，縮小問題範圍看看可否復現（這個應用和地址是我後期模擬的，測試的是一個空接口）：
[jboss@VM_10_91_centos tmp]$ 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 請求總耗時
從curl日誌上看，經過迴環地址調用一個空接口耗時也有73ms。這就奇怪了，跳過了中間全部調用節點（包括過濾器&攔截器之類），直接請求應用一個空接口，都有73ms的耗時，再請求一次看看：
[jboss@VM_10_91_centos tmp]$ 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，第二次請求耗時就正常了，變成了3ms。經查閱資料，linux curl是默認開啓http keep-alive的（Keep-Alive的介紹能夠參考個人另外一篇文章）。就算不開啓keep-alive，每次從新handshake，也不至於須要70ms。
通過不斷分析測試發現，連續請求的話時間就會很短，每次請求只須要幾毫秒，可是若是隔一段時間再請求，就會花費70ms以上。
從這個現象猜測，多是某些緩存機制致使的，連續請求由於有緩存，因此速度快，時間長緩存失效後致使時間長。
那麼這個問題點到底在哪一層呢？tomcat層仍是spring-webmvc呢？
光猜測定位不了問題，仍是得實際測試一下，把渠道系統的代碼放到本地ide裏啓動測試可否復現
可是導入本地Ide後，在Ide中啓動後並不能復現問題，並無70+ms的延遲問題。這下頭疼了，本地沒法復現，不能Debug，因爲問題點不在業務代碼，也不能經過加日誌的方式來Debug
這時候能夠祭出神器Arthas了
Arthas分析問題
Arthas 是Alibaba開源的Java診斷工具，深受開發者喜好。當你遇到如下相似問題而一籌莫展時，Arthas能夠幫助你解決：
這個類從哪一個 jar 包加載的？爲何會報各類類相關的 Exception？
我改的代碼爲何沒有執行到？難道是我沒 commit？分支搞錯了？
遇到問題沒法在線上 debug，難道只能經過加日誌再從新發布嗎？
線上遇到某個用戶的數據處理有問題，但線上一樣沒法 debug，線下沒法重現！
是否有一個全局視角來查看系統的運行情況？
有什麼辦法能夠監控到JVM的實時運行狀態？
上面是Arthas的官方簡介，此次我只須要用他的一個小功能trace。動態計算方法調用路徑和時間，這樣我就能夠定位時間在哪一個地方被消耗了。
trace 方法內部調用路徑，並輸出方法路徑上的每一個節點上耗時trace 命令能主動搜索 class-pattern／method-pattern
對應的方法調用路徑，渲染和統計整個調用鏈路上的全部性能開銷和追蹤調用鏈路。
有了神器，那麼該追蹤什麼方法呢？因爲我對Tomcat源碼不是很熟，因此只能從spring mvc下手，先來trace一下spring mvc的入口：
[arthas@24851]$ trace org.springframework.web.servlet.DispatcherServlet *
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:44) cost in 508 ms.
`---ts=2019-09-14 21:07:44;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=2019-09-14 21:07:44;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:<init>() #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:<init>() #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_centos tmp]$ 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
本次調用，調用端時間花費115ms，可是從arthas trace上看，spring mvc只消耗了18ms，那麼剩下的97ms去哪了呢？
本地測試後已經能夠排除spring mvc的問題了，最後也是惟一可能出問題的點就是tomcat
但是本人並不熟悉tomcat中的源碼，就連請求入口都不清楚，tomcat裏須要trace的類都很差找。。。
不過不要緊，有神器Arthas，能夠經過stack命令來反向查找調用路徑，以org.springframework.web.servlet.DispatcherServlet做爲參數：
stack 輸出當前方法被調用的調用路徑不少時候咱們都知道一個方法被執行，但這個方法被執行的路徑很是多，或者你根本就不知道這個方法是從那裏被執行了，此時你須要的是 stack 命令。
[arthas@24851]$ stack org.springframework.web.servlet.DispatcherServlet *
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:44) cost in 495 ms.
ts=2019-09-14 21:15:19;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()
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
ts=2019-09-14 21:15:19;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()
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:974)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:866)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:851)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
從stack日誌上能夠很直觀的看出DispatchServlet的調用棧，那麼這麼長的路徑，該trace哪一個類呢（這裏跳過spring mvc中的過濾器的trace過程，實際排查的時候也trace了一遍，但這詭異的時間消耗不是由這裏過濾器產生的）？有必定經驗的老司機從名字上大概也能猜出來從哪裏下手比較好，那就是org.apache.coyote.http11.Http11Processor.service，從名字上看，http1.1處理器，這多是一個比較好的切入點。下面來trace一下：
[arthas@24851]$ trace org.apache.coyote.http11.Http11Processor service
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 269 ms.
`---ts=2019-09-14 21:22:51;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
日誌裏有一個129ms的耗時點（時間比沒開arthas的時候更長是由於arthas自己帶來的性能消耗，因此生產環境當心使用），這個就是要找的問題點。
打問題點找到了，那怎麼定位是什麼致使的問題呢，又如何解決呢？
繼續trace吧，細化到具體的代碼塊或者內容。trace因爲性能考慮，不會展現全部的調用路徑，若是調用路徑過深，只有手動深刻trace，原則就是trace耗時長的那個方法：
[arthas@24851]$ trace org.apache.coyote.Adapter service
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 608 ms.
`---ts=2019-09-14 21:34:33;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:<init>() #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:<init>() #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
一段無聊的手動深刻trace以後………………
[arthas@24851]$ trace org.apache.catalina.webresources.AbstractArchiveResourceSet getArchiveEntries
Press Q or Ctrl+C to abort.
Affect(class-cnt:4 , method-cnt:2) cost in 150 ms.
`---ts=2019-09-14 21:36:26;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:<init>() #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:<init>() #113
+---[min=0.001175ms,max=0.001176ms,total=0.002351ms,count=2] java.lang.Integer:<init>() #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
發現了一個值得暫停思考的點：
+---[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74ms；從名字上看，應該是tomcat加載jar包時的耗時，那麼是加載了31個jar包的耗時，仍是加載了jar包內的某些資源31次耗時呢？
TomcatJarInputStream這個類源碼的註釋寫到：
The purpose of this sub-class is to obtain references to the JarEntry objects
for META-INF/ and META-INF/MANIFEST.MF that are otherwise swallowed by the
JarInputStream implementation.
大概意思也就是，獲取jar包內META-INF/，META-INF/MANIFEST的資源，這是一個子類，更多的功能在父類JarInputStream裏。
其實看到這裏大概也能猜到問題了，tomcat加載jar包內META-INF/，META-INF/MANIFEST的資源致使的耗時，至於爲何連續請求不會耗時，應該是tomcat的緩存機制（下面介紹源碼分析）
不着急定位問題，試着經過Arthas最終定位問題細節，繼續手動深刻trace
[arthas@24851]$ trace org.apache.catalina.webresources.TomcatJarInputStream *
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:4) cost in 44 ms.
`---ts=2019-09-14 21:37:47;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=2019-09-14 21:37:47;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
#這裏一共31個trace日誌，刪減了剩下的
從方法名上看，仍是加載資源之類的意思。都已經到jdk源碼了，這時候來看一下TomcatJarInputStream這個類的源碼:
/**
* Creates a new <code>JarEntry</code> (<code>ZipEntry</code>) for the
* specified JAR file entry name. The manifest attributes of
* the specified JAR file entry name will be copied to the new
* <CODE>JarEntry</CODE>.
*
* @param name the name of the JAR/ZIP file entry
* @return the <code>JarEntry</code> object just created
*/
protected ZipEntry createZipEntry(String name) {
JarEntry e = new JarEntry(name);
if (man != null) {
e.attr = man.getAttributes(name);
}
return e;
}
這個createZipEntry有個name參數，從註釋上看，是jar/zip文件名，若是能獲得文件名這種關鍵信息，就能夠直接定位問題了；仍是經過Arthas，使用watch命令，動態監測方法調用數據
watch方法執行數據觀測讓你能方便的觀察到指定方法的調用狀況。能觀察到的範圍爲：返回值、拋出異常、入參，經過編寫 OGNL 表達式進行對應變量的查看。
watch 該方法的入參
[arthas@24851]$ watch org.apache.catalina.webresources.TomcatJarInputStream createZipEntry "{params[0]}"
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 27 ms.
ts=2019-09-14 21:51:14; [cost=0.14547ms] result=@ArrayList[
@String[META-INF/],
]
ts=2019-09-14 21:51:14; [cost=0.048028ms] result=@ArrayList[
@String[META-INF/MANIFEST.MF],
]
ts=2019-09-14 21:51:14; [cost=0.046071ms] result=@ArrayList[
@String[META-INF/resources/],
]
ts=2019-09-14 21:51:14; [cost=0.033855ms] result=@ArrayList[
@String[META-INF/resources/swagger-ui.html],
]
ts=2019-09-14 21:51:14; [cost=0.039138ms] result=@ArrayList[
@String[META-INF/resources/webjars/],
]
ts=2019-09-14 21:51:14; [cost=0.033701ms] result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/],
]
ts=2019-09-14 21:51:14; [cost=0.033644ms] result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/favicon-16x16.png],
]
ts=2019-09-14 21:51:14; [cost=0.033976ms] result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/springfox.css],
]
ts=2019-09-14 21:51:14; [cost=0.032818ms] result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/swagger-ui-standalone-preset.js.map],
]
ts=2019-09-14 21:51:14; [cost=0.04651ms] result=@ArrayList[
@String[META-INF/resources/webjars/springfox-swagger-ui/swagger-ui.css],
]
ts=2019-09-14 21:51:14; [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，這麼熟悉的名字：swagger-ui，一個國外的rest接口文檔工具，又有國內開發者基於swagger-ui作了一套spring mvc的集成工具，經過註解就能夠自動生成swagger-ui須要的接口定義json文件，用起來還比較方便，就是侵入性較強。
刪除swagger的jar包後問題，詭異的70+ms就消失了
<!--pom 裏刪除這兩個引用，這兩個包時國內開發者封裝的，swagger-ui並無提供java spring-mvc的支持包，swagger只是一個瀏覽器端的ui+editor
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger2</artifactId>
<version>2.9.2</version>
</dependency>
<dependency>
<groupId>io.springfox</groupId>
<artifactId>springfox-swagger-ui</artifactId>
<version>2.9.2</version>
</dependency>
那麼爲何swagger會致使請求耗時呢，爲何每次請求偶讀會加載swagger內部的靜態資源呢？
其實這是tomcat-embed的一個bug吧，下面詳細介紹一下該Bug
Tomcat embed Bug分析&解決
源碼分析過程實在太漫長，並且也不是本文的重點，因此就不介紹了， 下面直接介紹下分析結果
順便貼一張tomcat處理請求的核心類圖
爲何每次請求會加載Jar包內的靜態資源
關鍵在於org.apache.catalina.mapper.Mapper#internalMapWrapper這個方法，該版本下處理請求的方式有問題，致使每次都校驗靜態資源。
爲何連續請求不會出現問題
由於Tomcat對於這種靜態資源的解析是有緩存的，優先從緩存查找，緩存過時後再從新解析。具體參考org.apache.catalina.webresources.Cache，默認過時時間ttl是5000ms。
爲何本地不會復現
其實確切的說，是經過spring-boot打包插件後不能復現。因爲啓動方式的不一樣，tomcat使用了不一樣的類去處理靜態資源，因此沒問題
如何解決
升級tomcat-embed版本便可
當前出現Bug的版本爲：
spring-boot:2.0.2.RELEASE，內置的tomcat embed版本爲8.5.31
升級tomcat embed版本至8.5.40+便可解決此問題，新版本已經修復了
經過替換springboot pom properties方式
若是項目是maven是繼承的springboot，即parent配置爲springboot的，或者dependencyManagement中import spring boot包的
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
pom中直接覆蓋properties便可：
<properties>
<tomcat.version>8.5.40</tomcat.version>
</properties>
升級spring boot版本
springboot 2.1.0.RELEASE中的tomcat embed版本已經大於8.5.31了，因此直接將springboot升級至該版本及以上版本就能夠解決此問題
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