線上GC異常排查

1、線上GC異常排查線上GC異常排查1現(xiàn)象最近去線上看了下gc情況，發(fā)現(xiàn)出現(xiàn)頻繁的fullGC。問(wèn)題如下圖:fir陽(yáng)陽(yáng)WJT55555559-912335-74699999912044B7&1BElCT3CTICT3inOOOOO0757575話75巧7S7515s9111112490-808792293B73173234&29-ual81618181slel8181el8181的slslMeleln95.6835.68沾聒血95.6605沾B35.95.6895.68券點(diǎn)北血95.6B95,6S北血958:statCCS9.ll96.1195119.ll96.1196.1195.1196.119

2、6.1145.1196.IL95.11%1145.11%11-gcutilY5C1295BL295B12358L295E-1235E12358128561235912S59129591235912S591235912359128591295912359129591541ieeeYGCT165JB5165.765165.7B5165.?E5165.765165.765165l?E5165.776165.776165.776165.776165.776165.77615,776165.77&FGC13530513530513530513530513530513530613530S135307135

3、30713530713530713530713S3QB13530B135309135309135309135309FKT395&2.461395B2.461395B2.461395B246139562.461GCTHM取2163974B.2263974E.2263974B.22639746.3163974E.22&39583.743e?4B,B40395B3.185395E3h詢539583.085395B9.ee33563.沖539563F2弼395B33T6395&3.51639563,316395B3.3K395B3J1639746r8tl3B?4B.8$13即4E冷百13974er8i

4、l30745.86139745.8=23974BJ5239749.892鶉碣上923974E.G5239749.82gc情況.jpg然后查看了下GC原因，如下:2.分析；?J2?42,?42?12M2.?J2J42?42.742?J2?42?42?12742.7J2J42.742.742.?42?Jisa11.51L3Wl&.l-?17.M勢(shì).廿21.22.732*.牌25.7-12&.es曲.廿知.14316137.5軸.昶41.9：皈無(wú)47.1(if創(chuàng)Bl.5701.5761,57Bl.57Bl.H61,57B1.S7Bl.761,57Bl.=781.Bl,5701.57Bl.；7BL,5

5、7B1.E761.7Bl.57Bl.=7-1$Fl95.6895.6395.6895.SS95.6395.6895.6996.6395.6895.6S95.6395.689S.G395.6395.689S.GS95.6395.6895.63CfiRS-gtCoue1:411000佩預(yù)TFOC12期15,4941翡時(shí)91293716S.494135刪129371粘.曲4135&3912期165.4941354912837IB.494135B4B13837Iffl.JW13SHB128刃165.49413541nanU5.4Mns&41120371M.49413EHL12fln165.494135

6、34113037165.494135&41120371M.4MU5H212W165.49413564213037IB.494135M31283JIM.49413S843-：gC原因圖.U037165.494135943129371M.4M135M312837165.K.494135944=KT3557.639-7.6H395Z-7.61-39:.6n3-7.3S53乃軒.的5即為丁.勺茁39-7.933;-7.93?四禽.弼39Z-7.93395JB2北3951-937C39UB37(pg39:：-B37639B37(39=5&.3739:&75GGCT.(KC3S6

7、?5.1STCHSinitialllark39671.167CHSInitialHark3967ar167(USInitialHark39672.197NoOC39671.339CHSFinalRenark站阻冷御015FmalRenark39673.433CHSInitialhark39673.433CMSInitialHark396,433CHSInitioHark3067.433CMSInitialMark39673.433015InitialHark站阻訂弭(USFmalRensrk39671531CHSFinal龍rsk395,364CHSIiLtialHark卻W笳4(USnark

8、39673.354CMSInitialMark39&Tjr364CHSIiLtialMark396.864CHSInitioHark2；躺克.鮎斗CHSInitialMark39&7J25&CHSFutalRenarkMGCKDooOCNNNcccccccccc_cc-uGG-uG6-uHu*G-H-GG-uG6-uQOOD-OO-QOOOOOOOOONNNNNNNNXNNNNNNN根據(jù)上面兩張圖，可以看出主要是老年代進(jìn)行了頻繁的CMSGC。而CMS回收的前提條件就是老年代達(dá)到一定的容量。這個(gè)容量可以數(shù)CMSInitiatingOccupancyFraction進(jìn)行設(shè)置。本項(xiàng)目的jvm配置如下

9、：-Xms4096m-Xmx4096m-Xmn3072m-Xss1024K-XX:PermSize=256m-XX:MaxPermSize=512m-XX:ParalleXX:+UseConcMarkSweepGC-XX:+UseParNewGC-XX:+UseCMSCompactAtFullCollection-XX:CMSInitiatingOccupancyFraction=80根據(jù)上面配置可以看出，老年代的容量為1G,且老年代達(dá)到80%的時(shí)候進(jìn)行CMS回收。而根據(jù)上圖可以發(fā)現(xiàn)老年代的占用率一直在,每次回收基本上都沒(méi)有釋放空間。所以一直在頻繁的出發(fā)CMS回收算法。3排查依據(jù)上面的推斷，使

10、用命令jmap-dump:live,format=b,file=heap.hprofpid觸發(fā)fullGC,并dump內(nèi)存快照。因?yàn)楸敬蝺?nèi)存主要是老年代頻繁GC導(dǎo)致的，而且每次回收都沒(méi)有回收到有效空間。所以才直接加上live屬性，防止年輕代對(duì)象干擾結(jié)果。然后使用mat分析內(nèi)存泄漏如下：iOven/ewHIHistogram很ulistobjectsseectioriofStringBuider，ulistobjectselectionofThreadLocalJCassNaneObjectsShaowHeapstainedHeapJ0diarSS+,191674.81怖=674.81MBOja

11、va.hnglhread剛0.D9MB=630.56MB0java.lang.ThreadLocalSHireadLocalMap1,9280.04MB=63031MB9java.hng.ThreadL)calSTlirefldLocalMap$Ertry1r928024MB=63027MB=629.68MB3java.lang.StrngBuider1110.02MB=514.02MBGbyteQ112636938MB=6938MB0jawa.hng.Object35,1533.13MB=61.18MB3java.lang.Strng586,92213.43MB=5939MBGjava.ut

12、iLArrayLst31,5510.72MB=44.34MB3sun.mk.Launcher$AppClas5Lodder10.00MB=35.41MBGcombj58spat.sbdient.connmuiiication.NIOChan.40.00MB=32.00MBGjava.util.Vectcr5r3790.16MB=31.56MB0java.niQ.HeapByteEiffer4580.02MB=28.09MB芒ictir卜廠1Deel1firmFuiD_irD7heap直方圖根據(jù)圖中shallowheap和Retainedheap可看出占用內(nèi)存最大的就是char數(shù)組。而threa

13、d、threadlocal還有StringBuilder都可能指向的就是char數(shù)組對(duì)象。下圖也驗(yàn)證了這個(gè)猜想。5匸LlUFYIIS.UbEliLU11JIUUJCLL33CICLLIUIIUlJLlbUUIIUCLU113LUUJCl.JpCICL.IUIIUlIIKClLULnpIIIIClassName手ShallowHeapRetainedHeapjava.ang.Thread0 x788b8Z9b0SCFasyncworker26-ttiread-11ThreadO.ODME1.77MBig沁ang.Thread0 x787a97c50SCFyncworkef11-tirec-9hr

14、eadO.ODMB1.77MBjava.ang.Thread0 x783728998SCFasynuvork&r14-tliread-5HireadO.ODME1.77MB.dva.ang.Thad0 x787a968tOSCFancwofer15-tac-BhreadO.ODMB1.76MB:.ava.ang.Thad0 x787a97ec8SCFasyncztirker11-thread-2IhreadO.ODME1.76MB-%.dva.ang.Thread0 x788dbhOSCF鞠帕加6-thread-8threadO.OD1.76MB沖臨ang.Thread0 x78a2OSDe0

15、SCF_a5yic_wcrker_5-thfead-10ThradO.ODME1.76MBang.Thread0 x787a9S43D5C=asyncwoer17-thread-7ThreadO.ODMB1.76MB:3j臨ang.Thread(h(7879c485BSCFa&yncworker25-thread-6HireadO.ODME1.76MB肚沁ang.Thread0 x783729558SCFyncworkef17-tirec-2hreadO.ODMB1.76MB：jdva,ang.Thread0 x7879c2960SCF_a&ync_worker_30-thread-2Hire

16、adO.ODME1.76MBang.Thread0 x788bS009DSCFasyncworker30-thfead-5hreadO.ODMB1.76MB:java.ang.Thread(h(78a203BSCFa&yncworker6-thfead-8hreadO.ODME1.76MBgdva.ano.Thread0 x783728eOO5CFasvrKworker16-thread-7ThreadO.ODMB1.76MBThreadnT召習(xí)閒5=州c=giSclassjavaJang.ThreadLocalfThreddLocaMaptEntry(M0.00MBczg令ubtablevj

17、thFeadLocalsjava,angThreadLocallThreadLocalap0 x78d0a96d60.00MB匚java.ang.Tliread0 x78SbB29b0SCFasyncworker26-thrq0.00MBczg*javalang.ThreadQx788b829bOSCFasyncworkerClassNameJiOverviewNHreferentjailangJveacLew0 x7805浙400.00MBc=g令Z3gstogran也istobjectsselectionofStringBuilder兇stobjectsseiectionofThreadL

18、ocalJlhreadI9WOOOZS：kE：0?W-?I.W閱26-thread-11Thread0.00MBa23aaaXUn二二X3XRetanedHeapCJOooooCdCJOooionCdCJOooffiKThread克世stringBui-derL31學(xué)口Jdca口d0ca口Jdca口d0ca口Jdca口E3J0CQ口C3Jdca口d0ca-kH口E3Jdcai-EUdCOClassNameStriigBuiclergfe/EdDfaDaB202D-12-142035:494NFOSCF_asynmrl(i,StriigBuicler3M6feeeie202D-12-1420:3

19、2:28r936INFOSCF_asynmrk(StriigBuicler&MSdddaB202D-12-142035:30.60lNFOSCF_asynmrl(i,StnigBuicler?M3581D3&2020-12-142D:34:5?.4J9INFOSCFjcwor,StriigBuicler3fe/8a1ft6602020-12-U20:3539,32INFOSCF_acwofk,StnigBuicler3O79m2020-12-1420：a4:135NFOSCF_asynmreStringBuilderft(7BSb300682020-12-1420:33:l2r417NFOSC

20、Fjol,StriigBuicler3Md1W2020-12-1420:35:292INFOSCF_asyr(work,StriigBuicler3fe/8(iDfa3aB202D-12-1420：a4:57727NFOSCF_asynmrl(i,Stnig3uilder?fe7btaad82020-12-1420:16.089訐0CaEdtkExecutoShdlowHeapNumerio務(wù)5_?5_t至5_?另5_t至5_?另5_i至5_p另5_t至5_?另5_t至-JIc_RLJ-1Y_inv_u_nY_inv_u_nY_inv_u_nY_COLJ-IVUJ1Y_coVdetainedH

21、eapjOverview一Hili=!ke-Kf耳蘭=一一Ikobjectsffiaoflcf-Th帀：】=5t&吾茗asc二目般-3s5ngBui-der-召3習(xí)11初2崗7-占邑豊一stmiS-甥Z亙匕士2S5出罷一N35芻:旨S至一已畐*口巫呂寧=尋三尋笑才7空_寸己孟7n7_v!二GFMm寫(xiě)二_=1SRi.EfifiWMily-WfileEditJndowijdpEthrKtclDT:DSArhgBuikki即卿“哎jjlJdddlAng5trifKulckrQ)0790124300啊占呼鼻姒啦徐斤凹血如.idvailangOflssLwderQrf?IT24CMIW.M2EJEl&r

22、4,HT3；retiredgIze陽(yáng)ECrm0hijpfdr：-iDwnlewHistoqurnjIselKlIanicfsii1nn_1Isttech|轉(zhuǎn)kclkmofItve_UlistcibiKhhelmlkinnlUwe.llst_dn|Kls|:CldWlMlrStdtifAlbrifc4iK-4匚IlAiHkTrch1WQjL.SiHfh直il血r爐OwWrcMdS2應(yīng)D-12小120:15:06/69INFO31恥kEwnjtc/曲|4：怕譏窗7柿國(guó)仙口2$順M21-I?-l+ajISSfeOeINFOi：llfe-：ktaei：UKii(I弗釘機(jī)pl臼呦MrimjEhilrkT

23、4).b70IJi：1?45OOSysbtr-iCImsMM-12-N20:1506iHFOI色k泌bcubor-Thnesd-pooh2J聲|毗5聞XcePrldig嗎)-caiAgVJF4i.u5DJu&3dnuT5l閑u田Igutli4ksy/1_501_験1：!肉q応!Ervi曲敘盤(pán)Hl護(hù)唧曲常曲電IXftIIMi.flW攸歲鶯弭7血：Vpri_ccrt3inrVI1CK1J(ZI中匕VudmthW2DlBCBrLft_prke斗需1西嚀.*0Vpikfl_jVaow.irr,Vpri(e_0flt)inBYlOflW.君I曲就Tflfld罰叱，A.rrAn1-Total:2wifrl

24、ips口lalHig.Stilnldef電QKHdDr酣闘JQ2O-li-142&MS7J27INF口MF呼rM_rtv4iviIue-char|90SPCwZb119dl4fl2A2i2-l420i3529.4l2INFQ5CFkpT呂das5：|hj站&山網(wǎng).InK旳日iiildfirQi7BDdf4KnTirtil:awifrlesMH!LkngStiln甲Jldtf0w陽(yáng)fl曲沁闘2U2012-142(02:12,417IhtfOSt!-laveJanq.Stnng&jIrieffec7fi7Wfl%丄論H450:34:1INFO5fafynwwrier-jjmJaTa.StiingB

25、uldCTINFO&CF_Mynr_wwkQjmkna.Stiinldwft(TB35BW3B施H&M2QH59期9INFOxf&呼哦啊Hi如4巾知iftfiB.川陽(yáng)矗饑7s鹹CcM閒2WO-I2-U2ft35血?jiǎng)?chuàng)I刊FO珂股g.打網(wǎng)心略知i啄til嶺血伽7朋礙用溯屈MBI42OL322&93&INF0咒F軒中k伽虹JlaJvig.StilngBLiildcfPjewiflftlHtwpfNtFTWTJCA0.00MB1.60MB160MBCOOMBThreadLocal.ThreadLocaMap對(duì)象-threadLocal$Entry-threadLocal$Entry-StringBui

26、lder對(duì)象。有了上面的路徑，就知道了內(nèi)存泄漏的對(duì)象主要是在ThreadLocal中了。那么我們就需要反向從StringBuilder找到對(duì)應(yīng)的ThreadLocal。排查步驟如下圖:壯毗腳l炯嘰卩咖加；也牌硒廁惋岡何：0酗協(xié)地曲【叩d-f曲加;:時(shí)1：浪期:斕棉換J，評(píng);血徊側(cè)ftb?：（rt第一步找到引用StringBuilder的對(duì)象.pngJif.ddlJIL：U肌山說(shuō)批Qm1-4典逍喲IlfLJ/LUMbIM:血珂刪規(guī)娜題込甘広訓(xùn)帆M1曲第一步展示效果J：leEiKic;-ef第二步找到對(duì)應(yīng)的ThreadLocalMap$Entry查看他指向的對(duì)象.png一血:的T（k苗肚*二應(yīng)皿I

27、p馳皿陽(yáng)肌蚯：亦詢?cè)冞笛Y【I珈i訃”恤血I11嗣則W協(xié)水虛：i申I薩i(krvi洌UHikOgiarrllistobjecs創(chuàng)Lllistcbjecis|select_llistijecissleet.Gkobjectisdect.Eiitobject!sefect.lktobertsel?CIcsNameShIcwFeap蛀加啣汽腕齢NlTlf，?J、中沁慣Im血即做曲慚帥嘰蠅期園0I.J懦禪心叭網(wǎng)汕斕恤刑血痕屈腳業(yè)巧(詡砒CO惴肛0關(guān)第二步展示效果1恤的牌刖帕世曲!哪:曲酈上魏鰹地1鼻百Fk絆百INuiiierk=NuffiericLijitw.lnngThrELcoIRhi咖lUxMM

28、nME肺y騎銅?卿QOOMB擊押足舊.|0叩1商歸1|_0飼恬ThfeadLo詢lyiapTE時(shí)ry(Is(州6aE000MB0.00MBjaraldriq.rer.ReclassJjvaJangJhreiLacal卷0 x7Scl8MJ0SystiljraiwoiavaJang.SirirBuilder睜OK7U2eccadB203SK12-142C工g|*rrt曲nnnhjRLktobjrchiShowDbirctEbycImghPathToGCRoatEEMergeShcflMilPAlhcIoGCRoatiBasicsLeakldenlikatkPEKpalSfU0&lv3*Immed

29、iateDnilortShamRetainedSetC-referaitjava,週JheMkxa$lte0LodM堿Entry0 x783211190ShiouvHeapRetainedHeap0.0DMB0.00Mb-referentava.迥血抽；亦t珈LowMapfEitry3Ox底脅她oODMB129MB-referentava.迥IheM恥伽囪訛5MapfEitry?加8熾5cfBQODMBIBMb-referentava.迥血抽；亦t珈LowMapfEitry31加832012題oODMB0.00MB-referentava.迥IheM恥伽囪訛5MapfEitry?血底4倂68Q

30、ODMB100Mb-referentava.迥口血恥阮t珈LowMapfEitry31加8344MMoODMB153MB-referaitjava,週JheMkxa$lte0LodM堿EntryOx78M)608QODMB129Mb-referentjava.迥IheM血北Tt珈應(yīng)測(cè)斛Eitry31加83440瑚uODMB0.80MB-referaitjava,週JheMkxa$lte0LodM堿Entry加8344哦QODMBIUM&-referentjava,眄.Th旳dka$ltedLodM堿Entry0 x7834411e8oODMB153MB-rpfArPdt仙smThrpfld旳1

31、燈hsrlln柑MantFnirv御fly?AWWRnnnmr1兀MR第三步效果圖步驟描述：右鍵某個(gè)StringBuilder對(duì)象，選擇listobjects-withincomingreferences（也就是找到指向當(dāng)前StringBuilder對(duì)象的對(duì)象）打開(kāi)引用鏈，找到引用當(dāng)前StringBuilder的ThreadLocal$ThreadLocalMap$Entry對(duì)象。然后右鍵，選擇listobjects-withoutgoingreferences（找到ThreadLocal$ThreadLocalMap$Entry對(duì)象引用的對(duì)象）找到當(dāng)前ThreadLocal$ThreadLo

32、calMap$Entry對(duì)象的屬性，referent屬性，右鍵listobjects-withincomingreferences（因?yàn)門(mén)hreadLocal$ThreadLocalMap$Entry類繼承了弱引用，其中的threadlocal對(duì)象就是在referent屬性中。所以此步驟是找到指向threadlocal對(duì)象的所有引用）因?yàn)橹赶騮hreadLocal的對(duì)象較多，所以需要排除很多ThreadLocal$ThreadLocalMap$Entry對(duì)象，最終我們找到了哪個(gè)我們期望的引用org.apache.logging.log4j.core.layout.AbstractStringL

33、ayout4代碼分析接下來(lái)查看代碼AbstractStringLayout。通過(guò)查找發(fā)現(xiàn)，我們這個(gè)類屬于log4j的。查看代碼發(fā)現(xiàn)threadLocal就是在這里使用的2，30*httE?5；f/i號(hào)sug芻，羽耳匸眩。早fjirmfbrpwsefLO54J2-9第fordetails539rji：public,abstiactcl-sssWbstract5cnngL*youtKt-edsAbacraccLsyoutiiipl-eiientsScncgLoutAlFsGefaMtletihforne*r5iringffalderinsTanres./tfvjrJwF.44*/procecced

34、staticfi/iaLintDfJLtJL5rf.W_FLTLDfK_5IZf-1324：4T1privatefinalstatii:ThreadLocalStringSuiIder-?*(占廠農(nóng)i3*acjij!n=ThreadLDcali):dqprivatestaticfinalserjal?ionUIfls1L;threadlocal引用地址而代碼中threadloca使用到的地方只有下圖這個(gè)地方:W31艇*returnaStringSuilder105i1瞞protetitECString0LiLdergetStringEiuilder()W7StrirgBuilderresult

35、=trreaosal.get:ioeifCresultniL109result=的StringEuilder(MLrSIRIAGBUILDERSIZE);1WthreadLocal.set(restIti:111112result.setLengthfST:B3_.threadlocaI使用的地方通過(guò)斷點(diǎn)發(fā)現(xiàn)，日志打印的時(shí)候，會(huì)先在StringBuilder中生成，而StringBuilder是存在于當(dāng)前線程中的。每次打印新的日志的時(shí)候，都是調(diào)用下result.setLength（O）方法，將原有的日志內(nèi)容置空。而StringBuilder的這個(gè)方法，只會(huì)count指針置為0,實(shí)際并不會(huì)釋放S

36、tringBuilder內(nèi)value占用的內(nèi)存。所以才導(dǎo)致了內(nèi)存的泄漏。（這里強(qiáng)調(diào)下，本項(xiàng)目使用的log4J的版本是2.5）5解決問(wèn)題發(fā)現(xiàn)了問(wèn)題就很容易解決了，通過(guò)查詢，只需要將log4J升級(jí)即可解決這個(gè)問(wèn)題（沒(méi)有挨個(gè)查看具體是那個(gè)版本解決的，但是就遇到過(guò)的2.8.2已經(jīng)解決了）。本項(xiàng)目直接使用了2.13.2先來(lái)看下解決之后的效果吧。1.內(nèi)存使用率6：2020-12-21n29:0810.144.11755:59355K2020-12-21巧四0010.HU6a.202:5952%2020-12-21n29:0010.14S.64.H6:59925K2020-12-21n29:0010.lM.

37、ffi.22l:砸I4：gc內(nèi)存占用率修復(fù)前.jpg2，2，12-2116:0312-2208CO16:0012-2316:0C30604020MCQ-12-23H:1UO1:I44.1K95:52.25KMCQ-12-23H:1UO1:II45.B:202:5275KKGQ-12-23HzlUO1:II45.&4.H6:52.66KKGQ-12-23HzlUO1:I44.6i.22:T.I為gc內(nèi)存占用率修復(fù)后.jpg根據(jù)上面兩張圖,2.cpu使用率可以看出來(lái)修復(fù)前后差不多差了百分之7%左右，而內(nèi)存總量為8G,所以前后相差差不多560M左右。gc前后cpu占用情況.jpg根據(jù)上圖可看出,3.

38、gc情況修復(fù)前cpu使用差不多為18%左右，修復(fù)后為4%左右，前后相差14左右，效果還是很明顯的5jftltcutit1M31M051ctaiCCS論TOCTFGCFGCTOCT心日劇47,S9.4S蟻5站7.SE1D3.6218.4221=.G3B.6952.1239.S3954S96.IB5307.8E158.EH3.422I1們5：7233.E&96.ie5沖7.8E1&9.6213,4221心53ja3S.E&眄.軸ss.ia5307.8E1：9.621&,4竝1/的5：6039.ca954S96.185=07.8E159.E21B.4391E.03乩陽(yáng)se.ii躬點(diǎn)85曲7.SC15

39、521B.4221.032.E&se.739.ea.48S3&7.8E1：0.5218.4221麗0.G9siei39.E8954896.185=07.8G159.5213.U21乩陽(yáng)61.5533.E&的軻%.ie河7.8E1&3.EH8*4221旳2.E&.ia39.ea$5,489$.iaS3&7.8E1D9.621a.4221S.G3O.EO64.6533.es954896.IB5=07.SE1s3.5218.43213,E966.6539.&的軻96.ie5307.891&3.sn3,4221旳2.E9J,G939.ES眄48魴,1$5307.fiEl:9,6Ua.4221們0.G5

40、69.639.G&954S96.ia5=07.8C13.S218.4391E.03S.E971.5731黑護(hù)4896.le5207.8G1521B.4221旳2.972.013乩E854?$.laS3&7.8E1：9.5218.4221麗0.G971.5B33M95.4496.185307.8G159.6213.U211D33,0974,e$翦.E8羽軻?6.ie5307.6&1&9.621S.422H_&中_q曲ru0尺Aftmi*_7API_I_AE_4Egc修復(fù)之后.jpg3S1AuooQ妙o0協(xié)SQSaSSCSSCG0朋51：2B52.0732.2652.9253.435斗，3154,

41、7555.56.6757,5353.9761.9462.66&3.MS4.B55.2E55.5Z67.BB6S.$2sS:1,1541.15M5.陽(yáng).95.軸.95.95195.阪55.M.95.55.95,95.55.泊.95,95.696.0196.01則M96.61軸血96.0196.01帕Ml5S.01騎忌96.019氣0196.01怕Ml弼血9,9196上196b019S.01$g.ei沾月J9g,0196.01旳匚1Q45104&16451B45104510451Q4514S104519451D451.6451045194S1B4S1045104516451B4

42、S194S16451B451045-TGCTL馬円MIA1914.919141L叫鄧14.191414.19田14.919雷用沖14.19L49Ml百占均皿鄧114,9114-eis14.919141514.91S14r19FOCTii1111111222J-2A-s-&$OCTLGCC15-539OlocationFiiTur#15.539ftlloiationFailure13-539AllocationFailure9iLllocatiDnFailure15.539AlldeAtianFtilurA15.39AllocationFailure15-539A.IlocationFiilur

43、*15.539AllocatioftFailure15.539Ul1)/LOG4J2-2368/RecursiveloggingmayclobberthecachedStringBuilder.returnnewStringBuilder(DEFAULT_STRING_BUILDER_SIZE);StringBuilderresult=threadLocal.get();if(result=null)/初始化StringBuilder的長(zhǎng)度為1024result=newStringBuilder(1024);threadLocal.set(result);/主要就是這里進(jìn)行了縮容trimToM

44、axSize(result);result.setLength(0);returnresult;333最主要的改進(jìn)就是上面的trimToMaxSize方法，再看下這個(gè)方法:/AbstractStringLayout的方法protectedstaticvoidtrimToMaxSize(finalStringBuilderstringBuilder)1024);/StringBuilder勺方法publicstaticvoidtrimToMaxSize(finalStringBuilderstringBuilder,finalintmaxSize)stringBuilder.setLength(

45、maxSize);/金融StringBuilder中去進(jìn)行縮容stringBuilder.trimToSize()publicvoidtrimToSize()/這里就是具體的縮容了if(countN4UKiHI2+Mi：刃MMIIKHI7I3WI：if(stringBuilder!=null&stringBuilder.capacity()maxSize)eMHKiS-iHWKiMrfIhlfCIhlRblKi：*iaiKI9333HKi/這里還有可能不設(shè)置屬性，取到2048/第二個(gè)參數(shù)的獲取，是根據(jù)這是的og4j的屬性log4j.layoutStringBuilder.maxSize和1042取較大值LJ叩7.叫91叫2jjb-J.M-VK*=IMiwllSkXJIEJdliuCUKJuM-|tKilZ4*X!：i416|nruWir3iUi3?kl.nF-MriiM|3Liiilti理列空LJHAaeSm:I4I3M-JWI2Lid!-WijiK|-.l5HC|2raKa2iliiix-T-.Hmcid-iaiiktaEi：2B5IH-r：ltKll42L7K!古XT