SpringBoot項(xiàng)目調(diào)優(yōu)及垃圾回收器的比較詳解

更新時(shí)間：2020年04月03日 09:36:30 作者：Pitt_96

這篇文章主要介紹了SpringBoot項(xiàng)目調(diào)優(yōu)及垃圾回收器的比較詳解，文中通過(guò)示例代碼介紹的非常詳細(xì)，對(duì)大家的學(xué)習(xí)或者工作具有一定的參考學(xué)習(xí)價(jià)值，需要的朋友們下面隨著小編來(lái)一起學(xué)習(xí)學(xué)習(xí)吧

一、SpringBoot項(xiàng)目在外部Tomcat啟動(dòng)時(shí)加載兩次

如下所示，spring標(biāo)志出現(xiàn)兩次(截取部分代碼)

.  ____     _      __ _ _
 /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/ ___)| |_)| | | | | || (_| | ) ) ) )
 ' |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::    (v1.5.7.RELEASE)

2020-04-02 16:57:29.505 INFO 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : Starting MainApplication on LAPTOP-1U9EARRO with PID 19964 (D:\apache-tomcat-8.5.42\apache-tomcat-8.5.42\webapps\kill-0.0.1-SNAPSHOT\WEB-INF\classes started by pitt in C:\Users\pitt\AppData\Local\MyEclipse 2017 CI)
2020-04-02 16:57:29.508 DEBUG 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : Running with Spring Boot v1.5.7.RELEASE, Spring v4.3.11.RELEASE
2020-04-02 16:57:29.509 INFO 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : No active profile set, falling back to default profiles: default
2020-04-02 16:57:29.539 INFO 19964 --- [ost-startStop-1] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@1e20bc0d: startup date [Thu Apr 02 16:57:29 GMT+08:00 2020]; root of context hierarchy
2020-04-02 16:57:30.097 INFO 19964 --- [ost-startStop-1] o.s.b.f.xml.XmlBeanDefinitionReader   : Loading XML bean definitions from class path resource [spring/spring-jdbc.xml]
2020-04-02 16:57:30.141 WARN 19964 --- [ost-startStop-1] o.m.s.mapper.ClassPathMapperScanner   : No MyBatis mapper was found in '[com.pitt.kill.model.mapper]' package. Please check your configuration.
2020-04-02 16:57:30.258 WARN 19964 --- [ost-startStop-1] o.m.s.mapper.ClassPathMapperScanner   : No MyBatis mapper was found in '[com.pitt.kill.server]' package. Please check your configuration.
2020-04-02 16:57:30.307 INFO 19964 --- [ost-startStop-1] .s.d.r.c.RepositoryConfigurationDelegate : Multiple Spring Data modules found, entering strict repository configuration mode!

 .  ____     _      __ _ _
 /\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/ ___)| |_)| | | | | || (_| | ) ) ) )
 ' |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::    (v1.5.7.RELEASE)

2020-04-02 16:57:37.069 INFO 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : Starting MainApplication on LAPTOP-1U9EARRO with PID 19964 (D:\apache-tomcat-8.5.42\apache-tomcat-8.5.42\webapps\server\WEB-INF\classes started by pitt in C:\Users\pitt\AppData\Local\MyEclipse 2017 CI)
2020-04-02 16:57:37.072 DEBUG 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : Running with Spring Boot v1.5.7.RELEASE, Spring v4.3.11.RELEASE
2020-04-02 16:57:37.072 INFO 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : No active profile set, falling back to default profiles: default
2020-04-02 16:57:37.102 INFO 19964 --- [ost-startStop-1] ationConfigEmbeddedWebApplicationContext : Refreshing org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext@1565ae71: startup date [Thu Apr 02 16:57:37 GMT+08:00 2020]; root of context hierarchy
2020-04-02 16:57:37.675 INFO 19964 --- [ost-startStop-1] o.s.b.f.xml.XmlBeanDefinitionReader   : Loading XML bean definitions from class path resource [spring/spring-jdbc.xml]
2020-04-02 16:57:37.863 INFO 19964 --- [ost-startStop-1] .s.d.r.c.RepositoryConfigurationDelegate : Multiple Spring Data modules found, entering strict repository configuration mode!
2020-04-02 16:57:38.422 INFO 19964 --- [ost-startStop-1] trationDelegate$BeanPostProcessorChecker : Bean 'org.springframework.amqp.rabbit.annotation.RabbitBootstrapConfiguration' of type [org.springframework.amqp.rabbit.annotation.RabbitBootstrapConfiguration$$EnhancerBySpringCGLIB$$6cdea02f] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2020-04-02 16:57:38.456 INFO 19964 --- [ost-startStop-1] trationDelegate$BeanPostProcessorChecker : Bean 'shiroConfig' of type [com.pitt.kill.server.config.ShiroConfig$$EnhancerBySpringCGLIB$$4392bed0] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)

加載時(shí)間30s

2020-04-02 16:57:42.825 INFO 19964 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : Started MainApplication in 6.091 seconds (JVM running for 30.348)
2020-04-02 16:57:42.946 INFO 19964 --- [      main] org.apache.catalina.startup.Catalina   : Server startup in 29361 ms

原因：打開(kāi)配置文件server.xml，Tomcat在啟動(dòng)web項(xiàng)目時(shí)，會(huì)首先在Host標(biāo)簽中找webapps下的項(xiàng)目，進(jìn)行加載后，又會(huì)在Context 標(biāo)簽中再次加載，導(dǎo)致加載兩次
解決: 將appBase="webapps"替換為appBase = " "

<Host appBase="webapps" autoDeploy="true" name="localhost" unpackWARs="true">

<Context docBase="D:\apache-tomcat-8.5.42\apache-tomcat-8.5.42\webapps\server" path="" reloadable="true" source="org.eclipse.jst.jee.server:server"/>

加載一次時(shí)間為12s

2020-04-02 17:03:12.759 INFO 952 --- [ost-startStop-1] com.pitt.kill.server.MainApplication   : Started MainApplication in 7.478 seconds (JVM running for 12.532)
2020-04-02 17:03:13.100 INFO 952 --- [      main] org.apache.catalina.startup.Catalina   : Server startup in 11772 ms

二、禁用字節(jié)碼驗(yàn)證過(guò)程

對(duì)類的加載時(shí)間進(jìn)行優(yōu)化，首先查看類的加載時(shí)間

C:\Program Files\Java\jdk1.8.0_211\bin>jps
16612 QuorumPeerMain
9172 Main
19416 MyEclipse
952 Bootstrap
19580 Jps

C:\Program Files\Java\jdk1.8.0_211\bin>jstat -class 952
Loaded Bytes Unloaded Bytes   Time
 10533 20062.0    0   0.0    7.83

我們默認(rèn)通過(guò)MyEclipse編譯的代碼是可靠的，不需要在加載的時(shí)候進(jìn)行字節(jié)碼驗(yàn)證，使用-Xverify:none參數(shù)將字節(jié)碼驗(yàn)證過(guò)程禁用掉，來(lái)提升類的加載速度

C:\Program Files\Java\jdk1.8.0_211\bin>jstat -class 12308
Loaded Bytes Unloaded Bytes   Time
 9822 18874.2    0   0.0    6.70

提升效果一般，只減少了1s
此外由于HotSpot采用了JIT編譯器可以提前加載熱代碼，1.8版本JVM的代碼編譯速度已經(jīng)比較優(yōu)秀，此處不做優(yōu)化

三、調(diào)整內(nèi)存設(shè)置控制垃圾收集頻率

Java8默認(rèn)的GC回收器為Parallel Scavenge + Parallel Old

用Jmeter發(fā)送請(qǐng)求作為輔助測(cè)試

可以看到，測(cè)試時(shí)間內(nèi)，發(fā)起了103次Minor GC，耗時(shí)不到1s，其實(shí)時(shí)間停頓并不多，但是5次Full GC占用了很大部分的GC時(shí)間，主要針對(duì)這部分時(shí)間進(jìn)行優(yōu)化。通過(guò)-Xloggc:gc.log -XX:+PrintGCTimeStamps -XX:+PrintGCDetails參數(shù)打印GC日志，將Full GC挑出如下：

7.934: [Full GC (Metadata GC Threshold) [PSYoungGen: 926K->0K(647680K)] [ParOldGen: 54198K->15711K(65024K)] 55125K->15711K(712704K), [Metaspace: 20674K->20674K(1069056K)], 0.0303162 secs] [Times: user=0.03 sys=0.00, real=0.03 secs] 
10.430: [Full GC (Metadata GC Threshold) [PSYoungGen: 3883K->0K(646656K)] [ParOldGen: 20986K->17184K(80896K)] 24870K->17184K(727552K), [Metaspace: 34377K->34377K(1081344K)], 0.0413074 secs] [Times: user=0.28 sys=0.00, real=0.04 secs] 
379.971: [Full GC (Metadata GC Threshold) [PSYoungGen: 2528K->0K(93696K)] [ParOldGen: 65885K->58730K(132096K)] 68413K->58730K(225792K), [Metaspace: 57642K->57535K(1101824K)], 0.3908541 secs] [Times: user=0.97 sys=0.00, real=0.39 secs] 
390.977: [Full GC (Ergonomics) [PSYoungGen: 8688K->0K(230400K)] [ParOldGen: 129221K->120704K(226304K)] 137909K->120704K(456704K), [Metaspace: 62151K->62115K(1105920K)], 0.1319683 secs] [Times: user=0.50 sys=0.02, real=0.13 secs] 
553.770: [Full GC (Ergonomics) [PSYoungGen: 47104K->0K(513536K)] [ParOldGen: 228052K->120789K(249344K)] 275156K->120789K(762880K), [Metaspace: 62330K->62330K(1105920K)], 0.1344527 secs] [Times: user=0.27 sys=0.02, real=0.13 secs]

每一次Full GC都伴隨著老年代的擴(kuò)容，日志還顯示有時(shí)候內(nèi)存回收狀況不理想，獲取可用的內(nèi)存主要通過(guò)空間的擴(kuò)容。
查看運(yùn)行期間的CPU使用情況，如下圖：

垃圾回收的CPU使用率曲線幾乎看不到，CPU資源還有可利用的余地，為此想到更換原有的垃圾回收器來(lái)進(jìn)行GC優(yōu)化

CMS:

相比于默認(rèn)的Parallel GC明顯改善了Full GC所消耗的時(shí)間，Stop The World時(shí)間減少，但是Minor GC大量增加，嘗試調(diào)整新生代的大小來(lái)減少M(fèi)inor GC的產(chǎn)生，在使用-XX:NewRatio=1 -XX:SurvivorRatio=3
-XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=85參數(shù)進(jìn)行調(diào)整后，Minor GC數(shù)量下降，但是相比而言還是很多

G1:

G1為最新的垃圾回收算法，將新生代和老年代同時(shí)進(jìn)行標(biāo)記和回收，采用標(biāo)記-整理算法，不會(huì)產(chǎn)生內(nèi)存碎片，在時(shí)間消耗上表現(xiàn)的最好，平均每次回收占用的時(shí)間最短，并且最好在內(nèi)存比較大的機(jī)器上使用G1算法進(jìn)行回收

G1的優(yōu)勢(shì)在于:
作為CMS的長(zhǎng)期替代品
1、G1是一個(gè)壓縮收集器，提供足夠強(qiáng)的壓縮來(lái)完全避免狹小的內(nèi)存分配
2、依賴Regions概念，大大簡(jiǎn)化收集器邏輯，大部分情況下規(guī)避潛在的內(nèi)存碎片問(wèn)題
3、比CMS的GC停頓時(shí)長(zhǎng)更加可預(yù)測(cè)，并允許用戶指定停頓時(shí)長(zhǎng)

總結(jié):

以上三種回收器都為多線程垃圾回收器，但是對(duì)于不同的環(huán)境，應(yīng)該具體問(wèn)題具體分析，而不是采用一刀切的方法，解決問(wèn)題的過(guò)程即為尋找最優(yōu)解的過(guò)程。

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