现象
- 性能测试，发现xx网站首页web接口的响应时间变慢，服务吞吐上不去
- 压力测试，并发数加大到20左右之后，系统的吞吐就不再增加，进程的cpu占用超过90%
观察和定位
使用50并发，不控制吞吐，对服务打压，取jstack
-
使用stackAnalysis工具对取出的jstack进行处理后，可以看到堆栈内的很多线程都blocked在velocity相关的逻辑上
"resin-tcp-connection-*:1907-57" daemon prio=10 tid=0x00002aaab8b09800 nid=0x522d waiting for monitor entry [0x0000000049779000] java.lang.Thread.State: BLOCKED (on object monitor) at java.util.Hashtable.get(Hashtable.java:333) - waiting to lock [***] (a org.apache.commons.collections.ExtendedProperties) at org.apache.commons.collections.ExtendedProperties.getBoolean(ExtendedProperties.java:1172) at org.apache.commons.collections.ExtendedProperties.getBoolean(ExtendedProperties.java:1157) at org.apache.velocity.runtime.RuntimeInstance.getBoolean(RuntimeInstance.java:1822) at org.apache.velocity.runtime.parser.node.ASTReference.init(ASTReference.java:139) at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:309) at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:309) at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:309) at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:309) at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:309) at org.apache.velocity.Template.initDocument(Template.java:227) at org.apache.velocity.Template.process(Template.java:135) at org.apache.velocity.runtime.resource.ResourceManagerImpl.loadResource(ResourceManagerImpl.java:437) at org.apache.velocity.runtime.resource.ResourceManagerImpl.getResource(ResourceManagerImpl.java:352) at org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:1533) at org.apache.velocity.runtime.directive.Parse.render(Parse.java:197) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72) at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:420) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:106) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342) at org.apache.velocity.runtime.directive.Parse.render(Parse.java:260) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72) at org.apache.velocity.runtime.directive.VelocimacroProxy.render(VelocimacroProxy.java:216) at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:311) at org.apache.velocity.runtime.directive.RuntimeMacro.render(RuntimeMacro.java:230) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72) at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:87) at org.apache.velocity.runtime.parser.node.ASTBlock.render(ASTBlock.java:72) at org.apache.velocity.runtime.directive.Foreach.render(Foreach.java:420) at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207) at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342) at org.apache.velocity.Template.merge(Template.java:356) at org.apache.velocity.Template.merge(Template.java:260) at org.springframework.web.servlet.view.velocity.VelocityView.mergeTemplate(VelocityView.java:517) at org.springframework.web.servlet.view.velocity.VelocityLayoutView.doRender(VelocityLayoutView.java:167) at org.springframework.web.servlet.view.velocity.VelocityView.renderMergedTemplateModel(VelocityView.java:291) at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:167) at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:250) at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1063) at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:801) at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:719) at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:644) at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:549) at javax.servlet.http.HttpServlet.service(HttpServlet.java:115) at javax.servlet.http.HttpServlet.service(HttpServlet.java:92) at com.caucho.server.dispatch.ServletFilterChain.doFilter(ServletFilterChain.java:106) at com.caucho.filters.RewriteFilter.doFilter(RewriteFilter.java:120) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at outfox.cps.auth.filter.AuthFilter.chainFilter(AuthFilter.java:201) at outfox.cps.auth.filter.AuthFilter.doFilter(AuthFilter.java:83) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at account.app.CheckFilter.doFilter(CheckFilter.java:329) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at outfox.cps.web.filters.ArmaniRequestFilter.doFilter(ArmaniRequestFilter.java:115) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at toolbox.acs.client.Dog.doFilter(Dog.java:78) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at toolbox.flagfilter.FlagFilter.doFilter(FlagFilter.java:40) at com.caucho.server.dispatch.FilterFilterChain.doFilter(FilterFilterChain.java:70) at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:173) at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:229) at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:274) at com.caucho.server.port.TcpConnection.run(TcpConnection.java:511) - locked [***] (a java.lang.Object) at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:516) at com.caucho.util.ThreadPool.run(ThreadPool.java:442) at java.lang.Thread.run(Thread.java:662) -
基本可以认为是velocity的配置有问题，src/web/WEB-INF/cps-servlet.xml中velocity相关的配置如下：
UTF-8 UTF-8 true macro/cps_web_combo.vm,macro/cps_web_global.vm,macro/cps_gs.vm -
velocity的velocimacro.library.autoreload与file.resource.loader.cache默认值均为false, 若不进行配置, 则每次请求都会reload一次相关的vm文件，从而严重影响性能, 因此建议开发将配置改为如下：
UTF-8 UTF-8 true false //可不配置, 默认即为falsetrue true //打开cache开关60 //load的间隔时间：其实若无动态修改的需求, 此处可改为-1，即只在启动时load一次, 此后不再load0 //resource.manager.defaultcache.size=0表示不限制cache大小macro/cps_web_combo.vm,macro/cps_web_global.vm,macro/cps_gs.vm
验证
- 修改配置后，性能大幅提升,由原来的90qps轻松飚至近300qps
经验
- 未设置file.resource.loader.cache=true时，对用户请求的每次响应都将reload一次vm资源(这与velocimacro.library.autoreload=true的效果相同)，从而严重影响性能
- 在性能测试时, 为寻找系统瓶颈, 可以对服务进行高并发打压，再取到stack进行分析
参考文献
- Velocity Developer Guide