vmtool¶
@since 3.5.1
vmtool
online tutorial
vmtool
uses the JVMTI
to support getInstances
in jvm and forceGc
.
getInstances¶
$ vmtool --action getInstances --className java.lang.String --limit 10
@String[][
@String[com/taobao/arthas/core/shell/session/Session],
@String[com.taobao.arthas.core.shell.session.Session],
@String[com/taobao/arthas/core/shell/session/Session],
@String[com/taobao/arthas/core/shell/session/Session],
@String[com/taobao/arthas/core/shell/session/Session.class],
@String[com/taobao/arthas/core/shell/session/Session.class],
@String[com/taobao/arthas/core/shell/session/Session.class],
@String[com/],
@String[java/util/concurrent/ConcurrentHashMap$ValueIterator],
@String[java/util/concurrent/locks/LockSupport],
]
Through the
--limit
parameter, you can limit the number of return values to avoid pressure on the JVM when obtaining large data. The default value of limit is 10.
Specify classloader name¶
vmtool --action getInstances --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader --className org.springframework.context.ApplicationContext
Specify classloader hash¶
The classloader that loads the class can be found through the sc
command.
$ sc -d org.springframework.context.ApplicationContext
class-info org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext
code-source file:/private/tmp/demo-arthas-spring-boot.jar!/BOOT-INF/lib/spring-boot-1.5.13.RELEASE.jar!/
name org.springframework.boot.context.embedded.AnnotationConfigEmbeddedWebApplicationContext
...
class-loader +-org.springframework.boot.loader.LaunchedURLClassLoader@19469ea2
+-sun.misc.Launcher$AppClassLoader@75b84c92
+-sun.misc.Launcher$ExtClassLoader@4f023edb
classLoaderHash 19469ea2
Then use the -c
/--classloader
parameter to specify:
vmtool --action getInstances -c 19469ea2 --className org.springframework.context.ApplicationContext
Specify the number of expanded layers of returned results¶
The return result of the
getInstances
action is bound to theinstances
variable, which is an array.
The expansion level of the result can be specified by the
-x
/--expand
parameter, the default value is 1.
vmtool --action getInstances -c 19469ea2 --className org.springframework.context.ApplicationContext -x 2
Execute expression¶
The return result of the
getInstances
action is bound to theinstances
variable, which is an array. The specified expression can be executed through the--express
parameter.
vmtool --action getInstances --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader --className org.springframework.context.ApplicationContext --express'instances[0].getBeanDefinitionNames()'