FAQ¶
For questions that are not in this list, please search in issues. https://github.com/alibaba/arthas/issues
How much impact does Arthas attach have on the performance of the original process?¶
Can commands such as trace/watch enhance the classes in jdk?¶
By default, classes beginning with java. are filtered out, but they can be turned on:
options unsafe trueSee more at options
Can arthas trace native methods¶
No.
Can arthas view the value of a variable in memory?¶
No. But you can use some tricks to intercept the object with the tt command, or fetch it from a static method.
How to filter method with the same name?¶
You can used all variables in fundamental fields in expressions for the condition express to filter method with the same name, you can use the number of parameters params.length ==1,parameter type params[0] instanceof java.lang.Integer,return value type returnObj instanceof java.util.List and so on in one or more combinations as condition express.
You can use -v to view the condition express result https://github.com/alibaba/arthas/issues/1348
example arthas-demo
watch demo.MathGame primeFactors traceE '{params,returnObj,throwExp}' -v -n 5 -x 3 'params.length >0 && returnObj instanceof java.util.List'How to watch or trace constructor?¶
watch demo.MathGame <init> '{params,returnObj,throwExp}' -v -n 5 -x 3 '1==1'java.lang.ClassFormatError: null, skywalking arthas compatible use¶
When error log appear java.lang.ClassFormatError: null, it is usually modified by other bytecode tools that are not compatible with arthas modified bytecode.
For example: use skywalking V8.1.0 below cannot trace, watch classes enhanced by skywalking agent, V8.1.0 or above is compatible, refer to skywalking configuration for more details. skywalking compatible with other javaagent bytecode processing.