arthas

## Arthas

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`Arthas` is a Java Diagnostic tool open sourced by Alibaba.

Arthas allows developers to troubleshoot production issues for Java applications without modifying code or restarting servers.

[中文说明/Chinese Documentation](README_CN.md)

### Background

Often times, the production system network is inaccessible from the local development environment. If issues are encountered in production systems, it is impossible to use IDEs to debug the application remotely. More importantly, debugging in production environment is unacceptable, as it will suspend all the threads, resulting in the suspension of business services. 

Developers could always try to reproduce the same issue on the test/staging environment. However, this is tricky as some issues cannot be reproduced easily on a different environment, or even disappear once restarted. 

And if you're thinking of adding some logs to your code to help troubleshoot the issue, you will have to go through the following lifecycle; test, staging, and then to production. Time is money! This approach is inefficient! Besides, the issue may not be reproducible once the JVM is restarted, as described above.

Arthas was built to solve these issues. A developer can troubleshoot your production issues on-the-fly. No JVM restart, no additional code changes. Arthas works as an observer, which will never suspend your existing threads.

### Key features

* Check whether a class is loaded, or where the class is being loaded. (Useful for troubleshooting jar file conflicts)
* Decompile a class to ensure the code is running as expected.
* View classloader statistics, e.g. the number of classloaders, the number of classes loaded per classloader, the classloader hierarchy, possible classloader leaks, etc.
* View the method invocation details, e.g. method parameter, return object, thrown exception, and etc.
* Check the stack trace of specified method invocation