Pylive: On-The-Fly Code Change For Python-Based Online Services

Python is becoming a popular language for building online web services in many companies. To improve online service robustness, this paper presents a new framework, called PYLIVE, to enable on-the-fly code change. PYLIVE leverages the unique language features of Python, meta-object protocol and dynamic typing, to support dynamic logging, profiling and bug-fixing without restarting online services. PYLIVE requires no modification to the underlying runtime systems (i.e., Python interpreters), making it easy to be adopted by online services with little portability concern.We evaluated PYLIVE with seven Python-based web applications that are widely used for online services. From these applications, we collected 20 existing real-world cases, including bugs, performance issues and patches for evaluation. PYLIVE can help resolve all the cases by providing dynamic logging, profiling and patching with little overhead. Additionally, PYLIVE also helped diagnose two new performance issues in two widely-used open-source applications.