S4 is a general-purpose, distributed, scalable, fault-tolerant, pluggable platform that allows programmers to easily develop applications for processing continuous unbounded streams of data. S4 fills the gap between complex proprietary systems and batch-oriented open source computing platforms. We aim to develop a high performance computing platform that hides the complexity inherent in parallel processing system from the application programmer. The core platform is written in Java. The implementation is modular and pluggable, and S4 applications can be easily and dynamically combined for creating more sophisticated stream processing systems. … Apache S4 (S4)