S4 is a general-purpose, distributed, scalable, partially 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.
S4 was released by Yahoo! Inc. in October 2010 under the Open Source Apache 2.0 license, which allows the user of the software the freedom to use the software for any purpose, to distribute it, to modify it, and to distribute modified versions of the software, under the terms of the license.