不多说，直接上干货！
一切来源于官网
http://kafka.apache.org/documentation/
Website Activity Tracking
网站活动追踪
The original use case for Kafka was to be able to rebuild a user activity tracking pipeline as a set of real-time publish-subscribe feeds. This means site activity (page views, searches, or other actions users may take) is published to central topics with one topic per activity type. These feeds are available for subscription for a range of use cases including real-time processing, real-time monitoring, and loading into Hadoop or offline data warehousing systems for offline processing and reporting.
kafka原本的使用场景：用户的活动追踪，网站的活动（网页游览，搜索或其他用户的操作信息）发布到不同的话题中心，
这些消息可实时处理，实时监测，也可加载到Hadoop或离线处理数据仓库。
Activity tracking is often very high volume as many activity messages are generated for each user page view.
每个用户页面视图都会产生非常高的量。