Chapter 1. Introducing event streams
Figure 1.1. The precision on the timestamps varies a little, but you can see that all four of these events are discrete, recordable occurrences that take place in the physical or digital worlds (or both).
Figure 1.2. Anatomy of a continuous event stream: time is progressing left to right, and individual events are ordered within this time frame. Note that the event stream is unterminated; it can extend in both directions beyond our ability to process it.
Figure 1.3. An application is running on two servers, with each application instance generating log messages. The log messages are written (rotated) to disk before being collected and forwarded to a systems-monitoring or log-file-analysis tool.
Figure 1.4. A JavaScript tracking tag sends visitors’ interactions with a website to Universal Analytics. This event stream is made available for analysis from within the Google Analytics user interface.
Figure 1.5. Google Analytics is recording a real-time stream of events generated by website visitors. At the bottom right, you can see the counts of views of individual web pages in the last 30 minutes.
Figure 1.6. NSQ pub/sub is facilitating communication between App 1, which is publishing messages into a single Topic 1, and Apps 2 and 3, which are each subscribing to receive messages from Topic 1.
(try again in a couple of minutes)