We now have a pretty good idea about what the HotROD application does, if not exactly how it does it. For example, why does the frontend service call the /customer endpoint of the customer service? Of course, we can look at the source code, but we are trying to approach this from the point of view of application monitoring. One direction we could take is to look at the logs the application writes to its standard output (Figure 2.7).
Figure 2.7: Typical logging output
It is quite difficult to follow the application logic from these logs and we are only looking at the logs when a single request was executed by the application.
We are also lucky that the logs from four different microservices are combined in a more-or-less consistent stream. Imagine many concurrent requests going through the system and through microservices running in different processes! The logs would become nearly useless in that case. So, let's take a different approach. Let's view the logs collected by...