The microservice architecture pattern solves many of the problems inherent with monolithic applications. But microservices also bring challenges of their own, one of which is figuring out what went wrong when something breaks. There are at least 3 related challenges here:

• Log collection
• Metric collection
• Distributed tracing

Log and metric collection is fairly straightforward (we'll cover these in a separate post), but only gets you so far.

Let's say your 20 microservice application starts behaving badly - you start getting timeouts on a particular API and want to find out why. The first place you look may be your centralized metrics service. This will likely confirm to you that you have a problem, as hopefully you have one or more metrics that are now showing out-of-band numbers.

But what if the issue only affects part of your user population, or worse, a single (but important) customer? In these cases your metrics - assuming you have the right ones in the first place - probably won't tell you much.

In cases like these, where you have minimal or no guidance from your configured metrics, you start trying to figure out where the problem may be. You know your system architecture, and you're pretty sure you've narrowed the issue down to three or four of your services.