Observability
Moving to microservices have some advantages under certain circumstances. Different teams within an organization are free to build and run them, owning them from beginning to end.
Observing a monolith and ensuring that it's working as expected is relatively easy -- as opposed to a constellation of microservices. With a monolith we have greater control of what is happening at any given time on the whole system, while losing development agility; with microservices now the challenge is how to understand the whole picture, and how a service can affect others when it's not behaving as expected.
However, while the microservices themselves have a lower complexity code-wise when looked at them independently, the challenge is now to observe the whole system, and that all components are working as expected, being able to detect anomalies as fast as possible. We have many moving targets.
Observability usually refers to the combination of the following practices:
-
Monitoring: we need to monitor all microservices, ensuring that they are running as expected with the resources that they are supposed to use. A bad deployed service could be restarting under certain code paths, monitoring allows us to better understand when is this happening.
-
Logging: since we have now a number of microservices, each one logging on its own, we need to perform logging aggregation, what allows us to send all logs from all services to a central logging service, that helps us isolate logs from different services at a given time window.
-
Tracing: now a request on a service can end up spawning a complex tree of requests between different services. By tracing these requests we can better understand what requests led to anothers, and what was the relationship between them.
-
Metrics: a microservice can expose metrics, so an external orchestrator is able to know if it needs to scale in or out a given microservice based on the demand.
Also, we have to monitor both the infrastructure (the Kubernetes cluster healthiness), as well as our applications running on top of it.