Monitoring is key when microservice-based systems are deployed on a production environment. You need a monitoring system in place that captures different metrics such as health services, request and response monitoring, circuit breakers, CPU/RAM/storage, hardware monitoring, security, and all different metrics.

We need a system that consistently sends all information, a collector that collects this information and makes it available for consumption, and a visualization tool that shows collected information in a meaningful way. You can also add a notification tool that generates alerts.

Spring Boot provides health data and other metrics using Spring Boot Actuator. Moreover, a micrometer is also included in Spring Boot 2's Actuator and is also back ported to older Spring Boot versions with the addition of dependencies. Micrometer is SLF4J of metrics, a dimensional-first metrics collection facade. As per the Spring documentation, the autoconfigured Spring Boot 2 application provides:

Memory and CPU metrics:

Processing statistics—threads, classes—loaded or unloaded

Memory statistics—cache, buffer pools and so on

Garbage Collection Statistics

Web Server Usages—Jetty, Tomcat and so on

Connection Pool, Data Source statistics or message broker connection statistics

Request latencies

Logging and other monitoring information like up time and so on

You can add/remove metrics by changing configuration. Hystrix streams would also add the request/response and circuit breaker metrics. As an exercise, you may wish to add DB and other stuff to metrics once done with the current implementation at the end of this chapter.

Now, we can discuss the metrics collector and the UI dashboard. We used Netflix Turbine and Hystrix Dashboard for the Hystrix stream combiner/collection and the UI dashboard respectively in previous editions of this book. Hystrix Dashboard was deprecated in 2018. We'll use new tools, Prometheus and Grafana, in this edition as the collector and monitoring dashboard for both health/system metrics and Hystrix.