What metrics were collected from the applications? How did you work with monitoring?

To monitor Java applications, the following metrics are usually collected:

• CPU and memory usage (heap, non-heap)
• Response time and request count (throughput)
• Error and exception counts
• Garbage collector metrics (GC pause time, frequency)
• Thread metrics (active threads, thread states)
• Database metrics (latency, connection count)

Tools like Prometheus + Grafana, Elastic Stack, or specialized APM systems (New Relic, AppDynamics) are often used for collecting and visualizing metrics.

Monitoring work includes:

• Setting up metric exporters (e.g., Micrometer for Spring Boot)
• Creating dashboards to track key indicators
• Setting alerts for critical metrics (e.g., high error percentage or increased response time)
• Log analysis and tracing to identify causes of issues

An example of setting up a simple metric validator with Micrometer:

@Bean
public MeterRegistryCustomizer<MeterRegistry> metricsCommonTags() {
    return registry -> registry.config().commonTags("application", "myApp");
}