system-metrics: `jvm.gc.promotion` does not yield data

[imRentable]

Hello,

we use the Kamon system-metrics library in two of our projects with two different exporters InfluxDb as well as Prometheus. In both cases we do not see any data for the above mentioned metric. However, we do see in the exported jvm.memory.pool.used metrics that data gets allocated to the tenured-gen pool which represents the old generation. Therefore, I think we should see data in the jvm.gc.promotion metric. Please correct me if I am wrong.

Versions we use:

Project 1:

kamon-core: 2.1.4 kamon-prometheus: 2.1.4 kamon-system-metrics: 2.1.4

Project 2:

kamon-core: 2.1.4 kamon-influxdb: 2.1.4 kamon-system-metrics: 2.1.4

[ivantopo]

Hey there!

Could you please tell me what Java versions were you using and if you had any GC-specific arguments when starting them?

[imRentable]

Hi,

on both services java -version yields

openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.2+9)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.2+9, mixed mode)

They use the following flags:

Service 1

• XX:MaxRAMPercentage=80
• XX:InitialRAMPercentage=60
• -Dscala.control.noTraceSuppression=true

Service 2

• XX:MaxRAMPercentage=80
• XX:InitialRAMPercentage=60

Both services are running inside a container within separate Kubernetes pods.