[ai-assisted=yes] Emit disk read/write operation counts

[ivan-asenchakarov-sys]

Adds system_disk_{system,ephemeral,persistent}_{read,write}_count gauges alongside the existing byte-throughput gauges.

There's currently no IOPS metric, only bytes/sec. gopsutil's disk.IOCountersStat already returns ReadCount/WriteCount per device; the collector just wasn't reading them.

Testing Done

• Extended the existing collector and Prometheus-sender unit tests with the new fields/gauges.
• Deployed to a real foundation across 3 different services, replacing the stock release via a runtime-config override. New counts landed live and increased over time:

Instance	system_disk_persistent_read_count	system_disk_persistent_write_count
VM 1	482	473
VM 2	363	179 → 348 → 456 → 511
VM 3	163	342 → 425 → 425

Also checked the system/ephemeral disk gauges on VM 1, all live and moving:

Metric	Values
system_disk_system_read_count	3780 → 3893
system_disk_system_write_count	1513 → 1721 → 1938 → 2148 → 2240
system_disk_ephemeral_read_count	86
system_disk_ephemeral_write_count	3875 → 4120 → 4315 → 4520 → 4618

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: ivan-asenchakarov-sys / name: ic005077 (2274b04)

[jorbaum]

Thanks for contributing. LGTM in general. Once you have signed the CLA we can go forward with this.

go test currently fails:

go test ./...
...
  [FAILED] Expected
      <int>: 144
  to equal
      <int>: 126
  In [It] at: /Users/myuser/Workspace/public/cloudfoundry/system-metrics-release/src/cmd/system-metrics-agent/app/system_metrics_agent_test.go:122 @ 09/15/26 08:07:49.52

AFAICS /tmp/expected-metrics in scripts/integration-tests.sh also needs your new metrics.

Please also disclose AI usage (if any).

[ivan-asenchakarov-sys]

Thanks @jorbaum , I have addressed your comment.
I have also added a ai-assisted=yes in the title

[ay901246]

Just need to sign the CLA; small nit is that you may want to remove the TNZ ticket title since it's not technically relevant to open source.

[ivan-asenchakarov-sys]

@ay901246 thanks, I have removed the ticket from the title

[jorbaum]

Thanks. LGTM.

Ah. One last thing: The documentation at https://github.com/cloudfoundry/system-metrics-release/blob/main/docs/system-metrics-agent.md is missing the new metrics. it looks to me like you need to add them there as well.

[ivan-asenchakarov-sys]

@jorbaum I added to docs, thank you.

[jorbaum]

LGTM

[ivan-asenchakarov-sys]

Hey @jorbaum what needs to be done now so a GH release is made with this?