cluster/health_overview: report high disk usage in health reports

[bharathv]

With this change the cluster health report has the following additions

• A list of nodes that exceed storage alert thresholds
• Overall health is marked unhealthy if there are any nodes that exceed ^^ reports

This came out of an incident where it was hard to tell which nodes were running out of disk since we didn’t have access to metrics. When a node starts running low on disk, it tends to cause weird issues, so it’s better to surface that in the cluster health reporting.

A follow-up will be to surface this in rpk (that needs a change in a different repo, so it’ll be handled separately).

Fixes: https://redpandadata.atlassian.net/browse/INC-1048

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v25.3.x
• v25.2.x
• v25.1.x

Release Notes

Features

• Cluster health report now includes node IDs of nodes that exceed the disk usage reporting thresholds.

[Copilot]

Pull request overview

This PR adds disk usage alerting to cluster health reports by identifying and reporting nodes that exceed storage alert thresholds. When any node has high disk usage, the cluster is marked as unhealthy with a new high_disk_usage_nodes field containing the affected node IDs.

Key Changes:

• Added high_disk_usage_nodes field to cluster health overview reporting
• Cluster health is marked unhealthy when nodes exceed disk usage thresholds
• Updated health monitoring backend to check disk alerts and populate the new field

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/v/cluster/health_monitor_types.h	Added high_disk_usage_nodes vector field to store node IDs exceeding disk thresholds
src/v/cluster/health_monitor_backend.cc	Implemented disk alert checking logic and population of high disk usage nodes list
src/v/cluster/health_monitor_types.cc	Updated output operator to include high disk usage nodes in formatted output
src/v/redpanda/admin/server.cc	Exposed high_disk_usage_nodes field in admin API response
src/v/redpanda/admin/api-doc/cluster.json	Added API documentation for new high_disk_usage_nodes field
tests/rptest/tests/cluster_health_overview_test.py	Added test coverage for disk usage alert reporting functionality

[Copilot]

The type should be "integer" instead of "int" to conform to JSON Schema specification. JSON Schema does not recognize "int" as a valid type keyword.

[vbotbuildovich]

Retry command for Build#78485

please wait until all jobs are finished before running the slash command

/ci-repeat 1
skip-redpanda-build
skip-units
skip-rebase
tests/rptest/tests/nodes_decommissioning_test.py::NodesDecommissioningTest.test_multiple_decommissions@{"cloud_topic":true}

[vbotbuildovich]

CI test results

test results on build#78485

test_class	test_method	test_arguments	test_kind	job_url	test_status	passed	reason	test_history
MountUnmountIcebergTest	test_simple_remount	{"cloud_storage_type": 1}	integration	https://buildkite.com/redpanda/redpanda/builds/78485#019b81af-e6c9-4c17-bfd2-8a6697ccb643	FLAKY	10/11	Test PASSES after retries.No significant increase in flaky rate(baseline=0.1957, p0=1.0000, reject_threshold=0.0100. adj_baseline=0.4796, p1=0.0015, trust_threshold=0.5000)	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=MountUnmountIcebergTest&test_method=test_simple_remount
NodesDecommissioningTest	test_multiple_decommissions	{"cloud_topic": true}	integration	https://buildkite.com/redpanda/redpanda/builds/78485#019b81af-e6d1-4148-bb64-60a77fe49527	FAIL	0/1		https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=NodesDecommissioningTest&test_method=test_multiple_decommissions

[bharathv]

Unrelated failures (cloud topics)

[vbotbuildovich]

/backport v25.3.x