Fix I/O stats showing 0/0 on cgroup v2 hosts - #375
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The Docker stats API reports the blkio operation as "Read"/"Write" under cgroup v1 but lowercase "read"/"write" under cgroup v2. ReadIO compared the op with a case-sensitive equality, so on cgroup v2 hosts neither branch matched and every container reported 0/0 for IO read/write. Compare the op case-insensitively with strings.EqualFold so the values are populated correctly on both cgroup v1 and v2.
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Problem
On cgroup v2 hosts, every container's IO column shows
0 / 0regardless of actual disk activity, whiledocker statsreports correct Block I/O for the same containers.Cause
The Docker stats API reports the blkio operation name differently between cgroup versions:
"Read"/"Write"(capitalized)"read"/"write"(lowercase)ReadIOinconnector/collector/docker.gocomparedblk.Opwith case-sensitive equality (== "Read"/== "Write"), so on cgroup v2 neither branch ever matches and the read/write totals stay at zero.Raw API sample from a cgroup v2 host (
io_service_bytes_recursive):{ "major": 259, "minor": 0, "op": "read", "value": 4096 } { "major": 259, "minor": 0, "op": "write", "value": 1781760 }Fix
Compare the operation case-insensitively with
strings.EqualFold, so the values populate correctly on both cgroup v1 and v2. No behavior change on cgroup v1.Testing
Verified on a Docker 27.5.1 host with cgroup v2 (systemd driver). After the change, ctop's IO read/write match
docker statsBlock I/O for the same containers.