fix(metrics): bound the owner-chain climb against circular ownerReferences

[mayankpande88]

Follow-up to #298. This change was pushed to that branch in response to review feedback, but #298 was merged from c7af3d5 moments earlier, so the fix did not land on main.

Problem

resolvePodDescriptor climbs the ownership chain with no termination condition other than reaching the top:

for {
    next, err := resolver.getControllerOfOwner(current)
    ...
}

ownerReferences are client-settable, so a cycle is reachable via a buggy controller or a hand-edited ref. A cycle spins forever and wedges the resolver goroutine, stalling every metric it feeds — all container_net_tcp_*, container_net_latency_seconds, and all L7 protocol families.

This is pre-existing, not introduced by #298: the original for owner != nil was equally unbounded.

Raised by gemini-code-assist in #298 (comment).

Change

Bound the walk at maxOwnerChainDepth = 10. Genuine chains are at most two hops (Pod -> ReplicaSet -> Deployment, Pod -> Job -> CronJob), leaving headroom for nested custom controllers.

The exhaustion case is explicit rather than a bare depth < 10 loop condition, because the code after the loop cannot otherwise distinguish "reached the top of the chain" from "gave up" — a malformed chain would be cached as though it had resolved cleanly:

for depth := 0; ; depth++ {
    if depth >= maxOwnerChainDepth {
        klog.Warningf("owner chain for pod %s/%s exceeded max depth %d at %s/%s — possible circular ownerReferences", ...)
        break
    }
    ...
}

Exhausting the bound is treated as terminal, not transient: a cycle cannot be fixed by retrying, and leaving the descriptor uncached would re-walk ten levels on every scrape. The identity resolved so far is kept, and the warning names the pod and the last owner reached so a real cycle is diagnosable rather than silent.

Test

TestResolvePodDescriptor_CircularOwnerChainTerminates builds a true A→B→A cycle, runs the resolve on a goroutine and fails on a 5s timeout — so removing the bound produces a failing test rather than a silent production hang.

Full ./common/ suite passes; go vet, gofmt, GOOS=linux GOARCH=amd64 build all clean.

[gemini-code-assist]

Code Review

This pull request introduces a depth-bound limit to the Kubernetes owner reference traversal in resolvePodDescriptor to prevent infinite loops and goroutine leaks caused by circular owner references, along with a unit test to verify termination. The reviewer suggests a more robust approach to detect circular references using a map of visited UIDs instead of relying on an arbitrary depth limit, which would also allow removing the maxOwnerChainDepth constant.