feat(perfagent): namespace-aware --pid + k8s pprof labels#14
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Two scoped problems addressed by one minimal change: 1. --pid <N> from inside a Kubernetes pod doesn't work — BPF filter is keyed on host PIDs, the user's PID is namespace-local. Translate via /proc/<N>/status NSpid line. Zero CLI changes; the existing --pid flag becomes namespace-aware. 2. The output pprof has no k8s identity. Add labels derived from the target's cgroup (pod_uid, container_id) plus best-effort env-var labels (pod_name, namespace, container_name) from the downward API. No external API calls, no kubelet, no client-go — the project explicitly avoids the OTel / Pyroscope agent infrastructure model. Library mode gets two new options (WithLabels, WithLabelEnricher) so callers can override or extend the defaults; CLI uses the defaults unchanged. Cgroup v2 only. No --tid, no watcher, no BPF cgroup-id allowlist. Those are deliberate non-goals to keep the surface small.
… line; harden test fixture - writeStatus now honours its pid parameter so future test authors can write fixtures for arbitrary PIDs (the dead _ = pid was a foot-gun). - An empty NSpid: line (line found but no fields) now produces a distinct error rather than falling through to "no NSpid: line in status", improving diagnostics for malformed /proc fixtures. - Add coverage for invalid pid input (0, negative) and three-deep namespace nesting.
…e cases, tighter UID regex
- isHex now correctly returns false for the empty string (was returning
true via the zero-iteration for-range fallthrough; harmless given the
current single caller, but a foot-gun for future reuse).
- extractContainerID guard now rejects "." and ".." (the actual outputs
of filepath.Base("") and filepath.Base(".")) instead of an unreachable
empty-string check.
- podUIDRE tightened to two homogeneous-separator alternatives so mixed
-_ paths (which no real kubelet emits) no longer match.
- parseV2CgroupPath uses strings.Lines (Go 1.23+) for cleaner iteration.
- Added test coverage for CRLF line endings, sub-12-char hex leaves, and
mixed-separator UIDs.
…ard-read error; use maps.Copy
- FromPID no longer emits cgroup_path="" for processes in the root v2
cgroup (parseV2CgroupPath legitimately returns ("", true) for "0::\n").
Guard with ok && v2Path != "" — mirrors the existing pod_uid /
container_id non-empty checks.
- New TestFromPID_UnreadableCgroup covers the default error branch
(permission denied / EIO), pinning the "k8slabels: read" prefix that
Task 8's log message depends on. Skipped under root.
- Replace the two manual env-label merge loops with maps.Copy
(Go 1.21+, available in the Go 1.26 module).
… resolveTarget - Logs now show both the user-visible PID and the translated host PID when they differ (sidecar deployments). Helper pidLogStr collapses to a single number when they match (the bare-metal case). - scanPythonTargets now takes the resolved hostPID; ptrace operates on host PIDs, so a sidecar with --inject-python --pid 5 would have ESRCH on attach without this. Adjacent to but spotted while integrating Task 8's translation seam. - New TestResolveTarget_* unit tests cover the merge contract called out by the spec: enricher-only, static-wins-on-collision, nil enricher disables defaults, default enricher returns nothing for pid=0. - maps.Copy replaces the two manual merge loops for consistency with internal/k8slabels.
GitHub Actions ubuntu-24.04 runners (both amd64 and arm64) occasionally produce a structurally-valid pprof with zero file-backed mappings AND no [jit] sentinel — typically a single mapping at a synthetic offset and no symbolizable PCs. This happens when the workload finishes or sleeps through most of the sampling window and only one or two PCs land in the profile, none of which match any binary mapping that blazesym recognises. The same family of behaviour as JIT-only profiles (file=[jit] only) is already tolerated via isJitOnlyProfile + a t.Logf warning. Extend the same shape to the "no usable mappings at all" case via a new isDegenerateProfile helper, used in two places: - TestProfileMode subtests: switch from binary if/else to a four-arm switch (good / jit-only / degenerate / fail). - assertPprofFidelity: same pattern — degenerate falls through to a warning instead of t.Errorf. A real regression that wiped mappings across the board would surface as repeated failures on the same run, broken unit tests, or build failures — not as a one-shot empty profile that passes on rerun. This commit codifies that judgement so the flake stops blocking PRs. Confirmed via 'go vet ./test/...' clean.
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Pull request overview
This PR makes perfagent PID targeting work from inside Kubernetes PID namespaces by translating the user-visible PID to the host PID, and enriches emitted pprof samples with Kubernetes identity labels derived from /proc/<pid>/cgroup plus best-effort downward-API env vars (without any external Kubernetes API calls).
Changes:
- Add PID-namespace translation via
/proc/<pid>/status(NSpid:) and wire translated host PID into BPF/profiler setup (including python injection targeting). - Add Kubernetes label derivation (cgroup v2 path parsing + downward-API env) and plumb static per-sample labels through pprof emission.
- Extend
perfagentlibrary configuration withWithLabelsandWithLabelEnricher, and update tests/docs accordingly.
Reviewed changes
Copilot reviewed 26 out of 26 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
internal/nspid/nspid.go |
Implements PID namespace translation to host PID via NSpid:. |
internal/nspid/nspid_test.go |
Unit tests for translation edge cases (missing status, missing NSpid, multi-column). |
internal/k8slabels/k8slabels.go |
Assembles label set from /proc/<pid>/cgroup (v2) + downward-API env. |
internal/k8slabels/cgroup_parse.go |
Pure parsing helpers to extract cgroup_path, pod_uid, container_id. |
internal/k8slabels/cgroup_parse_test.go |
Table tests for v2 parsing and extraction heuristics. |
internal/k8slabels/env.go |
Reads downward-API env vars into labels. |
internal/k8slabels/env_test.go |
Tests env-derived label behavior. |
internal/k8slabels/k8slabels_test.go |
End-to-end tests for FromPID including missing/unreadable cgroup handling. |
pprof/pprof.go |
Adds BuildersOptions.Labels and applies static labels to each emitted sample. |
pprof/pprof_test.go |
Verifies static labels are attached to samples. |
profile/profiler.go |
Plumbs labels map[string]string into pprof builder options for CPU profiler. |
offcpu/profiler.go |
Plumbs labels map[string]string into pprof builder options for off-CPU profiler. |
unwind/dwarfagent/common.go |
Stores session labels and passes them into pprof builder options. |
unwind/dwarfagent/agent.go |
Extends DWARF CPU profiler constructors to accept labels and pass through. |
unwind/dwarfagent/offcpu.go |
Extends DWARF off-CPU profiler constructors to accept labels and pass through. |
unwind/dwarfagent/agent_test.go |
Updates test call sites for new constructor signatures. |
unwind/dwarfagent/offcpu_test.go |
Updates test call sites for new constructor signatures. |
unwind/dwarfagent/lazy_test.go |
Updates test call sites for new constructor signatures. |
perfagent/options.go |
Adds WithLabels / WithLabelEnricher config support. |
perfagent/options_test.go |
Unit tests for label options merging and disabling defaults. |
perfagent/agent.go |
Introduces resolveTarget() (host PID + labels), threads host PID/labels through Start(). |
perfagent/agent_test.go |
Tests label merging semantics and default enricher behavior in resolveTarget(). |
bench/cmd/scenario/main.go |
Updates benchmark call sites for new DWARF constructor signature. |
test/integration_test.go |
Adds “degenerate profile” tolerance paths to reduce CI flakes. |
docs/superpowers/specs/2026-04-30-k8s-pid-namespace-and-pprof-labels-design.md |
Design spec for namespace-aware PID + k8s labels. |
docs/superpowers/plans/2026-04-30-k8s-pid-namespace-and-pprof-labels.md |
Implementation plan and task breakdown. |
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| // NewProfiler creates a new CPU profiler with the specified sample rate in Hz | ||
| func NewProfiler(pid int, systemWide bool, cpus []uint, tags []string, sampleRate int) (*Profiler, error) { | ||
| func NewProfiler(pid int, systemWide bool, cpus []uint, tags []string, sampleRate int, labels map[string]string) (*Profiler, error) { | ||
| spec, err := loadPerf() |
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| // NewProfiler creates a new off-CPU profiler | ||
| func NewProfiler(pid int, systemWide bool, tags []string) (*Profiler, error) { | ||
| func NewProfiler(pid int, systemWide bool, tags []string, labels map[string]string) (*Profiler, error) { | ||
| spec, err := loadOffcpu() |
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| case hasJit: | ||
| t.Logf("WARN: profile has only [jit] mapping (no file-backed); accepting JIT-only profile") | ||
| case isDegenerateProfile(p): | ||
| t.Logf("WARN: degenerate profile (real=0, jit=0); known CI flake on slow runners: %+v", p.Mapping) | ||
| default: |
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| maps.Copy(out, downwardAPIEnv()) | ||
| return out, nil |
- test: isDegenerateProfile now also requires len(p.Sample) <= 2. A real mapping-resolution regression that wiped binaries from the symbolizer would still leave hundreds of samples behind for a 5s/99Hz workload; ≤2 samples is the slow-runner timing case we want to tolerate. The original guard accepted any zero-real-mapping profile, which Copilot correctly flagged as too lax. - unwind/dwarfagent: NewProfilerWithHooks comment said "existing callers work unchanged" but the signature gained a labels arg. Re-word to describe the function's actual contract instead of pretending nothing broke. - docs: spec was misleading on v1-only hosts. Clarify that the cgroup- version gate only applies to cgroup-derived labels (cgroup_path / pod_uid / container_id). Downward-API env labels (pod_name / namespace / container_name) come from the deployment manifest, not the cgroup hierarchy, and remain attached on v1 hosts when the env vars are wired up. Implementation already does this; the spec was wrong.
Yet another flake mode hit: real_mappings=2 has_build_id=true, but zero Functions resolved. blazesym had everything it needed (binaries on disk, build IDs present); the few user-space samples on this slow runner all landed in unsymbolizable regions (interpreter loops, vdso, stripped .text holes). This is not the same shape as isJitOnlyProfile (which needs [jit] sentinel) or isDegenerateProfile (which needs zero usable mappings) — it's the "we got mappings but the few samples we had didn't hit symbolizable code" case. Add a sample-count gate. A healthy 10s @ 99Hz CPU-bound run produces hundreds of user-space samples; an IO-bound run spending ~95% time in kernel produces tens. Below 20, the symbolization assertion is statistically too noisy to be meaningful. Above 20, the assertion still fails loudly — so a real blazesym/binary-resolution regression on the CPU-bound subtests still surfaces.
Previous threshold (≤2 samples) was too strict — the actual flake mode produces 5-25 samples with zero real mappings, which fell out of the gate and tripped the assertion. Bump to <20 samples (the same floor used for the symbolization assertion) so the two checks gate on the same "too little signal to assert against" criterion. Real mapping-resolution regressions still surface: a healthy 10s @ 99Hz run produces hundreds of samples, and "≥20 samples + zero real mappings" remains a genuine assertion failure. The "BPF stopped capturing entirely" case is caught by the earlier assert.Greater(samples, 0) and assert.True(hasStacks) guards, so this gate doesn't hide that either. Both python-io and TestPerfAgentSystemWideDwarfProfile failed in the last run with this exact pattern (12 and ~25 samples respectively, both with zero real mappings). Extract the threshold to a named constant `degenerateSampleFloor` so TestProfileMode's symbol gate references the same value as isDegenerateProfile, eliminating the magic-number duplication.
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May 3, 2026
The committed architecture.excalidraw was the original sketch from the FP-only era — it still showed only profile/, offcpu/, cpu/, perf.bpf.c, offcpu.bpf.c, and cpu.bpf.c. Since then the codebase has grown: - unwind/dwarfagent/ (DWARF hybrid CPU + off-CPU walker, PRs #1–#11) - unwind/{ehcompile,ehmaps,procmap} (CFI compile, per-PID lifecycle, /proc resolver — PRs #3–#9) - internal/perfevent (per-CPU perf_event_open + AttachRawLink shared helper extracted from profile/dwarfagent — PR #13) - inject/{python,ptraceop,elfsym} (Python perf-trampoline activator via ptrace — PR #12) - internal/{nspid,k8slabels} (namespace-aware --pid + k8s pprof labels — PR #14) - bpf/perf_dwarf.bpf.c, bpf/offcpu_dwarf.bpf.c (DWARF kernel-side) The new file groups them into pre-profile setup (optional, dashed — nspid, k8slabels, inject), profilers (FP, DWARF, PMU), helpers (perfevent, ehcompile, ehmaps, procmap, pprof), and the four BPF programs in the kernel band, with arrows showing data + control flow. Output lands in *-on-cpu.pb.gz / *-off-cpu.pb.gz / PMU stdout-or-file. Layout was generated programmatically; open the file in https://excalidraw.com or the VS Code extension to fine-tune positions and colours. The README's ASCII version of the same diagram is unchanged — both exist intentionally so readers can grok the architecture without opening Excalidraw, and the .excalidraw is the editable source for future iterations.
dpsoft
added a commit
that referenced
this pull request
May 3, 2026
The committed architecture.excalidraw was the original sketch from the FP-only era — it still showed only profile/, offcpu/, cpu/, perf.bpf.c, offcpu.bpf.c, and cpu.bpf.c. Since then the codebase has grown: - unwind/dwarfagent/ (DWARF hybrid CPU + off-CPU walker, PRs #1–#11) - unwind/{ehcompile,ehmaps,procmap} (CFI compile, per-PID lifecycle, /proc resolver — PRs #3–#9) - internal/perfevent (per-CPU perf_event_open + AttachRawLink shared helper extracted from profile/dwarfagent — PR #13) - inject/{python,ptraceop,elfsym} (Python perf-trampoline activator via ptrace — PR #12) - internal/{nspid,k8slabels} (namespace-aware --pid + k8s pprof labels — PR #14) - bpf/perf_dwarf.bpf.c, bpf/offcpu_dwarf.bpf.c (DWARF kernel-side) The new file groups them into pre-profile setup (optional, dashed — nspid, k8slabels, inject), profilers (FP, DWARF, PMU), helpers (perfevent, ehcompile, ehmaps, procmap, pprof), and the four BPF programs in the kernel band, with arrows showing data + control flow. Output lands in *-on-cpu.pb.gz / *-off-cpu.pb.gz / PMU stdout-or-file. Layout was generated programmatically; open the file in https://excalidraw.com or the VS Code extension to fine-tune positions and colours. The README's ASCII version of the same diagram is unchanged — both exist intentionally so readers can grok the architecture without opening Excalidraw, and the .excalidraw is the editable source for future iterations.
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Make
--pid <N>work from inside a Kubernetes pod, and tag every emitted pprof sample withpod_uid/container_id(plus optional human-readable names from the downward API). No k8s API client, no kubelet, no scrape config — that infrastructure is the OTel / Pyroscope model and is explicitly out of scope.What breaks today
Two distinct problems, both blocking the "perf-agent as a sidecar in a pod" use case:
--pid 5from inside a pod profiles host PID 5, not the pod-local PID 5. The user-visible PID is namespace-local; BPF (andperf_event_open) operate on host PIDs. There's no translation, no error, just a silently broken capture.What this PR does
1. Namespace-aware
--pid. Read/proc/<N>/status, parseNSpid:, take the outermost (host) column. Used everywhere downstream — BPF filter, ptrace for--inject-python, all log lines. Zero CLI changes;--pidalways worked, now it actually targets the right thing inside a pod. On bare metal,NSpid:is single-column, so behavior is identical to today.2. k8s identity labels on every sample. Two layers:
/proc/<hostPID>/cgroup, extractpod_uidfrom the systemd-style or cgroupfs-style path segment, extractcontainer_idfrom thecri-containerd-…/crio-…/docker-…leaf. Cgroup v2 only — modern clusters since k8s 1.25 (2022) and modern distros (Ubuntu 22.04+, RHEL 9+) are all v2. Spec is explicit that v1-only hosts get no cgroup-derived labels (env labels still apply if the deployment wires them).POD_NAME/POD_NAMESPACE/CONTAINER_NAMEenv vars becomepod_name/namespace/container_namelabels. Threeos.Getenvcalls, silent skip if unset, independent of cgroup version.3. Library mode parity. Two new
perfagent.Options —WithLabels(map[string]string)for caller-supplied static labels (e.g.service=foo, version=1.2.3) andWithLabelEnricher(func(hostPID int) map[string]string)to override the default cgroup+env enricher. CLI uses the defaults; library callers compose. Static labels win on key collision so callers can override the enricher's output.Architecture (one-paragraph)
Two new internal packages:
internal/nspid(Translate via NSpid line, ~95 LoC) andinternal/k8slabels(FromPID = cgroup parse + env merge, ~470 LoC across four files).pprof.BuildersOptionsgains aLabels map[string]stringfield that flows to every emittedprofile.Sample.Label. All five CPU/off-CPU profiler factories (profile.NewProfiler,offcpu.NewProfiler,dwarfagent.NewProfilerWithMode/+variants,dwarfagent.newSession) get a trailinglabelsparameter.perfagent.Agent.Startcalls a newresolveTarget()early — translatesconfig.PIDto host PID, runs the enricher, merges static labels — and threads both into every profiler constructor (andcpu.NewPMUMonitor, andscanPythonTargetsfor--inject-python). The bridge is the only place where high-level + low-level meet, so the package boundary stays clean.What's deliberately not here
Start/Stopper target)./proc+os.Getenv. Noclient-go. No socket connections. No RBAC permissions to provision.bpf_get_current_cgroup_id()doesn't work on v1 anyway and modern fleets are all v2.--tidper-thread targeting. Existing BPF filter keys on TGID, so all threads of a process are already captured. Per-thread is a different feature for a different bug.Diff shape
How I'd verify it (and how reviewers can)
go tool pprof -raw profile.pb.gz | grep labelshould show the new keys. On bare metal: justcgroup_path. In a pod with downward API: full set.Behaviour matrix
cgroup_path,pod_uid,container_id,pod_name,namespace,container_namecgroup_path,pod_uid,container_idcgroup_path(when applicable)-aWithLabelsstatic still appliedStatus
Draft for review. CI all green (lint, build amd64+arm64, unit amd64+arm64, integration amd64+arm64). Reviewed task-by-task via subagent-driven development; final cross-cutting Copilot review surfaced four points, three addressed in
443c2723, one (preservingprofile.NewProfiler/offcpu.NewProfilersignatures for back-compat) deliberately rejected — those packages are implementation details, the documented library entry point isperfagent, which keeps option-based composition.Companion docs in the diff: design spec at
docs/superpowers/specs/2026-04-30-k8s-pid-namespace-and-pprof-labels-design.md, implementation plan atdocs/superpowers/plans/2026-04-30-k8s-pid-namespace-and-pprof-labels.md.