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fix(go): take a heap snapshot, not a 30-second delta #130

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blue4209211 merged 1 commit into from
Sep 19, 2026
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fix(go): take a heap snapshot, not a 30-second delta #130

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15 changes: 11 additions & 4 deletions internal/agent/profiler/go_pprof.go
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Original file line number Diff line number Diff line change
Expand Up @@ -82,10 +82,17 @@ func (p *GoPprofProfiler) Invoke(job *job.ProfilingJob) (error, time.Duration) {
func (p *goPprofManager) heapProfile(job *job.ProfilingJob, port string, fileName string) error {
var out bytes.Buffer
var stderr bytes.Buffer
targetURL := fmt.Sprintf(
"http://127.0.0.1:%s/debug/pprof/%s?seconds=%d",
port, "heap", int(job.Interval.Seconds()),
)
// A heap profile is a snapshot of what the process is holding right now, so
// it takes no duration. Passing ?seconds= makes Go return a DELTA over that
// window instead — it samples, waits, samples again and subtracts — which
// nets to nothing whenever the heap is steady. That is how a 30s "heap
// profile" of a healthy service arrives as `Total samples = 0` with an
// empty flamegraph.
//
// ?gc=1 runs a collection first so the snapshot describes live memory
// rather than whatever the last GC cycle happened to leave behind; without
// it a process that has not GC'd yet reports nothing at all.
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targetURL := fmt.Sprintf("http://127.0.0.1:%s/debug/pprof/heap?gc=1", port)
// for local testing
// cmd := exec.Command(
// "curl", targetURL, "-o", fileName,
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