anti
ba448bae13
Root cause of 'No python processes found in process <pid>': py-spy needs per-release ABI knowledge and 0.4.1 (latest PyPI) predates 3.14. Wrapper now detects the interpreter and points users at pyinstrument/memray/cProfile.
77 lines
2.4 KiB
Markdown
77 lines
2.4 KiB
Markdown
# DECNET Profiling
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Five complementary lenses. Pick whichever answers the question you have.
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## 1. Whole-process sampling — py-spy
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> **Note:** py-spy 0.4.1 (latest on PyPI as of 2026-04) does **not** yet support
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> Python 3.14, which DECNET currently runs on. Attaching fails with
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> *"No python processes found in process <pid>"* even when uvicorn is clearly
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> running. Use lenses 2–5 until upstream ships 3.14 support
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> (track https://github.com/benfred/py-spy/releases). The wrapper script aborts
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> with a clear message when it detects 3.14+.
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Attach to a running API and record a flamegraph for 30s. Requires `sudo`
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(Linux ptrace scope).
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```bash
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./scripts/profile/pyspy-attach.sh # auto-finds uvicorn pid
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sudo py-spy record -o profile.svg -p <PID> -d 30 --subprocesses
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```
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Other common failure modes (when py-spy *does* support your Python):
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- Attached to the Typer CLI PID, not the uvicorn worker PID (use `pgrep -f 'uvicorn decnet.web.api'`).
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- `kernel.yama.ptrace_scope=1` — run with `sudo` or `sudo sysctl kernel.yama.ptrace_scope=0`.
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- The API isn't actually running (a `--dry-run` deploy starts nothing).
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## 2. Per-request flamegraphs — Pyinstrument
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Set the env flag, hit endpoints, find HTML flamegraphs under `./profiles/`.
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```bash
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DECNET_PROFILE_REQUESTS=true decnet deploy --mode unihost --deckies 1
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# in another shell:
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curl http://127.0.0.1:8000/api/v1/health
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open profiles/*.html
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```
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Off by default — zero overhead when the flag is unset.
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## 3. Deterministic call graph — cProfile + snakeviz
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For one-shot profiling of CLI commands or scripts.
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```bash
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./scripts/profile/cprofile-cli.sh services # profiles `decnet services`
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snakeviz profiles/cprofile.prof
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```
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## 4. Micro-benchmarks — pytest-benchmark
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Regression-gate repository hot paths.
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```bash
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pytest -m bench tests/perf/ -n0 # SQLite backend (default)
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DECNET_DB_TYPE=mysql pytest -m bench tests/perf/ -n0
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```
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Note: `-n0` disables xdist. `pytest-benchmark` refuses to measure under
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parallel workers, which is the project default (`-n logical --dist loadscope`).
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## 5. Memory allocation — memray
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Hunt leaks and allocation hot spots in the API / workers.
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```bash
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./scripts/profile/memray-api.sh # runs uvicorn under memray
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memray flamegraph profiles/memray.bin
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```
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## Load generation
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Pair any of the in-process lenses (2, 5) with Locust for realistic traffic:
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```bash
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pytest -m stress tests/stress/
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```
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