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