LocalAI [bot] a4e6e01e4d fix(process): give backend workers a parent-death safety net (#10639) ...

* fix(grpc): self-terminate backend workers when LocalAI dies non-gracefully

Symptom: a backend model-worker subprocess (the per-model gRPC server LocalAI
spawns) can be orphaned and linger — holding VRAM and its listen port — if the
LocalAI process is killed non-gracefully (e.g. a supervisor's graceful-shutdown
grace period elapses and LocalAI is SIGKILLed) before its own teardown runs.

Root cause: LocalAI's graceful teardown (pkg/signals/handler.go installs the
SIGINT/SIGTERM handler; core/cli/run.go registers app.Shutdown ->
ModelLoader.StopAllGRPC -> process.Stop in pkg/model/process.go) only runs when
LocalAI receives a catchable signal and survives long enough to run its
handlers. Backends are spawned via github.com/mudler/go-processmanager v0.1.1,
whose getSysProcAttr() sets Setpgid:true (own process group, so the group can be
signalled) but never PR_SET_PDEATHSIG/Pdeathsig, and exposes no Config field or
option for a caller to inject/extend SysProcAttr. LocalAI fully delegates
spawning to that library (it never builds the exec.Cmd itself), so it cannot set
a kernel parent-death signal at the spawn site. If LocalAI is SIGKILLed, nothing
tells the backend to exit and it is reparented to init.

Fix: add a best-effort, backend-side safety net at the one shared choke point
every out-of-process Go backend routes through — grpc.StartServer / RunServer in
pkg/grpc. On startup it captures getppid() and polls; when the process is
reparented (getppid changes / becomes 1 — the standard POSIX signal the original
parent died) it logs and self-terminates. getppid() reparent detection is
portable (Linux + macOS), unlike Linux-only PR_SET_PDEATHSIG. Toggle via
LOCALAI_BACKEND_PARENT_WATCH (default on; off on Windows) and
LOCALAI_BACKEND_PARENT_WATCH_INTERVAL. This is strictly a backstop alongside the
existing graceful SIGTERM->grace->SIGKILL teardown, which is unchanged.

Scope/limitations: covers Go-based backends (everything using pkg/grpc). The
C++ backends (e.g. llama-cpp) and Python backends do not route through
pkg/grpc and are not covered by this mechanism — they would each need an
equivalent parent-death check (follow-up). The fully general fix is for
go-processmanager to expose SysProcAttr injection so LocalAI can set Pdeathsig
at spawn for every backend regardless of language (suggested upstream follow-up;
out of scope for this LocalAI-only PR).

Test: pkg/grpc/parentwatch_test.go builds a real test -> middle -> grandchild
process tree, lets the middle process exit to orphan the grandchild running the
real watchParentDeath, and asserts it detects the reparent and self-terminates.
Unix-only (build-tagged), runs in CI (Linux).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

* fix(process): extend parent-death backstop to C++ and Python backends

The Go parent-death watcher (pkg/grpc/parentwatch.go, commit 772b435d5)
only protects backends that route through pkg/grpc. C++ and Python
backends don't, so the originally-reported case — the llama.cpp gRPC
worker surviving a non-graceful LocalAI death — was still uncovered.

Extend the same best-effort backstop to both languages, reusing the
exact mechanism and semantics:

- capture getppid() at startup, skip if already orphaned (<=1)
- a background thread polls getppid() and self-exits on reparenting
  (getppid() != orig || == 1), portable across Linux/macOS, no-op on
  Windows
- same env vars: LOCALAI_BACKEND_PARENT_WATCH (default on; falsy
  false/0/no/off disable) and LOCALAI_BACKEND_PARENT_WATCH_INTERVAL
  (default 2s; accepts Go-style durations like 500ms/2s/1m)

C++: implemented in backend/cpp/llama-cpp (the reported, most-used C++
backend) as a dependency-free header parent_watch.h, wired into
grpc-server.cpp's main() and copied at build time via prepare.sh. C++
backends have no shared server scaffolding, so other C++ backends
(ds4, ik-llama-cpp, privacy-filter, ...) are not yet covered and would
each need the same one-line include+call as follow-ups.

Python: implemented once in the shared common/parent_watch.py and armed
from common/grpc_auth.py's get_auth_interceptors() — the single helper
every one of the 35 Python backends invokes while building its gRPC
server — so all Python backends (and future ones) are covered with no
per-backend edits and no duplicated implementation.

Tests (real process-tree reparent detection, mirroring the Go test):
- backend/cpp/llama-cpp/parent_watch_test.cpp (via run-unit-tests.sh)
- backend/python/common/parent_watch_test.py (python -m unittest)

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

---------

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

2026-07-02 19:16:48 +02:00

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