Rongsong Shen
06135954ff
Pre-existing uncommitted work: ha-repl-hardening payload data plane (7.x), heartbeat liveness fix (Req 1.3), connection-reuse ASAN fixes, doc cleanup. New: ha-consistency-invariants umbrella (requirements/design/research) and its four implementation sub-specs (specs generated via batch, cross-spec review applied), steering roadmap + product.md Raft+CP decision.
52 lines
2.2 KiB
Markdown
52 lines
2.2 KiB
Markdown
# P1-2: Host Resource Requirement Select — Investigation
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## Status
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- **C layer (P1-2a): COMPLETE** — `eval_select_simple` wired in `xce_select.c`
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(PEG grammar → AST → CSE, memoized eval). Scheduler integration (Phase 6) done.
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See `src/docs/resreq-ast-cse-design.md` for architecture reference.
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- **Go bridge (P1-2b): PENDING** — `EvalSelectForHost` remains a stub returning
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`errNoCGO`. CGO boundary, resource value lookup from in-memory store, and
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`FilterHostByResReqSelect` are still to implement.
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---
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## Background
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The `select` field in an LSF-style resource requirement string (e.g.
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`select[mem>4096 && type==X86_64]`) filters candidate hosts before slot
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allocation. Currently `EvalSelectForHost` is a no-CGO stub that always returns
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`errNoCGO`.
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The full feature requires two layers:
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1. **C parser + evaluator** — parse the boolean select expression into an
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AST and evaluate it against a host's resource values.
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2. **Go bridge** — call the C evaluator via CGO and wire it into
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`FilterHostByResReqSelect` in the controllers layer.
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---
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## Sub-tasks
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### #11 P1-2a: C select expression parser (PEG + eval) ✓ COMPLETE
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**Files implemented:**
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- `include/resreq.h` — expression-tree types, enums, `extern` declarations.
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- `lib/xce_select.peg` — PEG grammar for select boolean expressions.
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- `lib/xce_select.c` — `parse_select()`, `eval_select_simple()`, CSE tree.
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- `lib/meson.build` — `xce_select.peg` in build.
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### #12 P1-2b: Go EvalSelectForHost + FilterHostByResReqSelect (remaining)
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**Files to touch:**
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- `backend/clib.go` — Implement `EvalSelectForHost(hostname, selectExpr string) error`
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using `cgo.Handle` for callback context; add `#include "resreq.h"`, extern C
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declarations, `xce_select_destroy` helper.
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- `controllers/hosts.go` — Implement `FilterHostByResReqSelect(hosts []models.HostInfo, expr string)`,
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update `preCheckHostRequest()` limit from 4094 → 1024 bytes.
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**Open questions:**
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- Does `EvalSelectForHost` look up live resource values from the in-memory
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store, or are values passed directly from C?
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- `cgo.Handle` usage pattern — per-call or session-level?
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- Input validation: max expression length (1024 bytes), allowed characters.
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