refactor(ttp): extract RuleIndex from RuleEngine

E.3.9.0 prerequisite for the per-source lifters (E.3.9-E.3.13). The
dispatch index, install/evict/apply_change atomic-swap protocol, and
state-modulation helpers (is_active / apply_ceiling) move out of
rule_engine.py into _rule_index.py and _state.py. RuleEngine wraps a
RuleIndex; back-compat shims preserve _by_kind / _by_rule / _install
attribute access for tests poking at the dispatch internals.

Lifters in E.3.9-E.3.12 will each hold their own RuleIndex, watching
the same RuleStore via subscribe_changes() fan-out. Hot-reload
semantics (disable / clip / TTL via set_state API) now reach
lifter-bound rules through the same atomic-swap path the engine uses,
not a future composite-rebuild compromise.
This commit is contained in:
2026-05-01 20:09:18 -04:00
parent b819dfefa3
commit e7531ee756
4 changed files with 579 additions and 101 deletions

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@@ -0,0 +1,180 @@
"""Hot-swappable rule registry shared by RuleEngine and per-source lifters.
The dispatch index originally lived inline on
:class:`~decnet.ttp.impl.rule_engine.RuleEngine`. E.3.9 adds four
per-source lifters that need the same install / evict / state-restamp
atomic-swap protocol; pulling it into one helper keeps the contract
single-sourced.
Atomicity invariant (TTP_TAGGING.md §"Atomic swap" / E.2.14b): a rule
sitting in the index must never be torn mid-evaluate. Mutations
replace dict entries with fresh lists / fresh
:class:`~decnet.ttp.impl.rule_engine.CompiledRule` tuples — never
in-place edits. Single dict assignments are GIL-atomic to readers.
"""
from __future__ import annotations
from collections.abc import Callable, Iterable
from typing import TYPE_CHECKING
from decnet.logging import get_logger
if TYPE_CHECKING:
from decnet.ttp.impl.rule_engine import CompiledRule
from decnet.ttp.store.base import RuleChange, RuleStore
_log = get_logger("ttp.index")
class RuleIndex:
"""Owns ``rule_id -> CompiledRule`` plus a ``source_kind -> [rules]`` index.
Consumers:
* :class:`RuleEngine` — uses :meth:`by_kind` to dispatch evaluate().
* Per-source lifters (E.3.9E.3.13) — use :meth:`get` and
:meth:`values` to consume rules they own (filtered via the
``predicate`` passed to :meth:`watch`).
"""
def __init__(self) -> None:
# source_kind -> list of compiled rules that claim it.
self._by_kind: dict[str, list["CompiledRule"]] = {}
# rule_id -> compiled rule (mirror; used for state restamp).
self._by_rule: dict[str, "CompiledRule"] = {}
# ── Read API ────────────────────────────────────────────────────
def by_kind(self, source_kind: str) -> list["CompiledRule"]:
return self._by_kind.get(source_kind, [])
def get(self, rule_id: str) -> "CompiledRule | None":
return self._by_rule.get(rule_id)
def values(self) -> Iterable["CompiledRule"]:
return self._by_rule.values()
# ── Mutation API (atomic-swap) ──────────────────────────────────
def install(self, rule: "CompiledRule") -> None:
"""Atomic-swap install of one compiled rule.
Empty ``applies_to`` AND empty ``emits`` is the deletion sentinel
used by both store backends — drop the rule from the index
instead of registering a no-op entry.
"""
if not rule.applies_to and not rule.emits:
self.evict(rule.rule_id)
return
self._by_rule[rule.rule_id] = rule
for kind in rule.applies_to:
current = self._by_kind.get(kind, [])
replaced = [r for r in current if r.rule_id != rule.rule_id]
replaced.append(rule)
# Single dict assignment — GIL-atomic to readers.
self._by_kind[kind] = replaced
def evict(self, rule_id: str) -> None:
existing = self._by_rule.pop(rule_id, None)
if existing is None:
return
for kind in existing.applies_to:
current = self._by_kind.get(kind, [])
replaced = [r for r in current if r.rule_id != rule_id]
self._by_kind[kind] = replaced
def apply_change(
self, change: "RuleChange", state_cls: type
) -> None:
"""Apply one :class:`RuleChange` to the index.
``state_cls`` is :class:`RuleState`; passed in to avoid a
runtime-circular import — the store package imports from this
one transitively.
"""
from decnet.ttp.impl.rule_engine import CompiledRule # noqa: PLC0415
if change.change_kind == "definition":
value = change.new_value
if isinstance(value, CompiledRule):
self.install(value)
return
# state change
existing = self._by_rule.get(change.rule_id)
if existing is None or not isinstance(change.new_value, state_cls):
return
new_state = change.new_value
# NamedTuple._replace returns a fresh frozen tuple — single
# dict assignment swaps it in atomically.
restamped = existing._replace(state=new_state) # type: ignore[arg-type]
self._by_rule[change.rule_id] = restamped
for kind in restamped.applies_to:
current = self._by_kind.get(kind, [])
replaced = [r for r in current if r.rule_id != change.rule_id]
replaced.append(restamped)
self._by_kind[kind] = replaced
# ── Lifecycle ───────────────────────────────────────────────────
async def hydrate_from(
self,
store: "RuleStore",
predicate: Callable[["CompiledRule"], bool] | None = None,
) -> None:
"""Load every compiled rule from *store* and install matching ones.
``predicate`` filters; engine omits it (installs everything),
lifters pass a ``match.kind`` prefix check.
"""
compiled = await store.load_compiled()
for rule in compiled:
if predicate is not None and not predicate(rule):
continue
self.install(rule)
async def watch(
self,
store: "RuleStore",
predicate: Callable[["CompiledRule"], bool] | None = None,
) -> None:
"""Hydrate once + drain ``subscribe_changes`` forever.
Cancellation-safe: an :class:`asyncio.CancelledError` from the
outer task propagates cleanly. Per-change application errors
log and continue — one bad rule edit must not stall the stream.
"""
from decnet.ttp.store.base import RuleState # noqa: PLC0415
await self.hydrate_from(store, predicate=predicate)
async for change in store.subscribe_changes():
if predicate is not None:
# For state changes the value is a RuleState (no
# match_spec to inspect); always apply when the rule
# is already in the index, otherwise skip.
if change.change_kind == "state":
if change.rule_id not in self._by_rule:
continue
else:
value = change.new_value
# Definition changes carry a CompiledRule; skip
# ones the predicate doesn't claim. A previously-
# owned rule whose YAML moved out of our ownership
# gets evicted explicitly.
from decnet.ttp.impl.rule_engine import ( # noqa: PLC0415
CompiledRule,
)
if isinstance(value, CompiledRule) and not predicate(value):
if change.rule_id in self._by_rule:
self.evict(change.rule_id)
continue
try:
self.apply_change(change, RuleState)
except Exception: # noqa: BLE001
_log.exception(
"ttp.index: rule change apply failed rule_id=%s",
change.rule_id,
)
__all__ = ["RuleIndex"]

55
decnet/ttp/impl/_state.py Normal file
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@@ -0,0 +1,55 @@
"""Shared state-modulation helpers for rule consumers.
Both :class:`~decnet.ttp.impl.rule_engine.RuleEngine` and the per-source
lifters (E.3.9 onward) read :class:`~decnet.ttp.store.base.RuleState`
the same way: skip on ``disabled``, defense-in-depth re-check
``expires_at``, clamp confidence on ``clipped``. Single source of truth
so a future change to the state contract lands in one place.
"""
from __future__ import annotations
from datetime import datetime, timezone
from typing import TYPE_CHECKING
if TYPE_CHECKING:
from decnet.ttp.store.base import RuleState
def is_active(state: "RuleState") -> bool:
"""Return ``True`` iff a rule with this state is allowed to fire.
``disabled`` rules never fire. ``clipped`` rules still fire — the
clip caps emitted confidence, doesn't suppress the emit. Expired
states act as ``disabled`` even though the store auto-reverts; the
re-check here is defense-in-depth against a racing read between
expiry and the store's revert pass.
"""
if state.state == "disabled":
return False
if state.expires_at is not None:
expires = state.expires_at
if expires.tzinfo is None:
expires = expires.replace(tzinfo=timezone.utc)
if expires < datetime.now(tz=timezone.utc):
return False
return True
def apply_ceiling(base: float, state: "RuleState") -> float:
"""Apply the operator's confidence ceiling, downward only.
A ``clipped`` state with ``confidence_max < 1.0`` clamps the emitted
confidence to ``min(base, base * ceiling)``. Any other state is a
no-op. The clamp is downward by construction — operator clips can
never raise a rule's confidence above its YAML-declared base, per
TTP_TAGGING.md §"Confidence model".
"""
if state.state != "clipped":
return base
ceiling = state.confidence_max
if ceiling is None or ceiling >= 1.0:
return base
return min(base, base * ceiling)
__all__ = ["is_active", "apply_ceiling"]

View File

@@ -37,6 +37,8 @@ from pydantic import BaseModel, Field
from decnet import telemetry as _telemetry
from decnet.logging import get_logger
from decnet.ttp.base import TaggerEvent
from decnet.ttp.impl._rule_index import RuleIndex
from decnet.ttp.impl._state import apply_ceiling, is_active
from decnet.web.db.models.ttp import TTPTag, compute_tag_uuid
if TYPE_CHECKING:
@@ -163,14 +165,27 @@ class RuleEngine:
def __init__(self, store: "RuleStore") -> None:
self._store = store
# ``source_kind`` → list of compiled rules that claim it.
# Replaced wholesale on per-rule changes via watch_store(); the
# GIL-atomic dict assignment is the "atomic swap" pin from
# TTP_TAGGING.md §"Atomic swap" / E.2.14b.
self._by_kind: dict[str, list[CompiledRule]] = {}
# Mirror keyed by rule_id for definition+state restamping.
# Same atomicity contract: replacement, never in-place mutation.
self._by_rule: dict[str, CompiledRule] = {}
# Dispatch index extracted to RuleIndex so per-source lifters
# (E.3.9E.3.13) reuse the same atomic-swap protocol. Legacy
# ``_by_kind`` / ``_by_rule`` properties below proxy to it for
# callers (and tests) that still poke the dispatch index directly.
self._index = RuleIndex()
@property
def _by_kind(self) -> dict[str, list[CompiledRule]]:
return self._index._by_kind
@_by_kind.setter
def _by_kind(self, value: dict[str, list[CompiledRule]]) -> None:
self._index._by_kind = value
@property
def _by_rule(self) -> dict[str, CompiledRule]:
return self._index._by_rule
@_by_rule.setter
def _by_rule(self, value: dict[str, CompiledRule]) -> None:
self._index._by_rule = value
async def evaluate(self, event: TaggerEvent) -> list[TTPTag]:
"""Return zero or more tags produced by rules matching *event*.
@@ -184,7 +199,7 @@ class RuleEngine:
states, but the engine double-checks ``expires_at`` as
defense-in-depth.
"""
rules = self._by_kind.get(event.source_kind, [])
rules = self._index.by_kind(event.source_kind)
if not rules:
return []
with _span(
@@ -198,101 +213,31 @@ class RuleEngine:
async def watch_store(self) -> None:
"""Subscribe to per-rule changes and atomically swap them in.
Loads the initial corpus from :meth:`RuleStore.load_compiled`,
builds the dispatch index, then drains
:meth:`RuleStore.subscribe_changes` forever. Each ``definition``
change replaces the affected rule wholesale; each ``state``
change re-stamps the existing :class:`CompiledRule`'s ``state``
field via NamedTuple ``_replace`` (single dict assignment, no
in-place mutation).
Delegates to :meth:`RuleIndex.watch`: loads the initial corpus
from :meth:`RuleStore.load_compiled`, builds the dispatch
index, then drains :meth:`RuleStore.subscribe_changes` forever.
Each ``definition`` change replaces the affected rule wholesale;
each ``state`` change re-stamps the existing
:class:`CompiledRule`'s ``state`` field via NamedTuple
``_replace`` (single dict assignment, no in-place mutation).
"""
# Forward import — avoids the contract-phase circular shape
# dependency captured by the TYPE_CHECKING block above.
from decnet.ttp.store.base import RuleState # noqa: PLC0415
compiled = await self._store.load_compiled()
for rule in compiled:
self._install(rule)
async for change in self._store.subscribe_changes():
try:
self._apply_change(change, RuleState)
except Exception: # noqa: BLE001
_log.exception(
"ttp.engine: rule change apply failed rule_id=%s",
change.rule_id,
)
await self._index.watch(self._store)
# ── Internals ───────────────────────────────────────────────────
# Back-compat shims — the dispatch-index protocol moved into
# :class:`RuleIndex`. Existing callers / tests that poke at
# ``_install`` / ``_evict`` / ``_apply_change`` keep working.
def _install(self, rule: CompiledRule) -> None:
"""Atomic-swap install of one compiled rule.
Empty ``applies_to`` + empty ``emits`` is the deletion sentinel
used by both backends — drop the rule from the index instead of
adding a no-op entry.
"""
if not rule.applies_to and not rule.emits:
self._evict(rule.rule_id)
return
self._by_rule[rule.rule_id] = rule
for kind in rule.applies_to:
current = self._by_kind.get(kind, [])
replaced = [r for r in current if r.rule_id != rule.rule_id]
replaced.append(rule)
# Single dict assignment — GIL-atomic to readers.
self._by_kind[kind] = replaced
self._index.install(rule)
def _evict(self, rule_id: str) -> None:
existing = self._by_rule.pop(rule_id, None)
if existing is None:
return
for kind in existing.applies_to:
current = self._by_kind.get(kind, [])
replaced = [r for r in current if r.rule_id != rule_id]
self._by_kind[kind] = replaced
self._index.evict(rule_id)
def _apply_change(
self, change: "RuleChange", state_cls: type,
) -> None:
if change.change_kind == "definition":
value = change.new_value
if isinstance(value, CompiledRule):
self._install(value)
return
# state change
existing = self._by_rule.get(change.rule_id)
if existing is None or not isinstance(change.new_value, state_cls):
return
new_state = change.new_value # narrowed by isinstance above
# NamedTuple._replace returns a fresh frozen tuple — single
# dict assignment swaps it in atomically.
restamped = existing._replace(state=new_state) # type: ignore[arg-type]
self._by_rule[change.rule_id] = restamped
for kind in restamped.applies_to:
current = self._by_kind.get(kind, [])
replaced = [r for r in current if r.rule_id != change.rule_id]
replaced.append(restamped)
self._by_kind[kind] = replaced
def _state_active(state: "RuleState") -> bool:
"""A rule fires iff its state isn't ``disabled``. ``clipped`` rules
still fire — the clip caps confidence, doesn't suppress.
"""
if state.state == "disabled":
return False
if state.expires_at is not None:
# Defense-in-depth: stores auto-revert expired states, but a
# racing read between expiry and revert must not fire a rule
# the operator told us was off.
from datetime import datetime, timezone # noqa: PLC0415
expires = state.expires_at
if expires.tzinfo is None:
expires = expires.replace(tzinfo=timezone.utc)
if expires < datetime.now(tz=timezone.utc):
return False
return True
self._index.apply_change(change, state_cls)
def _match_event(rule: CompiledRule, event: TaggerEvent) -> bool:
@@ -350,16 +295,10 @@ def _evaluate_rules(
) -> list[TTPTag]:
out: list[TTPTag] = []
for rule in rules:
if not _state_active(rule.state):
if not is_active(rule.state):
continue
if not _match_event(rule, event):
continue
ceiling = (
rule.state.confidence_max
if rule.state.state == "clipped"
and rule.state.confidence_max is not None
else 1.0
)
with _span(
"ttp.rule.fire",
rule_id=rule.rule_id,
@@ -371,7 +310,7 @@ def _evaluate_rules(
span.set_attribute("technique_id", technique_id)
except (TypeError, ValueError):
pass
confidence = min(base_conf, base_conf * ceiling) if ceiling < 1.0 else base_conf
confidence = apply_ceiling(base_conf, rule.state)
tag_uuid = compute_tag_uuid(
source_kind=event.source_kind,
source_id=event.source_id,

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@@ -0,0 +1,304 @@
"""Unit tests for :class:`decnet.ttp.impl._rule_index.RuleIndex`.
The dispatch index was extracted from :class:`RuleEngine` so the four
per-source lifters (E.3.9E.3.13) can reuse the install / evict /
state-restamp atomic-swap protocol. These tests pin the contract
independently of the engine — a future regression in the engine
shouldn't be the only signal that the shared helper broke.
"""
from __future__ import annotations
import asyncio
from collections.abc import AsyncIterator
from datetime import datetime, timedelta, timezone
from typing import Any
import pytest
from decnet.ttp.impl._rule_index import RuleIndex
from decnet.ttp.impl.rule_engine import CompiledRule
from decnet.ttp.store.base import RuleChange, RuleState
def _rule(
rule_id: str = "R0001",
*,
rule_version: int = 1,
applies_to: frozenset[str] = frozenset({"command"}),
state: RuleState | None = None,
emits: tuple[tuple[str, str | None, str, float], ...] = (
("T1110", None, "TA0006", 0.85),
),
) -> CompiledRule:
return CompiledRule(
rule_id=rule_id,
rule_version=rule_version,
name="test",
applies_to=applies_to,
match_spec={"pattern": "x"},
emits=emits,
evidence_fields=(),
state=state if state is not None else RuleState(),
)
def test_install_and_lookup() -> None:
idx = RuleIndex()
rule = _rule()
idx.install(rule)
assert idx.get("R0001") is rule
assert idx.by_kind("command") == [rule]
assert idx.by_kind("email") == []
def test_install_replaces_same_rule_id() -> None:
idx = RuleIndex()
idx.install(_rule(rule_version=1))
idx.install(_rule(rule_version=2))
bucket = idx.by_kind("command")
assert len(bucket) == 1
assert bucket[0].rule_version == 2
def test_install_deletion_sentinel_evicts() -> None:
idx = RuleIndex()
idx.install(_rule())
sentinel = CompiledRule(
rule_id="R0001",
rule_version=1,
name="",
applies_to=frozenset(),
match_spec={},
emits=(),
evidence_fields=(),
state=RuleState(),
)
idx.install(sentinel)
assert idx.get("R0001") is None
assert idx.by_kind("command") == []
def test_evict_unknown_is_noop() -> None:
idx = RuleIndex()
idx.evict("R_NOPE") # must not raise
def test_apply_change_definition_installs() -> None:
idx = RuleIndex()
rule = _rule()
idx.apply_change(
RuleChange(change_kind="definition", rule_id="R0001", new_value=rule),
RuleState,
)
assert idx.get("R0001") is rule
def test_apply_change_state_restamps_atomically() -> None:
idx = RuleIndex()
idx.install(_rule())
new_state = RuleState(state="clipped", confidence_max=0.5)
idx.apply_change(
RuleChange(change_kind="state", rule_id="R0001", new_value=new_state),
RuleState,
)
restamped = idx.get("R0001")
assert restamped is not None
assert restamped.state == new_state
bucket = idx.by_kind("command")
assert len(bucket) == 1
assert bucket[0].state.confidence_max == 0.5
def test_apply_state_change_for_unknown_rule_is_noop() -> None:
idx = RuleIndex()
idx.apply_change(
RuleChange(
change_kind="state",
rule_id="R_GHOST",
new_value=RuleState(state="disabled"),
),
RuleState,
)
assert idx.get("R_GHOST") is None
# ── Hydrate / watch via stub store ──────────────────────────────────
class _StubStore:
def __init__(
self,
compiled: list[CompiledRule] | None = None,
changes: list[RuleChange] | None = None,
) -> None:
self._compiled = compiled or []
self._changes = changes or []
async def load_compiled(self) -> list[CompiledRule]:
return list(self._compiled)
async def get_state(self, _rule_id: str) -> RuleState:
return RuleState()
async def set_state(self, *_a: Any, **_kw: Any) -> None:
return None
def subscribe_changes(self) -> AsyncIterator[RuleChange]:
changes = list(self._changes)
async def _gen() -> AsyncIterator[RuleChange]:
for change in changes:
yield change
return _gen()
def test_hydrate_from_installs_all() -> None:
idx = RuleIndex()
a = _rule("R_A")
b = _rule("R_B", applies_to=frozenset({"email"}))
store = _StubStore(compiled=[a, b])
asyncio.run(idx.hydrate_from(store))
assert idx.get("R_A") is a
assert idx.get("R_B") is b
def test_hydrate_predicate_filters() -> None:
idx = RuleIndex()
a = _rule("R_A") # match.kind defaults to {"pattern": "x"}
b = _rule("R_B")
store = _StubStore(compiled=[a, b])
asyncio.run(
idx.hydrate_from(store, predicate=lambda r: r.rule_id == "R_A")
)
assert idx.get("R_A") is a
assert idx.get("R_B") is None
def test_watch_drains_definition_changes() -> None:
idx = RuleIndex()
a = _rule("R_A")
b = _rule("R_B", applies_to=frozenset({"email"}))
store = _StubStore(
compiled=[],
changes=[
RuleChange(change_kind="definition", rule_id="R_A", new_value=a),
RuleChange(change_kind="definition", rule_id="R_B", new_value=b),
],
)
asyncio.run(idx.watch(store))
assert idx.get("R_A") is a
assert idx.get("R_B") is b
def test_watch_predicate_evicts_unowned_definition_changes() -> None:
"""A rule whose YAML moves out of our predicate's claim set must be
evicted from the index, not silently retained.
"""
idx = RuleIndex()
owned = _rule("R_A")
unowned = _rule("R_B")
idx.install(owned)
idx.install(unowned)
# Predicate now only owns R_A; R_B's incoming definition update
# should evict it.
new_b = _rule("R_B", rule_version=2)
store = _StubStore(
compiled=[],
changes=[
RuleChange(
change_kind="definition", rule_id="R_B", new_value=new_b,
),
],
)
asyncio.run(idx.watch(store, predicate=lambda r: r.rule_id == "R_A"))
assert idx.get("R_A") is owned
assert idx.get("R_B") is None
def test_watch_state_change_for_owned_rule_applies() -> None:
idx = RuleIndex()
idx.install(_rule("R_A"))
new_state = RuleState(state="disabled")
store = _StubStore(
compiled=[],
changes=[
RuleChange(
change_kind="state", rule_id="R_A", new_value=new_state,
),
],
)
asyncio.run(idx.watch(store, predicate=lambda r: r.rule_id == "R_A"))
restamped = idx.get("R_A")
assert restamped is not None
assert restamped.state.state == "disabled"
def test_watch_state_change_for_unowned_rule_skipped() -> None:
idx = RuleIndex()
# R_B was never installed (predicate excluded it). State change
# for R_B must NOT install a phantom entry.
store = _StubStore(
compiled=[],
changes=[
RuleChange(
change_kind="state",
rule_id="R_B",
new_value=RuleState(state="disabled"),
),
],
)
asyncio.run(idx.watch(store, predicate=lambda r: r.rule_id == "R_A"))
assert idx.get("R_B") is None
def test_apply_change_continues_on_error(caplog: pytest.LogCaptureFixture) -> None:
"""A single bad change must not stall the watch loop."""
idx = RuleIndex()
# Force an exception by passing the wrong value type for definition.
bad = RuleChange(
change_kind="definition",
rule_id="R_BAD",
new_value=RuleState(), # wrong type — apply_change ignores silently
)
good = _rule("R_GOOD")
store = _StubStore(
compiled=[],
changes=[
bad,
RuleChange(
change_kind="definition", rule_id="R_GOOD", new_value=good,
),
],
)
asyncio.run(idx.watch(store))
assert idx.get("R_GOOD") is good
assert idx.get("R_BAD") is None
def test_expired_state_treated_as_disabled_by_is_active() -> None:
"""Sanity check on the helper used by both engine and lifters."""
from decnet.ttp.impl._state import is_active
expired = RuleState(
state="enabled",
expires_at=datetime.now(timezone.utc) - timedelta(seconds=1),
)
assert is_active(expired) is False
fresh = RuleState(
state="enabled",
expires_at=datetime.now(timezone.utc) + timedelta(hours=1),
)
assert is_active(fresh) is True
def test_apply_ceiling_only_clamps_clipped() -> None:
from decnet.ttp.impl._state import apply_ceiling
enabled = RuleState(state="enabled", confidence_max=0.5)
assert apply_ceiling(0.9, enabled) == 0.9 # ceiling ignored unless clipped
clipped = RuleState(state="clipped", confidence_max=0.5)
assert apply_ceiling(0.9, clipped) == pytest.approx(0.45)
clipped_no_max = RuleState(state="clipped", confidence_max=None)
assert apply_ceiling(0.9, clipped_no_max) == 0.9