Files
app/backend/fluksio/flow/metrics.py
T
stroblmeandClaude Opus 5 180da3d640 Stop paying five Redis round trips and a global lock per message
The engine was I/O-bound on its own state backend. `RedisState.lock()` is one
key — `pipeline:_lock` — for the whole process, taken five times a message at
two round trips each, and every cascade and every node read queued behind it.
Inside it, reading a node's inputs was three round trips per input (an EXISTS
for `in`, then EXISTS and GET for the value), writing was two updates that a
single transaction already gives, and the version counters went one INCR at a
time.

Replaced with the atomic command that was always available: `get_present` is
one MGET and tells a missing key from one holding null, so the lock it used to
be read under bought nothing; value and timestamp land in one `update`, which
is a MULTI/EXEC; `increment_multi` pipelines the counters. `values()` — what
every websocket snapshot calls — is two reads whatever the message count
instead of two per message.

Beside that: every webhook did its blocking XADD on the asyncio event loop
(MQTT already used `to_thread`); the per-execution `NodeOutcome` was built and
validated even with no run watching; `_minute` built a tz-aware datetime per
event on the loop thread to key a dict, and now keys on an int; `move_due`
promoted delayed items one round trip each, every second; `FLOW_MAX_CASCADES`
makes the in-flight ceiling a setting rather than a constant.

`orjson` replaces stdlib json where a message pays for it — state, the
journal, the engine side of the worker pipe. `fluksio-worker` stays
dependency-free, and the run-cache digest stays on stdlib so no stored key is
invalidated. A non-finite number now stores as `null` rather than the bare
`NaN` that was never JSON.

Measured with `scripts/bench_engine.py` against a real Redis, 200 messages:
a five-node chain went from 43.9 to 103.1 msg/s with p50 latency 2110ms →
782ms and p95 3913ms → 1439ms; one source into twenty consumers went from 5.4
to 33.7 msg/s. In memory, twenty consumers went from 187 to 448 msg/s.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BpfSinyCBfjuieikyfMPbf
2026-08-26 10:12:25 +02:00

411 lines
16 KiB
Python

"""What the engine did, kept long enough to answer for it.
The event bus already carries every execution, error and cascade; until now
nothing wrote any of it down, so "was it slow yesterday?" had no answer. This
subscriber folds those events into per-minute rollups, keeps the failures and
the audit trail whole, and records one row per cascade.
Accumulation is in memory and flushed every few seconds: a node firing at
10 Hz must not be 10 inserts a second, and the arithmetic that turns it into
one row a minute is cheaper than the round trip would be.
"""
from __future__ import annotations
import asyncio
import logging
import time
from datetime import UTC, datetime, timedelta
from typing import Any
from sqlalchemy import delete, func, update
from sqlalchemy.dialects.sqlite import insert
from sqlmodel import Session, col
from fluksio.core.config import settings
from fluksio.core.db import engine
from fluksio.flow.events import EventBus
from fluksio.models import EngineEvent, FlowRun, MetricBucket
logger = logging.getLogger(__name__)
#: How often the accumulated minute is written out.
FLUSH_INTERVAL_S = 15.0
#: A traceback is worth reading; a whole run of a chatty node is not.
DETAIL_CAP = 8000
#: A cascade still open this long after it started is never finishing.
RUN_STALE_S = 600.0
#: ``metric_minute.flow``/``node`` and ``flow_run.flow`` are this wide, and a
#: node id has no length of its own. One row over it aborts the transaction,
#: which would take every other row in the flush with it.
NAME_MAX = 255
#: How much unwritten history is held while the database is unreachable. Enough
#: for a long outage, bounded so the outage cannot become a memory leak.
HOLD_MAX = 10_000
#: Retention is checked this often, not on every flush.
PRUNE_INTERVAL_S = 3600.0
#: Bucket columns that add up over a minute, and the two that take the larger.
SUMMED = (
"executions",
"errors",
"messages",
"duration_sum_ms",
"lag_sum_ms",
"items",
)
MAXIMA = ("duration_max_ms", "lag_max_ms")
#: Engine events kept as rows. Everything else on the bus is traffic.
RECORDED = {
"flow_quarantined",
"task_crashed",
"engine_degraded",
"engine_fatal",
"cascade_dropped",
"queue_unavailable",
}
def _minute(ts: float) -> int:
"""The epoch second the minute containing ``ts`` starts at.
An integer rather than a datetime: this runs once per event on the API's
event loop, and building a tz-aware datetime to key a dict with cost more
than everything the collector does with the event afterwards. The row
still wants one, so `_write` builds it — once per minute per node rather
than once per event.
"""
return int(ts // 60) * 60
def _detail(event: dict[str, Any]) -> str:
text = str(event.get("error") or event.get("reason") or event.get("detail") or "")
if event.get("type") == "cascade_dropped":
text = f"Given up on after {event.get('deliveries')} deliveries. {text}"
return text[:DETAIL_CAP]
class MetricsCollector:
"""Folds engine events into rollups, failures and run records."""
def __init__(self, events: EventBus, flush_s: float = FLUSH_INTERVAL_S) -> None:
self._events = events
self._flush_s = flush_s
self._buckets: dict[tuple[str, str, int], dict[str, float]] = {}
self._runs: dict[str, dict[str, Any]] = {}
self._pending: list[EngineEvent] = []
# The traceback arrives one event before the failure it belongs to,
# held with the time it arrived so an unpaired one does not stay put.
self._tracebacks: dict[tuple[str, str], tuple[float, str]] = {}
self._last_prune = 0.0
# -------------------------------------------------------------------------
# The loop
# -------------------------------------------------------------------------
async def run(self) -> None:
"""Consume the bus until cancelled, flushing on a fixed interval."""
last = time.monotonic()
async with self._events.subscribe() as queue:
while True:
# A busy bus never idles, so the flush is on a deadline rather
# than on the timeout alone.
timeout = max(0.05, self._flush_s - (time.monotonic() - last))
try:
event = await asyncio.wait_for(queue.get(), timeout)
except TimeoutError:
pass
else:
try:
self.handle(event)
except Exception:
logger.exception("Could not record %s", event.get("type"))
if time.monotonic() - last >= self._flush_s:
await self.flush()
last = time.monotonic()
# -------------------------------------------------------------------------
# Accumulating
# -------------------------------------------------------------------------
def _bucket(self, event: dict[str, Any]) -> dict[str, float]:
# ponytail: one collector, one row per node per minute; coarsen the
# bucket if the node count ever reaches thousands.
key = (
str(event.get("flow") or "")[:NAME_MAX],
str(event.get("node") or "")[:NAME_MAX],
_minute(float(event.get("ts") or time.time())),
)
return self._buckets.setdefault(
key,
{
"executions": 0,
"errors": 0,
"messages": 0,
"duration_sum_ms": 0.0,
"duration_max_ms": 0.0,
"lag_sum_ms": 0.0,
"lag_max_ms": 0.0,
"items": 0,
},
)
def handle(self, event: dict[str, Any]) -> None:
"""Fold one event in. Synchronous: this is arithmetic on dicts."""
kind = str(event.get("type") or "")
ts = float(event.get("ts") or time.time())
run = self._runs.get(str(event.get("run") or ""))
if kind == "node_executed":
bucket = self._bucket(event)
bucket["executions"] += 1
bucket["messages"] += int(event.get("outputs") or 0)
duration = float(event.get("duration_ms") or 0.0)
bucket["duration_sum_ms"] += duration
bucket["duration_max_ms"] = max(bucket["duration_max_ms"], duration)
if run is not None:
run["nodes"] += 1
return
if kind == "work_latency":
bucket = self._bucket(event)
lag = float(event.get("lag_ms") or 0.0)
bucket["lag_sum_ms"] += lag
bucket["lag_max_ms"] = max(bucket["lag_max_ms"], lag)
bucket["items"] += 1
return
if kind == "node_log":
# Held for the node_error that follows it from the same thread.
if event.get("level") == "error":
key = (str(event.get("flow") or ""), str(event.get("node") or ""))
self._tracebacks[key] = (ts, str(event.get("text") or "")[:DETAIL_CAP])
return
if kind == "node_error":
self._bucket(event)["errors"] += 1
if run is not None:
run["errors"] += 1
key = (str(event.get("flow") or ""), str(event.get("node") or ""))
traceback = self._tracebacks.pop(key, (0.0, ""))[1]
error = str(event.get("error") or "")
self._pending.append(
EngineEvent(
ts=datetime.fromtimestamp(ts, UTC),
type="node_error",
flow=str(event.get("flow") or ""),
node=str(event.get("node") or ""),
detail=(f"{error}\n{traceback}" if traceback else error)[
:DETAIL_CAP
],
)
)
return
if kind == "cascade_started":
self._start_run(event, ts)
return
if kind == "cascade_finished":
if run is not None:
run["finished_at"] = datetime.fromtimestamp(ts, UTC)
run["duration_ms"] = round((ts - run["started_ts"]) * 1000, 2)
run["status"] = "error" if run["errors"] else "ok"
return
if kind == "node_health":
if event.get("health") == "down":
self._pending.append(
EngineEvent(
ts=datetime.fromtimestamp(ts, UTC),
type="node_health",
flow=str(event.get("flow") or ""),
node=str(event.get("node") or ""),
detail=_detail(event) or "Reported itself down.",
)
)
return
if kind == "audit":
self._pending.append(
EngineEvent(
ts=datetime.fromtimestamp(ts, UTC),
type="audit",
flow=str(event.get("flow") or ""),
detail=str(event.get("action") or ""),
actor=str(event.get("user") or ""),
)
)
return
if kind in RECORDED:
self._pending.append(
EngineEvent(
ts=datetime.fromtimestamp(ts, UTC),
type=kind,
flow=str(event.get("flow") or ""),
node=str(event.get("node") or event.get("task") or ""),
detail=_detail(event),
)
)
def _start_run(self, event: dict[str, Any], ts: float) -> None:
run_id = str(event.get("run") or "")
if not run_id:
return
existing = self._runs.get(run_id)
if existing is not None:
# A redelivery of the same item: one run, tried again.
existing["deliveries"] = int(event.get("deliveries") or 1)
existing["status"] = "running"
existing["finished_at"] = None
return
self._runs[run_id] = {
"id": run_id,
"flow": str(event.get("flow") or "")[:NAME_MAX],
"source": str(event.get("cause") or ""),
"started_ts": ts,
"started_at": datetime.fromtimestamp(ts, UTC),
"finished_at": None,
"status": "running",
"nodes": 0,
"errors": 0,
"duration_ms": 0.0,
"deliveries": int(event.get("deliveries") or 1),
}
# -------------------------------------------------------------------------
# Writing
# -------------------------------------------------------------------------
async def flush(self) -> None:
buckets, self._buckets = self._buckets, {}
pending, self._pending = self._pending, []
# Open runs stay in memory: their counts are still growing, and the row
# is written from the whole record each time rather than in deltas.
runs = list(self._runs.values())
prune = time.monotonic() - self._last_prune >= PRUNE_INTERVAL_S
if not (buckets or pending or runs or prune):
return
try:
await asyncio.to_thread(self._write, buckets, pending, runs, prune)
except Exception:
logger.exception("Could not write engine metrics")
self._hold(buckets, pending)
return
if prune:
self._last_prune = time.monotonic()
cutoff = time.time() - RUN_STALE_S
for run_id, run in list(self._runs.items()):
if run["status"] != "running" or run["started_ts"] < cutoff:
del self._runs[run_id]
# Held tracebacks survive the flush: the log and the failure it belongs
# to are two events, and a flush can fall between them. One per node,
# each replaced by that node's next failure — and dropped once it is
# clear the failure it was waiting for is never coming.
for key, (held, _) in list(self._tracebacks.items()):
if held < cutoff:
del self._tracebacks[key]
def _hold(
self,
buckets: dict[tuple[str, str, int], dict[str, float]],
pending: list[EngineEvent],
) -> None:
"""Take a batch the database refused back, rather than losing it.
These are the audit trail and the failures with their tracebacks — the
rows nobody can reconstruct afterwards. The batch goes in front of what
arrived since, so what a long outage drops is the oldest.
"""
for key, agg in self._buckets.items():
held = buckets.get(key)
if held is None:
buckets[key] = agg
continue
for name in SUMMED:
held[name] += agg[name]
for name in MAXIMA:
held[name] = max(held[name], agg[name])
self._buckets = buckets
# A failed commit puts the rows back to unsaved. One that got as far as
# being handed an id keeps it, and the sequence has already moved past
# it, so adding them to the next session inserts them cleanly.
self._pending[:0] = pending
for key in list(self._buckets)[: max(0, len(self._buckets) - HOLD_MAX)]:
del self._buckets[key]
del self._pending[: max(0, len(self._pending) - HOLD_MAX)]
def _write(
self,
buckets: dict[tuple[str, str, int], dict[str, float]],
pending: list[EngineEvent],
runs: list[dict[str, Any]],
prune: bool,
) -> None:
with Session(engine) as session:
for (flow, node, minute), agg in buckets.items():
statement = insert(MetricBucket).values(
flow=flow,
node=node,
bucket=datetime.fromtimestamp(minute, UTC),
**agg,
)
# The same minute is written several times, so the counters add
# and the maxima take whichever is larger. Columns are read by
# subscript: `excluded.items` is the collection's own method.
new = statement.excluded
session.execute(
statement.on_conflict_do_update(
index_elements=["flow", "node", "bucket"],
set_={
name: col(getattr(MetricBucket, name)) + new[name]
for name in SUMMED
}
| {
# `max` of two values, not the aggregate: SQLite's
# scalar form, which is what `greatest` is elsewhere.
name: func.max(col(getattr(MetricBucket, name)), new[name])
for name in MAXIMA
},
)
)
for run in runs:
values = {k: v for k, v in run.items() if k != "started_ts"}
statement = insert(FlowRun).values(**values)
session.execute(
statement.on_conflict_do_update(
index_elements=["id"],
set_={
key: statement.excluded[key]
for key in values
if key != "id"
},
)
)
session.add_all(pending)
if prune:
self._prune(session)
session.commit()
def _prune(self, session: Session) -> None:
now = datetime.now(UTC)
cutoff = now - timedelta(days=settings.OBS_RETENTION_DAYS)
session.execute(delete(MetricBucket).where(col(MetricBucket.bucket) < cutoff))
session.execute(delete(EngineEvent).where(col(EngineEvent.ts) < cutoff))
session.execute(delete(FlowRun).where(col(FlowRun.started_at) < cutoff))
# A run still open long after it started did not finish; saying so is
# more honest than leaving it running forever.
session.execute(
update(FlowRun)
.where(
col(FlowRun.status) == "running",
col(FlowRun.started_at) < now - timedelta(seconds=RUN_STALE_S),
)
.values(status="abandoned", finished_at=now)
)