Files
app/backend/fluksio/flow/nodes/mqtt.py
T
stroblmeandClaude Opus 5 da528340a9 Cut the round trips a message costs the engine
Measured with `make bench-engine` against a real Redis: 103.6 -> 164.4
messages a second on a five-node chain (p50 latency 2125 -> 1171 ms) and
34.8 -> 63.2 on a fan-out of twenty. Against the memory backend, which is
what a pip install runs on, 262 -> 626.

The two that bought most of it:

- `StateBackend.record` puts a published value, its timestamp, its series
  and its version counter in one round trip. They were four calls building
  four pipelines, and a value crossing an edge pays them twice. A released
  rate-limit hold rides along instead of a DEL per port.
- the readiness check reads a node's inputs and hands them to the node,
  rather than reading the triggering ones to count them and having the node
  read the same keys again a moment later.

`apply_outputs` was a second copy of `_record_outputs` and is now the same
code plus the event that distinguishes it.

The rest, each small:

- `_derive` builds a node-by-id map and a `consumes` index, so dispatching
  an item and publishing a value stop scanning every node in the
  installation.
- `read_all` is memoised against the store revision — it sits on the
  publish path, so a dashboard slider was reading and validating every
  flow file per value. Same mechanism `_wiring` already uses.
- the `message_value` source block is built once per node instead of per
  emission.
- both timer threads ask the queue to promote only when something is
  actually due, which takes an idle engine from ~4 Redis round trips a
  second to one.
- the shared httpx client is bounded (32 connections, one retry); its
  default pool is 100 with no per-host cap, so one slow endpoint could
  take it and every other sender node with it.
- the MQTT and delay nodes no longer log a line per message at INFO.

Robustness, in the same pass:

- `MemoryWorkQueue._done` was a set nothing ever removed from — one entry
  per non-idempotent node per item, for the life of the process, in the
  default configuration. Capped, the way the Redis side expires its
  markers.
- a saturated engine can claim from the due lane past the cascade limit.
  The capacity gate sits in front of the claim, so the due lane's priority
  — decided inside it — did not apply while every slot was held: a motor's
  stop was not behind the long nodes, it was unread. Only after a slot has
  genuinely failed to free for half a second, and briefly, so the backlog
  is not starved in turn.
- `reclaim_stale` dispatches through that same gate. It could return sixty
  entries and push in-flight far past the limit the gate exists to hold.
- a flow's nodes are stopped together rather than one after another. Each
  gets `NODE_STOP_TIMEOUT`, so a flow whose broker was unreachable took
  five seconds per node — long enough to outlast `REBUILD_WAIT` and 503
  the deploy.
- the worker pool and the HTTP client are closed on a thread, not on the
  event loop, and a run closes the state backend it built (on Redis, a
  client and a connection pool per run).
- the five background tasks say something when they die. Each catches
  exceptions inside its loop, so one raised anywhere else left the engine
  serving with no metrics, no alerts or no artifact sweep, silently.

`tests/flow/test_round_trips.py` counts the state operations one message
costs — four, where it was about eleven — because none of the above would
fail a behavioural test if it were undone.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M6hPWS6YEbT1P8LxhhFb2T
2026-08-29 19:58:39 +02:00

702 lines
26 KiB
Python

"""MQTT nodes: a subscriber that wakes the graph, a publisher that speaks for it."""
from __future__ import annotations
import asyncio
import json
import logging
from collections.abc import Iterable
from enum import Enum
from typing import TYPE_CHECKING, Any
from pydantic import BaseModel, ConfigDict, Field
from fluksio.flow.messages import MessageSpec
from fluksio.flow.nodes.base import Node
if TYPE_CHECKING:
from fastapi import FastAPI
logger = logging.getLogger(__name__)
def _aiomqtt() -> Any:
"""The client library, which is a `fluksio[server]` extra.
Imported per use rather than at module level, because the node type is
registered at boot and an installation that talks to no broker should not
have to carry the library to start.
"""
try:
import aiomqtt
except ImportError:
raise RuntimeError(
"the mqtt node needs the server extra: pip install 'fluksio[server]'"
) from None
return aiomqtt
def topic_matches(filter_: str, topic: str) -> bool:
"""Does an MQTT topic filter cover this topic?
The broker already decided to send it, so this is only about which port it
belongs to. ``+`` stands for one level, ``#`` for the rest of them; a
filter with neither is an exact string, which is the common case and the
one the caller checks first.
"""
if filter_ == topic:
return True
parts = filter_.split("/")
levels = topic.split("/")
for i, part in enumerate(parts):
if part == "#":
# Everything before it already matched, and '#' takes the rest —
# including nothing at all, so 'a/#' covers 'a' as the spec says.
return True
if i >= len(levels):
return False
if part != "+" and part != levels[i]:
return False
return len(parts) == len(levels)
class MqttNode(Node):
"""
MQTT node that can act as a subscriber (trigger) or publisher (sender).
This node integrates with an MQTT broker to either:
- **Trigger mode (Subscriber)**: Subscribe to MQTT topics and inject received
messages into the pipeline. Used when ``provides`` is specified but
``requires`` is empty.
- **Sender mode (Publisher)**: Publish pipeline data to MQTT topics. Used when
``requires`` is specified.
The ``topic`` parameter in ``params`` controls the mapping between pipeline
message names and MQTT topics:
- **dict**: Explicit mapping from message name to MQTT topic, e.g.
``{"temperature": "sensors/room1/temp", "humidity": "sensors/room1/hum"}``.
- **str** (legacy): A single topic string. All messages are mapped to this
one topic (subscriber receives from it, publisher sends to it).
:param requires: Messages required by this node (makes it a publisher node).
:type requires: MessageSpec | list[MessageSpec] | None
:param provides: Messages provided by this node (makes it a subscriber node).
:type provides: MessageSpec | list[MessageSpec] | None
:param params: Parameters dict containing:
- ``topic`` (str | dict): MQTT topic(s). A dict maps message names to
individual topics. A plain string uses that topic for all messages.
- ``broker_host`` (str): MQTT broker hostname (default: "localhost")
- ``broker_port`` (int): MQTT broker port (default: 1883)
- ``username`` (str | None): Optional username for authentication
- ``password`` (str | None): Optional password for authentication
- ``client_id`` (str | None): Optional client ID
- ``qos`` (int): Quality of Service level 0, 1, or 2 (default: 0)
- ``retain`` (bool): Retain flag for published messages (default: False)
- ``keepalive`` (int): Keepalive interval in seconds (default: 60)
- ``timeout`` (float): Deadline for a broker operation in seconds
(default: 10.0)
- ``publish_queue_size`` (int): Publisher backlog depth (default: 256)
:type params: dict
:param name: Optional name for the node.
:type name: str | None
:raises ValueError: If both ``requires`` and ``provides`` are empty.
:example:
Subscriber with per-message topics:
>>> subscriber = MqttNode(
... provides=[
... MessageSpec(name="inverter_input", dtype=DType.FLOAT),
... MessageSpec(name="inverter_output", dtype=DType.FLOAT),
... ],
... params={
... "topic": {
... "inverter_input": "sensors/pv",
... "inverter_output": "sensors/output",
... },
... "broker_host": "localhost",
... },
... )
Publisher with per-message topics:
>>> publisher = MqttNode(
... requires=[
... MessageSpec(name="target_temp", dtype=DType.FLOAT),
... MessageSpec(name="fan_speed", dtype=DType.INT),
... ],
... params={
... "topic": {
... "target_temp": "actuators/hvac/temp",
... "fan_speed": "actuators/hvac/fan",
... },
... "broker_host": "localhost",
... "qos": 1,
... },
... )
Legacy single-topic subscriber:
>>> subscriber = MqttNode(
... provides=[MessageSpec(name="temperature", dtype=DType.FLOAT)],
... params={"topic": "sensors/temperature", "broker_host": "localhost"},
... )
"""
class Mode(Enum):
"""Operating mode of the MQTT node."""
SUBSCRIBER = "subscriber" # Receives MQTT messages (trigger)
PUBLISHER = "publisher" # Sends MQTT messages (sender)
# Publishing again is a second command to whatever is listening.
idempotent = False
__slots__ = (
"topics",
"mode",
"broker_host",
"broker_port",
"username",
"password",
"client_id",
"qos",
"retain",
"keepalive",
"timeout",
"publish_queue_size",
"json_keys",
"_topic_to_ports",
"_wildcards",
"_subscription_task",
"_mqtt_client",
"_stop_event",
"_publish_queue",
"_publisher_task",
"_loop",
)
class Params(BaseModel):
model_config = ConfigDict(extra="allow")
# One topic for every port, or a per-port mapping.
topic: str | dict[str, str] = "*"
broker_host: str = "localhost"
broker_port: int = 1883
username: str | None = None
password: str | None = Field(default=None, json_schema_extra={"x-secret": True})
client_id: str | None = None
qos: int = 0
retain: bool = False
keepalive: int = 60
# Bounds every broker operation: subscribe, publish, and the
# disconnect acknowledgement on the way out. Without one a client
# whose socket died waits for that ack forever, and the task never
# finishes unwinding. Brokers differ, so it is per node.
timeout: float = Field(
default=10.0,
gt=0,
description="Give up on a broker operation after this many seconds.",
)
# Deep enough to ride out a broker hiccup, shallow enough that a
# publisher which cannot keep up drops old values instead of growing
# without bound. A node that bursts wants more than one that trickles.
publish_queue_size: int = Field(
default=256,
gt=0,
description=(
"How many payloads may wait for the broker. Past this the oldest "
"is dropped and the node reports degraded."
),
)
# Which key to lift out of a JSON object payload. A device that wraps
# its reading — Victron's ``{"value": 5}`` — is otherwise a Python node
# per port. One key for every port, or a per-port mapping.
json_key: str | dict[str, str] = ""
@classmethod
def instance_key(cls, params: dict[str, Any]) -> str | None:
"""The broker and topic, which is one physical thing.
A publisher and a subscriber on the same topic get the same key on
purpose: they are two ends of one wire, and drawing them as one neuron
is the only way the path through the broker shows up at all.
"""
# ponytail: publisher and subscriber merge into one neuron; key on mode
# as well if the two directions ever need telling apart.
fields = cls.Params.model_fields
topic = params.get("topic", fields["topic"].default)
if isinstance(topic, dict):
topic = json.dumps(topic, sort_keys=True)
host = params.get("broker_host", fields["broker_host"].default)
port = params.get("broker_port", fields["broker_port"].default)
return f"{host}:{port}/{topic}"
def __init__(
self,
requires: MessageSpec | Iterable[MessageSpec] = (),
provides: MessageSpec | Iterable[MessageSpec] = (),
params: dict[str, Any] | None = None,
name: str | None = None,
):
cfg = self.Params.model_validate(params or {})
requires = Node._normalize_ports(requires)
provides = Node._normalize_ports(provides)
if not requires and not provides:
raise ValueError(
"An MQTT node needs either inputs (to publish) or outputs "
"(to subscribe)"
)
# Inputs mean this node publishes; outputs mean it subscribes.
self.mode = MqttNode.Mode.PUBLISHER if requires else MqttNode.Mode.SUBSCRIBER
ports = provides if self.mode == MqttNode.Mode.SUBSCRIBER else requires
if isinstance(cfg.topic, dict):
self.topics: dict[str, str] = dict(cfg.topic)
else:
self.topics = {spec.port: cfg.topic for spec in ports}
# Reverse lookup for routing incoming payloads back to ports. A filter
# holding a wildcard cannot be found by the incoming topic, so those
# are kept aside and walked when the exact lookup misses.
self._topic_to_ports: dict[str, list[str]] = {}
for port, topic in self.topics.items():
self._topic_to_ports.setdefault(topic, []).append(port)
self._wildcards = [t for t in self._topic_to_ports if "+" in t or "#" in t]
if isinstance(cfg.json_key, dict):
self.json_keys: dict[str, str] = dict(cfg.json_key)
else:
self.json_keys = (
{spec.port: cfg.json_key for spec in ports} if cfg.json_key else {}
)
self.broker_host = cfg.broker_host
self.broker_port = cfg.broker_port
self.username = cfg.username
self.password = cfg.password
self.client_id = cfg.client_id
self.qos = cfg.qos
self.retain = cfg.retain
self.keepalive = cfg.keepalive
self.timeout = cfg.timeout
self.publish_queue_size = cfg.publish_queue_size
# Runtime state
self._subscription_task: asyncio.Task[None] | None = None
self._mqtt_client = None
self._stop_event: asyncio.Event | None = None
self._publish_queue: asyncio.Queue[dict[str, Any]] | None = None
self._publisher_task: asyncio.Task[None] | None = None
self._loop: asyncio.AbstractEventLoop | None = None
# Set default name based on mode and topics
if name is None:
unique_topics = set(self.topics.values())
if len(unique_topics) == 1:
safe_topic = (
next(iter(unique_topics))
.replace("/", "_")
.replace("+", "x")
.replace("#", "all")
.strip("_")
)
else:
safe_topic = f"{len(unique_topics)}topics"
name = f"mqtt_{self.mode.value}_{safe_topic}"
# Initialize parent with appropriate function
# For subscriber mode, f is a no-op since data is injected via inject()
# For publisher mode, f handles the outgoing MQTT publish
super().__init__(
f=(
self._noop_subscriber
if self.mode == MqttNode.Mode.SUBSCRIBER
else self._publisher_handler
),
requires=requires,
provides=provides,
params=params,
name=name,
)
@staticmethod
def _noop_subscriber(
params: dict[str, Any], **kwargs: Any
) -> dict[str, Any] | None:
"""
No-op function for subscriber mode nodes.
Subscriber mode nodes inject data via :meth:`inject`, not :meth:`__call__`.
This function exists only to satisfy the Node interface and should not
be called directly.
:param params: Node parameters (unused).
:type params: dict
:param kwargs: Additional arguments (unused).
:type kwargs: Any
:returns: Always returns None.
:rtype: None
"""
return None
def _publisher_handler(
self, params: dict[str, Any], **kwargs: Any
) -> dict[str, Any] | None:
"""
Publish pipeline data to MQTT topic (publisher mode).
This method is called when upstream dependencies are satisfied.
Handing the payload to the node's publisher task is all that happens
here: the task holds one connection for the node's lifetime, where
connecting per message would cost a full handshake every time.
:param params: Node parameters.
:type params: dict
:param kwargs: Pipeline data to publish (from required messages).
:type kwargs: Any
:returns: None (publishing is fire-and-forget).
:rtype: dict | None
"""
loop, queue = self._loop, self._publish_queue
if loop is not None and queue is not None:
loop.call_soon_threadsafe(self._enqueue, queue, dict(kwargs))
return None
# No publisher task: a node built for a draft preview or a test. Send it
# the one-shot way rather than silently dropping the message.
try:
asyncio.run(self._publish_once(kwargs))
except RuntimeError:
logger.warning(
"Node '%s' cannot publish from a running event loop unstarted",
self.name,
)
return None
def _enqueue(
self, queue: asyncio.Queue[dict[str, Any]], data: dict[str, Any]
) -> None:
"""Queue a payload, dropping the oldest when the broker cannot keep up."""
if queue.full():
try:
queue.get_nowait()
logger.warning("Publish queue full for node '%s', dropped", self.name)
self.report_health("degraded", "publish queue full")
except asyncio.QueueEmpty:
pass
queue.put_nowait(data)
async def _publisher_loop(self) -> None:
"""Hold one connection and drain the publish queue over it.
A dropped connection raises, and the supervisor decides when to
reconnect — the same arrangement the subscriber uses.
"""
aiomqtt = _aiomqtt()
queue = self._publish_queue
if queue is None:
return
async with aiomqtt.Client(
hostname=self.broker_host,
port=self.broker_port,
username=self.username,
password=self.password,
identifier=self.client_id,
keepalive=self.keepalive,
timeout=self.timeout,
) as client:
self.report_health("ok")
while True:
data = await queue.get()
try:
await self._publish_with(client, data)
except Exception as exc:
self.report_health("down", str(exc))
raise
async def _publish_once(self, data: dict[str, Any]) -> None:
"""Connect, publish, disconnect — the unstarted node's path."""
aiomqtt = _aiomqtt()
async with aiomqtt.Client(
hostname=self.broker_host,
port=self.broker_port,
username=self.username,
password=self.password,
identifier=self.client_id,
keepalive=self.keepalive,
timeout=self.timeout,
) as client:
await self._publish_with(client, data)
async def _publish_with(self, client: Any, data: dict[str, Any]) -> None:
"""
Publish messages to their mapped MQTT topics.
Each message in *data* is published to its corresponding topic
from the ``topics`` mapping. Messages are sent as individual
JSON payloads per topic.
:param data: Data to publish, keyed by port name.
:type data: dict
"""
import json
for port, value in data.items():
topic = self.topics.get(port)
if topic is None:
logger.warning(
"No topic mapping for port '%s' in node '%s', skipping",
port,
self.name,
)
continue
# A string goes on the wire as it stands. Devices on a shared
# broker expect bare values, and the subscriber below already
# falls back to the raw text when it is not JSON, so a
# fluksio-to-fluksio round trip is unaffected.
payload = value if isinstance(value, str) else json.dumps(value)
await client.publish(
topic,
payload=payload,
qos=self.qos,
retain=self.retain,
)
logger.info(
"Published to '%s' from node '%s': %s",
topic,
self.name,
payload,
)
async def start(self, app: FastAPI | None = None) -> None:
"""A subscriber listens; a publisher opens the connection it will reuse."""
if self.mode is MqttNode.Mode.SUBSCRIBER:
await self.start_subscription()
else:
await self.start_publisher()
async def stop(self, app: FastAPI | None = None) -> None:
await self.stop_subscription()
await self.stop_publisher()
async def start_publisher(self) -> None:
"""Run the task that owns this node's connection to the broker."""
if self._publish_queue is not None:
return
self._publish_queue = asyncio.Queue(maxsize=self.publish_queue_size)
self._loop = asyncio.get_running_loop()
self._publisher_task = self._run_supervised("mqtt-out", self._publisher_loop)
async def stop_publisher(self) -> None:
"""Drop the queue and let the connection go."""
if self._publish_queue is None:
return
if self._publisher_task is not None:
await self._cancel_task(self._publisher_task)
self._publisher_task = None
self._publish_queue = None
self._loop = None
async def start_subscription(self) -> None:
"""
Start the MQTT subscription for trigger mode nodes.
This method starts a background task that listens for messages
on the subscribed topic and triggers the pipeline when messages arrive.
:raises RuntimeError: If called on a publisher mode node.
:example:
>>> subscriber = MqttNode(
... topic="sensors/#",
... provides=[MessageSpec(name="value", dtype=DType.FLOAT)],
... params={"broker_host": "localhost"},
... )
>>> await subscriber.start_subscription()
"""
if self.mode != MqttNode.Mode.SUBSCRIBER:
raise RuntimeError("Can only start subscription for subscriber mode nodes")
if self._subscription_task is not None:
return # Already running
self._stop_event = asyncio.Event()
self._subscription_task = self._run_supervised("mqtt", self._subscription_loop)
logger.info(
"Started MQTT subscription for node '%s' to topics %s",
self.name,
list(self._topic_to_ports.keys()),
)
async def stop_subscription(self) -> None:
"""
Stop the MQTT subscription.
Gracefully stops the background subscription task. A supervised
subscription is cancelled with the rest of them at teardown; only an
unsupervised one is this method's to cancel.
"""
if self._stop_event is None:
return
self._stop_event.set()
if self._subscription_task is not None:
await self._cancel_task(self._subscription_task)
self._subscription_task = None
self._stop_event = None
logger.info(
"Stopped MQTT subscription for node '%s'",
self.name,
)
def _ports_for(self, topic: str) -> list[str]:
"""Which ports an arriving topic feeds — exact mapping, then filters."""
ports = self._topic_to_ports.get(topic)
if ports is not None:
return ports
matched: list[str] = []
for pattern in self._wildcards:
if topic_matches(pattern, topic):
matched.extend(self._topic_to_ports[pattern])
return matched
async def _subscription_loop(self) -> None:
"""
Listen for MQTT messages and trigger the pipeline.
Subscribes to all unique topics from the ``topics`` mapping and
uses the reverse lookup ``_topic_to_ports`` to route incoming
payloads to the correct pipeline message names.
One connection attempt: a dropped broker raises, and the supervisor
decides when to try again. Reconnecting here as well would mean two
backoff policies fighting over the same socket.
"""
import json
aiomqtt = _aiomqtt()
if not (self._stop_event and self._stop_event.is_set()):
try:
async with aiomqtt.Client(
hostname=self.broker_host,
port=self.broker_port,
username=self.username,
password=self.password,
identifier=self.client_id,
keepalive=self.keepalive,
timeout=self.timeout,
) as client:
# Subscribe to every unique topic
for topic in self._topic_to_ports:
await client.subscribe(topic, qos=self.qos)
logger.info("[%s] Subscribed to %s", self.name, topic)
self.report_health("ok")
async for message in client.messages:
if self._stop_event and self._stop_event.is_set():
break
try:
payload = message.payload.decode("utf-8")
incoming_topic = str(message.topic)
# Debug, not info: this is one formatted line and
# one write per message the broker sends, and the
# payload goes to the server log verbatim.
logger.debug(
"[%s] Received on %s: %s",
self.name,
incoming_topic,
payload,
)
# Find which port(s) this topic feeds
ports = self._ports_for(incoming_topic)
if not ports:
logger.debug(
"[%s] No mapping for topic '%s', ignoring",
self.name,
incoming_topic,
)
continue
# Parse the payload value
try:
parsed = json.loads(payload)
except json.JSONDecodeError:
parsed = payload
by_port = {s.port: s for s in self.output_ports}
typed_data = {}
for port in ports:
spec = by_port.get(port)
if spec is None:
continue
# A JSON object may carry the value under a
# named key — the port's own name, or whatever
# ``json_key`` says the device wraps it in.
key = self.json_keys.get(port, port)
if isinstance(parsed, dict) and key in parsed:
value = parsed[key]
else:
value = parsed
typed_data[port] = spec.coerce(value)
if typed_data:
await asyncio.to_thread(self.inject, typed_data)
except Exception as e:
logger.error(
"[%s] Error processing message: %s",
self.name,
e,
exc_info=True,
)
# Falling out of the message iterator without being told to
# stop means the broker went away quietly. Raising is how the
# supervisor hears about it.
if not (self._stop_event and self._stop_event.is_set()):
self.report_health("down", "subscription ended")
raise ConnectionError(
f"MQTT subscription for '{self.name}' ended unexpectedly"
)
except asyncio.CancelledError:
raise
except Exception as e:
logger.warning(
"MQTT subscription for node '%s' failed: %s", self.name, e
)
self.report_health("down", str(e))
if self._stop_event and self._stop_event.is_set():
return
raise
@property
def is_subscribed(self) -> bool:
"""
Check if the subscription is currently active.
:returns: True if subscription task is running.
:rtype: bool
"""
return (
self._subscription_task is not None and not self._subscription_task.done()
)