Set the number of parallel updates

This is a Silver rule. In quality_scale.yaml, it is called parallel-updates.

Every platform module of the integration, like sensor.py or light.py, must set PARALLEL_UPDATES explicitly. It is the maximum number of entity updates and entity actions of that platform that Home Assistant runs at the same time. 0 means no limit.

Some devices and services cannot handle many requests at once. A small device with ten entities can choke when all ten update at the same moment, or when a scene turns on ten of its switches at once. PARALLEL_UPDATES lets Home Assistant queue them instead.

Setting it explicitly also means someone thought about it. The right value depends on the device, and only the integration knows it.

A platform that talks to the device for every entity sends one request at a time:

PARALLEL_UPDATES = 1


class MySwitch(SwitchEntity):
    """A switch on the device."""

With a coordinator, the data is already fetched in one place, so entity updates do not need a limit. On a read-only platform, like sensor or binary_sensor, set it to 0:

# The coordinator fetches the data, so updates need no limit
PARALLEL_UPDATES = 0

A coordinator does not limit actions, though. On platforms with actions, like switch or light, think about how many commands the device accepts at once, and set the value to match.

• Pylint, when the rule is done: every platform module must define a module-level PARALLEL_UPDATES (home-assistant-missing-parallel-updates).
• Whether the value fits the device is checked in review.

If the integration has no entity platforms, this rule does not apply.

• appropriate-polling: poll at an appropriate interval.