WatchmanReloader

This class provides a file reloader implementation that utilizes the Facebook Watchman service for efficient file system monitoring. It manages subscriptions to file changes across multiple project roots and directories, supporting both direct file tracking and glob patterns. The reloader integrates with the Watchman client to receive real-time notifications, ensuring high-performance updates for large-scale projects.

Attributes

Attribute	Type	Description
roots	defaultdict = defaultdict(set)	A mapping of directory paths to sets of watched files used to track the filesystem hierarchy.
processed_request	threading.Event = threading.Event()	A thread synchronization event used to signal that a request has finished and watches should be updated.
client_timeout	int = 5	Maximum time in seconds to wait for a response from the Watchman service, controlled by the DJANGO_WATCHMAN_TIMEOUT environment variable.
client	pywatchman.client	The pywatchman client instance used to communicate with the Watchman service for queries and subscriptions.

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Constructor

Signature

def WatchmanReloader() - > null

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Methods

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client()

@classmethod
def client() - > pywatchman.client

Returns a cached pywatchman client instance configured with the specified timeout.

Returns

Type	Description
pywatchman.client	The active Watchman client used for issuing queries and subscriptions

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watched_roots()

@classmethod
def watched_roots(
    watched_files: list
) - > frozenset

Calculates the set of all unique directory roots that should be monitored based on watched files and system paths.

Parameters

Name	Type	Description
watched_files	list	A list of individual file paths currently being tracked

Returns

Type	Description
frozenset	A set of Path objects representing the directories to be watched

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update_watches()

@classmethod
def update_watches()

Updates the active Watchman watches and subscriptions, verifying server availability if an error occurs during the update.

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request_processed()

@classmethod
def request_processed(
    **kwargs: any
)

Signals that a request has been processed, triggering a refresh of watches on the next tick.

Parameters

Name	Type	Description
**kwargs	any	Arbitrary keyword arguments passed from the request_finished signal

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tick()

@classmethod
def tick() - > generator

The main loop of the reloader that listens for Watchman events and updates watches when requests are processed.

Returns

Type	Description
generator	A generator that yields control back to the caller between polling intervals

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stop()

@classmethod
def stop()

Closes the Watchman client connection and stops the reloader.

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check_server_status()

@classmethod
def check_server_status(
    inner_ex: Exception
) - > boolean

Return True if the server is available.

Parameters

Name	Type	Description
inner_ex	Exception	An optional exception to wrap if the server is unavailable

Returns

Type	Description
boolean	True if the Watchman server responds to a version query

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check_availability()

@classmethod
def check_availability()

Verifies that the pywatchman library is installed and that the Watchman service is running with a compatible version.

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