ServiceData

ClassSource

service = ServiceData(
    cache: CacheAbstract[CachedFileInfo, CachedData],
    service_name: str = "/cached-data",
    chunk_size: int = 1,
    allowed_cross_origin: str | None = None,
)

Service provider for streaming data.

This instance provides a cache for storing temporary data. A temporary data item will be accessed by the directly or downloaded.

Aliases

This class can be acquired by

import dash_file_cache as dfc


dfc.ServiceData
dfc.services.ServiceData
dfc.services.data.ServiceData

Arguments

Argument	Type	Required	Description
cache	CacheAbstract[CachedFileInfo, CachedData]		The cache instance hosting the temporary data. This value can be CachePlain, CacheQueue, or CacheFile.
service_name	str		The name of this service.
chunk_size	int		The chunk size when streaming the cached file to users. The unit is MB.
allowed_cross_origin	str | None		The allowed cross origin when serving the data. The usage should be the same as "Access-Control-Allow-Origin". If this value is empty or None, the cross-origin will not be configured.

Methods

register_request

addr: str = service.register_request(
    url: str | urllib.parse.ParseResult,
    headers: Mapping[str, str] | None = None,
    file_name_fallback: str = "",
    download: bool = False,
)

Register the a remote request to the cache.

Requires

Argument	Type	Required	Description
url	str | urllib.parse.ParseResult		The string-form or parsed URL of the remote file.
headers	Mapping[str, str] | None		The customized headers for this request. If not specified, will not use any headers.
file_name_fallback	str		The fall-back file name. If specified, it will be used as the saved file name when the remote service does not provide the file name.
download	bool		If specified, will mark the returned address as a downloadable link.

Returns

Argument	Type	Description
addr	str	The URL that would be used for accessing this temporarily cached file.

---

register

addr: str = service.register(
    fobj: str | os.PathLike | io.StringIO | io.BytesIO,
    file_name: str = "",
    content_type: str = "",
    mime_type: str = "image/jpeg",
    one_time_service: bool = False,
    download: bool = False,
)

Register the a new file (a path or a file-like object) to the cache.

Requires

Argument	Type	Required	Description
fobj	str | os.PathLike | io.StringIO | io.BytesIO		The path or a file-io object of a specific file to be registered.
file_name	str		The file name of fobj. If not provided, will attempt to solve the name from fobj if it is a path. randomly generate a dummy file name. Note that this value is used only when the file will be streamed as a downloadable file.
content_type	str		The content-type in the response. An optional encoding can be provided here. If this value is not specified, will use mime_type to fill this value.
mime_type	str		The mime-type of the response. Typically, it is only determined by the type of the file.
one_time_service	bool		A flag. When it is enabled, will use the on-exit mechanism to remove this cached data once it is served for once. This option is recommended if this cached item is used for one-time downloading.
download	bool		If specified, will mark the returned address as a downloadable link.

Returns

Argument	Type	Description
addr	str	The URL that would be used for accessing this temporarily cached file.

---

stream

resp: flask.Response = service.stream(uid: str, download: bool = False)

Wrap a cached data item with streaming data provider.

warning

Note that users do not need to explictly call this method. This method will be automatically called when the related service is accessed.

Requires

Argument	Type	Required	Description
uid	str		The UUID used for accessing the cached item. If not hit, raise FileNotFoundError.
download	bool		A flag. If enabled, will mark the streamed data as the data to be downloaded.

Returns

Argument	Type	Description
resp	flask.Response	The flask Response used for forwarding the data to the frontend.

---

serve

service.serve(app: dash.Dash | flask.Flask, endpoint: str | None = None)

Add the service to the Flask application.

Requires

Argument	Type	Required	Description
app	dash.Dash | flask.Flask		The application where the services will be bound.
endpoint	str | None		The endpoint of this serivce. If not specified, will use the service address to infer it.

Properties

cache

cache: CacheAbstract[CachedFileInfo, CachedData] = service.cache

The cache of this service.

---

chunk_size

chunk_size: int = service.chunk_size

new_chunk_size: int
service.chunk_size = new_chunk_size

The chunk size when streaming the cached file to users. The unit is MB.

---

allowed_cross_origin

allowed_cross_origin: str = service.allowed_cross_origin

The allowed cross origin. If this value is an empty string, the cross-origin data delivery will not be used.

Examples

See

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Flask services