FileSystem: FileSystem classes

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FileSystem classes

Description

FileSystem is an abstract file system API, LocalFileSystem is an implementation accessing files on the local machine. SubTreeFileSystem is an implementation that delegates to another implementation after prepending a fixed base path

Factory

LocalFileSystem$create() returns the object and takes no arguments.

SubTreeFileSystem$create() takes the following arguments:

• base_path, a string path

• base_fs, a FileSystem object

S3FileSystem$create() optionally takes arguments:

• anonymous: logical, default FALSE. If true, will not attempt to look up credentials using standard AWS configuration methods.

• access_key, secret_key: authentication credentials. If one is provided, the other must be as well. If both are provided, they will override any AWS configuration set at the environment level.

• session_token: optional string for authentication along with access_key and secret_key

• role_arn: string AWS ARN of an AccessRole. If provided instead of access_key and secret_key, temporary credentials will be fetched by assuming this role.

• session_name: optional string identifier for the assumed role session.

• external_id: optional unique string identifier that might be required when you assume a role in another account.

• load_frequency: integer, frequency (in seconds) with which temporary credentials from an assumed role session will be refreshed. Default is 900 (i.e. 15 minutes)

• region: AWS region to connect to. If omitted, the AWS library will provide a sensible default based on client configuration, falling back to "us-east-1" if no other alternatives are found.

• endpoint_override: If non-empty, override region with a connect string such as "localhost:9000". This is useful for connecting to file systems that emulate S3.

• scheme: S3 connection transport (default "https")

• proxy_options: optional string, URI of a proxy to use when connecting to S3

• background_writes: logical, whether OutputStream writes will be issued in the background, without blocking (default TRUE)

• allow_bucket_creation: logical, if TRUE, the filesystem will create buckets if ⁠$CreateDir()⁠ is called on the bucket level (default FALSE).

• allow_bucket_deletion: logical, if TRUE, the filesystem will delete buckets if⁠$DeleteDir()⁠ is called on the bucket level (default FALSE).

• request_timeout: Socket read time on Windows and macOS in seconds. If negative, the AWS SDK default (typically 3 seconds).

• connect_timeout: Socket connection timeout in seconds. If negative, AWS SDK default is used (typically 1 second).

GcsFileSystem$create() optionally takes arguments:

• anonymous: logical, default FALSE. If true, will not attempt to look up credentials using standard GCS configuration methods.

• access_token: optional string for authentication. Should be provided along with expiration

• expiration: POSIXct. optional datetime representing point at which access_token will expire.

• json_credentials: optional string for authentication. Either a string containing JSON credentials or a path to their location on the filesystem. If a path to credentials is given, the file should be UTF-8 encoded.

• endpoint_override: if non-empty, will connect to provided host name / port, such as "localhost:9001", instead of default GCS ones. This is primarily useful for testing purposes.

• scheme: connection transport (default "https")

• default_bucket_location: the default location (or "region") to create new buckets in.

• retry_limit_seconds: the maximum amount of time to spend retrying if the filesystem encounters errors. Default is 15 seconds.

• default_metadata: default metadata to write in new objects.

• project_id: the project to use for creating buckets.

Methods

• path(x): Create a SubTreeFileSystem from the current FileSystem rooted at the specified path x.

• cd(x): Create a SubTreeFileSystem from the current FileSystem rooted at the specified path x.

• ls(path, ...): List files or objects at the given path or from the root of the FileSystem if path is not provided. Additional arguments passed to FileSelector$create, see FileSelector.

• ⁠$GetFileInfo(x)⁠: x may be a FileSelector or a character vector of paths. Returns a list of FileInfo

• ⁠$CreateDir(path, recursive = TRUE)⁠: Create a directory and subdirectories.

• ⁠$DeleteDir(path)⁠: Delete a directory and its contents, recursively.

• ⁠$DeleteDirContents(path)⁠: Delete a directory's contents, recursively. Like ⁠$DeleteDir()⁠, but doesn't delete the directory itself. Passing an empty path ("") will wipe the entire filesystem tree.

• ⁠$DeleteFile(path)⁠ : Delete a file.

• ⁠$DeleteFiles(paths)⁠ : Delete many files. The default implementation issues individual delete operations in sequence.

• ⁠$Move(src, dest)⁠: Move / rename a file or directory. If the destination exists: if it is a non-empty directory, an error is returned otherwise, if it has the same type as the source, it is replaced otherwise, behavior is unspecified (implementation-dependent).

• ⁠$CopyFile(src, dest)⁠: Copy a file. If the destination exists and is a directory, an error is returned. Otherwise, it is replaced.

• ⁠$OpenInputStream(path)⁠: Open an input stream for sequential reading.

• ⁠$OpenInputFile(path)⁠: Open an input file for random access reading.

• ⁠$OpenOutputStream(path)⁠: Open an output stream for sequential writing.

• ⁠$OpenAppendStream(path)⁠: Open an output stream for appending.

Active bindings

• ⁠$type_name⁠: string filesystem type name, such as "local", "s3", etc.

• ⁠$region⁠: string AWS region, for S3FileSystem and SubTreeFileSystem containing a S3FileSystem

• ⁠$base_fs⁠: for SubTreeFileSystem, the FileSystem it contains

• ⁠$base_path⁠: for SubTreeFileSystem, the path in ⁠$base_fs⁠ which is considered root in this SubTreeFileSystem.

• ⁠$options⁠: for GcsFileSystem, the options used to create the GcsFileSystem instance as a list

Notes

On S3FileSystem, ⁠$CreateDir()⁠ on a top-level directory creates a new bucket. When S3FileSystem creates new buckets (assuming allow_bucket_creation is TRUE), it does not pass any non-default settings. In AWS S3, the bucket and all objects will be not publicly visible, and will have no bucket policies and no resource tags. To have more control over how buckets are created, use a different API to create them.

On S3FileSystem, output is only produced for fatal errors or when printing return values. For troubleshooting, the log level can be set using the environment variable ARROW_S3_LOG_LEVEL (e.g., Sys.setenv("ARROW_S3_LOG_LEVEL"="DEBUG")). The log level must be set prior to running any code that interacts with S3. Possible values include 'FATAL' (the default), 'ERROR', 'WARN', 'INFO', 'DEBUG' (recommended), 'TRACE', and 'OFF'.

arrow documentation built on Sept. 11, 2024, 8:02 p.m.