Storages

Overview

This library provides a generic interface for multiple file storages:

• local storage
• remote storage via SSH
• AWS S3 (https://aws.amazon.com/s3/)
• OpenStack Object Storage service Swift (https://docs.openstack.org/api-ref/object-store/)
• custom HTTP storage

Installation

pip install https://github.com/SYSTRAN/storages/archive/master.tar.gz

This installs the package systran-storages and command line utility systran-storages-cli allowing to easily test the connections to the different services.

Features

For each service, the library provides the following functions:

• get_file(remote_path, local_path): download a remote file to a local file. If the file is already present (based on checksum and/or date and/or file size), the local file is not modified.
• get_directory(remote_path, local_path): recursively download all the files from a given directory.
• stream(remote_path, buffer_size=1024): stream the content of the file through a generator function in buffer_size packets. If the service does not support streaming, file is first downloaded locally to a temporary directory then streamed.
• push(local_path, remote_path): push a local file to a remote location
• mkdir(local_path, remote_path): create a remote directory
• listdir(remote_path, recursive=False): list of the files and directory at the remote_path location. Returns dictionary where keys are the file/directory name and values are stat of files/directories.
• delete(remote_path, recursive=False): delete a file or a directory
• rename(remote_path, new_remote_path): rename a remote_file
• stat(remote_path): statistic on file or directory - returns {'is_dir': True} for directory, and {'size': SIZE, 'last_modified': TIMESTAMP} for files
• exists(remote_path): check if a remote file or directory exists

Configuration

Configuration of the services is done with a JSON dictionary: {"key1": DEF1, "key2": DEF2, ..., "keyN": DEFN}, where key1...keyN are the identifiers of each storage, and DEF1...DEFN their configuration.

Configurations DEFI are JSON dictionary with following fields:

{
	"description": "description of the storage (optional)",
	"type": "local|ssh|s3|swift|http",
	[STORAGE_OPTIONS]
}

The dictionary is passed to the StorageClient constructor:

from systran_storages import StorageClient

client = StorageClient(services)

systran_storages/bin/storages_cli.py gives a comprehensive usage example.

Usage

The different services are method of the client object where remote_path is a string in the format storage:path:

• storage is the identifier of the storage as defined in the configuration dictionary
• path is a path relative to the storage referenced by storage

Paths use / delimiter. Path starts with / and no relative path accessor like ., .. are supported. For the storages with actual directory structure (S3, Swift, ...), a hierarchical file organization is simulated.

Services

Local

Type of the service is local.

Storage options:

• (optional, default '/') basedir: defines the base directory where files are stored.

SSH

Type of the service is ssh.

Storage options:

• (required) server: name of IP of the remote server
• (option, default 22) port: name of the port to connect to
• (required) user: login to connect with on the server
• (optional) password: user password, preferably use pkey
• (optional) pkey: private key used to connect on the service. The value does not include header (-----BEGIN RSA PRIVATE KEY-----) and tail (-----END RSA PRIVATE KEY-----)
• (optional, default user home) basedir: defines the base directory where files are stored.

S3

Type of the service is s3.

Storage options:

• (required) bucket_name
• (required) access_key_id
• (required) secret_access_key
• (optional) region_name
• (optional) assume_role: arn of assume_role
• (optional) transfer_config: additional transfer configuration parameters as defined here: https://boto3.amazonaws.com/v1/documentation/api/latest/reference/customizations/s3.html.

Swift

Type of the service is swift.

Storage options:

• (required) container_name
• (optional) auth_config: if provided, defines the configuration for authentifying to the Open Stack service (https://docs.openstack.org/python-swiftclient/latest/service-api.html#authentication).
• (optional) transfer_config: https://docs.openstack.org/python-swiftclient/latest/service-api.html#configuration

HTTP

Type of the service is http.

Storage options:

• (required) pattern_get
• (required) pattern_push
• (required) pattern_list

Note HTTP storages do not define all the possible functions:

• rename is not defined
• exists and listdir are defined only if pattern_list option is defined.