Crate cloud_file

cloud-file

Simple reading of cloud files in Rust

Highlights

• HTTP, AWS S3, Azure, Google, or local
• Sequential or random access
• Simplifies use of the powerful object_store crate, focusing on a useful subset of its features
• Access files via URLs and string-based options
• Read binary or text
• Fully async
• Used by genomics crate BedReader, which is used by other Rust and Python projects
• Also see Nine Rules for Accessing Cloud Files from Your Rust Code Practical Lessons from Upgrading Bed-Reader, a Bioinformatics Library in Towards Data Science.

Install

cargo add cloud-file

Examples

Find the size of a cloud file.

use cloud_file::CloudFile;

let url = "https://raw.githubusercontent.com/fastlmm/bed-sample-files/main/toydata.5chrom.fam";
let cloud_file = CloudFile::new(url)?;
let file_size = cloud_file.read_file_size().await?;
assert_eq!(file_size, 14_361);

Find the number of lines in a cloud file.

use cloud_file::CloudFile;
use futures::StreamExt; // Enables `.next()` on streams.

let url = "https://raw.githubusercontent.com/fastlmm/bed-sample-files/main/toydata.5chrom.fam";
let cloud_file = CloudFile::new_with_options(url, [("timeout", "30s")])?;
let mut chunks = cloud_file.stream_chunks().await?;
let mut newline_count: usize = 0;
while let Some(chunk) = chunks.next().await {
    let chunk = chunk?;
    newline_count += bytecount::count(&chunk, b'\n');
}
assert_eq!(newline_count, 500);

More examples

Example	Demonstrates
line_count	Read a file as binary chunks.
nth_line	Read a file as text lines.
bigram_counts	Read random regions of a file, without regard to order.
aws_file_size	Find the size of a file on AWS.

Project Links

• Installation
• Documentation
• Discussion and Questions
• Source code
• Bug Reports
• Change Log

Main Functions

Function	Description
CloudFile::new	Use a URL string to specify a cloud file for reading.
CloudFile::new_with_options	Use a URL string and string options to specify a cloud file for reading.

URLs

Cloud Service	Example
HTTP	https://www.gutenberg.org/cache/epub/100/pg100.txt
local file	file:///M:/data%20files/small.bed
AWS S3	s3://bedreader/v1/toydata.5chrom.bed

Note: For local files, use the abs_path_to_url_string function to properly encode into a URL.

Options

Cloud Service	Details	Example
HTTP	ClientConfigKey	[("timeout", "30s")]
local file	none
AWS S3	AmazonS3ConfigKey	[("aws_region", "us-west-2"), ("aws_access_key_id", …), ("aws_secret_access_key", …)]
Azure	AzureConfigKey
Google	GoogleConfigKey

High-Level CloudFile Methods

Method	Retrieves
stream_chunks	File contents as a stream of Bytes
stream_line_chunks	File contents as a stream of Bytes, each containing one or more whole lines
read_all	Whole file contents as an in-memory Bytes
read_range	Bytes from a specified range
read_ranges	Vec of Bytes from specified ranges
read_range_and_file_size	Bytes from a specified range & the file’s size
read_file_size	Size of the file
count_lines	Number of lines in the file

Additional methods:

Method	Description
clone	Clone the CloudFile instance. Efficient by design.
set_extension	Change the CloudFile’s file extension (in place).

Low-Level CloudFile Methods

Method	Description
get	Call the object_store crate’s get method.
get_opts	Call the object_store crate’s get_opts method.

Lowest-Level CloudFile Methods

You can call any method from the object_store crate. For example, here we use head to get the metadata for a file and the last_modified time.

use cloud_file::CloudFile;

let url = "https://raw.githubusercontent.com/fastlmm/bed-sample-files/main/plink_sim_10s_100v_10pmiss.bed";
let cloud_file = CloudFile::new(url)?;
let meta = cloud_file.cloud_service.head(&cloud_file.store_path).await?;
let last_modified = meta.last_modified;
println!("last_modified: {}", last_modified);
assert_eq!(meta.size, 303);

Re-exports

• pub use object_store::path::Path as StorePath;

Structs

• CloudFile
  The main struct representing the location of a file in the cloud.
• DynObjectStore
  Wraps Box<dyn ObjectStore> for easier usage. An ObjectStore, from the powerful object_store crate, represents a cloud service.

Enums

• CloudFileError
  The error type for CloudFile methods.

Constants

• EMPTY_OPTIONS
  An empty set of cloud options

Functions

• abs_path_to_url_string
  Given a local file’s absolute path, return a URL string to that file.