rust-sequencefile

Hadoop SequenceFile library for Rust

Documentation

# Cargo.toml
[dependencies]
sequencefile = "0.2.0"

Status

Prototype status! I'm in the process of learning Rust. :) Feedback appreciated.

Unfortunately that means the API will change. If you depend on this crate, please fully qualify your versions for now.

Currently supports reading out your garden-variety sequence file. Handles uncompressed sequencefiles as well as block/record compressed files (deflate, gzip, and bzip2 only). LZO and Snappy are not (yet) handled.

There's a lot more to do:

• Varint decoding
• Block sizes are written with Varints
• Block decompression
• Gzip support
• Bzip2 support
• Sequencefile metadata
• Better error handling
• Tests
• Better error handling2
• More tests
• Better documentation
• Snappy support
• CRC file support
• 'Writables', e.g. generic deserialization for common Hadoop writable types
• Writer
• Gracefully handle version 4 sequencefiles
• Zero-copy implementation.
• LZO support.

Benchmarks

There aren't any formal benchmarks yet. However with deflate on my early 2012 MBP, 98.4% of CPU time was spent in miniz producing ~125MB/s of decompressed data.

Usage

let path = Path::new("/path/to/seqfile");
let file = File::open(&path).unwrap();

let seqfile = sequencefile::Reader::new(file).expect("Failed to open sequence file.");

for kv in seqfile {
    println!("{:?}", kv); // Some(([123, 123], [456, 456]))
}

// Until there's automatic deserialization, you can do something like this:
// VERY hacky
let kvs = seqfile.map(|e| e.unwrap()).map(|(key, value)| {
    (BigEndian::read_i64(&key),
     String::from_utf8_lossy(&value[2..value.len()]).to_string())
});

for (k,v) in kvs {
  println!("key: {}, value: {}", k, v);
}

License

rust-sequencefile is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.

See LICENSE-APACHE, and LICENSE-MIT for details.