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HDFS

HDFS interface for Julia as a wrapper over Hadoop HDFS library.

Readme

HDFS.jl

HDFS.jl wraps the HDFS C library libhdfs and provides APIs similar to Julia Filesystem APIs which can be used for direct access to HDFS files.

Types

HdfsFS

Holds a handle to the file system along with the connection specification (host, port and username). It can be obtained from a call to hdfs_connect and needs to be passed around in future API calls.

type HdfsFS
    host::AbstractString 
    port::Int
    user::AbstractString
    ptr::Ptr{Void}
    ...
end

HdfsFile

Returned from a call to open or hdfs_open, it holds a handle to the file, apart from the file system handle and the file URL. It needs to be passed around in future API calls involving the file.

type HdfsFile
    fs::HdfsFS
    path::AbstractString
    ptr::Ptr{Void}
end

HdfsFileInfo

Holds information about a HDFS file. Returned from a call to hdfs_get_path_info.

type HdfsFileInfo
    kind::Int8              # one of HDFS_OBJ_FILE, HDFS_OBJ_DIR, HDFS_OBJ_INVALID
    name::AbstractString    # full HDFS URL to the file
    last_mod::Int64
    size::Int64             # size in bytes
    replications::Int16     # number of replications
    block_sz::Int64         # block size in bytes
    owner::AbstractString
    grp::AbstractString
    permissions::Int16
    last_access::Int64
    ...
end

APIs

Connecting to HDFS

Open a connection to a HDFS cluster. Returns a HdfsFS.

hdfs_connect(host::AbstractString="default", port::Integer=0, user::AbstractString="")

Creating/Deleting Files

mkdir(fs::HdfsFS, path::AbstractString) 

mv(fs::HdfsFS, src::AbstractString, dst::AbstractString)

# replication and block_sz are relevant only while creating a new file
open(fs::HdfsFS, path::AbstractString, mode::AbstractString="r", buffer_sz::Integer=0, replication::Integer=0, block_sz::Integer=0)
open(f::HdfsFile, mode::AbstractString="r", buffer_sz::Integer=0, replication::Integer=0, block_sz::Integer=0)
hdfs_open(url::AbstractString, mode::AbstractString, buffer_sz::Integer=0, replication::Integer=0, block_sz::Integer=0)

close(f::HdfsFile)

cp(srcFS::HdfsFS, src::AbstractString, dstFS::HdfsFS, dst::AbstractString)
cp(fs::HdfsFS, src::AbstractString, dst::AbstractString)

mv(srcFS::HdfsFS, src::AbstractString, dstFS::HdfsFS, dst::AbstractString) 

rm(fs::HdfsFS, path::AbstractString) 

hdfs_set_replication(fs::HdfsFS, path::AbstractString, replication::Integer)

Reading/Writing Files

HDFSFile provides an IOStream interface. Most IO APIs would work as usual on it.

Getting Information about File system and files

stat(f::HdfsFile)
stat(fs::HdfsFS, path::AbstractString)

isdir(fs::HdfsFS, path::AbstractString)

pwd(fs::HdfsFS)

cd(fs::HdfsFS, path::AbstractString)

readdir(fs::HdfsFS, path::AbstractString=".")

hdfs_get_default_block_size(fs::HdfsFS)
hdfs_get_capacity(fs::HdfsFS)
hdfs_get_used(fs::HdfsFS)

hdfs_exists(fs::HdfsFS, path::AbstractString)
hdfs_blocks(fs::HdfsFS, path::AbstractString, start::Integer, length::Integer)

Files test/dfs_test1.jl and test/dfs_test2.jl have examples that illustrate API usage.

Here are also some installation instructions in case you have trouble installing on your platform.

Note: HDFS.jl is based on libhdfs.jl, originally written by Benjamin Yang (@benyang) and part of the julia/extras.

First Commit

04/08/2013

Last Touched

6 months ago

Commits

99 commits

Requires:

Used By: