FUSE SDK with Local Cache Quick Start

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The followings are the basic requirements running ALLUXIO POSIX API.

  • On one of the following supported operating systems
    • MacOS 10.10 or later
    • CentOS - 6.8 or 7
    • RHEL - 7.x
    • Ubuntu - 16.04
  • Install JDK 11, or newer
    • JDK 8 has been reported to have some bugs that may crash the FUSE applications, see issue for more details.
  • Install libfuse
    • On Linux, we support libfuse both version 2 and 3
      • To use with libfuse2, install libfuse 2.9.3 or newer (2.8.3 has been reported to also work with some warnings). For example on a Redhat, run yum install fuse
      • To use with libfuse3 (Default), install libfuse 3.2.6 or newer (We are currently testing against 3.2.6). For example on a Redhat, run yum install fuse3
      • See Select which libfuse version to use to learn more about the libfuse version used by alluxio
    • On MacOS, install osxfuse 3.7.1 or newer. For example, run brew install osxfuse

Build and Install

Download the Alluxio tarball from this page. Unpack the downloaded file with the following commands.

$ tar -xzf alluxio-308-SNAPSHOT-bin.tar.gz
$ cd alluxio-308-SNAPSHOT

The alluxio-fuse launch command will be dora/integration/fuse/bin/alluxio-fuse

Mount Under Storage Dataset

Alluxio POSIX API allows accessing data from under storage as local directories. This is enabled by using the mount command to mount a dataset from under storage to local mount point:

$ sudo yum install fuse3
$ alluxio-fuse mount <under_storage_dataset> <mount_point> -o option
  • under_storage_dataset: The full under storage dataset address. e.g. s3://bucket_name/path/to/dataset, hdfs://namenode_address:port/path/to/dataset
  • mount_point: The local mount point to mount the under storage dataset to. Note that the <mount_point> must be an existing and empty path in your local file system hierarchy. User that runs the mount command must own the mount point and have read and write permissions on it.
  • -o option: All the alluxio-fuse mount options are provided using this format. Options include
    • Alluxio property key value pair in -o alluxio_property_key=value format
      • Under storage credentials and configuration. Detailed configuration can be found under the Storage Integrations tap of the left of the doc page.
    • Local cache configuration. Detailed usage can be found in the local cache tuning guide
    • Generic mount options. Detailed supported mount options information can be found in the FUSE mount options section

After mounting, alluxio-fuse mount can be found locally

$ mount | grep "alluxio-fuse"
alluxio-fuse on mount_point type fuse.alluxio-fuse (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000)

AlluxioFuse process will be launched

$ jps
34884 AlluxioFuse

All the fuse logs can be found at logs/fuse.log and all the fuse outputs can be found at logs/fuse.out which are useful for troubleshooting when errors happen on operations under the filesystem.

Example: Mounts a S3 dataset

Mounts the dataset in target S3 bucket to a local folder:

$ alluxio-fuse mount s3://bucket_name/path/to/dataset/ /path/to/mount_point -o s3a.accessKeyId=<S3 ACCESS KEY> -o s3a.secretKey=<S3 SECRET KEY>

Other S3 configuration (e.g. -o alluxio.underfs.s3.region=<region>) can also be set via the -o alluxio_property_key=value format.

Example: Mounts a HDFS dataset

Mounts the dataset in target HDFS cluster to a local folder:

$ alluxio-fuse mount hdfs://nameservice/path/to/dataset /path/to/mount_point -o alluxio.underfs.hdfs.configuration=/path/to/hdfs/conf/core-site.xml:/path/to/hdfs/conf/hdfs-site.xml

The supported versions of HDFS can be specified via -o alluxio.underfs.version=2.7 or -o alluxio.underfs.version=3.3. Other HDFS configuration can also be set via the -o alluxio_property_key=value format.

Example: Run operations

After mounting the dataset from under storage to local mount point, standard tools (for example, ls, cat or mkdir) have basic access to the under storage. With the POSIX API integration, applications can interact with the remote under storage no matter what language (C, C++, Python, Ruby, Perl, or Java) they are written in without any under storage library integrations.

Write Through to Mounted Under Storage Dataset

All the write operations happening inside the local mount point will be directly translated to write operations against the mounted under storage dataset

$ cd /path/to/mount_point
$ mkdir testfolder
$ dd if=/dev/zero of=testfolder/testfile bs=5MB count=1

folder will be directly created at under_storage_dataset/testfolder (e.g. s3://bucket_name/path/to/dataset/testfolder testfolder/testfile will be directly written to under_storage_dataset/testfolder/testfile (e.g. s3://bucket_name/path/to/dataset/testfolder/testfile

Read Through from Mounted Under Storage Dataset

Without the local cache functionalities that we will talk about later, all the read operations via the local mount point will be translated to read operations against the underlying data storage:

$ cd /path/to/mount_point
$ cp -r /path/to/mount_point/testfolder /tmp/
$ ls /tmp/testfolder
-rwx------.  1 ec2-user ec2-user 5000000 Nov 22 00:27 testfile

The read from /path/to/mount_point/testfolder will be translated to a read targeting under_storage_dataset/testfolder/testfile (e.g. s3://bucket_name/path/to/dataset/testfolder/testfile. Data will be read from the under storage dataset directly.


Unmount a mounted FUSE mount point

$ alluxio-fuse unmount <mount_point>

After unmounting the FUSE mount point, the corresponding AlluxioFuse process should be killed and the mount point should be removed. For example:

$ alluxio-fuse unmount /path/to/mount_point
$ mount | grep "alluxio-fuse"
$ jps | grep "AlluxioFuse"


Most basic file system operations are supported. However, some operations are under active development

Category Supported Operations Not Supported Operations
Metadata Write Create file, delete file, create directory, delete directory, rename, change owner, change group, change mode Symlink, link, change access/modification time (utimens), change special file attributes (chattr), sticky bit
Metadata Read Get file status, get directory status, list directory status
Data Write Sequential write Append write, random write, overwrite, truncate, concurrently write the same file by multiple threads/clients
Data Read Sequential read, random read, multiple threads/clients concurrently read the same file
Combinations FIFO special file type, Rename when writing the source file, reading and writing concurrently on the same file

Note that all file/dir permissions are checked against the user launching the AlluxioFuse process instead of the end user running the operations.

Next Steps

Local Cache Tuning provides different local cache capabilities to speed up your workloads and reduce the pressure of storage services.