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A FUSE based file system to access Open Build Service (OBS) instances

Project description

OSC File System

Introduction

oscfs is a FUSE based user space file system that allows to access open build service (OBS) instances. It is based on the osc (openSUSE Commander) python package for interfacing with OBS. At the moment it provides read-only access for inspecting packages and their metadata.

Dependencies

oscfs itself is implemented in python and uses the fusepy module to implement the file system portion. There is another python fuse package called python-fuse which is not compatible with oscfs.

For accessing OBS instances the python osc module is required.

Currently oscfs only works with python2, because the osc module is not available for python3 at the moment.

Features

  • Representation of all OBS projects and packages in a hierarchical file system.
  • Access to individual package files including old revisions.
  • Access to project and package metadata via pseudo files.
  • Access to package buildlogs and artifacts.
  • Configurable runtime caching of cached data.

Usage

oscfs ships one main script called oscfs. It supports a couple of command line parameters to influence its behaviour. It should only be called by a regular user and never by the root user.

For mounting the file system simply provide the mountpoint argument to the oscfs main script. By default the openSUSE build service is accessed. For authentication at the OBS instance, the configuration file in the home directory in ~/.oscrc needs to be setup. This file is part of the osc python module for which you can find more documentation in the openSUSE wiki.

To specify a different OBS instance, provide the URL via the --apiurl parameter. For example to mount the SUSE internal build service (IBS) under the home directory in a directory ibs use the following command line:

$ oscfs --apiurl https://api.suse.de ~/ibs

By default oscfs detaches and runs in the background. For testing purposes it can be run in the foreground by passing the -f parameter.

Certain special OBS projects are excluded by default like the users’ home: projects, maintenance incident projects or PTF (Program Temporary Fix) projects. This is the case, because a lot of these projects can exist in an OBS which would clutter the file system contents.

If you want to include these types of projects you can pass the according command line parameter like --homes, --maintenance or --ptf. Your own home projects will always be included in the file system independently of the --homes switch.

Content that has been fetched from the OBS instance will be cached locally for a certain time to improve response times. The time before content will be refreshed can be tuned via the --cache-time parameter.

File System Structure

On the first level of the file system, a directory for each OBS project is found. When working against the openSUSE OBS you can find the openSUSE:Factory directory, for example. On the second level the packages within a project are found. Within openSUSE:Factory all packages that make up the openSUSE Tumbleweed rolling release codebase are found. For example you can find the package bash within openSUSE:Factory/bash.

Within each package directory you can find a list of flat files that make up the package’s data like RPM spec file, patches, source tarballs and so on. You can read the file contents like every other file with your editor or tools like cat and less. There are no regular subdirectories found in a package.

Each project and package directory contains a hidden .oscfs directory which contains metadata and pseudo files provided by oscfs. These files are not actually existing in OBS.

The following is a list of pseudo files provided in each project’s .oscfs directory:

  • bugowners: contains a list of the usernames of the bugowners of the project, one per line. If the name starts with an ‘@’ then the name refers to a group of users.
  • maintainers: just like bugowners but contains a list of the project’s maintainers.
  • debuginfo: returns a boolean “0” or “1”, indicating whether debuginfo generation is enabled.
  • locked: returns a boolean “0” or “1”, indicating whether the project is in the locked state.
  • meta: returns the complete XML metadata for the project as provided by the OBS instance.
  • refresh: this is a control file. When you write the value of “1” into the file then the cache for the project will be flushed. This can be used to force regeneration of cached content.
  • repositories: this file returns a list of all the repositories defined for the project. Each new repository starts with a line # <name>. Following are a number of lines providing additional information about the repository like archs: <...>, defining the architectures used in the repository.

The following is a list of pseudo files provided in each package’s .oscfs directory:

  • bugowners: the same as for projects above.
  • maintainers: the same as for projects above.
  • description: contains the human readable description of the package.
  • log: contains the changelog of the package.
  • meta: returns the complete XML metadata for the package as provided by the OBS instance.
  • num_revisions: returns an integer denoting the number of commit revisions that are available for the package.
  • commits: a directory that contains one file for each commit available for the package. Each file is named after the commit revision number. Each file returns a description of the commit user, date and description.
  • requests: a directory that contains one file for each OBS request that exists for the package. Each file is named in the format <num>:<state>, where <num> is the submit request ID and <state> is the current state of the request. Upon reading each file returns the description and history of the submit request it represents.
  • revisions: a directory that contains a subdirectory for each commit available for the package. Each directory is named after the commit revision number. Each directory contains the state of the package’s files as of that revision.
  • buildresults: A file that contains the current package build results for each repository/architecture combination.
  • buildlogs: a directory below which a hierarchy of repository/architecture files can be found. The architecture files are regular files that return the build log of the package for the repository/architecture combination it represents.
  • binaries: a directory below which a hierarchy of repository/architecture directories can be found. Within the architecture directory the binary artifacts can be found that have been produced in the package for the repository/architecture combination it represents.
  • incident: a symlink only present in package updates that originate from a maintenance incident. In this case this symlink points to the maintenance project where the package was built. For this to work the file system needs to be mounted with the --maintenance parameter.

Usage Hints

How the Runtime Caching Works

Each operation performed on the file system in some way needs to talk to the remote OBS instance. This is a slow process and needs to be minimized. The oscfs performs lazy evaluation of directory contents. This means that only when you access a certain path for the first time will the actual contents be determined by communicating with the OBS instance. This will take a noticeable amount of time. The second time you will access the same path a locally cached version of the file or directory will be served. This will take considerably less time.

Caching also means that the state of files shown in the file system may not correspond to the state on the remote server any more. Therefore oscfs refetches the contents of files and directories after the cache has reached a certain age as is determined by the --cache-time parameter. This only happens when a cached path is accessed after the configured cache time has passed since the last retrieval of data from the remote server. You can also explicitly invalidate the caching for a complete package by writing to the refresh control file documented above.

When oscfs is restarted then any previously cached contents are lost. This means that the cache is not written to the local disk in any form. Fetching a lot amount of data from the remote server should be avoided (e.g. don’t call find for the complete file system). This would be a kind of denial of service attack on the remote server.

Sorting of Directory Contents

Listing directories with ls can feel a bit on the slow side, even if data is cached by oscfs. This results from ls sorting the directory contents by name. Since e.g. openSUSE:Factory contains more than 10.000 entries this can take about a second to complete. When listing without sorting i.e. by running ls -f then the time required is considerably lower. Similar considerations need to be made when accessing the file system by other means like from programming languages that could sort directory contents by default.

Metadata of Pseudo Files

The pseudo files contained in the .oscfs directory of a package start out with a size of zero bytes, although they may actually contain data. The reason for this is that for determining the size of the content, the content would need to be accessed right away. This would slow down e.g. recursive searching for file names considerably. Therefore some metadata like the size of pseudo files is only calculated after it is accessed the first time. Since some of the pseudo files may return dynamic data the displayed file size is also subject to change at any time i.e. it only reflects a snapshot of the data as it was last seen by oscfs.

Usage Examples

Finding Packages

You can find packages by using tools like find or shell wildcards expansion. To find all fuse related packages you do this for example:

$ cd openSUSE:Factory
$ ls -d *fuse*
enblend-enfuse  fuse  fuse-exfat  fuseiso  fusepod  fusesmb  ifuse  ldapfuse  libconfuse0  python-defusedxml  python-fuse  python-fusepy  unionfs-fuse

Matching Lines from RPM Specs

You can query for packages containing certain RPM spec statements. For example to find packages that require some perl package by using grep like this:

$ cd openSUSE:Factory
$ grep -H "^Requires:.*perl" */*.spec

Note that this is going to take a long time, because each package needs to be queried on OBS.

Comparing Two Package Revisions

You can check two package revisions for differences by taking this approach:

$ cd openSUSE:Factory/bash/.oscfs/revisions
$ diff -r 1 2
<diff output...>

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