mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2024-12-26 23:55:23 +00:00
147 lines
6.7 KiB
HTML
147 lines
6.7 KiB
HTML
|
<?xml version="1.0" encoding="UTF-8"?>
|
||
|
|
<!DOCTYPE html>
|
||
|
|
<html xmlns="http://www.w3.org/1999/xhtml">
|
||
|
|
<body>
|
||
|
|
<h1>Project Strategy</h1>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
This document attempts to outline the libvirt project strategy for
|
||
|
|
the near future. Think of this as a high level vision or to-do list
|
||
|
|
setting the direction for the project and its developers to take.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<h2>Language consolidation</h2>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
At time of writing libvirt uses the following languages:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt>C</dt>
|
||
|
|
<dd>The core libvirt library, daemons, and helper tools are all written
|
||
|
|
in the C language.</dd>
|
||
|
|
<dt>Python</dt>
|
||
|
|
<dd>Various supporting build/test scripts are written in Python, with
|
||
|
|
compatibility for Python 2 and 3.</dd>
|
||
|
|
<dt>Perl</dt>
|
||
|
|
<dd>Various supporting build/test scripts are written in Perl. It is
|
||
|
|
also used for many syntax-check inline rules</dd>
|
||
|
|
<dt>Shell</dt>
|
||
|
|
<dd><code>configure</code>, generated by autoconf, is a shell script.
|
||
|
|
Shell is also used for some simple build/test scripts. At runtime
|
||
|
|
libvirt avoids shell except when using SSH tunnels to a remote
|
||
|
|
host</dd>
|
||
|
|
<dt>XSLT</dt>
|
||
|
|
<dd>The website uses XSLT for its templating system. The API
|
||
|
|
documentation is also autogenerated from an XML description
|
||
|
|
using XSLT</dd>
|
||
|
|
<dt>HTML</dt>
|
||
|
|
<dd>The website documentation is all written in plain HTML. Some HTML
|
||
|
|
is also auto-generated for API documentation</dd>
|
||
|
|
<dt>M4</dt>
|
||
|
|
<dd>The autoconf <code>configure</code> script uses a large number of
|
||
|
|
M4 macros to generate its content</dd>
|
||
|
|
<dt>make</dt>
|
||
|
|
<dd>The core build system uses the traditional GNU make recipes</dd>
|
||
|
|
<dt>automake</dt>
|
||
|
|
<dd>The make recipes use automake's language extensions which are
|
||
|
|
then turned into regular make rules</dd>
|
||
|
|
<dt>awk/sed</dt>
|
||
|
|
<dd>A number of the syntax-check inline rules involve use of awk/sed
|
||
|
|
scripts</dd>
|
||
|
|
<dt>POD</dt>
|
||
|
|
<dd>The command line manual pages are typically written in Perl's POD
|
||
|
|
format, and converted to troff</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The wide range of languages used present a knowledge burden for
|
||
|
|
developers involved in libvirt, especially when there are multiple
|
||
|
|
languages all used in the same problem spaces. This is most notable
|
||
|
|
in the build system which uses a combination of shell, M4, make,
|
||
|
|
automake, awk, sed, Perl and Python, with debugging requiring
|
||
|
|
understanding of the interactions between many languages. The
|
||
|
|
popularity of Perl has declined, while Python has become
|
||
|
|
more popular. This directly influences the amount and quality of
|
||
|
|
contributions that can be expected for programs written in the
|
||
|
|
respective languages.
|
||
|
|
</p>
|
||
|
|
<p>
|
||
|
|
The C language has served libvirt well over the years, but its age shows
|
||
|
|
giving rise to limitations which negatively impact the project in terms
|
||
|
|
of code quality, reliability, and efficiency of development. Most notably
|
||
|
|
its lack of memory safety means that many code bugs become trivially
|
||
|
|
exploitable security flaws or denial of service. The lack of a high
|
||
|
|
level portable runtime results in a lot of effort being spent to
|
||
|
|
ensure cross platform portability. The modern languages Rust and Go
|
||
|
|
provide viable options for low level systems programming, in a way that
|
||
|
|
is not practical with other common languages such as Python and Java.
|
||
|
|
There is thus a desire to make use of either Rust or Go, or a combination
|
||
|
|
of both, to incrementally replace existing use of C, and also for
|
||
|
|
greenfield development.
|
||
|
|
</p>
|
||
|
|
<p>
|
||
|
|
With this in mind the libvirt project has set a vision for language
|
||
|
|
usage in the future:
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<dl>
|
||
|
|
<dt>C</dt>
|
||
|
|
<dd>Large parts of the core libvirt library, daemons, and helper tools
|
||
|
|
will continue to make use in the C language. Integration of other
|
||
|
|
languages will be an incremental, targetted process where they can
|
||
|
|
bring the greatest benefit.</dd>
|
||
|
|
<dt>Rust / Go</dt>
|
||
|
|
<dd>Parts of the core libvirt library, daemons and helper tools are to
|
||
|
|
leverage Rust or Go or both to replace C.</dd>
|
||
|
|
<dt>Meson</dt>
|
||
|
|
<dd>The core build system is to be written in Meson.</dd>
|
||
|
|
<dt>Python</dt>
|
||
|
|
<dd>Various supporting build/test scripts are written in Python 3
|
||
|
|
compatible mode only.</dd>
|
||
|
|
<dt>reStructuredText</dt>
|
||
|
|
<dd>The website and command man pages are to be written in RST, using
|
||
|
|
Sphinx as the engine to convert to end user formats like HTML, troff,
|
||
|
|
etc</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
Some notable points from the above. Whether the core library / daemons
|
||
|
|
will use Rust or Go internally is still to be decided based on more
|
||
|
|
detailed evaluation to identify the best fit. The need to link and embed
|
||
|
|
this functionality in other processes has complex interactions both at a
|
||
|
|
technical and non-technical level. For standalone helper tools, either
|
||
|
|
language is viable, but there are fewer concerns around interactions with
|
||
|
|
other in-process code from 3rd parties. Thus a different decision may be
|
||
|
|
made for daemons/libraries vs tools. Any rewrite proposed for existing
|
||
|
|
functionality will have to weigh up the benefits of the new code,
|
||
|
|
against the risk of introducing regressions with respect to the previous
|
||
|
|
code.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
The Meson build system is written in Python 3. This directly informs the
|
||
|
|
choice of Python 3 as the language for all supporting build scripts,
|
||
|
|
re-inforcing the other benefits of Python over Perl, Shell, M4,
|
||
|
|
automake, etc. There is no intention to support Python 2 given Meson's
|
||
|
|
requirement for Python 3.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p>
|
||
|
|
Using the RST format for documentation allows for the use of XSLT to be
|
||
|
|
eliminated from the build process. RST and the Sphinx toolkit are widely
|
||
|
|
used, as seen by the huge repository of content on
|
||
|
|
<a href="https://readthedocs.org/">Read The Docs</a>.
|
||
|
|
The ability to embed raw HTML in the RST docs will greatly facilitate its
|
||
|
|
adoption, avoiding the need for a big bang conversion of existing content.
|
||
|
|
Given the desire to eliminate Perl usage, replacing the use of POD
|
||
|
|
documentation for manual pages is an obvious followup task. RST is the
|
||
|
|
obvious choice to achieve alignment with the website, allowing the man
|
||
|
|
pages to be easily published online with other docs. It is further
|
||
|
|
anticipated that the current API docs generator which uses XSLT to
|
||
|
|
convert the XML API description would be converted to something which
|
||
|
|
generates RST using Python instead of XSLT.
|
||
|
|
</p>
|
||
|
|
</body>
|
||
|
|
</html>
|