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cardoe |
1.1 |
GLEP: 61 |
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Title: Manifest2 compression |
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robbat2 |
1.7 |
Version: $Revision: 1.6 $ |
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Last-Modified: $Date: 2010/01/31 09:55:43 $ |
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cardoe |
1.1 |
Author: Robin Hugh Johnson <robbat2@gentoo.org> |
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Status: Draft |
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Type: Standards Track |
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Content-Type: text/x-rst |
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Requires: 44 |
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Created: July 2008 |
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robbat2 |
1.3 |
Updated: October 2008, January 2010 |
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cardoe |
1.1 |
Updates: 44 |
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robbat2 |
1.5 |
Post-History: December 2009, January 2010 |
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cardoe |
1.1 |
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Abstract |
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======== |
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Deals with compression of large Manifest2 files. |
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Motivation |
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========== |
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With the introduction of MetaManifest, and full-tree Manifest coverage, |
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we are faced with the possibility of having very large Manifests. |
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Preliminary experiments with MetaManifest, show that with just the |
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robbat2 |
1.5 |
existing per-package Manifests, the full MetaManifest (top-level only, |
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no first-level sub directories), for a tree including metadata/, exceeds |
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8MiB in size. Applying common compression can achieve a 50-60% reduction |
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in this size. |
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Additionally, some of the larger already-existing Manifests in the tree |
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can also be reduced. |
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cardoe |
1.1 |
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robbat2 |
1.6 |
This GLEP is not mandatory for the tree-signing specification, but |
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instead helps to cut down the size impact of large Manifest2 files, some |
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of which are already present in the tree. As such, it is also able to |
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stand on it's own. |
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cardoe |
1.1 |
Specification |
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============= |
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robbat2 |
1.5 |
Creation of compressed Manifests: |
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--------------------------------- |
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32KiB is suggested as a arbitrary cut-off point to start generating |
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compressed Manifest2 files. |
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The compression must only applied during the creation of a tree intended |
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for end users. No Manifests stored in a VCS should be compressed in the |
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VCS. For the main gentoo-portage tree, this means that the compressed |
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Manifests should be generated using the CVS to Rsync process. |
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The Manifest compression process is required to ensure that inconsistent |
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compressed versions do not exist. |
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Validation of Manifests: |
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------------------------ |
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cardoe |
1.1 |
When searching for a Manifest2 file, if the basename form does not |
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exist, the package manager should search in the same location using |
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common compressed suffixes, and use the compressed file in place of the |
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Manifest2. |
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robbat2 |
1.3 |
gzip, bzip2, lzma, xz should all be supported if available on the given |
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cardoe |
1.1 |
platform. In the case that multiple versions exist, the package manager |
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should simply pick one - they should be identical, differing only in |
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compression. |
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robbat2 |
1.5 |
Example Results with a 32KiB cut-off, gzip algorithm |
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==================================================== |
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As of 2010/01/30, the suggested cut-off would impact the following 21 existing |
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Manifests, for a saving of nearly 900KiB:: |
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Size Path |
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65788 app-doc/linux-gazette/Manifest |
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75739 app-office/openoffice-bin/Manifest |
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40534 app-text/texlive-core/Manifest |
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41710 dev-texlive/texlive-bibtexextra/Manifest |
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38197 dev-texlive/texlive-documentation-english/Manifest |
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129610 dev-texlive/texlive-fontsextra/Manifest |
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36022 dev-texlive/texlive-humanities/Manifest |
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686118 dev-texlive/texlive-latexextra/Manifest |
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43392 dev-texlive/texlive-latexrecommended/Manifest |
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33375 dev-texlive/texlive-mathextra/Manifest |
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39781 dev-texlive/texlive-pictures/Manifest |
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69567 dev-texlive/texlive-pstricks/Manifest |
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75460 dev-texlive/texlive-publishers/Manifest |
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50879 dev-texlive/texlive-science/Manifest |
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36711 kde-base/kde-l10n/Manifest |
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36539 media-gfx/bootsplash-themes/Manifest |
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33058 net-fs/autofs/Manifest |
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39781 www-client/firefox-bin/Manifest |
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48983 www-client/icecat/Manifest |
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60213 www-client/mozilla-firefox/Manifest |
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39065 x11-themes/gkrellm-themes/Manifest |
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Additionally, with the MetaManifest proposal, the following new manifests would |
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also be compressed, for a saving of nearly 4MiB:: |
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Size Path |
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33442 app-admin/Manifest |
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71073 app-dicts/Manifest |
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35923 app-emacs/Manifest |
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45808 app-misc/Manifest |
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50169 app-text/Manifest |
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112786 dev-java/Manifest |
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65581 dev-libs/Manifest |
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42619 dev-lisp/Manifest |
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182163 dev-perl/Manifest |
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96198 dev-python/Manifest |
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58963 dev-ruby/Manifest |
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59736 dev-util/Manifest |
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58338 eclass/Manifest |
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55749 kde-base/Manifest |
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110064 licenses/Manifest |
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35262 media-gfx/Manifest |
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53995 media-libs/Manifest |
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55607 media-plugins/Manifest |
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71911 media-sound/Manifest |
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34835 media-video/Manifest |
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5747849 metadata/Manifest |
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47452 net-analyzer/Manifest |
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65989 net-misc/Manifest |
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316787 profiles/Manifest |
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67784 sys-apps/Manifest |
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48971 x11-misc/Manifest |
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41475 x11-plugins/Manifest |
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cardoe |
1.1 |
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Backwards Compatibility |
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======================= |
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The package Manifests should also be maintained as ONLY uncompressed in |
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CVS. |
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For processing of all existing per-package Manifests, if compression is |
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used, it should be done in parallel to the existing Manifests, to |
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provide for a changeover period. Newer versions of Portage may later |
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choose to exclude all non-compressed Manifests during emerge --sync if |
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compressed versions are guaranteed to exist on the servers. |
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MetaManifests may come into existence as compressed from the start, as |
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do not have an backwards compatibility issues. |
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As a side note, this breaks all manual interaction with Manifests |
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such as grep, and so should only be applied to large Manifest2 files, |
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robbat2 |
1.5 |
such as the MetaManifest. |
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cardoe |
1.1 |
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References |
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========== |
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robbat2 |
1.7 |
.. [GLEP44] Mauch, M. (2005) GLEP44 - Manifest2 format. |
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http://www.gentoo.org/proj/en/glep/glep-0044.html |
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cardoe |
1.1 |
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Copyright |
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========= |
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robbat2 |
1.4 |
Copyright (c) 2008-2010 by Robin Hugh Johnson. This material may be |
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cardoe |
1.1 |
distributed only subject to the terms and conditions set forth in the |
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Open Publication License, v1.0. |
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robbat2 |
1.7 |
.. vim: tw=72 ts=2 expandtab: |
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