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Add a glep on package managers

1 GLEP: 49
2 Title: Alternative Package Manager requirements
3 Version: $Revision: 2213 $
4 Last-Modified: $Date: 2006-05-19 12:58:14 +0200 (Fri, 19 May 2006) $
5 Author: Paul de Vrieze <pauldv@gentoo.org>,
6 Status: Draft
7 Type: Standards Track
8 Content-Type: text/x-rst
9 Created: 18-May-2006
10 Post-History: 20-May-2006
11
12
13 Abstract
14 ========
15
16 This GLEP describes four classes of package managers. What the requirements for
17 them are, and what support they can receive.
18
19
20 Motivation
21 ==========
22
23 To set a standard that package managers that seek gentoo project approval and
24 support should adhere to.
25
26
27 Rationale
28 =========
29
30 Currently portage is showing its age. The code of portage does not seem to be
31 salvageable for new versions. There are two known alternative package managers
32 that claim a level of portage compatibility. These alternatives are `paludis`_
33 and `pkgcore`_. Before these alternatives are developed further, a set of rules
34 should be created to level the playing field and ensuring that decisions can be
35 made clearly.
36
37
38 Backwards Compatibility
39 =======================
40
41 Not a problem for this GLEP. There is no previous standard as the issue did not
42 exist before. This GLEP is to prevent future compatibility issues.
43
44
45 Categories of package managers
46 ==============================
47
48 We distinguish four categories of package managers. While a package manager can
49 transition from one category to another, it can not be in two categories at the
50 same time. It can be in a state of transition though.
51
52 *Primary Package Manager*
53 There is one primary package manager. Currently this position is held by
54 portage. The primary package manager is assigned by the council and all
55 packages in the official tree must be installable by a useable version of the
56 primary package manager.
57
58 *Candidate Primary Package Managers*
59 A candidate Primary Package Manager does aim, or show an aim, at replacing
60 the current primary package manager. At a point where the package manager is
61 deemed stable a decision must be made whether this package manager should
62 become the new primary package manager. At that point the `primary package
63 manager transition phase`_ starts.
64
65 *Secondary Package Managers*
66 A secondary package manager is a package manager that coexists with the
67 primary package manager, while not aiming to replace it. Package managers
68 that would fall into this category are:
69
70 - Experimental package managers. Package managers whose purpose it is to try
71 out new features.
72
73 - Focussed package managers. For example a package manager that allows the
74 use of rpm formatted binary packages would be an example.
75
76
77 *Third Party Package Managers*
78 A third party package manager is any package manager that lacks recognition
79 from gentoo as being in any other category. A third party package manager may
80 or may not have a gentoo package, but is not supported beyond that.
81
82
83 Package manager requirements
84 ============================
85
86 As a package manager is in a state of higher support there are higher
87 requirements to it. The purpose of these requirements is to ensure the unity of
88 the distribution and the package tree. For this purpose it is needed that there
89 is only one primary package manager.
90
91
92 primary package manager requirements
93 ------------------------------------
94
95 The primary package manager is the package manager that sets the standards for
96 the tree. All ebuilds in the tree must function with the primary package
97 manager. As the primary package manager sets the standard it does not have to
98 maintain compatibility with other package managers.
99
100 The primary package manager does however have the responsibility that it must be
101 very stable. The primary package manager must maintain compatibility with old
102 versions of itself for extended periods of time. This compatibilty time is set
103 by the council. The suggested time would be one year from the point that there
104 is a compatible stable version for all supported architectures.
105
106 Another compatibilty requirement for the primary package manager is a limited
107 forward compatibility. It must always be possible to transition from the
108 unstable version of the primary package manager to a stable version. This may be
109 done either by first introducing reading compatibility for a new format and only
110 having write support later. Another way would be the provision of a conversion
111 tool that ensures that the on disk information maintained by the package manager
112 is supported by the stable package manager.
113
114 The primary package manager is maintained on official gentoo infrastructure,
115 under control of gentoo developers.
116
117
118 candidate primary package manager requirements
119 ------------------------------------------------
120
121 A candidate primary package manager aims to replace the primary package
122 manager. The council is responsible for deciding whether this is done. The
123 requirements are there to ensure that it is actually possible to transition a
124 candidate primary package manager into the primary package manager.
125
126 First of all, there must exist a transition path. This means that the on disk
127 data of the primary package manager can be used by (or converted to a format
128 usable by) the candidate primary package manager.
129
130 Second, there must be a test path. It must be possible for the developers to
131 test out the candidate primary package manager on their working systems. This
132 means that the transition path must exist. This also means that there are no
133 serious obstacles for reverting to the current primary package manager.
134
135 Third, there must exist an ebuild test path. It must be possible for package
136 managers to test ebuilds in one tree for both the primary as well as the
137 candidate primary package manager. It is not an issue if this requires a special
138 mode for the candidate primary package manager. It is not an issue either if
139 compatibilty can be achieved by unmerging the package in the candidate primary
140 package manager.
141
142 Fourth, there must be support. This means that the package manager is actively
143 maintained under control of gentoo. If it is not maintained on gentoo
144 infrastructure, the means must be there to move the package manager, with its
145 change history, to gentoo infrastructure. This means that it must be maintained
146 on a gentoo supported versioning system, or on a version system whose history
147 can be converted to a gentoo supported versioning system.
148
149
150 secondary package manager requirements
151 --------------------------------------
152
153 A secondary package manager is a package manager that instead of directly aiming
154 at replacing portage as primary package manager. As such a secondary package
155 manager does not set the standard on the tree, but follows the standard set by
156 the primary package manager.
157
158 There are two kinds of secondary package managers. The first kind is formed by
159 those that do not maintain their own installed package database, but work with
160 the package database of the primary package manager. While these package
161 managers can put additional information in the database, these entries must
162 remain compatible with the primary package managers. Verification, reference,
163 and deinstallation by the primary package manager must remain functional.
164
165 The second kind is formed by those package managers that maintain their own
166 package database, or a package database incompatible with the primary package
167 manager. To ensure the secondary role of these package managers the support in
168 the tree for these package manager is provided along with restrictions.
169
170 The first restriction is that no packages in the tree must rely on the secondary
171 package manager. While packages may provide a level of support (while being
172 compatible with the primary package manager) this may not result in a
173 significant increase of features. If this were allowed, this would mean that
174 while they technically work with the primary package manager, there would be
175 significant incentive to use the secondary package manager. As the use of this
176 secondary package manager disallows the paralel use of the primary package
177 manager, this would result in users using the secondary package manager as their
178 primary package manager.
179
180 Users are allowed to make their own choices. However by making the tree favor a
181 package manager that is not the primary package manager, this will lead to the
182 secondary package manager becomming the effective primary package manager. As
183 this will be a decision by default instead of a concious choice by the council,
184 this is an undesirable result.
185
186 There is one exclusion for the restriction of packages that only work with or
187 have significant improvements with the secondary package manager. That is
188 packages that by their nature are only usable with this secondary package
189 manager. An example would be a graphical frontend to the secondary package
190 manager.
191
192 If a secondary package manager works along the primary package manager, but by
193 itself does not have the capabilities of becoming a primary package manager the
194 risks of choice by default are lower. As a result, the council could choose to
195 allow the inclusion of packages that work only or significantly better with this
196 secondary package manager. For example at a point where there is a stable,
197 functional, package manager that can handle RPM format packages, the council
198 could decide to include these packages directly in the tree, instead of using
199 wrapper scripts for those packages that are only provided in the RPM
200 format. Such a decision does imply that the maintainers of the primary package
201 manager must take this secondary package manager into account.
202
203
204 third party package manager requirements
205 ----------------------------------------
206
207 A third party package manager is just that. It is a package manager without any
208 support within gentoo. As there is no control by gentoo over the package manager
209 this means that there are no requirements on the package manager.
210
211 This complete lack of control however also translates to the fact that gentoo
212 can not make package manager specific changes to support this package
213 manager. Package manager specific means that it is possible to request changes
214 that make the tree more independent of the primary package manager. These
215 changes must however be agnostic of the package manager, and only make it easier
216 to have alternative package managers.
217
218
219 transition phases
220 =================
221
222 primary package manager transition phase
223 ----------------------------------------
224
225 A candidate primary package manager can be chosen to become primary package
226 manager. This can only happen by council decision. This decision can only be
227 made when the candiate primary package manager is stable on all stable
228 architectures. (all architectures except experimental ones).
229
230 After the decision has been made to replace the primary package manager, the
231 transition phase starts. The use of the old stable package manager must remain
232 supported for a period of 6 months. This means that core packages must be
233 installable by this package manager. Further the possibility to convert the
234 system automatically to the new primary package manager must be available for at
235 least 18 months, but preferably longer (enable installing the new package
236 manager from the old one).
237
238 During the transition phase packages are allowed in the tree that use the new
239 features of the new primary package manager. While backward compatibility with
240 the previous primary package manager must be maintained a forward compatibility
241 is no longer needed.
242
243
244 Secondary package manager to candidate primary package manager transition
245 -------------------------------------------------------------------------
246
247 The transition from secondary package manager to candidate primary package
248 manager is straightforward. The secondary package manager must satisfy all
249 requirements for a candidate primary package manager. At that point its
250 maintainers can announce that they are changing the status to candidate primary
251 package manager. This allows a greater support from gentoo in achieving that
252 goal.
253
254
255 Third party to other transition
256 -------------------------------
257
258 When a third party package manager wants to transition into one of the other
259 categories (except primary package manager) it must satisfy all requirements for
260 that category.
261
262
263 References
264 ==========
265
266 .. _paludis: http://paludis.berlios.de/
267 .. _pkgcore: http://gentooexperimental.org/~ferringb/bzr/pkgcore/
268 .. _Open Publication License: http://www.opencontent.org/openpub/
269
270
271 Copyright
272 =========
273
274 This document is copyright 2006 by Paul de Vrieze and licensed under the
275 `Open Publication License`_.

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