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1 GLEP: 49
2 Title: Alternative Package Manager requirements
3 Version: $Revision: 2218 $
4 Last-Modified: $Date: 2006-05-20 20:39:14 +0200 (Sat, 20 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: 19-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. As of the date of publication, there are two known
32 alternative package managers that claim a level of Portage compatibility. These
33 alternatives are `paludis`_ and `pkgcore`_. Before these alternatives are
34 developed further, a set of rules should be created to level the playing field
35 and ensuring that decisions can be 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 usable 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. Examples of package
68 managers 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 - Focused package managers. For example a package manager that allows the
74 use of RPM formatted binary packages would be an example.
75
76 - Alternate package managers. Package managers that aim to coexist with the
77 primary package manager. They might for example offer a nicer user
78 interface than the primary package manager (e.g. show a cow instead of
79 compilation messages).
80
81
82 *Third Party Package Managers*
83 A third party package manager is any package manager that lacks recognition
84 from Gentoo as being in any other category. A third party package manager may
85 or may not have a Gentoo package, but is not supported beyond that.
86
87
88 Package manager requirements
89 ============================
90
91 As a package manager is in a state of higher support there are higher
92 requirements to it. The purpose of these requirements is to ensure the unity of
93 the distribution and the package tree. For this purpose it is needed that there
94 is only one primary package manager. This is from gentoo's perspective. From a
95 user perspective it is perfectly possible to use another package
96 manager. Candidate primary package managers and secondary package managers are
97 also supported in regards to bugs etc.
98
99
100 Primary package manager requirements
101 ------------------------------------
102
103 The primary package manager is the package manager that sets the standards for
104 the tree. All ebuilds in the tree must function with the primary package
105 manager. As the primary package manager sets the standard it does not have to
106 maintain compatibility with other package managers. This does not mean that the
107 actual implementation is the standard, but that the maintainers have the ability
108 to define new standards, together with the other involved gentoo projects.
109
110 The primary package manager does however have the responsibility that it must be
111 very stable. The primary package manager must maintain compatibility with old
112 versions of itself for extended periods of time. This compatibility time is set
113 by the council. The suggested time would be one year from the point that there
114 is a compatible stable version for all supported architectures.
115
116 Another compatibility requirement for the primary package manager is a limited
117 forward compatibility. It must always be possible to transition from the
118 unstable version of the primary package manager to a stable version. This may be
119 done either by first introducing reading compatibility for a new format and only
120 having write support later. Another way would be the provision of a conversion
121 tool that ensures that the on disk information maintained by the package manager
122 is supported by the stable package manager.
123
124 The primary package manager maintainers further have the responsibility to allow
125 competition. This means that reasonable patches from the maintainers of
126 secondary or candidate primary package managers must be applied, given that
127 these patches are as independent of that package manager as possible.
128
129 The primary package manager is maintained on official Gentoo infrastructure,
130 under control of Gentoo developers.
131
132
133 Candidate primary package manager requirements
134 ------------------------------------------------
135
136 A candidate primary package manager aims to replace the primary package
137 manager. The council is responsible for deciding whether this is done. The
138 requirements are there to ensure that it is actually possible to transition a
139 candidate primary package manager into the primary package manager.
140
141 First of all, there must exist a transition path. This means that the on disk
142 data of the primary package manager can be used by (or converted to a format
143 usable by) the candidate primary package manager.
144
145 Second, there must be a test path. It must be possible for the developers to
146 test out the candidate primary package manager on their working systems. This
147 means that the transition path must exist. This also means that there are no
148 serious obstacles for reverting to the current primary package manager. This
149 reverting must also be usable when it is decided that the candidate will not
150 become primary package manager, for example because serious design flaws or bugs
151 were found. Ideally, the Candidate Primary Package Manager and the Primary
152 Package Manager can be installed simultaneously. If not, clear instructions must
153 be provided for both ways of transitioning.
154
155 Third, there must exist an ebuild test path. It must be possible for package
156 managers to test ebuilds in one tree for both the primary as well as the
157 candidate primary package manager. It is not an issue if this requires a special
158 mode for the candidate primary package manager. It is not an issue either if
159 compatibility can be achieved by having the candidate primary package manager
160 unmerge the package.
161
162 Fourth, there must be support. This means that the package manager is actively
163 maintained under control of Gentoo. If it is not maintained on Gentoo
164 infrastructure, the means must be there to move the package manager, with its
165 change history, to Gentoo infrastructure. This means that it must be maintained
166 on a Gentoo supported versioning system, or on a version system whose history
167 can be converted to a Gentoo supported versioning system.
168
169 Fifth, release capabilities. There must exist automated tools that use the
170 candidate primary package manager to create release media that have similar
171 capabilities as those released using the old primary package manager. The exact
172 requirements are determined by the Release Engineering project, but should not
173 be significantly beyond what is currently implemented using the primary package
174 manager.
175
176
177 Secondary package manager requirements
178 --------------------------------------
179
180 A secondary package manager is a package manager that instead of directly aiming
181 at replacing the current primary package manager as primary package manager aims
182 to cooperate with the primary package manager. As such a secondary package
183 manager does not set the standard on the tree, but follows the standard set by
184 the primary package manager.
185
186 There are two kinds of secondary package managers. The first kind is formed by
187 those that do not maintain their own installed package database, but work with
188 the package database of the primary package manager. While these package
189 managers can put additional information in the database, these entries must
190 remain compatible with the primary package managers. Verification, reference,
191 and deinstallation by the primary package manager must remain functional.
192
193 The second kind is formed by those package managers that maintain their own
194 package database, or a package database incompatible with the primary package
195 manager. To ensure the secondary role of these package managers the support in
196 the tree for these package managers is provided along with restrictions.
197
198 The first restriction is that no packages in the tree must rely on the secondary
199 package manager. While packages may provide a level of support (while being
200 compatible with the primary package manager) this may not result in a
201 significant increase of features. If this were allowed, this would mean that
202 while they technically work with the primary package manager, there would be
203 significant incentive to use the secondary package manager. As the use of this
204 secondary package manager disallows the parallel use of the primary package
205 manager, this would result in users using the secondary package manager as their
206 primary package manager.
207
208 Users are allowed to make their own choices. However by making the tree favour a
209 package manager that is not the primary package manager, this will lead to the
210 secondary package manager becoming the effective primary package manager. As
211 this will be a decision by default instead of a conscious choice by the council,
212 this is an undesirable result.
213
214 There is one exclusion for the restriction of packages that only work with or
215 have significant improvements with the secondary package manager. That is
216 packages that by their nature are only usable with this secondary package
217 manager. An example would be a graphical front-end to the secondary package
218 manager.
219
220 If a secondary package manager works along the primary package manager, but by
221 itself does not have the capabilities of becoming a primary package manager the
222 risks of choice by default are lower. As a result, the council could choose to
223 allow the inclusion of packages that work only or significantly better with this
224 secondary package manager. For example at a point where there is a stable,
225 functional, package manager that can handle RPM format packages, the council
226 could decide to include these packages directly in the tree, instead of using
227 wrapper scripts for those packages that are only provided in the RPM
228 format. Such a decision does imply that the maintainers of the primary package
229 manager must take this secondary package manager into account.
230
231
232 Third party package manager requirements
233 ----------------------------------------
234
235 A third party package manager is just that. It is a package manager without any
236 support within Gentoo. As there is no control by Gentoo over the package manager
237 this means that there are no requirements on the package manager.
238
239 This complete lack of control however also translates to the fact that Gentoo
240 can not make package manager specific changes to support this package
241 manager. Package manager specific means that it is possible to request changes
242 that make the tree more independent of the primary package manager. These
243 changes must however be agnostic of the package manager, and only make it easier
244 to have alternative package managers.
245
246
247 Transition phases
248 =================
249
250 Primary package manager transition phase
251 ----------------------------------------
252
253 A candidate primary package manager can be chosen to become primary package
254 manager. This can only happen by council decision. This decision can only be
255 made when the candidate primary package manager is stable on all stable
256 architectures. (all architectures except experimental ones). There is a
257 incubation period of at least 3 months before a candidate primary package
258 manager can become the primary package manager.
259
260 After the decision has been made to replace the primary package manager, the
261 transition phase starts. The use of the old stable package manager must remain
262 supported for a period of 6 months. This means that core packages must be
263 installable by this package manager. Further the possibility to convert the
264 system automatically to the new primary package manager must be available for at
265 least 18 months, but preferably longer (enable installing the new package
266 manager from the old one).
267
268 During the transition phase packages are allowed in the tree that use the new
269 features of the new primary package manager. While backward compatibility with
270 the previous primary package manager must be maintained a forward compatibility
271 is no longer needed.
272
273
274 Secondary package manager to candidate primary package manager transition
275 -------------------------------------------------------------------------
276
277 The transition from secondary package manager to candidate primary package
278 manager is straightforward. The secondary package manager must satisfy all
279 requirements for a candidate primary package manager. At that point its
280 maintainers can announce that they are changing the status to candidate primary
281 package manager. This allows a greater support from Gentoo in achieving that
282 goal.
283
284
285 Third party to other transition
286 -------------------------------
287
288 When a third party package manager wants to transition into one of the other
289 categories (except primary package manager) it must satisfy all requirements for
290 that category.
291
292
293 References
294 ==========
295
296 .. _paludis: http://paludis.berlios.de/
297 .. _pkgcore: http://gentooexperimental.org/~ferringb/bzr/pkgcore/
298 .. _Open Publication License: http://www.opencontent.org/openpub/
299
300
301 Copyright
302 =========
303
304 This document is copyright 2006 by Paul de Vrieze and licensed under the
305 `Open Publication License`_.

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