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On Wed, Feb 10, 2021 at 12:57 PM Andreas K. Hüttel <dilfridge@g.o> wrote: |
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> |
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> * what portage features are still needed or need improvements (e.g. binpkg |
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> signing and verification) |
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> * how should hosting look like |
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Some ideas for portage enhancements: |
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1. Ability to fetch binary packages from some kind of repo. |
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2. Ability to have multiple binary packages co-exist in a repo (local |
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or remote) with different build attributes (arch, USE, CFLAGS, |
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DEPENDS, whatever). |
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3. Ability to pick the most appropriate binary packages to use based |
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on user preferences (with a mix of hard and soft preferences). |
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One idea I've had around how #2-3 might be implemented is: |
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1. Binary packages already contain data on how they were built (USE |
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flags, dependencies, etc). Place this in a file using a deterministic |
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sorting/etc order so that two builds with the same settings will have |
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the same results. |
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2. Generate a hash of the file contents - this can go in the filename |
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so that the file can co-exist with other files, and be located |
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assuming you have a full matching set of metadata. |
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3. Start dropping attributes from the file based on a list of |
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priorities and generate additional hashes. Create symlinked files to |
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the original file using these hashes (overwriting or not existing |
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symlinks based on policy). This allows the binary package to be found |
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using either an exact set of attributes or a subset of higher-priority |
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attributes. This is analogous to shared object symlinking. |
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4. The package manager will look for a binary package first using the |
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user's full config, and then by dropping optional elements of the |
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config (so maybe it does the search without CFLAGs, then without USE |
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flags). Eventually it aborts based on user prefs (maybe the user only |
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wants an exact match, or is willing to accept alternate CFLAGs but not |
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USE flags, or maybe anything for the arch is selected. |
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5. As always the final selected binary package still gets evaluated |
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like any other binary package to ensure it is usable. |
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Such a system can identify whether a potentially usable file exists |
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using only filename, cutting down on fetching. In the interests of |
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avoiding useless fetches we would only carry step 3 reasonably far - |
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packages would have to match based on architecture and any dynamic |
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linking requirements. So we wouldn't generate hashes that didn't |
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include at least those minimums, and the package manager wouldn't |
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search for them. |
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Obviously you could do more (if you have 5 combinations of use flags, |
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look for the set that matches most closely). That couldn't be done |
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using hashes alone in an efficient way. You could have a small |
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manifest file alongside the binary package that could be fetched |
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separately if the package manager wants to narrow things down and |
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fetch a few of those to narrow it down further. |
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Or you could skip the hash searching and just fetch all the manifests |
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for a particular package/arch and just search all of those, but that |
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is more data to transfer just to do a query. A metadata cache of some |
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kind of might be another solution. Content hashes would probably |
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still be useful just to allow co-existence of alternate builds. |
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-- |
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Rich |
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